docs(design): add multi-user / profiles design (schema-of-record)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.cargo/audit.toml

@@ -5,8 +5,11 @@
 # means the audit job stops flagging it, so the reasoning must hold up.
 #
 # NOTE: `cargo audit` (no `--deny warnings`) fails only on *vulnerabilities*, not on the
-# `unmaintained` warnings (audiopus_sys / paste / rustls-pemfile). Those are left visible on purpose
+# `unmaintained` warnings (audiopus_sys via opus, paste via utoipa-axum). Both are transitive, at
-# so we keep getting the maintenance signal — they do not fail CI.
+# their latest published version with no successor, so there's nothing to bump — left visible on
+# purpose so we keep getting the maintenance signal; they do not fail CI. (rustls-pemfile was dropped
+# 2026-06-29 by removing axum-server's unused tls-rustls feature + moving our own PEM parsing to
+# rustls-pki-types; memmap2's unsoundness was fixed by the 0.9.11 bump.)
 
 [advisories]
 ignore = [

.gitea/workflows/android-screenshots.yml

@@ -0,0 +1,57 @@
+# Android client screenshots for the Play listing / marketing. Roborazzi renders the real Compose
+# UI with mock state on the host JVM via Robolectric — NO emulator, GPU, KVM, host, or JNI core
+# (`-PskipRustBuild` skips the cargo-ndk native build). The Android analogue of apple.yml's
+# `screenshots` job, gated to STABLE RELEASE tags only. Standalone + best-effort: a failure here
+# reds nothing else. PNGs land as a 30-day artifact; not committed or published.
+name: android-screenshots
+
+on:
+  push:
+    tags: ["v*"]
+  workflow_dispatch:
+
+jobs:
+  screenshots:
+    if: startsWith(github.ref, 'refs/tags/v') || github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-24.04
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: JDK 21 (AGP 9.2 + Robolectric's SDK-36 android-all jar both want 17–21)
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: "21"
+
+      - name: Android SDK
+        uses: android-actions/setup-android@v3
+
+      # No NDK/CMake — the screenshot unit tests are pure JVM. compileSdk 37 auto-downloads via AGP
+      # if the platform channel lacks it (same note as android.yml).
+      - name: platform-tools + platform 36 + build-tools
+        run: sdkmanager "platform-tools" "platforms;android-36" "build-tools;37.0.0"
+
+      - name: Cache (gradle)
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: android-screenshots-${{ hashFiles('clients/android/**/*.gradle.kts') }}
+          restore-keys: android-screenshots-
+
+      # Roborazzi renders Compose on the JVM (Robolectric Native Graphics). `-PskipRustBuild` keeps
+      # the cargo-ndk native build out of the graph — the tests never load libpunktfunk_android.so.
+      - name: Capture screenshots (Roborazzi)
+        working-directory: clients/android
+        run: ./gradlew :app:testDebugUnitTest -PskipRustBuild --stacktrace
+
+      - name: Upload screenshots
+        if: always()
+        # v3: Gitea's API rejects upload-artifact@v4 (see apple.yml). Download is a zip.
+        uses: actions/upload-artifact@v3
+        with:
+          name: punktfunk-android-screenshots
+          path: clients/android/app/build/outputs/roborazzi
+          retention-days: 30

.gitea/workflows/apple.yml

@@ -32,6 +32,25 @@ jobs:
           dirname "$RUSTUP" >> "$GITHUB_PATH"
           "$RUSTUP" target add aarch64-apple-darwin x86_64-apple-darwin
 
+      # `punktfunk-core` now decodes Opus in-core for the Apple client (surround), pulling
+      # `audiopus_sys`, which builds a vendored static libopus via CMake when pkg-config can't find a
+      # system Opus — so the xcframework is self-contained (no runtime libopus.dylib on end-user Macs).
+      # CMake must be on PATH; install it self-healing on a fresh runner.
+      - name: CMake (for the vendored libopus audiopus_sys builds)
+        run: |
+          # Runner steps run with `bash --noprofile --norc`, so Homebrew's bin dir isn't on PATH —
+          # locate brew explicitly, install cmake if missing, and export its bin dir to GITHUB_PATH so
+          # the xcframework build step (audiopus_sys → vendored libopus) finds `cmake`.
+          for B in /opt/homebrew/bin/brew /usr/local/bin/brew; do [ -x "$B" ] && BREW="$B" && break; done
+          if [ -z "$BREW" ]; then echo "::error::Homebrew not found on the runner"; exit 1; fi
+          BREW_BIN="$(dirname "$BREW")"; export PATH="$BREW_BIN:$PATH"
+          command -v cmake >/dev/null || "$BREW" install cmake
+          echo "$BREW_BIN" >> "$GITHUB_PATH"
+          # Homebrew's CMake 4 dropped compatibility with the vendored libopus's pre-3.5
+          # `cmake_minimum_required`; treat 3.5 as the policy minimum (the cmake crate's child cmake
+          # inherits this from the env during the xcframework build).
+          echo "CMAKE_POLICY_VERSION_MINIMUM=3.5" >> "$GITHUB_ENV"
+
       - name: Build PunktfunkCore.xcframework
         run: bash scripts/build-xcframework.sh
 
@@ -71,6 +90,22 @@ jobs:
           "$RUSTUP" target add aarch64-apple-darwin x86_64-apple-darwin \
             aarch64-apple-ios aarch64-apple-ios-sim x86_64-apple-ios
 
+      # See the swift job: audiopus_sys (via the in-core Opus decode) builds vendored libopus with CMake.
+      - name: CMake (for the vendored libopus audiopus_sys builds)
+        run: |
+          # Runner steps run with `bash --noprofile --norc`, so Homebrew's bin dir isn't on PATH —
+          # locate brew explicitly, install cmake if missing, and export its bin dir to GITHUB_PATH so
+          # the xcframework build step (audiopus_sys → vendored libopus) finds `cmake`.
+          for B in /opt/homebrew/bin/brew /usr/local/bin/brew; do [ -x "$B" ] && BREW="$B" && break; done
+          if [ -z "$BREW" ]; then echo "::error::Homebrew not found on the runner"; exit 1; fi
+          BREW_BIN="$(dirname "$BREW")"; export PATH="$BREW_BIN:$PATH"
+          command -v cmake >/dev/null || "$BREW" install cmake
+          echo "$BREW_BIN" >> "$GITHUB_PATH"
+          # Homebrew's CMake 4 dropped compatibility with the vendored libopus's pre-3.5
+          # `cmake_minimum_required`; treat 3.5 as the policy minimum (the cmake crate's child cmake
+          # inherits this from the env during the xcframework build).
+          echo "CMAKE_POLICY_VERSION_MINIMUM=3.5" >> "$GITHUB_ENV"
+
       - name: Build PunktfunkCore.xcframework (mac + iOS slices)
         run: BUILD_IOS=1 bash scripts/build-xcframework.sh
 

.gitea/workflows/decky.yml

@@ -11,12 +11,18 @@
 #   punktfunk.zip
 #     punktfunk/                  <- single top-level dir == plugin.json "name"
 #       plugin.json   [required]
-#       package.json  [required]
+#       package.json  [required; CI stamps "version" — Decky reads the installed version here]
 #       main.py       [required: python backend]
 #       dist/index.js [required: rollup output]
+#       update.json   [CI-baked {channel, manifest}: where the plugin's self-update check polls]
 #       README.md     (recommended)
 #       LICENSE       [required by the plugin store]
 #
+# SELF-UPDATE (no Decky store): alongside the zip we also publish a tiny per-channel
+# `manifest.json` ({version, artifact=<immutable per-version zip URL>, sha256}). The installed
+# plugin polls it (main.py check_update), and the frontend drives Decky's own install RPC to
+# apply a newer build. See clients/decky/README.md "Updating".
+#
 # REGISTRY_TOKEN: repo Actions secret, a PAT with write:package scope (shared with deb/rpm/docker).
 name: decky
 
@@ -56,20 +62,26 @@ jobs:
           pnpm install --frozen-lockfile
           pnpm run build          # rollup -> clients/decky/dist/index.js
 
-      - name: Version + channel
+      - name: Version + channel + stamp
-        # Tag vX.Y.Z -> X.Y.Z (stable `latest/` alias + Gitea Release); main push -> 0.3.0-ciN.g<sha>
+        # Tag vX.Y.Z -> X.Y.Z (stable `latest/` alias + Gitea Release); main push -> 0.3.<run>
-        # (`canary/` alias). Used for the registry version path + the zip name (the plugin.json
+        # (`canary/` alias). Decky reads a plugin's INSTALLED version from package.json (NOT
-        # version is the source of truth Decky reads after install — bump it in the release commit).
+        # plugin.json), and the plugin's own update check (clients/decky/main.py check_update)
+        # compares against it — so the build version is STAMPED into package.json here (mirrored
+        # into plugin.json for store parity). Canary is a PLAIN numeric semver, never a
+        # `-ci<N>` prerelease: compare-versions orders prerelease identifiers lexically
+        # (ci10 < ci9), which would break update detection; the run number is monotonic.
         working-directory: ${{ gitea.workspace }}
         run: |
-          SHORT=$(echo "$GITHUB_SHA" | cut -c1-8)
           case "$GITHUB_REF" in
             refs/tags/v*) V="${GITHUB_REF_NAME#v}"; ALIAS=latest ;;
-            *)            V="0.3.0-ci${GITHUB_RUN_NUMBER}.g${SHORT}"; ALIAS=canary ;;
+            *)            V="0.3.${GITHUB_RUN_NUMBER}"; ALIAS=canary ;;
           esac
+          BASE="https://$REGISTRY/api/packages/$OWNER/generic/$PACKAGE"
           echo "VERSION=$V" >> "$GITHUB_ENV"
           echo "ALIAS=$ALIAS" >> "$GITHUB_ENV"
+          echo "BASE=$BASE" >> "$GITHUB_ENV"
           echo "decky version $V -> alias '$ALIAS'"
+          VERSION="$V" node -e 'const fs=require("fs");for(const f of ["clients/decky/package.json","clients/decky/plugin.json"]){const j=JSON.parse(fs.readFileSync(f,"utf8"));j.version=process.env.VERSION;fs.writeFileSync(f,JSON.stringify(j,null,2)+"\n");}'
 
       - name: Assemble store-layout zip
         working-directory: ${{ gitea.workspace }}
@@ -89,9 +101,20 @@ jobs:
           chmod 0755 "$DEST/bin/punktfunkrun.sh"
           # Store requires a LICENSE in the plugin root; the project is MIT OR Apache-2.0.
           cp LICENSE-MIT                 "$DEST/LICENSE"
+          # Self-update channel pointer the backend reads (main.py check_update). It points at
+          # THIS channel's manifest.json (published below); that manifest in turn points at the
+          # immutable per-version zip, so its sha256 stays valid across future alias re-uploads.
+          printf '{"channel":"%s","manifest":"%s/%s/manifest.json"}\n' "$ALIAS" "$BASE" "$ALIAS" > "$DEST/update.json"
           ( cd "$STAGE" && zip -r "$RUNNER_TEMP/punktfunk.zip" "$PLUGIN" )
           ls -lh "$RUNNER_TEMP/punktfunk.zip"
           unzip -l "$RUNNER_TEMP/punktfunk.zip"
+          # The update manifest the plugin polls: the immutable per-version artifact + its
+          # sha256 (Decky's installer verifies the download against this hash, aborting on
+          # mismatch — so it MUST be the per-version URL, never the mutable alias).
+          SHA=$(sha256sum "$RUNNER_TEMP/punktfunk.zip" | cut -d' ' -f1)
+          printf '{"version":"%s","artifact":"%s/%s/punktfunk.zip","sha256":"%s"}\n' \
+            "$VERSION" "$BASE" "$VERSION" "$SHA" > "$RUNNER_TEMP/manifest.json"
+          cat "$RUNNER_TEMP/manifest.json"
 
       - name: Publish to the Gitea generic registry
         working-directory: ${{ gitea.workspace }}
@@ -99,18 +122,26 @@ jobs:
           TOKEN: ${{ secrets.REGISTRY_TOKEN }}
         run: |
           BASE="https://$REGISTRY/api/packages/$OWNER/generic/$PACKAGE"
-          # 1) Immutable, versioned URL.
+          # 1) Immutable, versioned URL + its update manifest (the manifest's `artifact` points
+          #    here, so the published sha256 keeps matching what Decky later downloads).
           curl -fsS --user "enricobuehler:$TOKEN" --upload-file "$RUNNER_TEMP/punktfunk.zip" \
             "$BASE/$VERSION/punktfunk.zip"
+          curl -fsS --user "enricobuehler:$TOKEN" --upload-file "$RUNNER_TEMP/manifest.json" \
+            "$BASE/$VERSION/manifest.json"
           echo "published $BASE/$VERSION/punktfunk.zip"
-          # 2) Channel alias (stable release -> latest/, canary main build -> canary/) — the link
+          # 2) Channel alias (stable release -> latest/, canary main build -> canary/) — the
-          #    to paste into Decky's "install from URL". The generic registry rejects re-uploading
+          #    zip is the "install from URL" link; manifest.json is what the installed plugin
-          #    an existing version/file (409), so delete the prior alias first (ignore 404 on run #1).
+          #    polls for updates. The generic registry rejects re-uploading an existing
-          curl -fsS -o /dev/null --user "enricobuehler:$TOKEN" -X DELETE \
+          #    version/file (409), so delete the prior alias copies first (ignore 404 on run #1).
-            "$BASE/$ALIAS/punktfunk.zip" || true
+          for f in punktfunk.zip manifest.json; do
+            curl -fsS -o /dev/null --user "enricobuehler:$TOKEN" -X DELETE "$BASE/$ALIAS/$f" || true
+          done
           curl -fsS --user "enricobuehler:$TOKEN" --upload-file "$RUNNER_TEMP/punktfunk.zip" \
             "$BASE/$ALIAS/punktfunk.zip"
+          curl -fsS --user "enricobuehler:$TOKEN" --upload-file "$RUNNER_TEMP/manifest.json" \
+            "$BASE/$ALIAS/manifest.json"
           echo "install-from-URL link: $BASE/$ALIAS/punktfunk.zip"
+          echo "update manifest:       $BASE/$ALIAS/manifest.json"
 
       - name: Attach zip to the Gitea release (stable tags only)
         if: startsWith(gitea.ref, 'refs/tags/v')

.gitea/workflows/linux-client-screenshots.yml

@@ -0,0 +1,67 @@
+# Native Linux client screenshots for the app/marketing listings. The client renders
+# host-free mock scenes (PUNKTFUNK_SHOT_SCENE) under a virtual X display; the driver
+# (clients/linux/tools/screenshots.sh) grabs each one — no host, GPU, or Wayland. The
+# Linux analogue of apple.yml's `screenshots` job, gated to STABLE RELEASE tags only.
+# Standalone + best-effort: a failure here reds nothing else. PNGs land as a 30-day
+# artifact; they are not committed or published.
+name: linux-client-screenshots
+
+on:
+  push:
+    tags: ["v*"]
+  workflow_dispatch:
+
+jobs:
+  screenshots:
+    if: startsWith(github.ref, 'refs/tags/v') || github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-24.04
+    # Same image as ci.yml/deb.yml — already carries the Rust toolchain + GTK/SDL build deps.
+    container:
+      image: git.unom.io/unom/punktfunk-rust-ci:latest
+    timeout-minutes: 90
+    steps:
+      - uses: actions/checkout@v4
+
+      # Client link deps (baked into the image; kept here so the job is green across image
+      # rebuilds — a no-op once present) PLUS the headless-render extras: a virtual X server,
+      # software GL+Vulkan (llvmpipe/lavapipe), the icon theme + fonts the UI draws with, and a
+      # root-window grab tool.
+      - name: Client link + headless-render deps
+        run: |
+          apt-get update
+          apt-get install -y --no-install-recommends \
+            libgtk-4-dev libadwaita-1-dev libsdl3-dev \
+            xvfb x11-utils imagemagick scrot \
+            libgl1-mesa-dri mesa-vulkan-drivers \
+            adwaita-icon-theme fonts-cantarell fonts-dejavu-core
+
+      # Reuse the workspace cargo caches (same keys as ci.yml/deb.yml).
+      - name: Cache keys
+        run: echo "rustc=$(rustc --version | cut -d' ' -f2)" >> "$GITHUB_ENV"
+      - uses: actions/cache@v4
+        with:
+          path: |
+            /usr/local/cargo/registry
+            /usr/local/cargo/git
+          key: cargo-home-${{ hashFiles('Cargo.lock') }}
+          restore-keys: cargo-home-
+      - uses: actions/cache@v4
+        with:
+          path: target
+          key: cargo-target-v3-${{ env.rustc }}-${{ hashFiles('Cargo.lock') }}
+          restore-keys: cargo-target-v3-${{ env.rustc }}-
+
+      - name: Build client
+        run: cargo build --release -p punktfunk-client-linux --locked
+
+      - name: Capture screenshots
+        run: bash clients/linux/tools/screenshots.sh
+
+      - name: Upload screenshots
+        if: always()
+        # v3: Gitea's API rejects upload-artifact@v4 (see apple.yml). Download is a zip.
+        uses: actions/upload-artifact@v3
+        with:
+          name: punktfunk-linux-client-screenshots
+          path: clients/linux/screenshots
+          retention-days: 30

.gitea/workflows/release.yml

@@ -118,6 +118,23 @@ jobs:
           "$RUSTUP" toolchain install nightly --profile minimal
           "$RUSTUP" component add rust-src --toolchain nightly
 
+      # The in-core Opus decode (surround) pulls audiopus_sys, which builds a vendored static libopus
+      # via CMake — keep the xcframework self-contained (no runtime libopus.dylib on end-user devices).
+      - name: CMake (for the vendored libopus audiopus_sys builds)
+        run: |
+          # Runner steps run with `bash --noprofile --norc`, so Homebrew's bin dir isn't on PATH —
+          # locate brew explicitly, install cmake if missing, and export its bin dir to GITHUB_PATH so
+          # the xcframework build step (audiopus_sys → vendored libopus) finds `cmake`.
+          for B in /opt/homebrew/bin/brew /usr/local/bin/brew; do [ -x "$B" ] && BREW="$B" && break; done
+          if [ -z "$BREW" ]; then echo "::error::Homebrew not found on the runner"; exit 1; fi
+          BREW_BIN="$(dirname "$BREW")"; export PATH="$BREW_BIN:$PATH"
+          command -v cmake >/dev/null || "$BREW" install cmake
+          echo "$BREW_BIN" >> "$GITHUB_PATH"
+          # Homebrew's CMake 4 dropped compatibility with the vendored libopus's pre-3.5
+          # `cmake_minimum_required`; treat 3.5 as the policy minimum (the cmake crate's child cmake
+          # inherits this from the env during the xcframework build).
+          echo "CMAKE_POLICY_VERSION_MINIMUM=3.5" >> "$GITHUB_ENV"
+
       - name: Build PunktfunkCore.xcframework (mac + iOS + tvOS)
         # tvOS is a tier-3 target (nightly -Zbuild-std): slow on the first build, then cached on
         # the self-hosted runner. Built on canary too so the tvOS archive/upload below runs on the

.gitea/workflows/web-screenshots.yml

@@ -0,0 +1,53 @@
+# Management-console screenshots for the app/marketing listings. Captured from the
+# built Storybook with headless Chromium (web/tools/screenshots.mjs) — the page
+# stories render from fixtures, so no live mgmt API, login, or GPU is needed. This
+# is the web analogue of apple.yml's `screenshots` job, but gated to STABLE RELEASE
+# tags only (the console has no release workflow of its own — it ships inside the
+# host packaging). Best-effort: a standalone workflow, so a failure here reds
+# nothing else. PNGs land as a 30-day artifact; they are not committed or published.
+name: web-screenshots
+
+on:
+  push:
+    tags: ["v*"]
+  workflow_dispatch:
+
+jobs:
+  screenshots:
+    if: startsWith(github.ref, 'refs/tags/v') || github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-24.04
+    container:
+      image: oven/bun:1
+    timeout-minutes: 30
+    defaults:
+      run:
+        working-directory: web
+    steps:
+      # oven/bun ships neither git nor a real node (the driver runs under node), and
+      # the slim Debian base lacks a CA bundle — without it actions/checkout's HTTPS
+      # fetch dies with "Problem with the SSL CA cert" (same as ci.yml's web job).
+      - name: Install git + node + CA certs
+        working-directory: /
+        run: apt-get update && apt-get install -y --no-install-recommends ca-certificates git nodejs
+      - uses: actions/checkout@v4
+      # --ignore-scripts skips the prepare→codegen hook (mirrors ci.yml); run codegen
+      # explicitly since build-storybook has no prebuild hook of its own.
+      - name: Install dependencies
+        run: bun install --frozen-lockfile --ignore-scripts
+      - name: Generate API client + i18n messages
+        run: bun run codegen
+      # Pulls the matching Chromium build + the apt libs it needs (root in-container).
+      - name: Install Chromium
+        run: bunx playwright install --with-deps chromium
+      - name: Build Storybook
+        run: bun run build-storybook
+      - name: Capture screenshots
+        run: bun run screenshots
+      - name: Upload screenshots
+        if: always()
+        # v3: Gitea's API rejects upload-artifact@v4 (see apple.yml). Download is a zip.
+        uses: actions/upload-artifact@v3
+        with:
+          name: punktfunk-web-console-screenshots
+          path: web/screenshots
+          retention-days: 30

.gitea/workflows/windows-host.yml

@@ -24,8 +24,9 @@
 # GPU backends: the host builds with --features nvenc,amf-qsv = all three vendors in one installer.
 #  - NVENC (NVIDIA, direct SDK): the only link need is nvencodeapi.lib, synthesised from a 2-export
 #    .def with llvm-dlltool (no GPU/SDK at build time).
-#  - AMF/QSV (AMD/Intel, libavcodec): link-imports the FFmpeg libs from FFMPEG_DIR (the BtbN gpl-shared
+#  - AMF/QSV (AMD/Intel, libavcodec): link-imports the FFmpeg libs from FFMPEG_DIR (the BtbN lgpl-shared
 #    tree the client uses; includes the *_amf/*_qsv encoders) and bundles its DLLs into the installer.
+#    lgpl-shared (not gpl-shared) keeps those bundled DLLs LGPL (we never use the GPL-only x264/x265).
 # CI never launches the exe, so no GPU is needed here — this is build + Windows clippy coverage only.
 name: windows-host
 
@@ -80,7 +81,7 @@ jobs:
           # (pwsh Out-File utf8 = no BOM, unlike Windows PowerShell 5.1 — keeps the first line clean).
           "CARGO_TARGET_DIR=C:\t" | Out-File -FilePath $env:GITHUB_ENV -Append -Encoding utf8
           "CARGO_WORKSPACE_DIR=$env:GITHUB_WORKSPACE" | Out-File -FilePath $env:GITHUB_ENV -Append -Encoding utf8
-          # FFMPEG_DIR: the same BtbN gpl-shared x64 tree the Windows CLIENT links against (provisioned
+          # FFMPEG_DIR: the same BtbN lgpl-shared x64 tree the Windows CLIENT links against (provisioned
           # by scripts/ci/setup-windows-runner.ps1). The host's AMD/Intel AMF/QSV encode backend
           # (--features amf-qsv) link-imports avcodec/avutil/swscale from it; pack-host-installer.ps1
           # then bundles its bin\*.dll into the installer. LIBCLANG_PATH is in the runner daemon env.

.gitignore

@@ -13,6 +13,7 @@ clients/apple/PunktfunkCore.xcframework/
 clients/apple/.swiftpm/
 # Generated App Store screenshots (tools/screenshots.sh output; uploaded as a CI artifact)
 clients/apple/screenshots/
+clients/linux/screenshots/
 # Xcode per-user state
 xcuserdata/
 

CLAUDE.md

@@ -346,7 +346,23 @@ FFI also link-needs `libGL`/`libgbm`/`libcuda` at build time). Env knobs: `PUNKT
 `PUNKTFUNK_COMPOSITOR=kwin|gamescope|mutter`, `PUNKTFUNK_ZEROCOPY=1`, `PUNKTFUNK_GAMESCOPE_APP=...`,
 `PUNKTFUNK_INPUT_BACKEND=...`, `PUNKTFUNK_PERF=1` (per-stage timing), `PUNKTFUNK_VIDEO_DROP=N` (FEC
 test), `PUNKTFUNK_FEC_PCT=N`, `PUNKTFUNK_DSCP=1` (opt-in DSCP/SO_PRIORITY media QoS on the data +
-GameStream video/audio sockets; no-op on the wire on Windows without a qWAVE policy).
+GameStream video/audio sockets; no-op on the wire on Windows without a qWAVE policy),
+`PUNKTFUNK_444=1` (full-chroma HEVC 4:4:4, see below).
+
+**HEVC 4:4:4 (full chroma, Range Extensions)**: opt-in via `PUNKTFUNK_444`, negotiated like 10-bit —
+the host emits 4:4:4 only when the client advertised `VIDEO_CAP_444` (wire bit `0x04` + ABI
+`PUNKTFUNK_VIDEO_CAP_444`), the codec is HEVC, the session is single-process, **and** a GPU probe
+(`encode::can_encode_444`, run before the Welcome) confirms support — else it resolves to 4:2:0 and
+`Welcome::chroma_format` reflects the real value (honest downgrade; the client reads it via
+`punktfunk_connection_chroma_format`). **punktfunk/1-native only** — GameStream/Moonlight stays 4:2:0
+(stock clients can't decode 4:4:4). **NVENC is the implemented path**: Linux `hevc_nvenc` feeds a
+swscale'd `yuv444p` (RGB-in is always 4:2:0 — verified on the RTX 5070 Ti — so the session forces CPU
+RGB capture for 4:4:4); Windows NVENC keeps ARGB input + FREXT profile + `chromaFormatIDC=3` and the
+DDA capturer delivers RGB. VAAPI / AMF / QSV **decline** (probe returns false — no validated 4:4:4
+hardware in the lab; they'd produce 4:2:0). Software (openh264) is 4:2:0-only. Test with
+`PUNKTFUNK_CLIENT_444=1 punktfunk-probe --out x.h265` then `ffprobe x.h265` (expect `pix_fmt yuv444p`).
+*Linux NVENC mechanism validated on the RTX 5070 Ti (ffmpeg CLI); Windows NVENC + 10-bit-4:4:4 not yet
+on-glass validated.*
 
 ## Conventions
 

CONTRIBUTING.md

@@ -0,0 +1,43 @@
+# Contributing to punktfunk
+
+Thanks for your interest in contributing!
+
+## Licensing of contributions (inbound = outbound)
+
+punktfunk is dual-licensed under **MIT OR Apache-2.0**.
+
+> Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in
+> the work by you, as defined in the Apache-2.0 license, shall be dual licensed as **MIT OR
+> Apache-2.0**, without any additional terms or conditions.
+
+By opening a pull request you agree to license your contribution under these terms. This is the
+standard Rust-ecosystem "inbound = outbound" model; it keeps the project's licensing unambiguous
+(including the Apache-2.0 §5 contributor patent grant) and any future relicensing clean. You retain
+the copyright to your contributions.
+
+### Do not paste copyleft (or otherwise incompatibly-licensed) code
+
+The single thing that could poison the permissive license is **copied source from a copyleft
+project**. Several adjacent projects (Sunshine, Apollo, Moonlight) are GPL-3.0. You may study them
+and reimplement a *technique*, protocol, or wire format — those are not copyrightable — but **never
+paste their code**, and do not translate a GPL implementation line-by-line. When a comment credits
+prior art, make clear it is an independent reimplementation, not a copy. The same applies to any
+third party's code under a license incompatible with MIT/Apache.
+
+If you add a new third-party dependency, it must be permissive (MIT / Apache-2.0 / BSD / ISC / Zlib /
+Unicode-3.0 / etc.). `about.toml` holds the accepted-license allow-list; regenerate the attribution
+file with `scripts/gen-third-party-notices.sh` when the dependency tree changes.
+
+## Before you push
+
+```sh
+cargo fmt --all --check
+cargo clippy --workspace --all-targets -- -D warnings
+cargo test  --workspace
+```
+
+Generated artifacts are checked in and CI fails on drift: `include/punktfunk_core.h` (cbindgen) and
+`api/openapi.json` (`cargo run -p punktfunk-host -- openapi`). Match the surrounding code's comment
+density and naming. Commit messages end with the `Co-Authored-By` trailer (see `git log`).
+
+See [`CLAUDE.md`](CLAUDE.md) for the full build/test/run guide and design invariants.

Cargo.lock

@@ -137,18 +137,9 @@ dependencies = [
 
 [[package]]
 name = "anyhow"
-version = "1.0.102"
+version = "1.0.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
+checksum = "2a4385e2e34eb35d6b3efe798b9eb88096925d87726c0798709bf56d9ed84af3"
-
-[[package]]
-name = "arc-swap"
-version = "1.9.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a3a1fd6f75306b68087b831f025c712524bcb19aad54e557b1129cfa0a2b207"
-dependencies = [
- "rustversion",
-]
 
 [[package]]
 name = "ash"
@@ -161,13 +152,13 @@ dependencies = [
 
 [[package]]
 name = "ashpd"
-version = "0.13.11"
+version = "0.13.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "340e0f6bf7f9ee78549c61454f1460a3ed97c011902ee76b58301bbc6d502a32"
+checksum = "281e6645758940dee594495e28807a7672ce40f11ebf4df6c22c4fcd59e2689f"
 dependencies = [
  "enumflags2",
  "futures-util",
- "getrandom 0.4.2",
+ "getrandom 0.4.3",
  "serde",
  "serde_repr",
  "tokio",
@@ -358,23 +349,18 @@ dependencies = [
 
 [[package]]
 name = "axum-server"
-version = "0.7.3"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c1ab4a3ec9ea8a657c72d99a03a824af695bd0fb5ec639ccbd9cd3543b41a5f9"
+checksum = "b1df331683d982a0b9492b38127151e6453639cd34926eb9c07d4cd8c6d22bfc"
 dependencies = [
- "arc-swap",
  "bytes",
+ "either",
  "fs-err",
  "http",
  "http-body",
  "hyper",
  "hyper-util",
- "pin-project-lite",
- "rustls",
- "rustls-pemfile",
- "rustls-pki-types",
  "tokio",
- "tokio-rustls",
  "tower-service",
 ]
 
@@ -476,9 +462,9 @@ dependencies = [
 
 [[package]]
 name = "bytes"
-version = "1.11.1"
+version = "1.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33"
+checksum = "8ae3f5d315924270530207e2a68396c3cc547f6dca3fbdca317cfb1a51edb593"
 
 [[package]]
 name = "cairo-rs"
@@ -520,9 +506,9 @@ dependencies = [
 
 [[package]]
 name = "cbindgen"
-version = "0.29.3"
+version = "0.29.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c95537b45400390270fae69ac098d057c8f5399001cde9d04f700c105ddfff2d"
+checksum = "2ecb53484c9c167ba674026b656d8a27d7657a58e6066aa902bfb1a4aa00ae20"
 dependencies = [
  "clap",
  "heck",
@@ -539,9 +525,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.2.63"
+version = "1.2.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "556e016178bb5662a08681bbe0f00f8e17631781a4dfc8c45e466e4b185ec27f"
+checksum = "e228eec9be7c17ccb640b59b36a5cd805ea2a564a4c5e162c2f659fea30d3b96"
 dependencies = [
  "find-msvc-tools",
  "jobserver",
@@ -906,9 +892,6 @@ name = "deranged"
 version = "0.5.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7cd812cc2bc1d69d4764bd80df88b4317eaef9e773c75226407d9bc0876b211c"
-dependencies = [
- "powerfmt",
-]
 
 [[package]]
 name = "digest"
@@ -1127,9 +1110,9 @@ dependencies = [
 
 [[package]]
 name = "flume"
-version = "0.11.1"
+version = "0.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da0e4dd2a88388a1f4ccc7c9ce104604dab68d9f408dc34cd45823d5a9069095"
+checksum = "5e139bc46ca777eb5efaf62df0ab8cc5fd400866427e56c68b22e414e53bd3be"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -1142,12 +1125,6 @@ version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
-[[package]]
-name = "foldhash"
-version = "0.1.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
-
 [[package]]
 name = "foldhash"
 version = "0.2.0"
@@ -1376,15 +1353,13 @@ dependencies = [
 
 [[package]]
 name = "getrandom"
-version = "0.4.2"
+version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0de51e6874e94e7bf76d726fc5d13ba782deca734ff60d5bb2fb2607c7406555"
+checksum = "300e883d756b2e4ec94e02791f39b04b522276138852cfc41d9fb7e904106099"
 dependencies = [
  "cfg-if",
  "libc",
  "r-efi 6.0.0",
- "wasip2",
- "wasip3",
 ]
 
 [[package]]
@@ -1595,9 +1570,9 @@ dependencies = [
 
 [[package]]
 name = "h2"
-version = "0.4.14"
+version = "0.4.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "171fefbc92fe4a4de27e0698d6a5b392d6a0e333506bc49133760b3bcf948733"
+checksum = "6cb093c84e8bd9b188d4c4a8cb6579fc016968d14c99882163cd3ff402a4f155"
 dependencies = [
  "atomic-waker",
  "bytes",
@@ -1623,22 +1598,13 @@ dependencies = [
  "zerocopy",
 ]
 
-[[package]]
-name = "hashbrown"
-version = "0.15.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
-dependencies = [
- "foldhash 0.1.5",
-]
-
 [[package]]
 name = "hashbrown"
 version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
 dependencies = [
- "foldhash 0.2.0",
+ "foldhash",
 ]
 
 [[package]]
@@ -1647,7 +1613,7 @@ version = "0.17.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed5909b6e89a2db4456e54cd5f673791d7eca6732202bbf2a9cc504fe2f9b84a"
 dependencies = [
- "foldhash 0.2.0",
+ "foldhash",
 ]
 
 [[package]]
@@ -1858,12 +1824,6 @@ dependencies = [
  "zerovec",
 ]
 
-[[package]]
-name = "id-arena"
-version = "2.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3d3067d79b975e8844ca9eb072e16b31c3c1c36928edf9c6789548c524d0d954"
-
 [[package]]
 name = "idna"
 version = "1.1.0"
@@ -2014,9 +1974,9 @@ dependencies = [
 
 [[package]]
 name = "js-sys"
-version = "0.3.100"
+version = "0.3.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2025f20d7a4fa7785846e7b63d10a76d3f1cee98ee5cb79ea59703f95e42162"
+checksum = "53b44bfcdb3f8d5837a46dae1ca9660a837176eee74a28b229bc626816589102"
 dependencies = [
  "cfg-if",
  "futures-util",
@@ -2035,7 +1995,7 @@ dependencies = [
 
 [[package]]
 name = "latency-probe"
-version = "0.0.1"
+version = "0.3.0"
 
 [[package]]
 name = "lazy_static"
@@ -2046,12 +2006,6 @@ dependencies = [
  "spin",
 ]
 
-[[package]]
-name = "leb128fmt"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
-
 [[package]]
 name = "libadwaita"
 version = "0.9.1"
@@ -2167,13 +2121,13 @@ dependencies = [
 
 [[package]]
 name = "log"
-version = "0.4.32"
+version = "0.4.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "953f07c43838f8e6f9758cab68bf5bed85465e7587ebe0b823f1bcd81978ad3a"
+checksum = "0ceec5bc11778974d1bcb055b18002eba7f4b3518b6a0081b3af5f21666da9ad"
 
 [[package]]
 name = "loss-harness"
-version = "0.0.1"
+version = "0.3.0"
 dependencies = [
  "punktfunk-core",
 ]
@@ -2201,9 +2155,9 @@ checksum = "47e1ffaa40ddd1f3ed91f717a33c8c0ee23fff369e3aa8772b9605cc1d22f4c3"
 
 [[package]]
 name = "mdns-sd"
-version = "0.20.0"
+version = "0.20.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "892f96f6d2ebe1ea641279f986ac52a2a6bac71e8f743bb258315cfe2bd7e88e"
+checksum = "fb75febbe5fa1837a52fdbd1c735e168286c5c645fc2ddd31526f65c49941c2e"
 dependencies = [
  "fastrand",
  "flume",
@@ -2216,15 +2170,15 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.8.1"
+version = "2.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6b947ae49db0d222b1dbc6b113ce7248a3fc3a6ca21b696717bfc000ba4484d8"
+checksum = "88904434abc2901f197fe8cc55f0445e7ded921dba5911dad2e2b39b48e663c4"
 
 [[package]]
 name = "memmap2"
-version = "0.9.10"
+version = "0.9.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "714098028fe011992e1c3962653c96b2d578c4b4bce9036e15ff220319b1e0e3"
+checksum = "d1219ed1b7f229ee7104d281dd01d6802fe28bb6e95d292942c4daacdeb798c0"
 dependencies = [
  "libc",
 ]
@@ -2716,16 +2670,6 @@ dependencies = [
  "zerocopy",
 ]
 
-[[package]]
-name = "prettyplease"
-version = "0.2.37"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "479ca8adacdd7ce8f1fb39ce9ecccbfe93a3f1344b3d0d97f20bc0196208f62b"
-dependencies = [
- "proc-macro2",
- "syn",
-]
-
 [[package]]
 name = "proc-macro-crate"
 version = "3.5.0"
@@ -2765,7 +2709,7 @@ dependencies = [
 
 [[package]]
 name = "punktfunk-client-android"
-version = "0.0.1"
+version = "0.3.0"
 dependencies = [
  "android_logger",
  "jni",
@@ -2779,7 +2723,7 @@ dependencies = [
 
 [[package]]
 name = "punktfunk-client-linux"
-version = "0.0.1"
+version = "0.3.0"
 dependencies = [
  "anyhow",
  "async-channel",
@@ -2799,7 +2743,7 @@ dependencies = [
 
 [[package]]
 name = "punktfunk-client-windows"
-version = "0.0.1"
+version = "0.3.0"
 dependencies = [
  "anyhow",
  "async-channel",
@@ -2819,7 +2763,7 @@ dependencies = [
 
 [[package]]
 name = "punktfunk-core"
-version = "0.0.1"
+version = "0.3.0"
 dependencies = [
  "aes-gcm",
  "bytes",
@@ -2828,6 +2772,7 @@ dependencies = [
  "fec-rs",
  "hmac",
  "libc",
+ "opus",
  "proptest",
  "quinn",
  "rand 0.9.4",
@@ -2848,14 +2793,13 @@ dependencies = [
 
 [[package]]
 name = "punktfunk-host"
-version = "0.0.1"
+version = "0.3.0"
 dependencies = [
  "aes",
  "aes-gcm",
  "anyhow",
  "ash",
  "ashpd",
- "audiopus_sys",
  "axum",
  "axum-server",
  "base64",
@@ -2885,7 +2829,6 @@ dependencies = [
  "rsa",
  "rusqlite",
  "rustls",
- "rustls-pemfile",
  "rusty_enet",
  "serde",
  "serde_json",
@@ -2914,7 +2857,7 @@ dependencies = [
 
 [[package]]
 name = "punktfunk-probe"
-version = "0.0.1"
+version = "0.3.0"
 dependencies = [
  "anyhow",
  "mdns-sd",
@@ -2943,9 +2886,9 @@ dependencies = [
 
 [[package]]
 name = "quinn"
-version = "0.11.9"
+version = "0.11.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b9e20a958963c291dc322d98411f541009df2ced7b5a4f2bd52337638cfccf20"
+checksum = "0c1a41e437b6bbd489372cd4971de128e85c855f56c57f283d20ff016cf7c0a8"
 dependencies = [
  "bytes",
  "cfg_aliases",
@@ -2963,9 +2906,9 @@ dependencies = [
 
 [[package]]
 name = "quinn-proto"
-version = "0.11.14"
+version = "0.11.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "434b42fec591c96ef50e21e886936e66d3cc3f737104fdb9b737c40ffb94c098"
+checksum = "4fcb935c5bec503c2f0e306bdd3e58bb9029dcb14fa8d9ac76e3a5256ac0763e"
 dependencies = [
  "bytes",
  "fastbloom",
@@ -3000,9 +2943,9 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.45"
+version = "1.0.46"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "41f2619966050689382d2b44f664f4bc593e129785a36d6ee376ddf37259b924"
+checksum = "dfbc457d0c7a0759a614551b11a6409e5951f6c7537be1f1b7682b9ae9230368"
 dependencies = [
  "proc-macro2",
 ]
@@ -3156,9 +3099,9 @@ dependencies = [
 
 [[package]]
 name = "regex"
-version = "1.12.3"
+version = "1.12.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e10754a14b9137dd7b1e3e5b0493cc9171fdd105e0ab477f51b72e7f3ac0e276"
+checksum = "f1292b7759ae1cb9ec195452d1390a074f0cd8541ab7a5a8c31cd6db45d4a6ba"
 dependencies = [
  "aho-corasick",
  "memchr",
@@ -3179,9 +3122,9 @@ dependencies = [
 
 [[package]]
 name = "regex-syntax"
-version = "0.8.10"
+version = "0.8.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc897dd8d9e8bd1ed8cdad82b5966c3e0ecae09fb1907d58efaa013543185d0a"
+checksum = "d6f6ff9a378485b298a5286656da665ba74413d36db0979633275d2e708145d4"
 
 [[package]]
 name = "reis"
@@ -3309,9 +3252,9 @@ dependencies = [
 
 [[package]]
 name = "rustls"
-version = "0.23.40"
+version = "0.23.41"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef86cd5876211988985292b91c96a8f2d298df24e75989a43a3c73f2d4d8168b"
+checksum = "6b92b125634d9b795e7beca796cc790df15a7fb38323bf3196fda83292d06b1f"
 dependencies = [
  "aws-lc-rs",
  "log",
@@ -3335,15 +3278,6 @@ dependencies = [
  "security-framework",
 ]
 
-[[package]]
-name = "rustls-pemfile"
-version = "2.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dce314e5fee3f39953d46bb63bb8a46d40c2f8fb7cc5a3b6cab2bde9721d6e50"
-dependencies = [
- "rustls-pki-types",
-]
-
 [[package]]
 name = "rustls-pki-types"
 version = "1.14.1"
@@ -3740,19 +3674,19 @@ checksum = "0c790de23124f9ab44544d7ac05d60440adc586479ce501c1d6d7da3cd8c9cf5"
 
 [[package]]
 name = "smallvec"
-version = "1.15.1"
+version = "1.15.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "67b1b7a3b5fe4f1376887184045fcf45c69e92af734b7aaddc05fb777b6fbd03"
+checksum = "8ed6a63f02c8539c91a8685a86f4099661ba3da017932f6ebbea6de3f0fa7c90"
 
 [[package]]
 name = "socket-pktinfo"
-version = "0.3.2"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "927136cc2ae6a1b0e66ac6b1210902b75c3f726db004a73bc18686dcd0dcd22f"
+checksum = "3e8e43b4bdce7cff8a4d3f8025ee38fce5ca138fab868ebbf9529c81328fbf9d"
 dependencies = [
  "libc",
  "socket2",
- "windows-sys 0.60.2",
+ "windows-sys 0.61.2",
 ]
 
 [[package]]
@@ -3828,9 +3762,9 @@ checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
 
 [[package]]
 name = "syn"
-version = "2.0.117"
+version = "2.0.118"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e665b8803e7b1d2a727f4023456bbbbe74da67099c585258af0ad9c5013b9b99"
+checksum = "1b9ae57f904213ebb649ce6895b8a66c66f0203b9319718f69a5612a065b1422"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3880,7 +3814,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
 dependencies = [
  "fastrand",
- "getrandom 0.4.2",
+ "getrandom 0.4.3",
  "once_cell",
  "rustix",
  "windows-sys 0.61.2",
@@ -3937,12 +3871,11 @@ dependencies = [
 
 [[package]]
 name = "time"
-version = "0.3.47"
+version = "0.3.51"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "743bd48c283afc0388f9b8827b976905fb217ad9e647fae3a379a9283c4def2c"
+checksum = "85c17d80feb7334b40c484e45ed1a5273dfd8bfda537c3be2e74a06a6686f327"
 dependencies = [
  "deranged",
- "itoa",
  "num-conv",
  "powerfmt",
  "serde_core",
@@ -3952,15 +3885,15 @@ dependencies = [
 
 [[package]]
 name = "time-core"
-version = "0.1.8"
+version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7694e1cfe791f8d31026952abf09c69ca6f6fa4e1a1229e18988f06a04a12dca"
+checksum = "9e1c906769ad99c88eaa54e728060edef082f8e358ff32030cb7c7d315e81109"
 
 [[package]]
 name = "time-macros"
-version = "0.2.27"
+version = "0.2.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e70e4c5a0e0a8a4823ad65dfe1a6930e4f4d756dcd9dd7939022b5e8c501215"
+checksum = "dcef1a61bdb119096e153208ec5cbec23944ce8bca13be5c7f60c634f7403935"
 dependencies = [
  "num-conv",
  "time-core",
@@ -4259,12 +4192,6 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4ac048d71ede7ee76d585517add45da530660ef4390e49b098733c6e897f254"
 
-[[package]]
-name = "unicode-xid"
-version = "0.2.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ebc1c04c71510c7f702b52b7c350734c9ff1295c464a03335b00bb84fc54f853"
-
 [[package]]
 name = "universal-hash"
 version = "0.5.1"
@@ -4372,9 +4299,9 @@ dependencies = [
 
 [[package]]
 name = "uuid"
-version = "1.23.2"
+version = "1.23.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d258b83ceec21034727ecee8c382cfa6c3e133699b0742c64571814fb420c9f7"
+checksum = "bf80a72845275afea99e7f2b434723d3bc7e38470fcd1c7ed39a599c73319a53"
 dependencies = [
  "js-sys",
  "serde_core",
@@ -4445,27 +4372,18 @@ checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
 
 [[package]]
 name = "wasip2"
-version = "1.0.3+wasi-0.2.9"
+version = "1.0.4+wasi-0.2.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "20064672db26d7cdc89c7798c48a0fdfac8213434a1186e5ef29fd560ae223d6"
+checksum = "b67efb37e106e55ce722a510d6b5f9c17f083e5fc79afc2badeb12cc313d9487"
 dependencies = [
- "wit-bindgen 0.57.1",
+ "wit-bindgen",
-]
-
-[[package]]
-name = "wasip3"
-version = "0.4.0+wasi-0.3.0-rc-2026-01-06"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5428f8bf88ea5ddc08faddef2ac4a67e390b88186c703ce6dbd955e1c145aca5"
-dependencies = [
- "wit-bindgen 0.51.0",
 ]
 
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.123"
+version = "0.2.126"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a254a4b10c19a76f09a27640e7ffbf9bc30bf67e16a3bf28aaefa4920fe81563"
+checksum = "4b067c0c11094aef6b7a801c1e34a26affafdf3d051dba08456b868789aaf9a4"
 dependencies = [
  "cfg-if",
  "once_cell",
@@ -4476,9 +4394,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.123"
+version = "0.2.126"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "24a40fc75b0ec6f3746ceb10d36f53a93dcd68a93b11b6445983945d79eba0dc"
+checksum = "167ce5e579f6bcf889c4f7175a8a5a585de84e8ff93976ce393efa5f2837aab1"
 dependencies = [
  "quote",
  "wasm-bindgen-macro-support",
@@ -4486,9 +4404,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.123"
+version = "0.2.126"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "908f34bd9b9ce3d4caf07b72dfab63d61504d156856c6bd3cd87fa350cf3985b"
+checksum = "f3997c7839262f4ef12cf90b818d6340c18e80f263f1a94bf157d0ec4420380e"
 dependencies = [
  "bumpalo",
  "proc-macro2",
@@ -4499,47 +4417,13 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.123"
+version = "0.2.126"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7acbf7616c27b194bbb550bf77ed0c2c3e5b7fd1260a93082b95fb7f47959b92"
+checksum = "dc1b4cb0cc549fcf58d7dfc081778139b3d283a081644e833e84682ad71cea24"
 dependencies = [
  "unicode-ident",
 ]
 
-[[package]]
-name = "wasm-encoder"
-version = "0.244.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "990065f2fe63003fe337b932cfb5e3b80e0b4d0f5ff650e6985b1048f62c8319"
-dependencies = [
- "leb128fmt",
- "wasmparser",
-]
-
-[[package]]
-name = "wasm-metadata"
-version = "0.244.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bb0e353e6a2fbdc176932bbaab493762eb1255a7900fe0fea1a2f96c296cc909"
-dependencies = [
- "anyhow",
- "indexmap",
- "wasm-encoder",
- "wasmparser",
-]
-
-[[package]]
-name = "wasmparser"
-version = "0.244.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "47b807c72e1bac69382b3a6fb3dbe8ea4c0ed87ff5629b8685ae6b9a611028fe"
-dependencies = [
- "bitflags",
- "hashbrown 0.15.5",
- "indexmap",
- "semver",
-]
-
 [[package]]
 name = "wayland-backend"
 version = "0.3.15"
@@ -4567,9 +4451,9 @@ dependencies = [
 
 [[package]]
 name = "wayland-protocols"
-version = "0.32.12"
+version = "0.32.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "563a85523cade2429938e790815fd7319062103b9f4a2dc806e9b53b95982d8f"
+checksum = "23d0c813de3daa2ed6520af85a3bd49b0e722a3078506899aa9686fea58dc4b6"
 dependencies = [
  "bitflags",
  "wayland-backend",
@@ -4635,9 +4519,9 @@ dependencies = [
 
 [[package]]
 name = "webpki-root-certs"
-version = "1.0.7"
+version = "1.0.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f31141ce3fc3e300ae89b78c0dd67f9708061d1d2eda54b8209346fd6be9a92c"
+checksum = "0d46a5a140e6f7afeccd8eae97eff335163939eac8b929834875168b29b3d267"
 dependencies = [
  "rustls-pki-types",
 ]
@@ -5195,100 +5079,12 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
-[[package]]
-name = "wit-bindgen"
-version = "0.51.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d7249219f66ced02969388cf2bb044a09756a083d0fab1e566056b04d9fbcaa5"
-dependencies = [
- "wit-bindgen-rust-macro",
-]
-
 [[package]]
 name = "wit-bindgen"
 version = "0.57.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1ebf944e87a7c253233ad6766e082e3cd714b5d03812acc24c318f549614536e"
 
-[[package]]
-name = "wit-bindgen-core"
-version = "0.51.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ea61de684c3ea68cb082b7a88508a8b27fcc8b797d738bfc99a82facf1d752dc"
-dependencies = [
- "anyhow",
- "heck",
- "wit-parser",
-]
-
-[[package]]
-name = "wit-bindgen-rust"
-version = "0.51.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b7c566e0f4b284dd6561c786d9cb0142da491f46a9fbed79ea69cdad5db17f21"
-dependencies = [
- "anyhow",
- "heck",
- "indexmap",
- "prettyplease",
- "syn",
- "wasm-metadata",
- "wit-bindgen-core",
- "wit-component",
-]
-
-[[package]]
-name = "wit-bindgen-rust-macro"
-version = "0.51.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0c0f9bfd77e6a48eccf51359e3ae77140a7f50b1e2ebfe62422d8afdaffab17a"
-dependencies = [
- "anyhow",
- "prettyplease",
- "proc-macro2",
- "quote",
- "syn",
- "wit-bindgen-core",
- "wit-bindgen-rust",
-]
-
-[[package]]
-name = "wit-component"
-version = "0.244.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9d66ea20e9553b30172b5e831994e35fbde2d165325bec84fc43dbf6f4eb9cb2"
-dependencies = [
- "anyhow",
- "bitflags",
- "indexmap",
- "log",
- "serde",
- "serde_derive",
- "serde_json",
- "wasm-encoder",
- "wasm-metadata",
- "wasmparser",
- "wit-parser",
-]
-
-[[package]]
-name = "wit-parser"
-version = "0.244.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ecc8ac4bc1dc3381b7f59c34f00b67e18f910c2c0f50015669dde7def656a736"
-dependencies = [
- "anyhow",
- "id-arena",
- "indexmap",
- "log",
- "semver",
- "serde",
- "serde_derive",
- "serde_json",
- "unicode-xid",
- "wasmparser",
-]
-
 [[package]]
 name = "writeable"
 version = "0.6.3"
@@ -5419,18 +5215,18 @@ dependencies = [
 
 [[package]]
 name = "zerocopy"
-version = "0.8.50"
+version = "0.8.52"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3b065d4f0e55f82fae73202e189638116a87c55ab6b8e6c2721e13dd9d854ad1"
+checksum = "ce1022995ff5ff5d841ad7d994facc23098cd40152f2c1d11cd607c6f530653f"
 dependencies = [
  "zerocopy-derive",
 ]
 
 [[package]]
 name = "zerocopy-derive"
-version = "0.8.50"
+version = "0.8.52"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b631b19d36a892ab55420c92dbc83ccd79274f25be714855d3074aa71cab639"
+checksum = "1ae7f38b72ec2a254e2b87ef277cf2cd4fb97cbebf944faa6f33354da0867930"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -5460,9 +5256,9 @@ dependencies = [
 
 [[package]]
 name = "zeroize"
-version = "1.8.2"
+version = "1.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b97154e67e32c85465826e8bcc1c59429aaaf107c1e4a9e53c8d8ccd5eff88d0"
+checksum = "e13c156562582aa81c60cb29407084cdb54c4164760106ab78e6c5b0858cf64e"
 
 [[package]]
 name = "zerotrie"

Cargo.toml

@@ -13,7 +13,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.0.1"
+version = "0.3.0"
 edition = "2021"
 rust-version = "1.82"
 license = "MIT OR Apache-2.0"

README.md

@@ -155,4 +155,31 @@ tools/                       latency-probe · loss-harness (measurement)
 
 ## License
 
-MIT OR Apache-2.0.
+Licensed under either of
+
+- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
+  <https://www.apache.org/licenses/LICENSE-2.0>)
+- MIT license ([LICENSE-MIT](LICENSE-MIT) or <https://opensource.org/licenses/MIT>)
+
+at your option — `SPDX-License-Identifier: MIT OR Apache-2.0`.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in
+the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any
+additional terms or conditions. See [CONTRIBUTING.md](CONTRIBUTING.md).
+
+### Third-party components
+
+punktfunk's own source is MIT/Apache-2.0. Shipped binaries additionally link third-party components
+under their own (permissive) licenses — see [`THIRD-PARTY-NOTICES.txt`](THIRD-PARTY-NOTICES.txt)
+(regenerate with `scripts/gen-third-party-notices.sh`). The Windows host and client builds also
+bundle FFmpeg under the **LGPL v2.1+** (dynamically linked, replaceable DLLs; the license text and
+notice ship in the installed `licenses/` folder).
+
+### Trademarks
+
+punktfunk is an independent project and is **not affiliated with, endorsed by, or sponsored by**
+NVIDIA, Microsoft, Sony, Valve, or the Moonlight project. "GameStream", "Moonlight", "Xbox",
+"DualSense", "DualShock", and "PlayStation" are trademarks of their respective owners and are used
+here only to describe interoperability.

about.hbs

@@ -0,0 +1,23 @@
+THIRD-PARTY SOFTWARE NOTICES
+============================================================================
+
+punktfunk (https://git.unom.io/unom/punktfunk) is licensed under MIT OR Apache-2.0.
+The binaries it ships statically/dynamically link the third-party Rust crates below.
+Each is distributed under its own permissive license; full texts follow.
+Generated by `cargo about generate about.hbs` (see about.toml) — do not edit by hand.
+
+Overview:
+{{#each overview}}
+  {{name}} ({{id}}): {{count}} crate(s)
+{{/each}}
+
+{{#each licenses}}
+----------------------------------------------------------------------------
+{{name}} ({{id}})
+Used by:
+{{#each used_by}}  - {{crate.name}} {{crate.version}}{{#if crate.repository}}  ({{crate.repository}}){{/if}}
+{{/each}}
+----------------------------------------------------------------------------
+{{text}}
+
+{{/each}}

about.toml

@@ -0,0 +1,49 @@
+# cargo-about config — full-fidelity third-party license harvest for CI.
+#
+#   cargo install cargo-about
+#   cargo about generate about.hbs > THIRD-PARTY-NOTICES.txt   # (or use scripts/gen-third-party-notices.sh)
+#
+# `accepted` is the allow-list of SPDX licenses permitted in the dependency tree. CI fails if a crate
+# carries anything not listed here — which is exactly the regression guard we want against a copyleft
+# dependency silently entering the linked set. All entries
+# below are permissive / attribution-only; deliberately NO GPL/LGPL/AGPL/MPL-link/SSPL/EPL.
+#
+# The dependency-free fallback is scripts/gen-third-party-notices.py (reads the cargo registry cache),
+# which is what produced the committed baseline when cargo-about is unavailable offline.
+
+accepted = [
+    "MIT",
+    "MIT-0",
+    "Apache-2.0",
+    "Apache-2.0 WITH LLVM-exception",
+    "BSD-2-Clause",
+    "BSD-3-Clause",
+    "ISC",
+    "Zlib",
+    "0BSD",
+    "BSL-1.0",
+    "Unicode-3.0",
+    "Unicode-DFS-2016",
+    "CDLA-Permissive-2.0",
+    "CC0-1.0",
+    "Unlicense",
+    "WTFPL",
+    "OpenSSL",
+]
+
+# cbindgen is MPL-2.0 but it is a BUILD-ONLY codegen tool that never links into a shipped artifact
+# (its generated header is not a derivative work), so it is excluded from the notices rather than
+# accepted as a linked license.
+ignore-build-dependencies = true
+ignore-dev-dependencies = true
+
+# r-efi offers an LGPL-2.1-or-later arm but is tri-licensed; take a permissive arm. (It is also
+# UEFI-target-gated out of every shipped build.)
+[r-efi.clarify]
+license = "MIT OR Apache-2.0"
+
+[ring.clarify]
+license = "MIT AND ISC AND OpenSSL"
+
+[aws-lc-sys.clarify]
+license = "ISC AND Apache-2.0 AND MIT AND BSD-3-Clause AND OpenSSL"

clients/android/app/build.gradle.kts

@@ -62,6 +62,10 @@ android {
 
     buildFeatures { compose = true }
 
+    // Roborazzi/Robolectric render Compose on the host JVM (the CI screenshot harness) and need the
+    // merged Android resources + the app's manifest/theme available to the unit tests.
+    testOptions { unitTests { isIncludeAndroidResources = true } }
+
     compileOptions {
         sourceCompatibility = JavaVersion.VERSION_21
         targetCompatibility = JavaVersion.VERSION_21
@@ -99,4 +103,21 @@ dependencies {
     // Android TV components (we target phone + TV) land in the TV-UI milestone:
     //   implementation("androidx.tv:tv-material:1.1.0")
     // The manifest already declares leanback so the scaffold installs on TV.
+
+    // --- CI screenshot harness (Roborazzi on the JVM via Robolectric — no emulator/GPU). The
+    // screenshot tests render the real Compose UI with mock state; never load the JNI core, so the
+    // job runs `:app:testDebugUnitTest -PskipRustBuild` (see kit/build.gradle.kts). ---
+    testImplementation(composeBom)
+    testImplementation("androidx.compose.ui:ui-test-junit4")
+    debugImplementation("androidx.compose.ui:ui-test-manifest") // the ComponentActivity test host
+    testImplementation("junit:junit:4.13.2")
+    testImplementation("org.robolectric:robolectric:4.16.1")
+    testImplementation("io.github.takahirom.roborazzi:roborazzi:1.64.0")
+    testImplementation("io.github.takahirom.roborazzi:roborazzi-compose:1.64.0")
+}
+
+// Record (write) the screenshots when the unit tests run. These tests exist to GENERATE marketing
+// images, not to diff goldens, so always capture rather than verify.
+tasks.withType<Test>().configureEach {
+    systemProperty("roborazzi.test.record", "true")
 }

clients/android/app/src/main/kotlin/io/unom/punktfunk/ConnectScreen.kt

@@ -74,10 +74,31 @@ import io.unom.punktfunk.kit.security.KnownHostStore
 import io.unom.punktfunk.kit.security.obtainIdentity
 import io.unom.punktfunk.models.HostStatus
 import io.unom.punktfunk.models.PendingTrust
+import java.util.concurrent.atomic.AtomicBoolean
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 
+/** Handshake budget for a normal connect (the prior hardcoded value, now passed explicitly). */
+private const val CONNECT_TIMEOUT_MS = 10_000
+
+/**
+ * Handshake budget for the no-PIN "request access" connect. Must exceed the host's approval-park
+ * window (~180 s) so a slow operator approval still lands on this same parked connection rather than
+ * timing the client out first. Mirrors the Linux client's 185 s.
+ */
+private const val REQUEST_ACCESS_TIMEOUT_MS = 185_000
+
+/**
+ * A no-PIN "request access" connect in flight — the host being requested (drives the cancelable
+ * "Waiting for approval…" dialog) and a per-attempt flag the Cancel button trips. The connect is a
+ * blocking call with no abort, so Cancel returns the UI immediately and a late result checks
+ * [cancelled] and tears the (possibly just-approved) session down silently rather than navigating.
+ */
+private class RequestAccessState(val target: PendingTrust) {
+    val cancelled = AtomicBoolean(false)
+}
+
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
@@ -128,8 +149,11 @@ fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
             .onSuccess { identity = it }
             .onFailure { status = "Identity unavailable: ${it.message} — re-pair may be required" }
     }
-    // A trust decision awaiting the user (first-connect TOFU / fp changed / PIN pairing).
+    // A trust decision awaiting the user (first-connect TOFU / fp changed / PIN pairing / the
+    // request-access-or-PIN choice).
     var pendingTrust by remember { mutableStateOf<PendingTrust?>(null) }
+    // A no-PIN "request access" connect in flight (the cancelable "Waiting for approval…" dialog).
+    var awaiting by remember { mutableStateOf<RequestAccessState?>(null) }
     // A saved host whose label is being edited (the Rename dialog).
     var renameTarget by remember { mutableStateOf<KnownHost?>(null) }
 
@@ -163,7 +187,7 @@ fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
                     targetHost, targetPort, w, h, hz,
                     id.certPem, id.privateKeyPem, pinHex ?: "",
                     settings.bitrateKbps, settings.compositor, gamepadPref,
-                    hdrEnabled,
+                    hdrEnabled, settings.audioChannels, CONNECT_TIMEOUT_MS,
                 )
             }
             connecting = false
@@ -182,10 +206,66 @@ fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
         }
     }
 
-    // Decide pinned-reconnect vs fp-changed vs TOFU vs PIN pairing before connecting. Trust state is
+    // The no-PIN "request access" path (delegated approval): open a normal identified connect that
+    // the host PARKS until the operator clicks Approve in its console/web UI, showing a cancelable
+    // "Waiting for approval…" dialog meanwhile. The SAME connection is admitted on approval (no
+    // reconnect), so on success we record the host as PAIRED — the operator's approval IS the pairing.
+    // The connect can't be aborted, so Cancel returns the UI immediately and a late result is torn
+    // down silently via the per-attempt flag (mirrors the Linux client's request-access flow).
+    fun requestAccess(target: PendingTrust) {
+        val id = identity
+        if (id == null) {
+            status = "Identity not ready yet — try again in a moment"
+            return
+        }
+        val req = RequestAccessState(target)
+        awaiting = req
+        connecting = true
+        status = null
+        discovery.stop() // free the Wi-Fi radio before the (parked) stream session
+        scope.launch {
+            val hdrEnabled = displaySupportsHdr(context)
+            val gamepadPref = Gamepad.resolvePref(settings.gamepad)
+            // Pin the advertised fingerprint for a discovered host (defence against an impostor while
+            // we wait); a manually-typed host has none, so trust-on-first-use.
+            val pinHex = target.advertisedFp ?: ""
+            val handle = withContext(Dispatchers.IO) {
+                NativeBridge.nativeConnect(
+                    target.host, target.port, w, h, hz,
+                    id.certPem, id.privateKeyPem, pinHex,
+                    settings.bitrateKbps, settings.compositor, gamepadPref,
+                    hdrEnabled, settings.audioChannels, REQUEST_ACCESS_TIMEOUT_MS,
+                )
+            }
+            // Cancelled while we were parked: tear the (possibly just-approved) session down and
+            // don't touch UI a fresh action may now own.
+            if (req.cancelled.get()) {
+                if (handle != 0L) withContext(Dispatchers.IO) { NativeBridge.nativeClose(handle) }
+                return@launch
+            }
+            awaiting = null
+            connecting = false
+            if (handle != 0L) {
+                // Approved — save the host as PAIRED, pinning the fingerprint it presented, so
+                // future connects are silent (exactly like after a PIN ceremony).
+                val fp = NativeBridge.nativeHostFingerprint(handle)
+                if (fp.isNotEmpty()) {
+                    knownHostStore.save(KnownHost(target.host, target.port, target.name, fp, paired = true))
+                    savedHosts = knownHostStore.all()
+                }
+                onConnected(handle)
+            } else {
+                status = "Request timed out — approve this device in the host's console, then retry."
+                discovery.start()
+            }
+        }
+    }
+
+    // Decide pinned-reconnect vs fp-changed vs TOFU vs pairing before connecting. Trust state is
     // keyed by address:port, so a discovered and a manually-typed connection to the same host share
     // one record. Trust-on-first-use is permitted ONLY when the host advertised pair=optional; a
-    // pair=required host, or a manual/unknown-policy host, must pair by PIN.
+    // pair=required host, or a manual/unknown-policy host, must pair — either by no-PIN request
+    // access (approve in the console) or by the SPAKE2 PIN ceremony.
     fun connect(
         targetHost: String,
         targetPort: Int,
@@ -208,9 +288,10 @@ fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
             // clearly labeled, alongside PIN pairing). Smart-cast: this branch ⇒ dh != null.
             dh?.pairingRequired == false -> pendingTrust =
                 PendingTrust(targetHost, targetPort, name, dh.fingerprint, PendingTrust.Kind.TRUST_NEW)
-            // pair=required, or a manual/unknown-policy host → PIN pairing is mandatory.
+            // pair=required, or a manual/unknown-policy host → offer the two ways in: a no-PIN
+            // "request access" (approve in the console) or the SPAKE2 PIN ceremony.
             else -> pendingTrust =
-                PendingTrust(targetHost, targetPort, name, adv, PendingTrust.Kind.PAIR)
+                PendingTrust(targetHost, targetPort, name, adv, PendingTrust.Kind.REQUEST_ACCESS)
         }
     }
 
@@ -471,6 +552,33 @@ fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
                     TextButton({ pendingTrust = null }) { Text("Cancel") }
                 },
             )
+            // A fresh pair=required (or manual/unknown-policy) host: offer the two ways in. "Request
+            // access" is the no-PIN path — connect and wait for the operator to click Approve in the
+            // host's console; "Use a PIN…" switches to the SPAKE2 ceremony.
+            PendingTrust.Kind.REQUEST_ACCESS -> AlertDialog(
+                onDismissRequest = { pendingTrust = null },
+                title = { Text("Pairing required") },
+                text = {
+                    Column {
+                        Text("${pt.host}:${pt.port} requires pairing before it will stream.")
+                        Text(
+                            "Request access and approve this device in the host's console (or web " +
+                                "UI) — no PIN needed. Or pair with the 4-digit PIN the host displays.",
+                        )
+                    }
+                },
+                confirmButton = {
+                    TextButton({ pendingTrust = null; requestAccess(pt) }) { Text("Request access") }
+                },
+                dismissButton = {
+                    Row {
+                        TextButton({ pendingTrust = pt.copy(kind = PendingTrust.Kind.PAIR) }) {
+                            Text("Use a PIN…")
+                        }
+                        TextButton({ pendingTrust = null }) { Text("Cancel") }
+                    }
+                },
+            )
             PendingTrust.Kind.PAIR -> {
                 var pin by remember(pt) { mutableStateOf("") }
                 var name by remember(pt) { mutableStateOf(Build.MODEL ?: "Android") }
@@ -537,6 +645,44 @@ fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
         }
     }
 
+    // The no-PIN "request access" wait: the connect is parked on the host until the operator
+    // approves this device. Cancel returns the UI immediately — it trips the per-attempt flag so a
+    // late approval is torn down silently (see requestAccess) and resumes discovery.
+    awaiting?.let { req ->
+        fun cancel() {
+            req.cancelled.set(true)
+            awaiting = null
+            connecting = false
+            discovery.start() // the request may still be pending on the host; keep scanning
+        }
+        AlertDialog(
+            onDismissRequest = { cancel() },
+            title = { Text("Waiting for approval") },
+            text = {
+                val deviceName = Build.MODEL ?: "this device"
+                Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                    Row(
+                        verticalAlignment = Alignment.CenterVertically,
+                        horizontalArrangement = Arrangement.spacedBy(12.dp),
+                    ) {
+                        CircularProgressIndicator(modifier = Modifier.size(20.dp), strokeWidth = 2.dp)
+                        Text("Approve this device on ${req.target.name}.")
+                    }
+                    Text(
+                        "Open the host's console (or web UI) and approve “$deviceName”. It connects " +
+                            "automatically once you approve — no PIN needed.",
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+            },
+            confirmButton = {},
+            dismissButton = {
+                TextButton(onClick = { cancel() }) { Text("Cancel") }
+            },
+        )
+    }
+
     // Rename a saved host's label (discovered hosts are named by mDNS; this is how you give one a
     // friendly name like "Living Room" after pairing). Keyed by the host so reopening resets the field.
     renameTarget?.let { kh ->

clients/android/app/src/main/kotlin/io/unom/punktfunk/LicensesScreen.kt

@@ -0,0 +1,66 @@
+package io.unom.punktfunk
+
+import androidx.activity.compose.BackHandler
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.unit.dp
+
+/**
+ * Open-source licenses: punktfunk's own license (MIT OR Apache-2.0) plus the third-party software
+ * notices, read from the bundled `THIRD-PARTY-NOTICES.txt` asset (generated by
+ * scripts/gen-third-party-notices.sh). Reached from [SettingsScreen]; Back returns there.
+ */
+@Composable
+fun LicensesScreen(onBack: () -> Unit) {
+    val context = LocalContext.current
+    BackHandler(onBack = onBack)
+
+    val notices = remember {
+        runCatching {
+            context.assets.open("THIRD-PARTY-NOTICES.txt").bufferedReader().use { it.readText() }
+        }.getOrDefault("Third-party notices unavailable.")
+    }
+    val version = remember {
+        runCatching {
+            @Suppress("DEPRECATION")
+            context.packageManager.getPackageInfo(context.packageName, 0).versionName
+        }.getOrNull()
+    }
+
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .verticalScroll(rememberScrollState())
+            .padding(horizontal = 20.dp, vertical = 24.dp),
+        verticalArrangement = Arrangement.spacedBy(16.dp),
+    ) {
+        Text("Open-source licenses", style = MaterialTheme.typography.headlineMedium)
+        if (version != null) {
+            Text(
+                "punktfunk $version",
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+        Text(
+            "punktfunk is licensed under MIT OR Apache-2.0, at your option. It uses the open-source " +
+                "components below, each under its own license.",
+            style = MaterialTheme.typography.bodyMedium,
+        )
+        Text(
+            notices,
+            style = MaterialTheme.typography.bodySmall.copy(fontFamily = FontFamily.Monospace),
+        )
+    }
+}

clients/android/app/src/main/kotlin/io/unom/punktfunk/Settings.kt

@@ -16,6 +16,9 @@ data class Settings(
     val bitrateKbps: Int = 0,
     val compositor: Int = 0,
     val gamepad: Int = 0,
+    /** Requested audio channel count: 2 (stereo), 6 (5.1) or 8 (7.1). The host clamps to what it
+     * can capture; the resolved count drives the decoder + AAudio layout. */
+    val audioChannels: Int = 2,
     val micEnabled: Boolean = false,
     /** Show the live stats overlay (FPS / throughput / latency) during a stream. */
     val statsHudEnabled: Boolean = true,
@@ -39,6 +42,7 @@ class SettingsStore(context: Context) {
         bitrateKbps = prefs.getInt(K_BITRATE, 0),
         compositor = prefs.getInt(K_COMPOSITOR, 0),
         gamepad = prefs.getInt(K_GAMEPAD, 0),
+        audioChannels = prefs.getInt(K_AUDIO_CH, 2),
         micEnabled = prefs.getBoolean(K_MIC, false),
         statsHudEnabled = prefs.getBoolean(K_HUD, true),
         trackpadMode = prefs.getBoolean(K_TRACKPAD, true),
@@ -52,6 +56,7 @@ class SettingsStore(context: Context) {
             .putInt(K_BITRATE, s.bitrateKbps)
             .putInt(K_COMPOSITOR, s.compositor)
             .putInt(K_GAMEPAD, s.gamepad)
+            .putInt(K_AUDIO_CH, s.audioChannels)
             .putBoolean(K_MIC, s.micEnabled)
             .putBoolean(K_HUD, s.statsHudEnabled)
             .putBoolean(K_TRACKPAD, s.trackpadMode)
@@ -65,6 +70,7 @@ class SettingsStore(context: Context) {
         const val K_BITRATE = "bitrate_kbps"
         const val K_COMPOSITOR = "compositor"
         const val K_GAMEPAD = "gamepad"
+        const val K_AUDIO_CH = "audio_channels"
         const val K_MIC = "mic_enabled"
         const val K_HUD = "stats_hud_enabled"
         const val K_TRACKPAD = "trackpad_mode"
@@ -133,6 +139,13 @@ val REFRESH_OPTIONS = listOf(
     240 to "240 Hz",
 )
 
+/** (channel count, label). 2 = stereo (default), 6 = 5.1, 8 = 7.1. */
+val AUDIO_CHANNEL_OPTIONS = listOf(
+    2 to "Stereo",
+    6 to "5.1 Surround",
+    8 to "7.1 Surround",
+)
+
 /** (kbps, label). `0` = host default. */
 val BITRATE_OPTIONS = listOf(
     0 to "Automatic",

clients/android/app/src/main/kotlin/io/unom/punktfunk/SettingsScreen.kt

@@ -5,6 +5,7 @@ import android.content.pm.PackageManager
 import androidx.activity.compose.BackHandler
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.ColumnScope
@@ -44,6 +45,7 @@ import androidx.core.content.ContextCompat
 fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -> Unit) {
     var s by remember { mutableStateOf(initial) }
     val context = LocalContext.current
+    var showLicenses by remember { mutableStateOf(false) }
     fun update(next: Settings) {
         s = next
         onChange(next)
@@ -56,6 +58,11 @@ fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -
         ActivityResultContracts.RequestPermission(),
     ) { granted -> update(s.copy(micEnabled = granted)) }
 
+    if (showLicenses) {
+        LicensesScreen(onBack = { showLicenses = false })
+        return
+    }
+
     Column(
         modifier = Modifier
             .fillMaxSize()
@@ -104,6 +111,12 @@ fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -
         }
 
         SettingsGroup("Audio") {
+            SettingDropdown(
+                label = "Audio channels",
+                options = AUDIO_CHANNEL_OPTIONS,
+                selected = s.audioChannels,
+            ) { ch -> update(s.copy(audioChannels = ch)) }
+
             ToggleRow(
                 title = "Microphone",
                 subtitle = "Send your mic to the host's virtual microphone",
@@ -137,6 +150,14 @@ fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -
                 onCheckedChange = { on -> update(s.copy(statsHudEnabled = on)) },
             )
         }
+
+        SettingsGroup("About") {
+            ClickableRow(
+                title = "Open-source licenses",
+                subtitle = "Third-party notices and credits",
+                onClick = { showLicenses = true },
+            )
+        }
     }
 }
 
@@ -181,6 +202,24 @@ private fun ToggleRow(
     }
 }
 
+/** A title + subtitle on the left; the whole row is clickable (opens a sub-screen). */
+@Composable
+private fun ClickableRow(title: String, subtitle: String, onClick: () -> Unit) {
+    Row(
+        modifier = Modifier.fillMaxWidth().clickable(onClick = onClick),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Column(Modifier.weight(1f)) {
+            Text(title, style = MaterialTheme.typography.bodyLarge)
+            Text(
+                subtitle,
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}
+
 /** A labelled read-only dropdown over [options] (value → label); calls [onSelect] on a pick. */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable

clients/android/app/src/main/kotlin/io/unom/punktfunk/StreamScreen.kt

@@ -319,7 +319,7 @@ fun StreamScreen(handle: Long, micEnabled: Boolean, onDisconnect: () -> Unit) {
  * `[fps, mbps, latP50Ms, latP95Ms, latValid, skew, w, h, hz, dropped]`.
  */
 @Composable
-private fun StatsOverlay(s: DoubleArray, modifier: Modifier = Modifier) {
+internal fun StatsOverlay(s: DoubleArray, modifier: Modifier = Modifier) {
     if (s.size < 10) return
     val w = s[6].toInt()
     val h = s[7].toInt()

clients/android/app/src/main/kotlin/io/unom/punktfunk/Theme.kt

@@ -10,7 +10,9 @@ import androidx.compose.ui.platform.LocalContext
 
 // punktfunk brand violets (from the app icon: #6C5BF3 / #A79FF8 / #D2C9FB on a #16132A indigo).
 // Used as the fallback dark scheme on pre-Android-12 devices; on 12+ we defer to Material You.
-private val BrandDark = darkColorScheme(
+// `internal` (not private) so the CI screenshot tests can force the deterministic brand palette —
+// Material You dynamic colour has no wallpaper to seed from under the Robolectric JVM renderer.
+internal val BrandDark = darkColorScheme(
     primary = Color(0xFFA79FF8),
     onPrimary = Color(0xFF1B1442),
     primaryContainer = Color(0xFF4C3FB3),

clients/android/app/src/main/kotlin/io/unom/punktfunk/models/UiModels.kt

@@ -14,8 +14,10 @@ enum class Tab(val label: String, val icon: ImageVector) {
 /**
  * A trust decision awaiting the user before a connect proceeds. [name] is the label to save the
  * host under. Trust-on-first-use ([Kind.TRUST_NEW]) is only ever offered when the host ADVERTISED
- * pair=optional; a pair=required host or a manually-typed/unknown-policy host goes straight to PIN
+ * pair=optional; a pair=required host or a manually-typed/unknown-policy host is offered the
- * pairing ([Kind.PAIR]), and a changed fingerprint forces re-pairing — never a silent re-trust.
+ * two ways in ([Kind.REQUEST_ACCESS]): a no-PIN "request access" connect the operator approves in
+ * the host's console, or the SPAKE2 PIN ceremony ([Kind.PAIR]). A changed fingerprint forces
+ * re-pairing by PIN ([Kind.FP_CHANGED]) — never a silent re-trust.
  */
 data class PendingTrust(
     val host: String,
@@ -24,7 +26,7 @@ data class PendingTrust(
     val advertisedFp: String?,
     val kind: Kind,
 ) {
-    enum class Kind { TRUST_NEW, FP_CHANGED, PAIR }
+    enum class Kind { TRUST_NEW, FP_CHANGED, PAIR, REQUEST_ACCESS }
 }
 
 /** Trust state of a host, shown as a colored pill on its card. */

clients/android/app/src/test/kotlin/io/unom/punktfunk/screenshots/ScreenshotTest.kt

@@ -0,0 +1,74 @@
+package io.unom.punktfunk.screenshots
+
+import androidx.activity.ComponentActivity
+import androidx.compose.ui.test.junit4.createAndroidComposeRule
+import androidx.compose.ui.test.onRoot
+import com.github.takahirom.roborazzi.captureRoboImage
+import com.github.takahirom.roborazzi.captureScreenRoboImage
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import org.robolectric.annotation.GraphicsMode
+
+/**
+ * App-store / marketing screenshots of the native Android client, rendered on the JVM by Roborazzi
+ * (Robolectric Native Graphics) — no emulator, GPU, host, or JNI core. The scenes (ShotScenes.kt)
+ * render the REAL Compose UI with mock state.
+ *
+ * `sdk = [36]` is mandatory: Robolectric ships android-all jars only up to API 36 (Android 16), and
+ * the app's compileSdk is 37. PNGs land in build/outputs/roborazzi/.
+ */
+@RunWith(RobolectricTestRunner::class)
+@GraphicsMode(GraphicsMode.Mode.NATIVE)
+@Config(sdk = [36], qualifiers = "w360dp-h800dp-xxhdpi")
+class ScreenshotTest {
+    @get:Rule
+    val compose = createAndroidComposeRule<ComponentActivity>()
+
+    private val out = "build/outputs/roborazzi"
+
+    // Pausing the animation clock before composing (then advancing once past the entrance animation
+    // and freezing) is what makes a text-field-bearing scene capturable: a focused field blinks its
+    // cursor via an infinite animation that otherwise keeps Compose perpetually "busy", so
+    // setContent's wait-for-idle never returns. Frozen, the capture is also deterministic.
+
+    /** Full-screen content scenes: the compose root fills the device, so a root capture is the shot. */
+    private fun shootRoot(name: String, content: @androidx.compose.runtime.Composable () -> Unit) {
+        compose.mainClock.autoAdvance = false
+        compose.setContent { ShotTheme(content) }
+        compose.mainClock.advanceTimeBy(800)
+        compose.onRoot().captureRoboImage("$out/phone-$name.png")
+    }
+
+    /** Dialog scenes: the AlertDialog is a separate window, so capture the whole screen (all windows). */
+    private fun shootScreen(name: String, content: @androidx.compose.runtime.Composable () -> Unit) {
+        compose.mainClock.autoAdvance = false
+        compose.setContent { ShotTheme(content) }
+        compose.mainClock.advanceTimeBy(800)
+        captureScreenRoboImage("$out/phone-$name.png")
+    }
+
+    @Test
+    fun hosts() = shootRoot("hosts") { HostsScene() }
+
+    @Test
+    fun settings() = shootRoot("settings") { SettingsScene() }
+
+    @Test
+    @Config(sdk = [36], qualifiers = "w800dp-h360dp-xxhdpi") // landscape — the stream is immersive
+    fun stream() = shootRoot("stream") { StreamScene() }
+
+    @Test
+    fun trust() = shootScreen("trust") {
+        HostsScene()
+        TrustDialog()
+    }
+
+    @Test
+    fun pair() = shootScreen("pair") {
+        HostsScene()
+        PairDialog()
+    }
+}

clients/android/app/src/test/kotlin/io/unom/punktfunk/screenshots/ShotScenes.kt

@@ -0,0 +1,195 @@
+package io.unom.punktfunk.screenshots
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.grid.GridCells
+import androidx.compose.foundation.lazy.grid.GridItemSpan
+import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
+import androidx.compose.foundation.lazy.grid.items
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Brush
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import io.unom.punktfunk.BrandDark
+import io.unom.punktfunk.Settings
+import io.unom.punktfunk.SettingsScreen
+import io.unom.punktfunk.StatsOverlay
+import io.unom.punktfunk.components.HostCard
+import io.unom.punktfunk.components.SectionLabel
+import io.unom.punktfunk.models.HostStatus
+
+// The CI screenshot scenes: the REAL app composables, fed embedded mock state, under the forced
+// brand palette (Material You has no wallpaper to seed from on the JVM). The stream-video surface
+// and ConnectScreen/App are intentionally absent — they require the live JNI core / a session.
+
+/** Forces the deterministic punktfunk brand scheme (see Theme.kt) instead of dynamic colour. */
+@Composable
+internal fun ShotTheme(content: @Composable () -> Unit) {
+    MaterialTheme(colorScheme = BrandDark, content = content)
+}
+
+private data class MockHost(val name: String, val address: String, val status: HostStatus)
+
+private val SAVED = listOf(
+    MockHost("Living Room PC", "192.168.1.42:9777", HostStatus.PAIRED),
+    MockHost("Office", "192.168.1.50:9777", HostStatus.TOFU),
+)
+private val DISCOVERED = listOf(
+    MockHost("studio-deck", "192.168.1.61:9777", HostStatus.PAIRING),
+    MockHost("HTPC", "192.168.1.70:9777", HostStatus.TOFU),
+)
+
+/** The connect screen's host grid, reconstructed from the real HostCard/SectionLabel components. */
+@Composable
+internal fun HostsScene() {
+    Surface(Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {
+        LazyVerticalGrid(
+            columns = GridCells.Adaptive(minSize = 160.dp),
+            modifier = Modifier.fillMaxSize(),
+            contentPadding = androidx.compose.foundation.layout.PaddingValues(16.dp),
+            horizontalArrangement = Arrangement.spacedBy(8.dp),
+            verticalArrangement = Arrangement.spacedBy(8.dp),
+        ) {
+            item(span = { GridItemSpan(maxLineSpan) }) {
+                Column(
+                    horizontalAlignment = Alignment.CenterHorizontally,
+                    modifier = Modifier.fillMaxWidth(),
+                ) {
+                    Spacer(Modifier.height(8.dp))
+                    Text("Punktfunk", style = MaterialTheme.typography.headlineLarge)
+                    Text(
+                        "stream a remote desktop",
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                    Spacer(Modifier.height(24.dp))
+                }
+            }
+            item(span = { GridItemSpan(maxLineSpan) }) { SectionLabel("Saved hosts") }
+            items(SAVED) { h ->
+                HostCard(h.name, h.address, h.status, enabled = true, onConnect = {}, onForget = {}, onRename = {})
+            }
+            item(span = { GridItemSpan(maxLineSpan) }) {
+                Spacer(Modifier.height(12.dp))
+                SectionLabel("Discovered on the network")
+            }
+            items(DISCOVERED) { h ->
+                HostCard(h.name, h.address, h.status, enabled = true, onConnect = {}, onForget = null)
+            }
+        }
+    }
+}
+
+/** The real SettingsScreen, fed a representative non-default Settings. */
+@Composable
+internal fun SettingsScene() {
+    Surface(Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {
+        SettingsScreen(
+            initial = Settings(
+                width = 1920,
+                height = 1080,
+                hz = 120,
+                bitrateKbps = 50_000,
+                compositor = 1,
+                gamepad = 2,
+                micEnabled = true,
+                statsHudEnabled = true,
+                trackpadMode = true,
+            ),
+            onChange = {},
+            onBack = {},
+        )
+    }
+}
+
+/** The real TOFU AlertDialog (mirrors ConnectScreen's PendingTrust.Kind.TRUST_NEW), shown over the host grid. */
+@Composable
+internal fun TrustDialog() {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Trust this host?") },
+        text = {
+            Column {
+                Text("First connection to 192.168.1.61:9777.")
+                Text("Fingerprint 9f8e7d6c5b4a3928…")
+                Text(
+                    "This host allows trust-on-first-use, but that can't tell an impostor " +
+                        "from the real host. Pairing with a PIN is stronger — it proves both sides.",
+                )
+            }
+        },
+        confirmButton = { TextButton({}) { Text("Trust (TOFU)") } },
+        dismissButton = { TextButton({}) { Text("Pair with PIN…") } },
+    )
+}
+
+/** The PIN-pairing AlertDialog (mirrors ConnectScreen's PendingTrust.Kind.PAIR). The live screen
+ *  uses OutlinedTextFields, but a TextField inside a Dialog window never reaches idle under
+ *  Robolectric (its focus/cursor machinery animates forever) — so the PIN is shown as a static
+ *  display here, which also reads better in a marketing shot. */
+@Composable
+internal fun PairDialog() {
+    AlertDialog(
+        onDismissRequest = {},
+        title = { Text("Pair with PIN") },
+        text = {
+            Column {
+                Text("Enter the 4-digit PIN shown on the host.")
+                Spacer(Modifier.height(16.dp))
+                Surface(
+                    color = MaterialTheme.colorScheme.surfaceVariant,
+                    shape = MaterialTheme.shapes.medium,
+                    modifier = Modifier.fillMaxWidth(),
+                ) {
+                    Text(
+                        "4  8  2  7",
+                        style = MaterialTheme.typography.headlineMedium,
+                        textAlign = TextAlign.Center,
+                        modifier = Modifier.fillMaxWidth().padding(vertical = 16.dp),
+                    )
+                }
+                Spacer(Modifier.height(12.dp))
+                Text(
+                    "This device: Pixel 9 Pro",
+                    style = MaterialTheme.typography.bodyMedium,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+            }
+        },
+        confirmButton = { TextButton({}) { Text("Pair") } },
+        dismissButton = { TextButton({}) { Text("Cancel") } },
+    )
+}
+
+/** The live stats HUD (the real StatsOverlay) over a synthetic "streamed frame" gradient. */
+@Composable
+internal fun StreamScene() {
+    Box(
+        Modifier
+            .fillMaxSize()
+            .background(
+                Brush.linearGradient(listOf(Color(0xFF2A1E5C), Color(0xFF0E1B3D), Color(0xFF06122B))),
+            ),
+    ) {
+        // [fps, mbps, latP50, latP95, latValid, skew, w, h, hz, dropped]
+        StatsOverlay(
+            doubleArrayOf(238.0, 921.4, 1.3, 2.1, 1.0, 1.0, 5120.0, 1440.0, 240.0, 0.0),
+            Modifier.align(Alignment.TopStart).padding(12.dp),
+        )
+    }
+}

clients/android/kit/build.gradle.kts

@@ -99,6 +99,12 @@ val cargoNdkDebug = registerCargoNdk("cargoNdkDebug", release = false)
 val cargoNdkRelease = registerCargoNdk("cargoNdkRelease", release = true)
 
 afterEvaluate {
+    // `-PskipRustBuild` skips the cargo-ndk native build — for JVM-only tasks (the Roborazzi
+    // screenshot unit tests render Compose on the JVM and never load libpunktfunk_android.so), so
+    // CI/local screenshot runs don't need the Rust toolchain or NDK. The native build stays wired
+    // for every normal APK/AAR build.
+    if (!project.hasProperty("skipRustBuild")) {
         tasks.named("preDebugBuild").configure { dependsOn(cargoNdkDebug) }
         tasks.named("preReleaseBuild").configure { dependsOn(cargoNdkRelease) }
+    }
 }

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/NativeBridge.kt

@@ -29,8 +29,10 @@ object NativeBridge {
      * trust-on-first-use — read [nativeHostFingerprint] after; else 64-hex host SHA-256, mismatch →
      * `0`). [width]/[height]/[refreshHz] are the requested virtual-output mode (the host streams at
      * exactly this); [bitrateKbps] 0 = host default; [compositorPref]/[gamepadPref] are the
-     * `CompositorPref`/`GamepadPref` wire bytes (0 = Auto). Returns an opaque session handle, or `0`
+     * `CompositorPref`/`GamepadPref` wire bytes (0 = Auto). [timeoutMs] is the handshake budget — the
-     * on failure. Pair with exactly one [nativeClose].
+     * normal path passes a short value, the no-PIN "request access" path a long one (≥ the host's
+     * approval-park window) so a slow operator approval lands on this same parked connection. Returns
+     * an opaque session handle, or `0` on failure. Pair with exactly one [nativeClose].
      */
     external fun nativeConnect(
         host: String,
@@ -45,6 +47,8 @@ object NativeBridge {
         compositorPref: Int,
         gamepadPref: Int,
         hdrEnabled: Boolean,
+        audioChannels: Int,
+        timeoutMs: Int,
     ): Long
 
     /** 64-hex SHA-256 of the cert the host presented on [handle]; valid after a successful connect. */

clients/android/native/src/audio.rs

@@ -1,7 +1,11 @@
 //! Android audio playback (android-only): pull Opus packets from the connector, decode to
-//! interleaved f32 stereo, and feed AAudio (LowLatency) via its realtime data callback through a
+//! interleaved f32 (stereo or 5.1/7.1 surround), and feed AAudio (LowLatency) via its realtime data
-//! jitter ring. Mirrors [`crate::decode`]: one thread we own (the Opus decode producer) plus a
+//! callback through a jitter ring. Mirrors [`crate::decode`]: one thread we own (the Opus decode
-//! shutdown flag; the realtime callback thread is owned by AAudio.
+//! producer) plus a shutdown flag; the realtime callback thread is owned by AAudio.
+//!
+//! The layout is the host-RESOLVED channel count (`NativeClient::audio_channels`, negotiated at
+//! connect), so an older/clamping host that can only capture stereo is decoded + played as stereo.
+//! 2 = stereo / 6 = 5.1 / 8 = 7.1, in the canonical wire order FL FR FC LFE RL RR SL SR.
 //!
 //! The ring started as a port of `punktfunk-client-linux/src/audio.rs`, but AAudio — unlike
 //! PipeWire, which adaptively rate-matches the stream and absorbs a shallow buffer — hands us a raw
@@ -26,36 +30,72 @@ use std::sync::mpsc::{sync_channel, Receiver, SyncSender, TrySendError};
 use std::sync::Arc;
 use std::time::Duration;
 
-const CHANNELS: usize = 2;
 const SAMPLE_RATE: i32 = 48_000;
 /// Decoded-chunk hand-off depth: 64 × 5 ms = 320 ms slack (matches the core's AUDIO_QUEUE).
 const RING_CHUNKS: usize = 64;
-/// Opus decode scratch: worst-case 120 ms stereo frame (5760 samples/ch × 2 ch).
-const PCM_SCRATCH: usize = 5760 * CHANNELS;
 
-// --- Jitter-ring depths, in interleaved-f32 samples (all expressed in ms via `MS`). -----------
+// --- Jitter-ring depths, in MILLISECONDS (scaled to interleaved-f32 samples at runtime). --------
+// The channel count is negotiated, not a compile-time const, so these are kept in ms and multiplied
+// by `ms` (interleaved-f32 samples per millisecond at the resolved layout) inside `start`.
 // Unlike the Linux client (PipeWire adaptively rate-matches the stream to the graph clock, masking
 // host↔DAC drift + a shallow ring), AAudio hands us a raw callback and we own the buffer: drift and
 // WiFi power-save bunching land as underruns/overflows = crackle. So Android runs a deliberately
 // deeper, smoothly-managed ring than Linux — keep the two clients' depths intentionally divergent.
-/// Interleaved f32 samples per millisecond (48 kHz × 2 ch).
-const MS: usize = (SAMPLE_RATE as usize / 1000) * CHANNELS; // 96
 /// Prime/target floor: fill to ~40 ms before playing (and after a sustained drain). Deep enough to
 /// ride out WiFi arrival jitter + clock drift; the dominant Android-only anti-crackle lever.
-const PRIME_FLOOR: usize = 40 * MS;
+const PRIME_FLOOR_MS: usize = 40;
 /// Ceiling for the burst-scaled target (so a large quantum can't push the prime depth too high).
-const PRIME_CEIL: usize = 80 * MS;
+const PRIME_CEIL_MS: usize = 80;
 /// Drop-oldest headroom above the target before trimming — a ~80 ms band swallows an arrival burst
 /// without overflowing.
-const JITTER_HEADROOM: usize = 80 * MS;
+const JITTER_HEADROOM_MS: usize = 80;
 /// Hard latency bound: never let the ring exceed ~150 ms (the only thing that caps added latency).
-const HARD_CAP: usize = 150 * MS;
+const HARD_CAP_MS: usize = 150;
 /// Re-prime (go silent to refill) only after this many CONSECUTIVE empty callbacks, so one transient
 /// drain doesn't manufacture a fresh 40 ms silence (the old `if ring.is_empty()` re-primed instantly).
 const DEPRIME_AFTER_CALLBACKS: u32 = 5;
 /// Throttle the AAudio XRun-driven HW-buffer grow check (cheap, but no need to poll every quantum).
 const XRUN_CHECK_EVERY: u32 = 128;
 
+/// Opus decoder for the audio plane: a plain stereo decoder (the validated path) or a multistream
+/// decoder for 5.1/7.1, both behind one `decode_float`. Built from the host-RESOLVED channel count
+/// via the shared layout table. Mirrors the Linux client's `AudioDec`.
+enum AudioDec {
+    Stereo(opus::Decoder),
+    Surround(opus::MSDecoder),
+}
+
+impl AudioDec {
+    fn new(channels: u8) -> Result<AudioDec, opus::Error> {
+        if channels == 2 {
+            Ok(AudioDec::Stereo(opus::Decoder::new(
+                SAMPLE_RATE as u32,
+                opus::Channels::Stereo,
+            )?))
+        } else {
+            let l = punktfunk_core::audio::layout_for(channels, false);
+            Ok(AudioDec::Surround(opus::MSDecoder::new(
+                SAMPLE_RATE as u32,
+                l.streams,
+                l.coupled,
+                l.mapping,
+            )?))
+        }
+    }
+
+    fn decode_float(
+        &mut self,
+        input: &[u8],
+        out: &mut [f32],
+        fec: bool,
+    ) -> Result<usize, opus::Error> {
+        match self {
+            AudioDec::Stereo(d) => d.decode_float(input, out, fec),
+            AudioDec::Surround(d) => d.decode_float(input, out, fec),
+        }
+    }
+}
+
 /// Diagnostics — written by the decode thread + the realtime callback, logged periodically. The
 /// audio analogue of the video `fed`/`rendered` counters (we can't "screenshot" sound).
 #[derive(Default)]
@@ -74,9 +114,20 @@ pub struct AudioPlayback {
 }
 
 impl AudioPlayback {
-    /// Open AAudio (LowLatency, 48 kHz/stereo/f32) with a realtime callback draining a jitter ring,
+    /// Open AAudio (LowLatency, 48 kHz/f32, the host-resolved channel layout) with a realtime
-    /// then spawn the Opus decode thread. `None` on failure (the caller leaves video streaming).
+    /// callback draining a jitter ring, then spawn the Opus decode thread. `None` on failure (the
+    /// caller leaves video streaming).
     pub fn start(client: Arc<NativeClient>) -> Option<AudioPlayback> {
+        // Build playback from the host-RESOLVED channel count (never the request): 2 = stereo /
+        // 6 = 5.1 / 8 = 7.1, canonical wire order FL FR FC LFE RL RR SL SR.
+        let channels = punktfunk_core::audio::normalize_channels(client.audio_channels) as usize;
+        // Interleaved f32 samples per millisecond at this layout (48 kHz × channels); the ms-
+        // denominated jitter-ring depths scale by it.
+        let ms = (SAMPLE_RATE as usize / 1000) * channels;
+        let prime_floor = PRIME_FLOOR_MS * ms;
+        let prime_ceil = PRIME_CEIL_MS * ms;
+        let jitter_headroom = JITTER_HEADROOM_MS * ms;
+        let hard_cap_max = HARD_CAP_MS * ms;
         let counters = Arc::new(Counters::default());
         let (tx, rx) = sync_channel::<Vec<f32>>(RING_CHUNKS);
         // Recycle free-list: drained PCM buffers go BACK to the decode thread to be refilled, so the
@@ -92,13 +143,13 @@ impl AudioPlayback {
         // before the trim below = the hard cap plus one full channel of 5 ms (480-f32) frames — the
         // punktfunk protocol always sends 5 ms Opus frames (host `audio_thread`); a larger frame
         // would force a one-time realloc, asserted (not silently corrupted) in `decode_loop`.
-        let mut ring: VecDeque<f32> = VecDeque::with_capacity(HARD_CAP + RING_CHUNKS * 5 * MS);
+        let mut ring: VecDeque<f32> = VecDeque::with_capacity(hard_cap_max + RING_CHUNKS * 5 * ms);
         let mut primed = false;
         let mut empties: u32 = 0; // consecutive empty callbacks (de-prime hysteresis)
         let mut cb_count: u32 = 0; // callbacks since open (throttles the XRun grow check)
         let mut last_xrun: i32 = 0; // last AAudio XRun count we grew the buffer for
         let callback = move |s: &AudioStream, data: *mut c_void, num_frames: i32| {
-            let want = num_frames as usize * CHANNELS;
+            let want = num_frames as usize * channels;
             // SAFETY: AAudio provides `num_frames * channel_count` F32 slots at `data`.
             let out = unsafe { std::slice::from_raw_parts_mut(data as *mut f32, want) };
             // Drain decoded chunks into the ring WITHOUT freeing on the RT thread: `drain(..)` empties
@@ -108,11 +159,11 @@ impl AudioPlayback {
                 ring.extend(chunk.drain(..));
                 let _ = free_tx.try_send(chunk);
             }
-            // Jitter buffer: prime to ~40 ms (PRIME_FLOOR) before playing and after a sustained drain;
+            // Jitter buffer: prime to ~40 ms (prime_floor) before playing and after a sustained drain;
             // drop-oldest only above a wide ~120 ms band. Decoupled from the AAudio burst `want` (tiny
             // on the LowLatency MMAP path) so the depth doesn't collapse to a single quantum.
-            let target = (3 * want).clamp(PRIME_FLOOR, PRIME_CEIL);
+            let target = (3 * want).clamp(prime_floor, prime_ceil);
-            let hard_cap = (target + JITTER_HEADROOM).min(HARD_CAP);
+            let hard_cap = (target + jitter_headroom).min(hard_cap_max);
             while ring.len() > hard_cap {
                 ring.pop_front();
             }
@@ -166,7 +217,11 @@ impl AudioPlayback {
             .ok()?
             .direction(AudioDirection::Output)
             .sample_rate(SAMPLE_RATE)
-            .channel_count(CHANNELS as i32)
+            // The wire order (FL FR FC LFE RL RR SL SR) is the standard AAudio/Android channel
+            // order, so this is an IDENTITY mapping — no permute. AAudio infers the 5.1/7.1 mask
+            // from `channel_count` (the ndk crate's builder exposes no setChannelMask); the host
+            // captures + Opus-encodes in exactly this order.
+            .channel_count(channels as i32)
             .format(AudioFormat::PCM_Float)
             .performance_mode(AudioPerformanceMode::LowLatency)
             .sharing_mode(AudioSharingMode::Shared)
@@ -206,7 +261,7 @@ impl AudioPlayback {
         let sd = shutdown.clone();
         let join = std::thread::Builder::new()
             .name("pf-audio".into())
-            .spawn(move || decode_loop(client, tx, free_rx, sd, counters))
+            .spawn(move || decode_loop(client, tx, free_rx, sd, counters, channels))
             .ok();
 
         Some(AudioPlayback {
@@ -236,29 +291,34 @@ fn decode_loop(
     free_rx: Receiver<Vec<f32>>,
     shutdown: Arc<AtomicBool>,
     counters: Arc<Counters>,
+    channels: usize,
 ) {
-    let mut dec = match opus::Decoder::new(SAMPLE_RATE as u32, opus::Channels::Stereo) {
+    // Interleaved f32 samples per millisecond at this layout — the ring's 5 ms reserve check below.
+    let ms = (SAMPLE_RATE as usize / 1000) * channels;
+    // Opus decode scratch: worst-case 120 ms frame (5760 samples/ch) × channels.
+    let pcm_scratch = 5760 * channels;
+    let mut dec = match AudioDec::new(channels as u8) {
         Ok(d) => d,
         Err(e) => {
             log::error!("audio: opus decoder init: {e} — audio disabled");
             return;
         }
     };
-    let mut pcm = vec![0f32; PCM_SCRATCH];
+    let mut pcm = vec![0f32; pcm_scratch];
     let mut window_peak = 0f32; // loudest |sample| since the last log — tells a tone from silence
     while !shutdown.load(Ordering::Relaxed) {
         match client.next_audio(Duration::from_millis(5)) {
             Ok(pkt) => match dec.decode_float(&pkt.data, &mut pcm, false) {
                 Ok(samples) => {
-                    let n = samples * CHANNELS;
+                    let n = samples * channels;
                     for &s in &pcm[..n] {
                         window_peak = window_peak.max(s.abs());
                     }
-                    // The ring's pre-reservation in `start` assumes the protocol's 5 ms (≤480-f32)
+                    // The ring's pre-reservation in `start` assumes the protocol's 5 ms (≤480-f32/ch)
                     // frames; a larger frame would force a one-time realloc on the RT thread. Catch a
                     // future host frame-size change here in debug, not as a silent audio glitch.
                     debug_assert!(
-                        n <= 5 * MS,
+                        n <= 5 * ms,
                         "audio frame {n} f32 exceeds the 5 ms ring reserve"
                     );
                     let count = counters.opus_decoded.fetch_add(1, Ordering::Relaxed) + 1;
@@ -266,7 +326,7 @@ fn decode_loop(
                     // free-list is momentarily empty (startup / after a backpressure drop).
                     let mut buf = free_rx
                         .try_recv()
-                        .unwrap_or_else(|_| Vec::with_capacity(PCM_SCRATCH));
+                        .unwrap_or_else(|_| Vec::with_capacity(pcm_scratch));
                     buf.clear();
                     buf.extend_from_slice(&pcm[..n]);
                     match tx.try_send(buf) {

clients/android/native/src/session.rs

@@ -140,11 +140,15 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeGenerateIde
 }
 
 /// `NativeBridge.nativeConnect(host, port, w, h, hz, certPem, keyPem, pinHex, bitrateKbps,
-/// compositorPref, gamepadPref): Long`. `certPem`/`keyPem` empty = anonymous, else presented as the
+/// compositorPref, gamepadPref, hdrEnabled, audioChannels, timeoutMs): Long`. `certPem`/`keyPem`
-/// persistent identity. `pinHex` empty = TOFU (read `nativeHostFingerprint` after), else 64-hex
+/// empty = anonymous, else presented as the persistent identity. `pinHex` empty = TOFU (read
-/// SHA-256 to pin the host (mismatch → 0). `bitrateKbps` 0 = host default. `compositorPref`/
+/// `nativeHostFingerprint` after), else 64-hex SHA-256 to pin the host (mismatch → 0). `bitrateKbps`
-/// `gamepadPref` are `CompositorPref`/`GamepadPref` wire bytes (0 = Auto; unknown → Auto).
+/// 0 = host default. `compositorPref`/`gamepadPref` are `CompositorPref`/`GamepadPref` wire bytes
-/// Returns an opaque handle, or 0 on failure (logged).
+/// (0 = Auto; unknown → Auto). `audioChannels` is the requested surround layout (2/6/8; normalized,
+/// anything else → stereo) — the host clamps it and the resolved count drives playback. `timeoutMs`
+/// is the handshake budget: the normal path passes a short value, the no-PIN "request access" path a
+/// long one (≥ the host's approval-park window) so a slow operator approval lands on this same parked
+/// connection rather than timing the client out first. Returns an opaque handle, or 0 on failure.
 #[no_mangle]
 #[allow(clippy::too_many_arguments)]
 pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeConnect<'local>(
@@ -162,6 +166,8 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeConnect<'lo
     compositor_pref: jint,
     gamepad_pref: jint,
     hdr_enabled: jboolean,
+    audio_channels: jint,
+    timeout_ms: jint,
 ) -> jlong {
     let host: String = match env.get_string(&host) {
         Ok(s) => s.into(),
@@ -213,10 +219,17 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeConnect<'lo
         } else {
             0
         },
+        // Requested surround layout (2 = stereo / 6 = 5.1 / 8 = 7.1). The host clamps to what it can
+        // capture and echoes the resolved count in `connector.audio_channels`, which drives the
+        // decoder + AAudio layout (read in `crate::audio::AudioPlayback::start`). Anything else
+        // normalizes to stereo here.
+        punktfunk_core::audio::normalize_channels(audio_channels.clamp(0, u8::MAX as jint) as u8),
         None,     // launch: default app
         pin,      // Some → Crypto on host-fp mismatch
         identity, // owned (cert, key) PEM, or None (anonymous)
-        Duration::from_secs(10),
+        // Handshake budget from Kotlin: ~10 s for a normal connect, ~185 s for "request access"
+        // (the host parks the connection until the operator approves the device — see ConnectScreen).
+        Duration::from_millis(timeout_ms.max(0) as u64),
     ) {
         Ok(client) => {
             let handle = SessionHandle {

clients/apple/Package.swift

@@ -16,6 +16,15 @@ let package = Package(
         .target(
             name: "PunktfunkKit",
             dependencies: ["PunktfunkCore"],
+            // OSS attribution shown by the app's Acknowledgements screen. Bundled here (not in the
+            // app target) so it rides along via Bundle.module in both `swift build` and the Xcode
+            // app, which links the PunktfunkKit product. Refresh with
+            // scripts/gen-third-party-notices.sh (it copies the generated file into Resources/).
+            resources: [
+                .copy("Resources/THIRD-PARTY-NOTICES.txt"),
+                .copy("Resources/LICENSE-MIT.txt"),
+                .copy("Resources/LICENSE-APACHE.txt"),
+            ],
             linkerSettings: [
                 // Rust staticlib system deps.
                 .linkedFramework("Security"),

clients/apple/Sources/PunktfunkClient/AcknowledgementsView.swift

@@ -0,0 +1,60 @@
+import PunktfunkKit
+import SwiftUI
+
+/// Open-source acknowledgements: punktfunk's own license (MIT OR Apache-2.0) followed by the
+/// third-party software notices. Used as a pushed view on iOS/tvOS and a preferences tab on macOS.
+struct AcknowledgementsView: View {
+    private var version: String? {
+        Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String
+    }
+
+    var body: some View {
+        ScrollView {
+            VStack(alignment: .leading, spacing: 18) {
+                Text("punktfunk")
+                    .font(.title2).bold()
+                if let version {
+                    Text("Version \(version)")
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                }
+                Text(Licenses.appLicense)
+                    .font(.caption.monospaced())
+                    .modifier(SelectableText())
+
+                Divider()
+
+                Text("Third-party software")
+                    .font(.headline)
+                Text(
+                    "punktfunk uses the open-source components below, each under its own license. "
+                        + "On some platforms FFmpeg is additionally bundled under the LGPL v2.1+ "
+                        + "(dynamically linked, replaceable)."
+                )
+                .font(.caption)
+                .foregroundStyle(.secondary)
+                Text(Licenses.thirdPartyNotices)
+                    .font(.caption2.monospaced())
+                    .modifier(SelectableText())
+            }
+            .frame(maxWidth: 900, alignment: .leading)
+            .frame(maxWidth: .infinity, alignment: .leading)
+            .padding()
+            #if os(tvOS)
+                .padding(40)
+            #endif
+        }
+        .navigationTitle("Acknowledgements")
+    }
+}
+
+/// `textSelection(.enabled)` is unavailable on tvOS, so apply it only where it exists.
+private struct SelectableText: ViewModifier {
+    func body(content: Content) -> some View {
+        #if os(tvOS)
+            content
+        #else
+            content.textSelection(.enabled)
+        #endif
+    }
+}

clients/apple/Sources/PunktfunkClient/ContentView.swift

@@ -4,10 +4,12 @@
 // (HomeView/HostCards), the trust prompt (TrustCardView), and the HUD (StreamHUDView) live in
 // their own files.
 //
-// Two ways to establish trust on first contact: the TOFU prompt (host fingerprint over the
+// Ways to establish trust on first contact: the TOFU prompt (host fingerprint over the
-// live-but-blurred stream, compared with the host's log) or the PIN pairing ceremony — pairing
+// live-but-blurred stream, compared with the host's log; only for a host advertising pair=optional),
-// verifies both sides at once and is the only way into hosts running --require-pairing. Once
+// the PIN pairing ceremony (verifies both sides at once), or — for a host that requires pairing —
-// pinned, reconnects are silent and a changed host identity refuses to connect.
+// delegated approval ("Request Access": a plain identified connect the host parks until the operator
+// approves this device in its console, no PIN). Once pinned, reconnects are silent and a changed
+// host identity refuses to connect.
 
 #if os(macOS)
 import AppKit
@@ -25,11 +27,18 @@ struct ContentView: View {
     @AppStorage(DefaultsKey.compositor) private var compositor = 0
     @AppStorage(DefaultsKey.gamepadType) private var gamepadType = 0
     @AppStorage(DefaultsKey.bitrateKbps) private var bitrateKbps = 0
+    @AppStorage(DefaultsKey.audioChannels) private var audioChannels = 2
     @AppStorage(DefaultsKey.fullscreenWhileStreaming) private var fullscreenWhileStreaming = true
     @AppStorage(DefaultsKey.hudEnabled) private var hudEnabled = true
     @AppStorage(DefaultsKey.hudPlacement) private var hudPlacement = HUDPlacement.topTrailing.rawValue
     @State private var showAddHost = false
     @State private var pairingTarget: StoredHost?
+    /// A fresh `pair=required`/unknown host the user tapped: drives the choice between no-PIN
+    /// delegated approval ("Request Access") and the SPAKE2 PIN ceremony (rule 3b).
+    @State private var approvalChoice: ApprovalRequest?
+    /// A delegated-approval connect is in flight (host parks it until the operator approves):
+    /// drives the cancelable "Waiting for approval" prompt and the pin-as-paired on success.
+    @State private var awaitingApproval: ApprovalRequest?
     @State private var speedTestTarget: StoredHost?
     @State private var libraryTarget: StoredHost?
     #if !os(macOS)
@@ -54,10 +63,27 @@ struct ContentView: View {
             autoConnectIfAsked()
         }
         .onChange(of: model.phase) { _, phase in
+            switch phase {
+            case .streaming:
                 // A session actually started — remember it on the card ("Connected … ago"
                 // plus the accent ring on the most recent host).
-            if case .streaming = phase, let host = model.activeHost {
+                guard let host = model.activeHost else { break }
                 store.markConnected(host.id)
+                // Delegated approval just succeeded: the operator let this device in, so pin the
+                // host's observed fingerprint and remember it as paired — future connects are then
+                // silent (rule 1), exactly like after a PIN/TOFU success. Dismisses the wait prompt.
+                if awaitingApproval?.host.id == host.id {
+                    if let fp = model.connection?.hostFingerprint {
+                        store.pin(host.id, fingerprint: fp)
+                    }
+                    awaitingApproval = nil
+                }
+            case .idle:
+                // The delegated-approval connect failed, timed out, or was cancelled — drop the
+                // wait prompt (SessionModel surfaces any error via `errorMessage`).
+                if awaitingApproval != nil { awaitingApproval = nil }
+            default:
+                break
             }
         }
         .onDisappear { model.disconnect() } // window closed mid-session (Cmd+N spawns more)
@@ -89,6 +115,47 @@ struct ContentView: View {
             }
         }
         #endif
+        // Fresh pair=required / unknown host: offer the two ways in. An action sheet (not an
+        // alert) so it never collides with the wait alert below. "Request Access" is the no-PIN
+        // delegated-approval path; "Pair with PIN…" runs the SPAKE2 ceremony. The follow-on
+        // presentation is deferred a tick so this dialog is fully dismissed first.
+        .confirmationDialog(
+            "Pairing required",
+            isPresented: Binding(
+                get: { approvalChoice != nil },
+                set: { if !$0 { approvalChoice = nil } }),
+            titleVisibility: .visible,
+            presenting: approvalChoice
+        ) { req in
+            Button("Request Access") {
+                DispatchQueue.main.async { requestAccess(req) }
+            }
+            Button("Pair with PIN…") {
+                DispatchQueue.main.async { pairingTarget = req.host }
+            }
+            Button("Cancel", role: .cancel) {}
+        } message: { req in
+            Text("\(req.host.displayName) requires pairing. Request access and approve this "
+                + "device in the host's web console (port 3000 → Pairing) — no PIN needed. Or "
+                + "pair with the 4-digit PIN it can display.")
+        }
+        // The delegated-approval wait: the host holds the connection open until the operator
+        // approves it. Cancel returns the UI at once; the in-flight connect is left to time out
+        // and its late result is discarded by SessionModel's connect guard (disconnect resets the
+        // phase/host it checks).
+        .alert(
+            "Waiting for approval",
+            isPresented: Binding(
+                get: { awaitingApproval != nil },
+                set: { if !$0 { awaitingApproval = nil } }),
+            presenting: awaitingApproval
+        ) { _ in
+            Button("Cancel", role: .cancel) { model.disconnect() }
+        } message: { req in
+            Text("Approve \u{201C}\(localDeviceName)\u{201D} in \(req.host.displayName)'s web "
+                + "console (port 3000 → Pairing). This device connects automatically once you "
+                + "approve it — no need to reconnect.")
+        }
     }
 
     private var home: some View {
@@ -229,19 +296,32 @@ struct ContentView: View {
         // A pinned host connects on its stored fingerprint; an unpinned host may only TOFU when
         // the host's LIVE advert says `pair=optional` (rule 3a). When the caller doesn't already
         // know the policy (a saved-card tap / manual entry), resolve it from the current mDNS set:
-        // an unpinned host with no matching `pair=optional` advert routes to PIN pairing instead
+        // an unpinned host with no matching `pair=optional` advert routes to the approval choice
-        // of silently entering the trust prompt (rules 3b + 4). A pinned host ignores all of this.
+        // (request access / pair with PIN) instead of silently entering the trust prompt (rules
+        // 3b + 4). A pinned host ignores all of this.
         if host.pinnedSHA256 == nil {
             let tofuOK = allowTofu ?? discovery.hosts.contains {
                 host.matches($0) && $0.allowsTofu
             }
             if !tofuOK {
-                pairingTarget = host
+                // pair=required / unknown policy / manual entry (rule 3b): never a silent
+                // connect — offer no-PIN delegated approval or the PIN ceremony.
+                approvalChoice = ApprovalRequest(
+                    host: host, advertisedFingerprint: advertisedFingerprint(for: host))
                 return
             }
         }
-        // The gamepad-type setting resolves NOW (Automatic → match the active physical
+        startSession(host, launchID: launchID, allowTofu: host.pinnedSHA256 == nil)
-        // controller): the host's virtual pad backend is fixed per session.
+    }
+
+    /// Resolve the @AppStorage stream mode + input prefs and hand off to the session model. The
+    /// gamepad-type setting resolves NOW (Automatic → match the active physical controller): the
+    /// host's virtual pad backend is fixed per session. `requestAccess` opens the no-PIN
+    /// delegated-approval connect (host parks it until the operator approves).
+    private func startSession(
+        _ host: StoredHost, launchID: String? = nil,
+        allowTofu: Bool, requestAccess: Bool = false
+    ) {
         model.connect(
             to: host,
             width: UInt32(clamping: width), height: UInt32(clamping: height),
@@ -252,8 +332,24 @@ struct ContentView: View {
                 setting: PunktfunkConnection.GamepadType(
                     rawValue: UInt32(clamping: gamepadType)) ?? .auto),
             bitrateKbps: UInt32(clamping: bitrateKbps),
+            audioChannels: UInt8(clamping: audioChannels),
             launchID: launchID,
-            allowTofu: host.pinnedSHA256 == nil)
+            allowTofu: allowTofu,
+            requestAccess: requestAccess)
+    }
+
+    /// The no-PIN delegated-approval flow: open an identified connect the host parks until the
+    /// operator approves it in the console, showing the cancelable "Waiting for approval" prompt
+    /// meanwhile. On success the SAME connection is admitted (no reconnect) and the host is pinned
+    /// as paired (see the `.streaming` branch of `onChange`).
+    private func requestAccess(_ req: ApprovalRequest) {
+        guard !model.isBusy else { return }
+        awaitingApproval = req
+        // Pin the advertised certificate for a discovered host (impostor defence during the long
+        // wait); a manually-typed host has no advertised fingerprint, so trust-on-first-use.
+        var host = req.host
+        host.pinnedSHA256 = req.advertisedFingerprint
+        startSession(host, allowTofu: false, requestAccess: true)
     }
 
     /// Picked a title in the (experimental) library: dismiss the browser and start a session that
@@ -266,8 +362,9 @@ struct ContentView: View {
     /// Tap a discovered host: save it (so the session has a stored identity and the trust pin
     /// persists), then connect or pair per the host's advertised policy. The host is the policy
     /// authority — TOFU is offered ONLY when it explicitly advertised `pair=optional` (rule 3a);
-    /// a `pair=required` host, or one with no/unknown `pair` field, goes straight to the PIN
+    /// a `pair=required` host, or one with no/unknown `pair` field, gets the approval choice
-    /// pairing ceremony (rule 3b). (A pinned discovered host connects silently inside `connect`.)
+    /// (request access / pair with PIN) (rule 3b). (A pinned discovered host connects silently
+    /// inside `connect`.)
     private func connectDiscovered(_ d: DiscoveredHost) {
         guard !model.isBusy else { return }
         let host = StoredHost(name: d.name, address: d.host, port: d.port)
@@ -275,7 +372,9 @@ struct ContentView: View {
         if d.allowsTofu {
             connect(host, allowTofu: true)
         } else {
-            pairingTarget = host
+            // pair=required / unknown policy (rule 3b): offer no-PIN delegated approval or PIN.
+            approvalChoice = ApprovalRequest(
+                host: host, advertisedFingerprint: pinFingerprint(d.fingerprintHex))
         }
     }
 
@@ -289,6 +388,30 @@ struct ContentView: View {
         connect(pinned)
     }
 
+    /// The certificate fingerprint a live mDNS advert carries for this saved host (advisory — see
+    /// `HostDiscovery`), to pin during a delegated-approval wait. nil if the host isn't currently
+    /// advertising or advertised no/invalid `fp`.
+    private func advertisedFingerprint(for host: StoredHost) -> Data? {
+        pinFingerprint(discovery.hosts.first { host.matches($0) }?.fingerprintHex)
+    }
+
+    /// Parse an advertised cert fingerprint (lowercase hex) into the 32-byte pin the connect
+    /// expects; nil unless it's exactly a 32-byte (SHA-256) value, so a malformed advert falls
+    /// back to trust-on-first-use rather than failing the connect closed.
+    private func pinFingerprint(_ hex: String?) -> Data? {
+        guard let hex, let data = Data(hexString: hex), data.count == 32 else { return nil }
+        return data
+    }
+
+    /// How the host lists this device in its approval prompt (matches PairSheet's client name).
+    private var localDeviceName: String {
+        #if os(macOS)
+        Host.current().localizedName ?? "Mac"
+        #else
+        UIDevice.current.name
+        #endif
+    }
+
     // MARK: - First-run + dev hooks
 
     /// First run on iOS: default the stream mode to this device's native screen so the
@@ -351,6 +474,7 @@ struct ContentView: View {
             compositor: pref,
             gamepad: pad,
             bitrateKbps: bitrate,
+            audioChannels: UInt8(clamping: audioChannels),
             autoTrust: true)
     }
 }
@@ -375,3 +499,31 @@ private struct FullscreenController: NSViewRepresentable {
     }
 }
 #endif
+
+/// A fresh `pair=required`/unknown host pending a trust decision: drives both the "request access
+/// vs. pair with PIN" choice and the subsequent approval wait. `advertisedFingerprint` is the
+/// discovered host's advertised cert (nil for a manually-typed host → trust-on-first-use).
+private struct ApprovalRequest {
+    let host: StoredHost
+    let advertisedFingerprint: Data?
+}
+
+private extension Data {
+    /// Parse an even-length hex string into bytes; nil on any non-hex character or odd length.
+    /// Used to turn an mDNS-advertised cert fingerprint into a connect pin.
+    init?(hexString: String) {
+        let chars = Array(hexString)
+        guard chars.count.isMultiple(of: 2) else { return nil }
+        var bytes = [UInt8]()
+        bytes.reserveCapacity(chars.count / 2)
+        var i = 0
+        while i < chars.count {
+            guard let hi = chars[i].hexDigitValue, let lo = chars[i + 1].hexDigitValue else {
+                return nil
+            }
+            bytes.append(UInt8(hi << 4 | lo))
+            i += 2
+        }
+        self = Data(bytes)
+    }
+}

clients/apple/Sources/PunktfunkClient/SessionModel.swift

@@ -95,14 +95,23 @@ final class SessionModel: ObservableObject {
     /// field — TOFU is forbidden (rule 3b): the connect refuses rather than offering trust, and
     /// the user is routed to PIN pairing by the caller. (A pinned host connects regardless: its
     /// stored fingerprint is the trust decision.)
+    ///
+    /// `requestAccess` is the no-PIN delegated-approval path: open an identified connect the host
+    /// PARKS until the operator clicks Approve in its console, then admits the SAME connection (no
+    /// reconnect). The handshake budget is widened to exceed the host's park window, and a
+    /// successful connect streams directly (the approval IS the trust decision) — the caller pins
+    /// the observed fingerprint as paired. `host.pinnedSHA256`, when set, pins the advertised cert
+    /// for the wait; nil = trust-on-first-use.
     func connect(to host: StoredHost, width: UInt32, height: UInt32, hz: UInt32,
                  compositor: PunktfunkConnection.Compositor = .auto,
                  gamepad: PunktfunkConnection.GamepadType = .auto,
                  bitrateKbps: UInt32 = 0,
+                 audioChannels: UInt8 = 2,
                  hdrEnabled: Bool = true,
                  launchID: String? = nil,
                  allowTofu: Bool = false,
-                 autoTrust: Bool = false) {
+                 autoTrust: Bool = false,
+                 requestAccess: Bool = false) {
         guard phase == .idle else { return }
         phase = .connecting
         activeHost = host
@@ -137,7 +146,11 @@ final class SessionModel: ObservableObject {
                 width: width, height: height, refreshHz: hz,
                 pinSHA256: pin, identity: identity, compositor: compositor,
                 gamepad: gamepad, bitrateKbps: bitrateKbps, videoCaps: videoCaps,
-                launchID: launchID) }
+                audioChannels: audioChannels, launchID: launchID,
+                // Delegated approval: the host holds this connect open until the operator approves
+                // it (~180 s) — outwait that window so a slow approval still lands here. Normal
+                // connects keep the snappy default.
+                timeoutMs: requestAccess ? 185_000 : 10_000) }
             await MainActor.run { [weak self] in
                 guard let self else { return }
                 // The user may have abandoned this attempt (window closed, another host
@@ -151,7 +164,9 @@ final class SessionModel: ObservableObject {
                 }
                 switch result {
                 case .success(let conn):
-                    if pin != nil || autoTrust {
+                    if pin != nil || autoTrust || requestAccess {
+                        // requestAccess: the operator approved this device on the host, so the
+                        // session is trusted — stream directly (the caller pins it as paired).
                         self.connection = conn
                         self.startStatsTimer()
                         self.beginStreaming()
@@ -173,6 +188,14 @@ final class SessionModel: ObservableObject {
                 case .failure:
                     self.phase = .idle
                     self.activeHost = nil
+                    if requestAccess {
+                        // The delegated-approval connect ended without being admitted: the
+                        // operator didn't approve it before the host's park window elapsed (or
+                        // the host was unreachable).
+                        self.errorMessage = "\(host.displayName) didn't let this device in. "
+                            + "Approve it in the host's web console (port 3000 → Pairing), then "
+                            + "request access again — the request expires after a few minutes."
+                    } else {
                         self.errorMessage = pin != nil
                             ? "Could not connect to \(host.displayName) — host unreachable, "
                                 + "not running, its identity no longer matches the pinned "
@@ -187,6 +210,7 @@ final class SessionModel: ObservableObject {
                 }
             }
         }
+    }
 
     /// The user confirmed the fingerprint: returns it for pinning and enters streaming.
     func confirmTrust() -> Data? {

clients/apple/Sources/PunktfunkClient/SettingsView.swift

@@ -25,6 +25,7 @@ struct SettingsView: View {
     @AppStorage(DefaultsKey.libraryEnabled) private var libraryEnabled = false
     @AppStorage(DefaultsKey.fullscreenWhileStreaming) private var fullscreenWhileStreaming = true
     @AppStorage(DefaultsKey.micEnabled) private var micEnabled = true
+    @AppStorage(DefaultsKey.audioChannels) private var audioChannels = 2
     @AppStorage(DefaultsKey.hudEnabled) private var hudEnabled = true
     @AppStorage(DefaultsKey.hudPlacement) private var hudPlacement = HUDPlacement.topTrailing.rawValue
     @ObservedObject private var gamepads = GamepadManager.shared
@@ -97,6 +98,9 @@ struct SettingsView: View {
             }
             .formStyle(.grouped)
             .tabItem { Label("Advanced", systemImage: "slider.horizontal.3") }
+
+            AcknowledgementsView()
+                .tabItem { Label("About", systemImage: "info.circle") }
         }
         .frame(width: 480, height: 460)
     }
@@ -114,6 +118,9 @@ struct SettingsView: View {
             statisticsSection
             experimentalSection
             controllersSection
+            Section {
+                NavigationLink("Acknowledgements") { AcknowledgementsView() }
+            }
         }
         .formStyle(.grouped)
         .onAppear {
@@ -173,6 +180,10 @@ struct SettingsView: View {
                 TVSelectionRow(title: "Stream mode", options: options, selection: modeTag)
                 TVSelectionRow(
                     title: "Bitrate", options: bitrateOptions, selection: $bitrateKbps)
+                TVSelectionRow(
+                    title: "Audio channels",
+                    options: [("Stereo", 2), ("5.1 Surround", 6), ("7.1 Surround", 8)],
+                    selection: $audioChannels)
                 if bitrateKbps > 1_000_000 {
                     Label(Self.gigabitWarning, systemImage: "exclamationmark.triangle.fill")
                         .font(.caption)
@@ -212,6 +223,8 @@ struct SettingsView: View {
                     .foregroundStyle(.secondary)
                     .multilineTextAlignment(.center)
                     .padding(.top, 8)
+                NavigationLink("Acknowledgements") { AcknowledgementsView() }
+                    .padding(.top, 8)
             }
             .frame(maxWidth: 1000)
             .frame(maxWidth: .infinity)
@@ -271,6 +284,11 @@ struct SettingsView: View {
 
     @ViewBuilder private var audioSection: some View {
         Section {
+            Picker("Audio channels", selection: $audioChannels) {
+                Text("Stereo").tag(2)
+                Text("5.1 Surround").tag(6)
+                Text("7.1 Surround").tag(8)
+            }
             #if os(macOS)
             Picker("Speaker", selection: $speakerUID) {
                 Text("System default").tag("")

clients/apple/Sources/PunktfunkKit/DefaultsKeys.swift

@@ -15,6 +15,9 @@ public enum DefaultsKey {
     public static let gamepadType = "punktfunk.gamepadType"
     public static let gamepadID = "punktfunk.gamepadID"
     public static let bitrateKbps = "punktfunk.bitrateKbps"
+    /// Requested audio channel count: 2 (stereo), 6 (5.1) or 8 (7.1). The host clamps to what it
+    /// can capture; the resolved count drives the in-core decode + AVAudioEngine layout.
+    public static let audioChannels = "punktfunk.audioChannels"
     public static let micEnabled = "punktfunk.micEnabled"
     public static let speakerUID = "punktfunk.speakerUID"
     public static let micUID = "punktfunk.micUID"

clients/apple/Sources/PunktfunkKit/Licenses.swift

@@ -0,0 +1,36 @@
+import Foundation
+
+/// Open-source license / attribution text bundled with PunktfunkKit (see `Resources/`).
+///
+/// Exposed from the kit so the app shell can show an Acknowledgements screen. The text files are
+/// bundled as SwiftPM resources and read via `Bundle.module`, which works both for `swift build`
+/// and for the Xcode app (it links the PunktfunkKit product, so the resource bundle rides along).
+public enum Licenses {
+    private static func resource(_ name: String) -> String {
+        guard let url = Bundle.module.url(forResource: name, withExtension: "txt"),
+            let text = try? String(contentsOf: url, encoding: .utf8)
+        else { return "" }
+        return text
+    }
+
+    /// punktfunk's own license — MIT OR Apache-2.0, at your option.
+    public static var appLicense: String {
+        let mit = resource("LICENSE-MIT")
+        let apache = resource("LICENSE-APACHE")
+        if mit.isEmpty && apache.isEmpty {
+            return "punktfunk is licensed under MIT OR Apache-2.0, at your option."
+        }
+        return "punktfunk is licensed under MIT OR Apache-2.0, at your option.\n\n"
+            + "================================ MIT ================================\n\n"
+            + mit
+            + "\n\n============================== Apache-2.0 ==============================\n\n"
+            + apache
+    }
+
+    /// Third-party software notices for the linked Rust crates (generated by
+    /// `scripts/gen-third-party-notices.sh`).
+    public static var thirdPartyNotices: String {
+        let text = resource("THIRD-PARTY-NOTICES")
+        return text.isEmpty ? "Third-party notices unavailable." : text
+    }
+}

clients/apple/Sources/PunktfunkKit/PunktfunkConnection.swift

@@ -235,6 +235,12 @@ public final class PunktfunkConnection {
     /// drain `nextHdrMeta`.
     public var isHDR: Bool { colorTransfer == 16 || colorTransfer == 18 }
 
+    /// The audio channel count the host resolved for this session (the Welcome's echo of the
+    /// requested `audioChannels`, clamped to what the host can capture): `2` (stereo), `6` (5.1)
+    /// or `8` (7.1). Build the playback layout from THIS, never the request. `2` for an older host.
+    /// PCM from `nextAudioPcm` is interleaved in the canonical wire order FL FR FC LFE RL RR SL SR.
+    public private(set) var resolvedAudioChannels: UInt8 = 2
+
     /// Connect and start a session at the requested mode (the host creates a native virtual
     /// output at exactly this size/refresh). Blocks up to `timeoutMs`.
     ///
@@ -264,6 +270,7 @@ public final class PunktfunkConnection {
         gamepad: GamepadType = .auto,
         bitrateKbps: UInt32 = 0,
         videoCaps: UInt8 = 0,
+        audioChannels: UInt8 = 2,
         launchID: String? = nil,
         timeoutMs: UInt32 = 10_000
     ) throws {
@@ -279,16 +286,16 @@ public final class PunktfunkConnection {
                     withOptionalCString(launchID) { launch in
                         if let pin = pinSHA256 {
                             return pin.withUnsafeBytes { p in
-                                punktfunk_connect_ex5(
+                                punktfunk_connect_ex6(
                                     cs, port, width, height, refreshHz, compositor.rawValue,
-                                    gamepad.rawValue, bitrateKbps, videoCaps, launch,
+                                    gamepad.rawValue, bitrateKbps, videoCaps, audioChannels, launch,
                                     p.bindMemory(to: UInt8.self).baseAddress, &observed,
                                     cert, key, timeoutMs)
                             }
                         }
-                        return punktfunk_connect_ex5(
+                        return punktfunk_connect_ex6(
                             cs, port, width, height, refreshHz, compositor.rawValue,
-                            gamepad.rawValue, bitrateKbps, videoCaps, launch,
+                            gamepad.rawValue, bitrateKbps, videoCaps, audioChannels, launch,
                             nil, &observed, cert, key, timeoutMs)
                     }
                 }
@@ -320,6 +327,9 @@ public final class PunktfunkConnection {
         colorMatrix = mtx
         colorFullRange = fullRange != 0
         bitDepth = depth
+        var ac: UInt8 = 2
+        _ = punktfunk_connection_audio_channels(handle, &ac)
+        resolvedAudioChannels = ac
     }
 
     /// A bandwidth speed-test measurement (see `startSpeedTest`). Partial until `done`.
@@ -468,6 +478,50 @@ public final class PunktfunkConnection {
         }
     }
 
+    /// One decoded audio frame from `nextAudioPcm`: interleaved 32-bit float at 48 kHz, in the
+    /// canonical wire channel order FL FR FC LFE RL RR SL SR (the first `channels`).
+    public struct AudioPCM: Sendable {
+        /// Interleaved f32 samples (`frameCount * channels` long), wire channel order.
+        public let samples: [Float]
+        /// Samples per channel.
+        public let frameCount: Int
+        /// Channel count (2/6/8) — `resolvedAudioChannels`.
+        public let channels: Int
+        public let ptsNs: UInt64
+        public let seq: UInt32
+    }
+
+    /// Pull the next audio frame, **decoded in-core** to interleaved f32 PCM — Apple's AudioToolbox
+    /// Opus path is stereo-only, so surround (and, for uniformity, stereo too) is decoded by the
+    /// Rust core (libopus multistream) and handed back as PCM. nil on timeout, throws `.closed` once
+    /// the session ended. Drain from a dedicated audio thread (do NOT also call `nextAudio` — they
+    /// share the underlying queue). The returned `samples` are copied out, so the buffer is owned.
+    public func nextAudioPcm(timeoutMs: UInt32 = 100) throws -> AudioPCM? {
+        audioLock.lock()
+        defer { audioLock.unlock() }
+        guard let h = liveHandle() else { throw PunktfunkClientError.closed }
+
+        var out = PunktfunkAudioPcm()
+        let rc = punktfunk_connection_next_audio_pcm(h, &out, timeoutMs)
+        switch rc {
+        case statusOK:
+            let channels = Int(out.channels)
+            let total = Int(out.frame_count) * channels
+            guard let base = out.samples, total > 0 else { return nil }
+            // Copy: the pointer borrows connection memory only until the next PCM call.
+            let samples = Array(UnsafeBufferPointer(start: base, count: total))
+            return AudioPCM(
+                samples: samples, frameCount: Int(out.frame_count),
+                channels: channels, ptsNs: out.pts_ns, seq: out.seq)
+        case statusNoFrame:
+            return nil
+        case statusClosed:
+            throw PunktfunkClientError.closed
+        default:
+            throw PunktfunkClientError.status(rc)
+        }
+    }
+
     /// Pull the next force-feedback update for the GCController haptics engine:
     /// `(pad, lowFrequency, highFrequency)` with 0...0xFFFF amplitudes, (0, 0) = stop.
     /// Drain from the (single) feedback thread, alongside `nextHidOutput`.

clients/apple/Sources/PunktfunkKit/Resources/LICENSE-APACHE.txt

@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
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+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
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clients/apple/Sources/PunktfunkKit/Resources/LICENSE-MIT.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 unom
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

clients/apple/Sources/PunktfunkKit/SessionAudio.swift

@@ -19,13 +19,13 @@ import os
 
 private let log = Logger(subsystem: "io.unom.punktfunk", category: "audio")
 
-/// SPSC-ish jitter ring (interleaved stereo float), drain thread → render callback.
+/// SPSC-ish jitter ring (interleaved float, `channels` per frame), drain thread → render
-/// The unfair lock is held for microseconds; fine at render-callback rates. Priming:
+/// callback. The unfair lock is held for microseconds; fine at render-callback rates. Priming:
 /// reads return silence until enough is buffered (at least `prefill`, and at least one
 /// packet more than the device's render quantum — large-buffer devices would otherwise
 /// chronically out-demand the prefill and oscillate prime → dropout → re-prime), and an
 /// underrun re-primes, concealing jitter as one short dip instead of sustained crackle.
-/// All counts stay even (whole stereo frames), so L/R interleave can never flip.
+/// All counts stay whole frames (multiples of `channels`), so the interleave can never slip.
 final class AudioRing: @unchecked Sendable {
     private var buf: [Float]
     private var readIdx = 0
@@ -34,12 +34,14 @@ final class AudioRing: @unchecked Sendable {
     private var renderQuantum = 0
     private let prefill: Int
     private let highWater: Int
+    private let channels: Int
     private let lock = OSAllocatedUnfairLock()
 
-    /// `capacity`/`prefill` in samples (interleaved — 2 per frame, both must be even).
+    /// `capacity`/`prefill` in samples (interleaved — `channels` per frame, both whole frames).
-    init(capacity: Int, prefill: Int) {
+    init(capacity: Int, prefill: Int, channels: Int) {
         buf = [Float](repeating: 0, count: capacity)
         self.prefill = prefill
+        self.channels = channels
         highWater = prefill * 4
     }
 
@@ -74,8 +76,8 @@ final class AudioRing: @unchecked Sendable {
         renderQuantum = max(renderQuantum, count)
         let available = writeIdx - readIdx
         if !primed {
-            // 480 samples = one 5 ms host packet of slack beyond the device's demand.
+            // One 5 ms host packet (240 frames × channels) of slack beyond the device's demand.
-            if available >= max(prefill, renderQuantum + 480) {
+            if available >= max(prefill, renderQuantum + 240 * channels) {
                 primed = true
             } else {
                 for i in 0..<count { out[i] = 0 }
@@ -113,10 +115,55 @@ private final class StopFlag: @unchecked Sendable {
 /// Render-block-owned scratch storage: freed exactly when the closure (and thus the
 /// last possible render call) is released — never racing CoreAudio.
 private final class ScratchBuffer {
-    let ptr = UnsafeMutablePointer<Float>.allocate(capacity: 8192 * 2)
+    // 8192 frames × up to 8 channels (7.1) — the render block caps `frames` at 8192.
+    let ptr = UnsafeMutablePointer<Float>.allocate(capacity: 8192 * 8)
     deinit { ptr.deallocate() }
 }
 
+/// CoreAudio channel layout for the canonical wire order FL FR FC LFE RL RR [SL SR]. nil for
+/// stereo (the standard layout is correct). For 5.1/7.1 we list explicit channel labels via
+/// `kAudioChannelLayoutTag_UseChannelDescriptions` — preset tags (DTS_5_1 etc.) don't reliably
+/// match Moonlight's order. NB the 7.1 mapping (verified against the WASAPI 0x63F + SPA orderings):
+/// wire idx 4-5 = RL/RR = the WAVE *back* pair → LeftSurround/RightSurround; idx 6-7 = SL/SR = the
+/// WAVE *side* pair → LeftSurroundDirect/RightSurroundDirect. (Using RearSurround* for 6-7 would
+/// swap side/back vs the Windows/Linux clients.)
+private func wireChannelLayout(channels: Int) -> AVAudioChannelLayout? {
+    let labels: [AudioChannelLabel]
+    switch channels {
+    case 6:
+        labels = [
+            kAudioChannelLabel_Left, kAudioChannelLabel_Right, kAudioChannelLabel_Center,
+            kAudioChannelLabel_LFEScreen, kAudioChannelLabel_LeftSurround,
+            kAudioChannelLabel_RightSurround,
+        ]
+    case 8:
+        labels = [
+            kAudioChannelLabel_Left, kAudioChannelLabel_Right, kAudioChannelLabel_Center,
+            kAudioChannelLabel_LFEScreen,
+            kAudioChannelLabel_LeftSurround, kAudioChannelLabel_RightSurround, // wire RL/RR (back)
+            kAudioChannelLabel_LeftSurroundDirect, kAudioChannelLabel_RightSurroundDirect, // wire SL/SR (side)
+        ]
+    default:
+        return nil
+    }
+    let size = MemoryLayout<AudioChannelLayout>.size
+        + (labels.count - 1) * MemoryLayout<AudioChannelDescription>.stride
+    let raw = UnsafeMutableRawPointer.allocate(byteCount: size, alignment: 16)
+    defer { raw.deallocate() }
+    let layout = raw.bindMemory(to: AudioChannelLayout.self, capacity: 1)
+    layout.pointee.mChannelLayoutTag = kAudioChannelLayoutTag_UseChannelDescriptions
+    layout.pointee.mChannelBitmap = AudioChannelBitmap(rawValue: 0)
+    layout.pointee.mNumberChannelDescriptions = UInt32(labels.count)
+    let descs = UnsafeMutableBufferPointer(
+        start: &layout.pointee.mChannelDescriptions, count: labels.count)
+    for (i, lbl) in labels.enumerated() {
+        descs[i] = AudioChannelDescription(
+            mChannelLabel: lbl, mChannelFlags: AudioChannelFlags(rawValue: 0),
+            mCoordinates: (0, 0, 0))
+    }
+    return AVAudioChannelLayout(layout: layout)
+}
+
 public final class SessionAudio {
     private let connection: PunktfunkConnection
     private let flag = StopFlag()
@@ -229,9 +276,13 @@ public final class SessionAudio {
     // MARK: - Playback (host → speaker)
 
     private func startPlayback(speakerUID: String) {
-        // 1 s of interleaved stereo capacity, ~20 ms prefill: four 5 ms host packets of
+        // Build the playback layout from the host-RESOLVED channel count (never the request):
-        // jitter absorption before the first sample plays.
+        // 2 = stereo / 6 = 5.1 / 8 = 7.1, canonical wire order FL FR FC LFE RL RR SL SR.
-        let ring = AudioRing(capacity: 96_000, prefill: 1920)
+        let channels = Int(connection.resolvedAudioChannels)
+        // 1 s interleaved capacity, ~20 ms prefill (four 5 ms host packets of jitter absorption
+        // before the first sample plays), both scaled by the channel count.
+        let ring = AudioRing(
+            capacity: 48_000 * channels, prefill: 960 * channels, channels: channels)
 
         let engine = AVAudioEngine()
         #if os(macOS)
@@ -247,21 +298,32 @@ public final class SessionAudio {
         }
         #endif
 
-        // Engine-native deinterleaved float; the render block deinterleaves from the ring.
+        // Engine-native deinterleaved float; the render block deinterleaves from the ring. Surround
-        guard let format = AVAudioFormat(standardFormatWithSampleRate: 48_000, channels: 2)
+        // uses an explicit wire-order channel layout; the mixer downmixes to the output device when
-        else { return }
+        // it has fewer speakers (e.g. an iPhone's stereo built-ins). (Explicit if/else rather than
+        // map/flatMap so it's correct whether the channelLayout initializer is failable or not.)
+        var format: AVAudioFormat?
+        if channels == 2 {
+            format = AVAudioFormat(standardFormatWithSampleRate: 48_000, channels: 2)
+        } else if let layout = wireChannelLayout(channels: channels) {
+            format = AVAudioFormat(standardFormatWithSampleRate: 48_000, channelLayout: layout)
+        }
+        guard let format else {
+            log.error("could not build \(channels)-channel audio format — audio disabled")
+            return
+        }
         let scratch = ScratchBuffer() // block-owned; freed with the closure
         let source = AVAudioSourceNode(format: format) { _, _, frameCount, abl -> OSStatus in
             let frames = Int(frameCount)
             guard frames <= 8192 else { return kAudioUnitErr_TooManyFramesToProcess }
-            ring.read(into: scratch.ptr, count: frames * 2)
+            ring.read(into: scratch.ptr, count: frames * channels)
             let buffers = UnsafeMutableAudioBufferListPointer(abl)
-            if buffers.count >= 2,
+            // Deinterleave the wire-order interleaved ring into the engine's per-channel buses.
-               let left = buffers[0].mData?.assumingMemoryBound(to: Float.self),
+            if buffers.count >= channels {
-               let right = buffers[1].mData?.assumingMemoryBound(to: Float.self) {
+                for ch in 0..<channels {
-                for f in 0..<frames {
+                    if let dst = buffers[ch].mData?.assumingMemoryBound(to: Float.self) {
-                    left[f] = scratch.ptr[f * 2]
+                        for f in 0..<frames { dst[f] = scratch.ptr[f * channels + ch] }
-                    right[f] = scratch.ptr[f * 2 + 1]
+                    }
                 }
             }
             return noErr
@@ -292,29 +354,20 @@ public final class SessionAudio {
         stateLock.unlock()
         let thread = Thread { [connection, flag, drainDone] in
             defer { drainDone.signal() }
-            guard let decoder = try? OpusDecoder(framesPerPacket: 240),
+            // Decode happens IN-CORE (libopus multistream) — AudioToolbox's Opus path is
-                  let pcm = AVAudioPCMBuffer(
+            // stereo-only — and is handed back as interleaved f32 PCM in wire channel order.
-                      pcmFormat: decoder.pcmFormat, frameCapacity: 5760)
-            else {
-                log.error("Opus decoder unavailable — audio playback disabled")
-                return
-            }
             while !flag.isStopped {
-                let packet: AudioPacket?
+                let pcm: PunktfunkConnection.AudioPCM?
                 do {
-                    packet = try connection.nextAudio(timeoutMs: 100)
+                    pcm = try connection.nextAudioPcm(timeoutMs: 100)
                 } catch {
                     break // session closed
                 }
-                guard let packet else { continue }
+                guard let pcm, pcm.frameCount > 0 else { continue }
-                do {
+                pcm.samples.withUnsafeBufferPointer { p in
-                    let frames = try decoder.decode(packet.data, into: pcm)
+                    if let base = p.baseAddress {
-                    if frames > 0, let p = pcm.floatChannelData?[0] {
+                        ring.write(base, count: pcm.frameCount * pcm.channels)
-                        ring.write(p, count: Int(frames) * 2)
                     }
-                } catch {
-                    // One corrupt packet ≠ a dead stream; skip it.
-                    log.warning("audio decode failed: \(error.localizedDescription)")
                 }
             }
         }

clients/decky/README.md

@@ -45,8 +45,9 @@ Gaming Mode automatically.
 | `src/steam.ts` | Steam-shortcut launch (`AddShortcut` / `SetAppLaunchOptions` / `RunGame`) — the focus-correct stream start. |
 | `src/backend.ts` | Typed `callable` bridges to `main.py`. |
 | `bin/punktfunkrun.sh` | The launch wrapper the Steam shortcut targets (so the window is focusable). |
-| `main.py` | Backend: `discover` / `pair` / `runner_info` / `get_settings` / `set_settings` / `kill_stream`. |
+| `main.py` | Backend: `discover` / `pair` / `runner_info` / `get_settings` / `set_settings` / `kill_stream` / `check_update`. |
 | `plugin.json` | Decky plugin manifest. |
+| `update.json` | CI-baked `{channel, manifest}` — where `check_update()` polls (absent on dev builds). |
 | `decky.pyi` | Type stub for the injected `decky` module (vendored from the template). |
 
 ### Discovery (`discover()`)
@@ -140,6 +141,40 @@ shows up in the Quick Access Menu.
 > [`../../packaging/flatpak/README.md`](../../packaging/flatpak/README.md)) — install that on
 > the Deck too, or the panel's Connect surfaces a `client-not-found` error.
 
+## Updating (self-update, no store)
+
+The plugin updates itself without the official Decky store. CI (`decky.yml`) publishes a tiny
+per-channel `manifest.json` next to the zip in the Gitea registry:
+
+```json
+{"version":"0.3.123","artifact":".../punktfunk-decky/0.3.123/punktfunk.zip","sha256":"…"}
+```
+
+and bakes an `update.json` (`{channel, manifest}`) into the plugin so it knows which channel it was
+installed from. The backend `check_update()` reads the **installed** version from `package.json` —
+the value Decky itself reports (it does **not** read `plugin.json`) — fetches the channel manifest,
+and compares. When a newer build exists the frontend shows an **Update to vX** button that drives
+Decky Loader's own install RPC:
+
+```ts
+window.DeckyBackend.callable("utilities/install_plugin")(artifact, "punktfunk", version, hash, /*UPDATE=*/2)
+```
+
+The loader (root) downloads the immutable per-version zip, **SHA-256-verifies** it against `hash`,
+replaces `~/homebrew/plugins/punktfunk`, and hot-reloads — the unprivileged backend never writes the
+root-owned plugins dir itself. `window.DeckyBackend` / `utilities/install_plugin` are loader
+internals (not `@decky/api`), so every access is guarded; missing them, the button falls back to a
+toast pointing at **Install Plugin from URL**.
+
+> CI stamps a **plain numeric** semver per channel (`0.3.<run>` canary, `X.Y.Z` stable) into
+> `package.json`. Decky's `compare-versions` orders pre-release identifiers lexically (so `ci10 < ci9`)
+> — a `-ciN` suffix would mis-detect updates.
+
+**Optional — native Updates tab:** Decky's store is single-source (a custom store URL *replaces* the
+official catalog), so punktfunk doesn't ship one by default. A user who wants the native update badge
+can point Decky → Settings → **Custom store** at a punktfunk-only store JSON — not recommended if you
+use other plugins, since it hides the official catalog.
+
 ## Limitations / next steps
 
 - **Needs on-Deck validation in Gaming Mode**: the Steam-shortcut launch (`AddShortcut` /

clients/decky/bin/punktfunkrun.sh

@@ -31,4 +31,6 @@ fi
 echo "punktfunkrun: streaming $APPID --connect $PF_HOST" >&2
 # exec so the flatpak client IS the game process — when it exits, Steam ends the "game" and
 # Gaming Mode reclaims focus automatically (no manual refocus needed).
-exec "$FLATPAK" run --arch=x86_64 "$APPID" --connect "$PF_HOST"
+# --fullscreen: present the stream chrome-less and fullscreen (the client also auto-detects the
+# Deck/gamescope env, and ignores the flag harmlessly on older builds that predate it).
+exec "$FLATPAK" run --arch=x86_64 "$APPID" --connect "$PF_HOST" --fullscreen

clients/decky/main.py

@@ -17,6 +17,8 @@ The backend's jobs are the things Steam can't do:
 * **get_settings() / set_settings()** — read/write the flatpak client's stream settings JSON
   (resolution / bitrate / gamepad), so the Deck UI configures the stream the client reads.
 * **kill_stream()** — force-stop a wedged stream (``flatpak kill``).
+* **check_update()** — poll the registry's per-channel ``manifest.json`` and report whether a
+  newer build is available (the frontend then drives Decky's own install RPC to apply it).
 
 The TXT-record keys parsed (``proto`` / ``fp`` / ``pair`` / ``id``) are defined by the host
 advert in ``crates/punktfunk-host/src/discovery.rs``.
@@ -26,7 +28,10 @@ import asyncio
 import json
 import os
 import shutil
+import ssl
 import stat
+import time
+import urllib.request
 from pathlib import Path
 
 import decky
@@ -37,22 +42,99 @@ APP_ID = "io.unom.Punktfunk"
 # Service type advertised by punktfunk/1 hosts (matches NATIVE_SERVICE in the Rust host).
 SERVICE_TYPE = "_punktfunk._udp"
 
-# The flatpak client persists identity / known-hosts / settings under HOME/.config/punktfunk;
+# The flatpak client persists identity / known-hosts / settings under HOME/.config/punktfunk.
-# inside the flatpak sandbox HOME is ~/.var/app/<APP_ID>, so the real on-disk location is this.
+# The sandbox HOME resolves to the REAL user home (== DECKY_USER_HOME), NOT the per-app
-# The backend writes settings here so the (sandboxed) client reads them.
+# ~/.var/app/<APP_ID> dir — verified on-device (`flatpak run … sh -c 'echo $HOME'` prints
+# /home/deck, and the manifest's `--filesystem=~/.config/punktfunk` grants exactly that path;
+# we also pass HOME=DECKY_USER_HOME into `flatpak run`, see _flatpak_env). Pointing here is what
+# lets plugin settings actually reach the client AND lets us read the client's known-hosts to
+# tell whether THIS device is already paired with a given host.
 def _client_config_dir() -> Path:
-    return Path(decky.DECKY_USER_HOME) / ".var" / "app" / APP_ID / ".config" / "punktfunk"
+    return Path(decky.DECKY_USER_HOME) / ".config" / "punktfunk"
 
 
 def _settings_path() -> Path:
     return _client_config_dir() / "client-gtk-settings.json"
 
 
+def _paired_fingerprints() -> set[str]:
+    """Host cert fingerprints (lowercase hex) this client has PIN-paired, from the client's
+    known-hosts store. Keyed by fingerprint so it survives a host changing IP address."""
+    try:
+        data = json.loads((_client_config_dir() / "client-known-hosts.json").read_text())
+    except (OSError, json.JSONDecodeError):
+        return set()
+    hosts = data.get("hosts", []) if isinstance(data, dict) else []
+    return {
+        h["fp_hex"].lower()
+        for h in hosts
+        if isinstance(h, dict) and h.get("paired") and isinstance(h.get("fp_hex"), str)
+    }
+
+
 def _runner_path() -> str:
     """Absolute path to the launch wrapper shipped with the plugin (bin/punktfunkrun.sh)."""
     return str(Path(decky.DECKY_PLUGIN_DIR) / "bin" / "punktfunkrun.sh")
 
 
+# ----------------------------------------------------------------------------------------
+# Self-update check (no Decky store). The plugin is distributed via "Install Plugin from
+# URL" pointing at our Gitea generic registry, so the official store never sees it and
+# can't offer updates. Instead the backend polls a tiny per-channel ``manifest.json`` the
+# CI publishes next to the zip, compares it to the installed version, and the frontend
+# offers a one-tap update that drives Decky's own (root, privileged) install RPC. The
+# channel + manifest URL are baked into ``update.json`` by CI (.gitea/workflows/decky.yml);
+# a dev/sideload build has no ``update.json`` and update checks are simply disabled.
+_UPDATE_TTL_S = 1800.0  # cache a successful check for 30 min (the QAM remounts often)
+_update_cache: dict = {"at": 0.0, "data": None}
+
+
+def _update_config() -> dict:
+    """The CI-baked ``{channel, manifest}`` next to the plugin (absent on dev builds)."""
+    try:
+        return json.loads((Path(decky.DECKY_PLUGIN_DIR) / "update.json").read_text())
+    except (OSError, json.JSONDecodeError):
+        return {}
+
+
+def _installed_version() -> str:
+    """The version Decky itself reports for this plugin — it reads ``package.json`` (NOT
+    plugin.json), so the CI stamps the build version there."""
+    try:
+        pkg = json.loads((Path(decky.DECKY_PLUGIN_DIR) / "package.json").read_text())
+        return str(pkg.get("version", "0.0.0"))
+    except (OSError, json.JSONDecodeError):
+        return "0.0.0"
+
+
+def _semver_tuple(v: str) -> tuple[int, int, int]:
+    """A tolerant (major, minor, patch) tuple for ``>`` comparison. We control the version
+    format (plain numeric ``X.Y.Z`` on both channels), so leading-int-per-component is
+    enough; any pre-release suffix is dropped before comparing."""
+    parts: list[int] = []
+    for comp in str(v).split("-", 1)[0].split(".")[:3]:
+        digits = ""
+        for ch in comp:
+            if ch.isdigit():
+                digits += ch
+            else:
+                break
+        parts.append(int(digits) if digits else 0)
+    while len(parts) < 3:
+        parts.append(0)
+    return (parts[0], parts[1], parts[2])
+
+
+def _fetch_json(url: str, timeout: float = 8.0) -> dict:
+    """Blocking HTTPS GET of a small JSON document (run in an executor)."""
+    req = urllib.request.Request(
+        url, headers={"Accept": "application/json", "User-Agent": "punktfunk-decky"}
+    )
+    ctx = ssl.create_default_context()
+    with urllib.request.urlopen(req, timeout=timeout, context=ctx) as resp:
+        return json.loads(resp.read().decode("utf-8", errors="replace"))
+
+
 def _flatpak() -> str | None:
     return shutil.which("flatpak") or (
         "/usr/bin/flatpak" if Path("/usr/bin/flatpak").exists() else None
@@ -179,6 +261,13 @@ class Plugin:
         if stderr:
             decky.logger.debug("avahi-browse stderr: %s", stderr.decode(errors="replace"))
         hosts = _parse_avahi_browse(stdout.decode(errors="replace"))
+        # Mark which hosts THIS device has already paired (by cert fingerprint), so the UI can
+        # show "Stream" instead of "Pair" — the mDNS `pair` field is the host's policy, not our
+        # per-device pairing state.
+        paired = _paired_fingerprints()
+        for h in hosts:
+            fp = h.get("fp") or ""
+            h["paired"] = bool(fp) and fp.lower() in paired
         decky.logger.info("discovered %d punktfunk host(s)", len(hosts))
         return hosts
 
@@ -279,6 +368,54 @@ class Plugin:
             return {"ok": False}
         return {"ok": True}
 
+    async def check_update(self, force: bool = False) -> dict:
+        """Is a newer build available in our registry? Compares the installed version
+        (``package.json``) against the per-channel ``manifest.json`` the CI publishes, and
+        returns everything the frontend needs to drive Decky's install RPC. Non-fatal: any
+        failure (no channel baked in, network down) returns ``update_available: False``.
+        """
+        current = _installed_version()
+        cfg = _update_config()
+        result = {
+            "current": current,
+            "latest": current,
+            "artifact": "",
+            "hash": "",
+            "channel": str(cfg.get("channel", "")),
+            "update_available": False,
+        }
+
+        manifest_url = cfg.get("manifest")
+        if not manifest_url:
+            result["error"] = "update-channel-unknown"  # dev / sideloaded build
+            return result
+
+        now = time.monotonic()
+        cached = _update_cache["data"]
+        if not force and cached and (now - _update_cache["at"]) < _UPDATE_TTL_S:
+            return cached
+
+        try:
+            loop = asyncio.get_running_loop()
+            manifest = await loop.run_in_executor(None, _fetch_json, manifest_url)
+        except Exception as exc:  # noqa: BLE001
+            decky.logger.warning("update check failed: %s", exc)
+            result["error"] = "fetch-failed"
+            return result  # transient — don't cache, retry next open
+
+        latest = str(manifest.get("version", current))
+        result["latest"] = latest
+        result["artifact"] = str(manifest.get("artifact", ""))
+        result["hash"] = str(manifest.get("sha256", ""))
+        result["update_available"] = bool(result["artifact"]) and (
+            _semver_tuple(latest) > _semver_tuple(current)
+        )
+        if result["update_available"]:
+            decky.logger.info("update available: %s -> %s (%s)", current, latest, result["channel"])
+        _update_cache["at"] = now
+        _update_cache["data"] = result
+        return result
+
     # ---- Decky lifecycle ----
 
     async def _main(self):

clients/decky/src/backend.ts

@@ -5,8 +5,9 @@ export interface Host {
   name: string;
   host: string;
   port: number;
-  pair: string; // "required" | "optional"
+  pair: string; // "required" | "optional" — the HOST's policy
   fp: string;
+  paired: boolean; // whether THIS device has already PIN-paired this host (by fingerprint)
 }
 
 export interface PairResult {
@@ -32,6 +33,16 @@ export interface StreamSettings {
   mic_enabled: boolean;
 }
 
+export interface UpdateInfo {
+  current: string; // installed version (package.json)
+  latest: string; // newest version in our registry for this channel
+  artifact: string; // immutable zip URL Decky should install
+  hash: string; // sha256 of that zip (Decky verifies it)
+  channel: string; // "latest" (stable) | "canary"
+  update_available: boolean;
+  error?: string; // "update-channel-unknown" (dev build) | "fetch-failed"
+}
+
 export const discover = callable<[], Host[]>("discover");
 export const pair = callable<
   [host: string, port: number, pin: string, name: string],
@@ -43,3 +54,4 @@ export const setSettings = callable<[settings: StreamSettings], { ok: boolean }>
   "set_settings",
 );
 export const killStream = callable<[], { ok: boolean }>("kill_stream");
+export const checkUpdate = callable<[force: boolean], UpdateInfo>("check_update");

clients/decky/src/index.tsx

@@ -10,12 +10,22 @@ import {
   PanelSectionRow,
   SliderField,
   Spinner,
+  Tabs,
   ToggleField,
   showModal,
   staticClasses,
 } from "@decky/ui";
 import { definePlugin, routerHook, toaster } from "@decky/api";
-import { FC, useCallback, useEffect, useState } from "react";
+import {
+  Component,
+  CSSProperties,
+  ErrorInfo,
+  FC,
+  ReactNode,
+  useCallback,
+  useEffect,
+  useState,
+} from "react";
 import {
   FaTv,
   FaSyncAlt,
@@ -23,19 +33,130 @@ import {
   FaLockOpen,
   FaPlay,
   FaArrowLeft,
+  FaDownload,
 } from "react-icons/fa";
 import {
   discover,
   getSettings,
   pair,
   setSettings,
+  checkUpdate,
   Host,
   StreamSettings,
+  UpdateInfo,
 } from "./backend";
 import { launchStream } from "./steam";
 
 const ROUTE = "/punktfunk";
 
+// Decky Loader exposes its already-authenticated WSRouter as a global. This is NOT part of
+// @decky/api (it's a loader internal), so we treat it as optional and guard every use — on a
+// loader without it we fall back to manual "Install Plugin from URL". We use it to drive
+// Decky's own privileged install path (the root loader does the download + SHA-256 verify +
+// extract + hot-reload), which is the only way a plugin can update itself: ~/homebrew/plugins
+// is root-owned, so our unprivileged backend can't swap its own files.
+declare global {
+  interface Window {
+    DeckyBackend?: {
+      callable: (route: string) => (...args: unknown[]) => Promise<unknown>;
+    };
+  }
+}
+
+// PluginInstallType.UPDATE in decky-loader's browser.py (INSTALL=0/REINSTALL=1/UPDATE=2/…).
+const INSTALL_TYPE_UPDATE = 2;
+
+// ----------------------------------------------------------------------------------------
+// Error boundary — contains ANY render failure in our UI so a single bad render can never take
+// down the whole Quick Access "Decky" section (Decky's tab-level boundary shows the generic
+// "Something went wrong while displaying this content" for the entire tab when one plugin
+// throws). The realistic trigger is a future Steam client update that makes a @decky/ui
+// component resolve to `undefined` (React then throws "Element type is invalid"). The fallback
+// is built from ONLY plain DOM elements + inline styles, so it cannot itself depend on a
+// (possibly broken) Steam-internal component — it is guaranteed to render.
+// ----------------------------------------------------------------------------------------
+class PluginErrorBoundary extends Component<
+  { children: ReactNode },
+  { error: Error | null }
+> {
+  state: { error: Error | null } = { error: null };
+
+  static getDerivedStateFromError(error: Error) {
+    return { error };
+  }
+
+  componentDidCatch(error: Error, info: ErrorInfo) {
+    // Surface it for diagnosis, but never rethrow — containment is the whole point.
+    // eslint-disable-next-line no-console
+    console.error("[punktfunk] contained UI render error:", error, info?.componentStack);
+  }
+
+  render() {
+    const { error } = this.state;
+    if (!error) return this.props.children;
+    return (
+      <div style={{ padding: "1em", lineHeight: 1.45 }}>
+        <div style={{ fontWeight: "bold", marginBottom: "0.4em" }}>
+          punktfunk couldn’t draw this view
+        </div>
+        <div style={{ opacity: 0.8, marginBottom: "0.6em" }}>
+          The plugin hit a display error — your Steam Deck is fine. Reload punktfunk from
+          Decky&apos;s plugin list, or update the plugin.
+        </div>
+        <div
+          style={{
+            opacity: 0.55,
+            fontFamily: "monospace",
+            fontSize: "0.8em",
+            wordBreak: "break-word",
+          }}
+        >
+          {String(error?.message ?? error)}
+        </div>
+      </div>
+    );
+  }
+}
+
+// Checks our registry for a newer build on mount (the backend caches + is non-fatal offline).
+function useUpdate() {
+  const [info, setInfo] = useState<UpdateInfo | null>(null);
+  useEffect(() => {
+    void checkUpdate(false)
+      .then(setInfo)
+      .catch(() => {});
+  }, []);
+  return info;
+}
+
+async function applyUpdate(info: UpdateInfo) {
+  try {
+    const backend = window.DeckyBackend;
+    if (backend?.callable) {
+      // Fire-and-forget: the loader reinstalls + reloads THIS plugin, tearing the panel down
+      // before any result could arrive — so never await it. Decky shows its own confirm prompt.
+      void backend.callable("utilities/install_plugin")(
+        info.artifact,
+        "punktfunk",
+        info.latest,
+        info.hash,
+        INSTALL_TYPE_UPDATE,
+      );
+      toaster.toast({
+        title: "punktfunk",
+        body: `Updating to v${info.latest}… confirm the Decky prompt.`,
+      });
+      return;
+    }
+  } catch {
+    // fall through to the manual path
+  }
+  toaster.toast({
+    title: "punktfunk",
+    body: "Update from Decky → Developer → Install Plugin from URL.",
+  });
+}
+
 // ----------------------------------------------------------------------------------------
 // Discovery hook — shared by the QAM panel and the full page.
 // ----------------------------------------------------------------------------------------
@@ -255,20 +376,24 @@ const SettingsSection: FC = () => {
 // One host row on the full page.
 // ----------------------------------------------------------------------------------------
 const HostRow: FC<{ host: Host }> = ({ host }) => {
-  const pairRequired = host.pair === "required";
+  // The host's policy is `pair=required`, but if THIS device is already paired we don't need to
+  // pair again — show it as trusted and go straight to Stream.
+  const needsPair = host.pair === "required" && !host.paired;
   return (
     <Field
       label={
         <span style={{ display: "inline-flex", alignItems: "center", gap: "0.4em" }}>
-          {pairRequired ? <FaLock /> : <FaLockOpen />}
+          {needsPair ? <FaLock /> : <FaLockOpen />}
           {host.name}
         </span>
       }
-      description={`${host.host}:${host.port}${pairRequired ? " · pairing required" : ""}`}
+      description={`${host.host}:${host.port}${
+        needsPair ? " · pairing required" : host.paired ? " · paired" : ""
+      }`}
       childrenContainerWidth="max"
     >
       <Focusable style={{ display: "flex", gap: "0.5em" }}>
-        {pairRequired && (
+        {needsPair && (
           <DialogButton
             style={{ minWidth: "5em" }}
             onClick={() =>
@@ -288,31 +413,40 @@ const HostRow: FC<{ host: Host }> = ({ host }) => {
 };
 
 // ----------------------------------------------------------------------------------------
-// The fullscreen page (registered as the /punktfunk route).
+// The fullscreen page (registered as the /punktfunk route) — a tabbed Hosts / Settings view.
 // ----------------------------------------------------------------------------------------
-const PunktfunkPage: FC = () => {
-  const { hosts, scanning, refresh } = useHosts();
 
-  return (
+// Bottom inset so the last control clears Gaming Mode's footer hint bar. Routed pages render
-    <div
+// *under* that bar otherwise — that's why the last Stream-settings row was getting hidden. The
-      style={{
+// value is generous on purpose (and harmless where the tab area already insets); tune to taste.
-        marginTop: "40px",
+const SAFE_BOTTOM = "80px";
-        height: "calc(100% - 40px)",
+
+// Each tab is its own scroll area so long content is always reachable above the footer.
+const tabScroll: CSSProperties = {
+  height: "100%",
   overflowY: "auto",
-        padding: "0 2.5em 2.5em",
+  padding: "0.5em 2.5em",
-      }}
+  paddingBottom: SAFE_BOTTOM,
+  boxSizing: "border-box",
+};
+
+const HostsTab: FC<{
+  hosts: Host[];
+  scanning: boolean;
+  refresh: () => void;
+}> = ({ hosts, scanning, refresh }) => (
+  <div style={tabScroll}>
+    <Field
+      label="Discover"
+      description={
+        scanning
+          ? "Scanning the LAN…"
+          : `${hosts.length} host${hosts.length === 1 ? "" : "s"} on your network`
+      }
+      childrenContainerWidth="max"
+      bottomSeparator={hosts.length ? "standard" : "none"}
     >
-      <Focusable style={{ display: "flex", alignItems: "center", gap: "1em", marginBottom: "1em" }}>
+      <DialogButton style={{ minWidth: "8em" }} disabled={scanning} onClick={refresh}>
-        <DialogButton
-          style={{ width: "3em", minWidth: "3em" }}
-          onClick={() => Navigation.NavigateBack()}
-        >
-          <FaArrowLeft />
-        </DialogButton>
-        <div className={staticClasses.Title} style={{ flex: 1 }}>
-          punktfunk
-        </div>
-        <DialogButton style={{ width: "10em" }} disabled={scanning} onClick={refresh}>
         {scanning ? (
           <Spinner style={{ height: "1em", marginRight: "0.5em" }} />
         ) : (
@@ -320,21 +454,89 @@ const PunktfunkPage: FC = () => {
         )}
         {scanning ? "Scanning…" : "Refresh"}
       </DialogButton>
-      </Focusable>
+    </Field>
 
-      <div style={{ fontSize: "1.1em", fontWeight: "bold", margin: "0.5em 0" }}>Hosts</div>
     {hosts.length === 0 && !scanning && (
-        <Field focusable={false}>No hosts discovered on the LAN.</Field>
+      <Field
+        focusable={false}
+        description="No punktfunk hosts found. Make sure a host is running on the same network."
+      >
+        No hosts found
+      </Field>
     )}
     {hosts.map((h) => (
       <HostRow key={h.fp || `${h.host}:${h.port}`} host={h} />
     ))}
-
-      <div style={{ fontSize: "1.1em", fontWeight: "bold", margin: "1.5em 0 0.5em" }}>
-        Stream settings
   </div>
+);
+
+const SettingsTab: FC = () => (
+  <div style={tabScroll}>
     <SettingsSection />
   </div>
+);
+
+const PunktfunkPage: FC = () => {
+  const { hosts, scanning, refresh } = useHosts();
+  const update = useUpdate();
+  const [tab, setTab] = useState("hosts");
+
+  return (
+    <div
+      style={{
+        marginTop: "40px",
+        height: "calc(100% - 40px)",
+        display: "flex",
+        flexDirection: "column",
+      }}
+    >
+      <Focusable
+        style={{
+          display: "flex",
+          alignItems: "center",
+          gap: "1em",
+          padding: "0 2.5em",
+          marginBottom: "0.4em",
+          flexShrink: 0,
+        }}
+      >
+        <DialogButton
+          style={{ width: "3em", minWidth: "3em", padding: 0 }}
+          onClick={() => Navigation.NavigateBack()}
+        >
+          <FaArrowLeft />
+        </DialogButton>
+        <div className={staticClasses?.Title} style={{ flex: 1, margin: 0 }}>
+          punktfunk
+        </div>
+        {update?.update_available && (
+          <DialogButton style={{ minWidth: "9em" }} onClick={() => applyUpdate(update)}>
+            <FaDownload style={{ marginRight: "0.4em" }} />
+            Update v{update.latest}
+          </DialogButton>
+        )}
+      </Focusable>
+
+      <div style={{ flex: 1, minHeight: 0 }}>
+        <Tabs
+          activeTab={tab}
+          onShowTab={(id: string) => setTab(id)}
+          autoFocusContents
+          tabs={[
+            {
+              id: "hosts",
+              title: "Hosts",
+              content: <HostsTab hosts={hosts} scanning={scanning} refresh={refresh} />,
+            },
+            {
+              id: "settings",
+              title: "Settings",
+              content: <SettingsTab />,
+            },
+          ]}
+        />
+      </div>
+    </div>
   );
 };
 
@@ -343,9 +545,25 @@ const PunktfunkPage: FC = () => {
 // ----------------------------------------------------------------------------------------
 const QamPanel: FC = () => {
   const { hosts, scanning, refresh } = useHosts();
+  const update = useUpdate();
 
   return (
     <>
+      {update?.update_available && (
+        <PanelSection title="Update">
+          <PanelSectionRow>
+            <ButtonItem
+              layout="below"
+              onClick={() => applyUpdate(update)}
+              label={`v${update.current} → v${update.latest}`}
+            >
+              <FaDownload style={{ marginRight: "0.5em" }} />
+              Update punktfunk
+            </ButtonItem>
+          </PanelSectionRow>
+        </PanelSection>
+      )}
+
       <PanelSection title="punktfunk">
         <PanelSectionRow>
           <ButtonItem
@@ -378,25 +596,25 @@ const QamPanel: FC = () => {
           </PanelSectionRow>
         )}
         {hosts.map((h) => {
-          const pairRequired = h.pair === "required";
+          const needsPair = h.pair === "required" && !h.paired;
           return (
             <PanelSectionRow key={h.fp || `${h.host}:${h.port}`}>
               <ButtonItem
                 layout="below"
                 onClick={() =>
-                  pairRequired
+                  needsPair
                     ? showModal(<PairModal host={h} onPaired={() => startStream(h)} />)
                     : startStream(h)
                 }
                 label={
                   <span style={{ display: "inline-flex", alignItems: "center", gap: "0.4em" }}>
-                    {pairRequired ? <FaLock /> : <FaLockOpen />}
+                    {needsPair ? <FaLock /> : <FaLockOpen />}
                     {h.name}
                   </span>
                 }
-                description={`${h.host}:${h.port}`}
+                description={`${h.host}:${h.port}${h.paired ? " · paired" : ""}`}
               >
-                {pairRequired ? "Pair & Stream" : "Stream"}
+                {needsPair ? "Pair & Stream" : "Stream"}
               </ButtonItem>
             </PanelSectionRow>
           );
@@ -406,12 +624,25 @@ const QamPanel: FC = () => {
   );
 };
 
+// Full page behind the boundary — registered as the /punktfunk route.
+const PunktfunkRoute: FC = () => (
+  <PluginErrorBoundary>
+    <PunktfunkPage />
+  </PluginErrorBoundary>
+);
+
 export default definePlugin(() => {
-  routerHook.addRoute(ROUTE, PunktfunkPage, { exact: true });
+  routerHook.addRoute(ROUTE, PunktfunkRoute, { exact: true });
   return {
     name: "punktfunk",
-    titleView: <div className={staticClasses.Title}>punktfunk</div>,
+    // `staticClasses?.Title` is guarded so a future client that drops the export can't throw
-    content: <QamPanel />,
+    // at plugin-load time (an error boundary only catches render-time, not load-time, errors).
+    titleView: <div className={staticClasses?.Title}>punktfunk</div>,
+    content: (
+      <PluginErrorBoundary>
+        <QamPanel />
+      </PluginErrorBoundary>
+    ),
     icon: <FaTv />,
     onDismount() {
       routerHook.removeRoute(ROUTE);

clients/decky/src/steam.ts

@@ -24,12 +24,31 @@ declare const SteamClient: {
     SetShortcutExe(appId: number, exe: string): void;
     SetShortcutStartDir(appId: number, dir: string): void;
     SetAppLaunchOptions(appId: number, options: string): void;
-    SetAppHidden(appId: number, hidden: boolean): void;
     RunGame(gameId: string, _unused: string, _i: number, _j: number): void;
     TerminateApp(gameId: string, _b: boolean): void;
   };
 };
 
+// Steam removed `SteamClient.Apps.SetAppHidden`. Hiding a non-Steam shortcut now goes through
+// `collectionStore.SetAppsAsHidden([appId], true)` — but that looks the app up in appStore, which
+// only registers a freshly-created shortcut a moment later (calling it immediately throws on a
+// null overview). So hiding is BEST-EFFORT + DEFERRED and must NEVER block the launch.
+declare const collectionStore:
+  | { SetAppsAsHidden?: (appIds: number[], hidden: boolean) => void }
+  | undefined;
+
+function hideShortcut(appId: number): void {
+  const attempt = () => {
+    try {
+      collectionStore?.SetAppsAsHidden?.([appId], true);
+    } catch {
+      /* overview not registered yet, or the API changed — cosmetic, ignore */
+    }
+  };
+  attempt(); // succeeds immediately for an already-registered (reused) shortcut
+  setTimeout(attempt, 2500); // fresh shortcut: retry once its app overview lands
+}
+
 const SHORTCUT_NAME = "punktfunk";
 
 // The 64-bit "gameid" RunGame wants, derived from a 32-bit non-Steam shortcut appId: the
@@ -88,7 +107,8 @@ async function ensureShortcut(): Promise<number> {
   );
   SteamClient.Apps.SetShortcutName(appId, SHORTCUT_NAME);
   // Hide it from the library — it's an implementation detail, launched programmatically.
-  SteamClient.Apps.SetAppHidden(appId, true);
+  // Best-effort + deferred (see hideShortcut); never let it block the launch.
+  hideShortcut(appId);
   rememberAppId(appId);
   return appId;
 }

clients/linux/src/app.rs

@@ -22,6 +22,8 @@ struct App {
     gamepad: crate::gamepad::GamepadService,
     /// One session at a time — ignore connects while one is starting/running.
     busy: std::cell::Cell<bool>,
+    /// Steam Deck / Gaming-Mode launch: fullscreen the window (chrome-less) when a stream starts.
+    fullscreen: bool,
 }
 
 impl App {
@@ -41,7 +43,13 @@ pub fn run() -> glib::ExitCode {
     if let Some(pin) = arg_value("--pair") {
         return headless_pair(&pin);
     }
-    let app = adw::Application::builder().application_id(APP_ID).build();
+    let mut builder = adw::Application::builder().application_id(APP_ID);
+    // Screenshot mode launches the app once per scene back-to-back; NON_UNIQUE keeps each
+    // launch its own primary instance instead of forwarding to a still-registered name.
+    if shot_scene().is_some() {
+        builder = builder.flags(gtk::gio::ApplicationFlags::NON_UNIQUE);
+    }
+    let app = builder.build();
     app.connect_activate(build_ui);
     // GTK doesn't see our argv (`--connect` is handled in `build_ui`); an empty argv also
     // keeps GApplication from rejecting unknown options.
@@ -56,6 +64,20 @@ fn arg_value(flag: &str) -> Option<String> {
         .filter(|v| !v.starts_with("--"))
 }
 
+/// True if argv contains `flag` (a valueless switch).
+fn arg_flag(flag: &str) -> bool {
+    std::env::args().any(|a| a == flag)
+}
+
+/// Run the stream fullscreen with no window chrome — the Steam Deck / Gaming-Mode launch path.
+/// The Decky wrapper passes `--fullscreen`; we also honor the Deck/gamescope env as a fallback
+/// so a manual launch under Gaming Mode does the right thing too.
+fn fullscreen_mode() -> bool {
+    arg_flag("--fullscreen")
+        || std::env::var_os("SteamDeck").is_some()
+        || std::env::var_os("GAMESCOPE_WAYLAND_DISPLAY").is_some()
+}
+
 /// Run the SPAKE2 PIN ceremony without a GTK window and persist the verified host to the
 /// known-hosts store as paired, so a later `--connect` connects silently. Same identity
 /// store the streaming path uses (same binary), so pairing here makes the stream work.
@@ -161,6 +183,7 @@ fn build_ui(gtk_app: &adw::Application) {
         identity,
         gamepad: crate::gamepad::GamepadService::start(),
         busy: std::cell::Cell::new(false),
+        fullscreen: fullscreen_mode(),
     });
 
     let hosts_page = crate::ui_hosts::new(
@@ -182,11 +205,65 @@ fn build_ui(gtk_app: &adw::Application) {
     nav.add(&hosts_page);
     window.present();
 
+    // CI screenshot mode: render one scripted, host-free scene and signal readiness
+    // (clients/linux/tools/screenshots.sh). Mutually exclusive with a real connect.
+    if let Some(scene) = shot_scene() {
+        run_shot(app, &scene);
+        return;
+    }
+
     if let Some(req) = cli_connect_request() {
         initiate_connect(app, req);
     }
 }
 
+/// `PUNKTFUNK_SHOT_SCENE`, when set, selects a scripted host-free scene for CI screenshots.
+fn shot_scene() -> Option<String> {
+    std::env::var("PUNKTFUNK_SHOT_SCENE")
+        .ok()
+        .filter(|s| !s.is_empty())
+}
+
+/// Render one mock-populated, host-free scene over the already-presented window, then print
+/// `PF_SHOT_READY` once it has had a moment to map + settle so the driver knows when to capture.
+/// No `NativeClient` or session is created. The stream scene is deliberately absent — its page
+/// requires a live connector (`ui_stream::new` takes an `Arc<NativeClient>`).
+fn run_shot(app: Rc<App>, scene: &str) {
+    // A plausible host for the trust/pair dialogs (fp_hex is 64 hex chars, like a real SHA-256).
+    let mock_req = || ConnectRequest {
+        name: "Living Room PC".to_string(),
+        addr: "192.168.1.42".to_string(),
+        port: 9777,
+        fp_hex: Some(
+            "9f8e7d6c5b4a39281706f5e4d3c2b1a0998877665544332211ffeeddccbbaa00".to_string(),
+        ),
+        pair_optional: true,
+    };
+
+    match scene {
+        // The saved-hosts grid reads ~/.config/punktfunk/client-known-hosts.json, which the
+        // driver seeds — so the already-shown hosts page is the scene; nothing to do here.
+        "hosts" | "02-hosts" => {}
+        "settings" | "03-settings" => {
+            crate::ui_settings::show(&app.window, app.settings.clone(), &app.gamepad);
+        }
+        "trust" | "04-trust" => tofu_dialog(app.clone(), mock_req()),
+        "pair" | "05-pair" => pin_dialog(app.clone(), mock_req()),
+        other => tracing::warn!("unknown PUNKTFUNK_SHOT_SCENE={other:?}; showing hosts only"),
+    }
+
+    let settle_ms = std::env::var("PUNKTFUNK_SHOT_SETTLE_MS")
+        .ok()
+        .and_then(|v| v.parse().ok())
+        .unwrap_or(900);
+    let scene = scene.to_string();
+    glib::timeout_add_local_once(std::time::Duration::from_millis(settle_ms), move || {
+        use std::io::Write as _;
+        println!("PF_SHOT_READY scene={scene}");
+        let _ = std::io::stdout().flush();
+    });
+}
+
 /// The trust gate in front of every connect. The host is the policy authority (it
 /// advertises `pair=optional` only when it accepts unpaired clients); the client renders
 /// its trust UI from that:
@@ -218,19 +295,21 @@ fn initiate_connect(app: Rc<App>, req: ConnectRequest) {
                 // Rule 3a: the host opted into reduced-security TOFU; offer it alongside PIN.
                 tofu_dialog(app, req);
             } else {
-                // Rule 3b: pair=required or unknown policy — PIN pairing is mandatory.
+                // Rule 3b: pair=required or unknown policy — offer no-PIN delegated approval
-                pin_dialog(app, req);
+                // (request access → approve in the console) or the PIN ceremony.
+                approval_dialog(app, req);
             }
         }
         None => {
             // Manual entry (no advertised fingerprint). A known address connects silently
-            // on its stored pin (rule 1); an unknown one must pair — never silent TOFU.
+            // on its stored pin (rule 1); an unknown one must pair — request access (approve in
+            // the console) or use a PIN; never silent TOFU.
             match known
                 .find_by_addr(&req.addr, req.port)
                 .and_then(|k| crate::trust::parse_hex32(&k.fp_hex))
             {
                 Some(pin) => start_session(app, req, Some(pin)),
-                None => pin_dialog(app, req), // rule 3b
+                None => approval_dialog(app, req), // rule 3b
             }
         }
     }
@@ -341,6 +420,83 @@ fn pin_dialog(app: Rc<App>, req: ConnectRequest) {
     dialog.present(Some(&parent));
 }
 
+/// A fresh host that requires pairing: offer the two ways in. "Request access" is the no-PIN
+/// path — connect and wait for the operator to click Approve in the host's console/web UI
+/// (delegated approval); "Use a PIN instead…" runs the SPAKE2 ceremony.
+fn approval_dialog(app: Rc<App>, req: ConnectRequest) {
+    let dialog = adw::AlertDialog::new(
+        Some("Pairing Required"),
+        Some(&format!(
+            "{} requires pairing.\n\nRequest access and approve this device in the host's console \
+             (or web UI) — no PIN needed. Or pair with the 4-digit PIN it can display.",
+            req.name
+        )),
+    );
+    dialog.add_responses(&[
+        ("cancel", "Cancel"),
+        ("pin", "Use a PIN instead…"),
+        ("request", "Request Access"),
+    ]);
+    dialog.set_response_appearance("request", adw::ResponseAppearance::Suggested);
+    dialog.set_default_response(Some("request"));
+    dialog.set_close_response("cancel");
+    let parent = app.window.clone();
+    dialog.connect_response(None, move |_, response| match response {
+        "request" => request_access(app.clone(), req.clone()),
+        "pin" => pin_dialog(app.clone(), req.clone()),
+        _ => {}
+    });
+    dialog.present(Some(&parent));
+}
+
+/// The no-PIN "request access" flow: open an identified connect that the host PARKS until the
+/// operator approves it in the console, showing a cancelable "waiting" dialog meanwhile. On
+/// approval the same connection is admitted (no reconnect) and the host is saved as paired.
+fn request_access(app: Rc<App>, req: ConnectRequest) {
+    // Pin the advertised certificate for a discovered host (defence against a host impostor while
+    // we wait); a manually-typed host has no advertised fingerprint, so trust-on-first-use.
+    let pin = req.fp_hex.as_deref().and_then(crate::trust::parse_hex32);
+    let cancel = Rc::new(std::cell::Cell::new(false));
+
+    let waiting = adw::AlertDialog::new(
+        Some("Waiting for Approval"),
+        Some(&format!(
+            "Approve “{}” in {}’s console or web UI.\n\nThis device is waiting to be let in — it \
+             connects automatically once you approve it.",
+            glib::host_name(),
+            req.name
+        )),
+    );
+    waiting.add_responses(&[("cancel", "Cancel")]);
+    waiting.set_close_response("cancel");
+    {
+        let app = app.clone();
+        let cancel = cancel.clone();
+        waiting.connect_response(Some("cancel"), move |_, _| {
+            // Return the UI immediately; the in-flight connect is left to time out and is torn
+            // down silently by the event loop (see StartOpts::cancel).
+            cancel.set(true);
+            app.busy.set(false);
+            app.toast("Cancelled — the request may still be pending on the host.");
+        });
+    }
+    waiting.present(Some(&app.window));
+
+    start_session_with(
+        app,
+        req,
+        pin,
+        StartOpts {
+            // Must exceed the host's approval window (PENDING_APPROVAL_WAIT) so a slow operator
+            // approval still lands on this connection rather than timing the client out first.
+            connect_timeout: std::time::Duration::from_secs(185),
+            persist_paired: true,
+            waiting: Some(waiting),
+            cancel: Some(cancel),
+        },
+    );
+}
+
 /// Measure the path to a host over the real data plane (Swift's "Test Network Speed…"):
 /// connect, have the host burst probe filler for 2 s up to its 3 Gbps ceiling, report
 /// goodput · loss · a recommended bitrate (≈70 % of measured), and apply it in one tap.
@@ -375,6 +531,7 @@ fn speed_test(app: Rc<App>, req: ConnectRequest) {
                 GamepadPref::Auto,
                 0,    // bitrate_kbps (host default)
                 0,    // video_caps: the Linux client has no 10-bit/HDR present path yet
+                2,    // audio_channels: speed-test probe, stereo
                 None, // launch: speed-test probe connect, no game
                 pin,
                 Some(identity),
@@ -443,11 +600,19 @@ fn resolve_mode(app: &App) -> punktfunk_core::config::Mode {
         refresh_hz: s.refresh_hz,
     };
     if mode.width == 0 || mode.refresh_hz == 0 {
+        // Prefer the monitor the window is on; fall back to the display's first monitor. On a
+        // `--connect` launch the window may not be mapped yet when this runs, and without the
+        // fallback we'd drop to the 1920×1080 floor below — wrong on the Deck (1280×800).
         let monitor = app
             .window
             .surface()
             .zip(gdk::Display::default())
-            .and_then(|(surf, d)| d.monitor_at_surface(&surf));
+            .and_then(|(surf, d)| d.monitor_at_surface(&surf))
+            .or_else(|| {
+                gdk::Display::default()
+                    .and_then(|d| d.monitors().item(0))
+                    .and_then(|o| o.downcast::<gdk::Monitor>().ok())
+            });
         if let Some(m) = monitor {
             let geo = m.geometry();
             let scale = m.scale_factor().max(1);
@@ -470,7 +635,42 @@ fn resolve_mode(app: &App) -> punktfunk_core::config::Mode {
     mode
 }
 
+/// Tunables for a session start that differ between the normal connect and the "request access"
+/// (delegated-approval) flow. `Default` is the normal connect.
+struct StartOpts {
+    /// Handshake budget. The request-access flow uses a long one because the host PARKS the
+    /// connection until the operator clicks Approve (see the host's `PENDING_APPROVAL_WAIT`).
+    connect_timeout: std::time::Duration,
+    /// Persist the host as *paired* on a successful connect. Set for request-access, where the
+    /// operator's approval IS the pairing, so future connects are silent (rule 1). Normal TOFU
+    /// persists the host *unpaired* (pinned, but not PIN/approval-verified).
+    persist_paired: bool,
+    /// A "waiting for approval" dialog to dismiss on the first session event (request-access only).
+    waiting: Option<adw::AlertDialog>,
+    /// Set by the waiting dialog's Cancel button. `NativeClient::connect` is a blocking call with
+    /// no abort, so Cancel returns the UI immediately (clears busy, closes the dialog) and leaves
+    /// the in-flight connect to time out; when it finally resolves, the event loop sees this flag
+    /// and tears down silently (drops the connector → closes the connection) without touching the
+    /// UI a new session may already own.
+    cancel: Option<Rc<std::cell::Cell<bool>>>,
+}
+
+impl Default for StartOpts {
+    fn default() -> Self {
+        Self {
+            connect_timeout: std::time::Duration::from_secs(15),
+            persist_paired: false,
+            waiting: None,
+            cancel: None,
+        }
+    }
+}
+
 fn start_session(app: Rc<App>, req: ConnectRequest, pin: Option<[u8; 32]>) {
+    start_session_with(app, req, pin, StartOpts::default());
+}
+
+fn start_session_with(app: Rc<App>, req: ConnectRequest, pin: Option<[u8; 32]>, opts: StartOpts) {
     if app.busy.replace(true) {
         return;
     }
@@ -488,12 +688,17 @@ fn start_session(app: Rc<App>, req: ConnectRequest, pin: Option<[u8; 32]>) {
         },
         bitrate_kbps: s.bitrate_kbps,
         mic_enabled: s.mic_enabled,
+        audio_channels: s.audio_channels,
         pin,
         identity: app.identity.clone(),
+        connect_timeout: opts.connect_timeout,
     };
     let inhibit = s.inhibit_shortcuts;
     drop(s);
     let tofu = pin.is_none();
+    let persist_paired = opts.persist_paired;
+    let mut waiting = opts.waiting;
+    let cancel = opts.cancel;
 
     let mut handle = crate::session::start(params);
     let frames = std::mem::replace(&mut handle.frames, async_channel::bounded(1).1);
@@ -501,14 +706,41 @@ fn start_session(app: Rc<App>, req: ConnectRequest, pin: Option<[u8; 32]>) {
         let mut frames = Some(frames);
         let mut page: Option<crate::ui_stream::StreamPage> = None;
         while let Ok(event) = handle.events.recv().await {
+            // A cancelled request-access connect resolved late: tear down silently. Don't touch
+            // app.busy — Cancel already cleared it, and a fresh session may now own it.
+            if cancel.as_ref().is_some_and(|c| c.get()) {
+                if let Some(w) = waiting.take() {
+                    w.close();
+                }
+                break;
+            }
             match event {
                 SessionEvent::Connected {
                     connector,
                     mode,
                     fingerprint,
                 } => {
+                    // Dismiss the "waiting for approval" dialog (request-access flow), if any.
+                    if let Some(w) = waiting.take() {
+                        w.close();
+                    }
+                    if persist_paired {
+                        // Request-access: the operator approved this device, so record the host as
+                        // a trusted PAIRED host (pinning the fingerprint we observed) — future
+                        // connects are then silent (rule 1), exactly like after a PIN ceremony.
+                        let fp_hex = crate::trust::hex(&fingerprint);
+                        let mut known = KnownHosts::load();
+                        known.upsert(KnownHost {
+                            name: req.name.clone(),
+                            addr: req.addr.clone(),
+                            port: req.port,
+                            fp_hex,
+                            paired: true,
+                        });
+                        let _ = known.save();
+                        app.toast("Approved — connecting…");
+                    } else if tofu {
                         // A TOFU connect just observed the real fingerprint — pin it from now on.
-                    if tofu {
                         let fp_hex = crate::trust::hex(&fingerprint);
                         let mut known = KnownHosts::load();
                         known.upsert(KnownHost {
@@ -540,6 +772,12 @@ fn start_session(app: Rc<App>, req: ConnectRequest, pin: Option<[u8; 32]>) {
                         &title,
                     );
                     app.nav.push(&p.page);
+                    // Steam Deck / Gaming Mode: gamescope fullscreens the window but GTK doesn't
+                    // know it, so its header bar stays drawn. Enter GTK fullscreen explicitly —
+                    // the stream page's `connect_fullscreened_notify` then hides all chrome.
+                    if app.fullscreen {
+                        app.window.fullscreen();
+                    }
                     page = Some(p);
                 }
                 SessionEvent::Stats(s) => {
@@ -551,6 +789,9 @@ fn start_session(app: Rc<App>, req: ConnectRequest, pin: Option<[u8; 32]>) {
                     msg,
                     trust_rejected,
                 } => {
+                    if let Some(w) = waiting.take() {
+                        w.close();
+                    }
                     tracing::warn!(%msg, trust_rejected, "connect failed");
                     app.busy.set(false);
                     // A pinned connect rejected on trust grounds means the host's cert no
@@ -565,6 +806,9 @@ fn start_session(app: Rc<App>, req: ConnectRequest, pin: Option<[u8; 32]>) {
                     break;
                 }
                 SessionEvent::Ended(err) => {
+                    if let Some(w) = waiting.take() {
+                        w.close();
+                    }
                     app.gamepad.detach();
                     app.nav.pop_to_tag("hosts");
                     if let Some(e) = err {

clients/linux/src/audio.rs

@@ -27,16 +27,17 @@ pub struct AudioPlayer {
 }
 
 impl AudioPlayer {
-    /// Spawn the PipeWire playback thread. Failure (no PipeWire in the session) is
+    /// Spawn the PipeWire playback thread for `channels` (2/6/8, canonical wire order
-    /// survivable — the caller streams video-only.
+    /// FL FR FC LFE RL RR SL SR). Failure (no PipeWire in the session) is survivable — the
-    pub fn spawn() -> Result<AudioPlayer> {
+    /// caller streams video-only.
+    pub fn spawn(channels: u32) -> Result<AudioPlayer> {
         // 64 × 5 ms = 320 ms of slack between the pump and the PipeWire loop.
         let (pcm_tx, pcm_rx) = std::sync::mpsc::sync_channel::<Vec<f32>>(64);
         let (quit_tx, quit_rx) = pipewire::channel::channel::<Terminate>();
         let thread = std::thread::Builder::new()
             .name("punktfunk-audio".into())
             .spawn(move || {
-                if let Err(e) = pw_thread(pcm_rx, quit_rx) {
+                if let Err(e) = pw_thread(pcm_rx, quit_rx, channels as usize) {
                     tracing::warn!(error = %e, "audio playback thread ended");
                 }
             })
@@ -48,8 +49,8 @@ impl AudioPlayer {
         })
     }
 
-    /// Queue one interleaved-stereo f32 chunk. Drops the chunk if the PipeWire side is
+    /// Queue one interleaved f32 chunk (in the session's channel layout). Drops the chunk if the
-    /// wedged (the renderer conceals the gap; never block the session pump).
+    /// PipeWire side is wedged (the renderer conceals the gap; never block the session pump).
     pub fn push(&self, pcm: Vec<f32>) {
         if let Err(TrySendError::Disconnected(_)) = self.pcm_tx.try_send(pcm) {
             // Thread already dead — Drop will reap it; nothing to do per-chunk.
@@ -71,11 +72,14 @@ struct PlayerData {
     rx: Receiver<Vec<f32>>,
     ring: VecDeque<f32>,
     primed: bool,
+    /// Interleaved channel count this stream was opened with (2/6/8).
+    channels: usize,
 }
 
 fn pw_thread(
     pcm_rx: Receiver<Vec<f32>>,
     quit_rx: pipewire::channel::Receiver<Terminate>,
+    channels: usize,
 ) -> Result<()> {
     use pipewire as pw;
     use pw::{properties::properties, spa};
@@ -115,6 +119,7 @@ fn pw_thread(
         rx: pcm_rx,
         ring: VecDeque::new(),
         primed: false,
+        channels,
     };
 
     let _listener = stream
@@ -130,19 +135,19 @@ fn pw_thread(
                 while let Ok(chunk) = ud.rx.try_recv() {
                     ud.ring.extend(chunk);
                 }
-                let stride = 4 * CHANNELS; // F32LE interleaved
+                let stride = 4 * ud.channels; // F32LE interleaved
                 let datas = buffer.datas_mut();
                 if datas.is_empty() {
                     return;
                 }
                 let data = &mut datas[0];
                 let want_frames = data.data().map(|s| s.len() / stride).unwrap_or(0);
-                let want = want_frames * CHANNELS;
+                let want = want_frames * ud.channels;
 
                 // Adaptive jitter buffer (same shape as the host's virtual mic): prime to
                 // ~3 quanta, cap at ~1 quantum of slack beyond that, re-prime after a
                 // genuine drain.
-                let target = (3 * want).clamp(720 * CHANNELS, 9600 * CHANNELS);
+                let target = (3 * want).clamp(720 * ud.channels, 9600 * ud.channels);
                 while ud.ring.len() > target.max(want) + want {
                     ud.ring.pop_front();
                 }
@@ -182,7 +187,13 @@ fn pw_thread(
     let mut info = AudioInfoRaw::new();
     info.set_format(AudioFormat::F32LE);
     info.set_rate(SAMPLE_RATE);
-    info.set_channels(CHANNELS as u32);
+    info.set_channels(channels as u32);
+    // Channel positions in canonical wire order (FL FR FC LFE RL RR SL SR) so PipeWire routes each
+    // slot to the matching speaker (and downmixes when the sink has fewer). Identity, no permute.
+    let order = punktfunk_core::audio::spa_positions(channels as u8);
+    let mut positions = [0u32; 64];
+    positions[..order.len()].copy_from_slice(order);
+    info.set_position(positions);
     let obj = pw::spa::pod::Object {
         type_: pw::spa::utils::SpaTypes::ObjectParamFormat.as_raw(),
         id: pw::spa::param::ParamType::EnumFormat.as_raw(),

clients/linux/src/session.rs

@@ -20,11 +20,18 @@ pub struct SessionParams {
     pub compositor: CompositorPref,
     pub gamepad: GamepadPref,
     pub bitrate_kbps: u32,
+    /// Requested audio channel count (2/6/8); the host echoes the resolved value.
+    pub audio_channels: u8,
     /// Stream the default microphone to the host's virtual mic source.
     pub mic_enabled: bool,
     /// Pinned host fingerprint; `None` = trust on first use (caller persists the observed one).
     pub pin: Option<[u8; 32]>,
     pub identity: (String, String),
+    /// How long to wait for the handshake. The normal path uses a short budget; the
+    /// "request access" (delegated-approval) path uses a long one, because the host PARKS the
+    /// connection until the operator clicks Approve in its console (so this must exceed the
+    /// host's approval window — see `PENDING_APPROVAL_WAIT`).
+    pub connect_timeout: Duration,
 }
 
 #[derive(Clone, Copy, Default)]
@@ -83,6 +90,42 @@ fn now_ns() -> u64 {
         .unwrap_or(0)
 }
 
+/// Opus decoder for the audio plane: a plain stereo decoder (the validated path) or a multistream
+/// decoder for 5.1/7.1, both behind one `decode_float`. Built from the host-RESOLVED channel count
+/// via the shared layout table.
+enum AudioDec {
+    Stereo(opus::Decoder),
+    Surround(opus::MSDecoder),
+}
+
+impl AudioDec {
+    fn new(channels: u8) -> Result<AudioDec, opus::Error> {
+        if channels == 2 {
+            Ok(AudioDec::Stereo(opus::Decoder::new(
+                48_000,
+                opus::Channels::Stereo,
+            )?))
+        } else {
+            let l = punktfunk_core::audio::layout_for(channels, false);
+            Ok(AudioDec::Surround(opus::MSDecoder::new(
+                48_000, l.streams, l.coupled, l.mapping,
+            )?))
+        }
+    }
+
+    fn decode_float(
+        &mut self,
+        input: &[u8],
+        out: &mut [f32],
+        fec: bool,
+    ) -> Result<usize, opus::Error> {
+        match self {
+            AudioDec::Stereo(d) => d.decode_float(input, out, fec),
+            AudioDec::Surround(d) => d.decode_float(input, out, fec),
+        }
+    }
+}
+
 fn pump(
     params: SessionParams,
     ev_tx: async_channel::Sender<SessionEvent>,
@@ -97,10 +140,11 @@ fn pump(
         params.gamepad,
         params.bitrate_kbps,
         0, // video_caps: the Linux client has no 10-bit/HDR present path yet
+        params.audio_channels,
         None, // launch: the Linux client has no library picker yet
         params.pin,
         Some(params.identity),
-        Duration::from_secs(15),
+        params.connect_timeout,
     ) {
         Ok(c) => Arc::new(c),
         Err(e) => {
@@ -134,11 +178,14 @@ fn pump(
         }
     };
     // Audio is best-effort: a session without it still streams. Gamepads are the
-    // app-lifetime service's job (the UI attaches it on Connected).
+    // app-lifetime service's job (the UI attaches it on Connected). Build the decoder + playback
-    let player = audio::AudioPlayer::spawn()
+    // from the host-RESOLVED channel count (never the request), so an older/clamping host that
+    // resolves stereo is decoded as stereo.
+    let channels = connector.audio_channels;
+    let player = audio::AudioPlayer::spawn(channels as u32)
         .map_err(|e| tracing::warn!(error = %e, "audio disabled"))
         .ok();
-    let mut opus_dec = opus::Decoder::new(48_000, opus::Channels::Stereo)
+    let mut opus_dec = AudioDec::new(channels)
         .map_err(|e| tracing::warn!(error = %e, "opus decoder failed — audio disabled"))
         .ok();
     let _mic = params
@@ -157,7 +204,7 @@ fn pump(
     let mut bytes_n = 0u64;
     let mut decode_us_sum = 0u64;
     let mut lat_us: Vec<u64> = Vec::with_capacity(256);
-    let mut pcm = vec![0f32; 5760 * 2]; // decode scratch: max Opus frame (120 ms stereo)
+    let mut pcm = vec![0f32; 5760 * channels as usize]; // scratch: max Opus frame (120 ms) × channels
                                                         // Loss recovery: watch the host→client unrecoverable-drop count and ask for an IDR when it climbs.
     let mut last_dropped = connector.frames_dropped();
     let mut last_kf_req: Option<Instant> = None;
@@ -221,7 +268,8 @@ fn pump(
         while let Ok(pkt) = connector.next_audio(Duration::ZERO) {
             if let (Some(player), Some(dec)) = (&player, opus_dec.as_mut()) {
                 match dec.decode_float(&pkt.data, &mut pcm, false) {
-                    Ok(samples) => player.push(pcm[..samples * 2].to_vec()),
+                    // `samples` is per-channel; the interleaved frame is `samples * channels`.
+                    Ok(samples) => player.push(pcm[..samples * channels as usize].to_vec()),
                     Err(e) => tracing::debug!(error = %e, "opus decode"),
                 }
             }

clients/linux/src/trust.rs

@@ -90,6 +90,14 @@ impl KnownHosts {
         self.hosts.iter().find(|h| h.addr == addr && h.port == port)
     }
 
+    /// Forget the entry with this fingerprint. Returns true if one was removed (the user
+    /// will have to pair/trust again to reconnect).
+    pub fn remove_by_fp(&mut self, fp_hex: &str) -> bool {
+        let before = self.hosts.len();
+        self.hosts.retain(|h| h.fp_hex != fp_hex);
+        self.hosts.len() != before
+    }
+
     /// Insert or refresh an entry, keyed by fingerprint. `paired` only ever upgrades
     /// (a later TOFU connect must not demote a PIN-paired host).
     pub fn upsert(&mut self, entry: KnownHost) {
@@ -124,6 +132,9 @@ pub struct Settings {
     pub inhibit_shortcuts: bool,
     /// Stream the default microphone to the host's virtual mic source.
     pub mic_enabled: bool,
+    /// Requested audio channel count: 2 (stereo), 6 (5.1) or 8 (7.1). The host clamps to what it
+    /// can capture; the resolved count drives the decoder + playback layout.
+    pub audio_channels: u8,
 }
 
 impl Default for Settings {
@@ -137,6 +148,7 @@ impl Default for Settings {
             compositor: "auto".into(),
             inhibit_shortcuts: true,
             mic_enabled: false,
+            audio_channels: 2,
         }
     }
 }

clients/linux/src/ui_hosts.rs

@@ -181,6 +181,52 @@ pub fn new(
                     // pinned connect; TOFU eligibility is irrelevant.
                     pair_optional: false,
                 };
+                // Forget this host (drops the pinned fingerprint — a later connect re-pairs).
+                // Confirmed first, since it's destructive and a misclick on the Deck is easy.
+                let remove_btn = gtk::Button::from_icon_name("user-trash-symbolic");
+                remove_btn.set_tooltip_text(Some("Remove saved host"));
+                remove_btn.set_valign(gtk::Align::Center);
+                remove_btn.add_css_class("flat");
+                {
+                    let fp = k.fp_hex.clone();
+                    let name = k.name.clone();
+                    let saved_list = saved_list.clone();
+                    let saved_label = saved_label.clone();
+                    let row = row.clone();
+                    remove_btn.connect_clicked(move |_| {
+                        let dialog = adw::AlertDialog::new(
+                            Some("Remove saved host?"),
+                            Some(&format!(
+                                "Forget “{name}”? You'll need to pair (or trust) it again to reconnect."
+                            )),
+                        );
+                        dialog.add_responses(&[("cancel", "Cancel"), ("remove", "Remove")]);
+                        dialog.set_response_appearance(
+                            "remove",
+                            adw::ResponseAppearance::Destructive,
+                        );
+                        dialog.set_default_response(Some("cancel"));
+                        dialog.set_close_response("cancel");
+                        {
+                            // Scoped clones for the response handler so `row` survives for present().
+                            let fp = fp.clone();
+                            let saved_list = saved_list.clone();
+                            let saved_label = saved_label.clone();
+                            let row = row.clone();
+                            dialog.connect_response(Some("remove"), move |_, _| {
+                                let mut known = KnownHosts::load();
+                                known.remove_by_fp(&fp);
+                                let _ = known.save();
+                                saved_list.remove(&row);
+                                let empty = known.hosts.is_empty();
+                                saved_list.set_visible(!empty);
+                                saved_label.set_visible(!empty);
+                            });
+                        }
+                        dialog.present(Some(&row));
+                    });
+                }
+                row.add_suffix(&remove_btn);
                 let speed_btn = gtk::Button::from_icon_name("network-transmit-receive-symbolic");
                 speed_btn.set_tooltip_text(Some("Test network speed"));
                 speed_btn.set_valign(gtk::Align::Center);

clients/linux/src/ui_settings.rs

@@ -19,6 +19,49 @@ const REFRESH: &[u32] = &[0, 30, 60, 90, 120, 144, 165, 240];
 const GAMEPADS: &[&str] = &["auto", "xbox360", "dualsense", "xboxone", "dualshock4"];
 const COMPOSITORS: &[&str] = &["auto", "kwin", "wlroots", "mutter", "gamescope"];
 
+/// punktfunk's own license (MIT OR Apache-2.0), shown on the About dialog's Legal page.
+const APP_LICENSE: &str = concat!(
+    "punktfunk is licensed under MIT OR Apache-2.0, at your option.\n\n",
+    "================================ MIT ================================\n\n",
+    include_str!("../../../LICENSE-MIT"),
+    "\n\n=============================== Apache-2.0 ===============================\n\n",
+    include_str!("../../../LICENSE-APACHE"),
+);
+/// Third-party software notices for the linked Rust crates (generated by
+/// scripts/gen-third-party-notices.sh; shown as a Legal section in the About dialog).
+const THIRD_PARTY_NOTICES: &str = include_str!("../../../THIRD-PARTY-NOTICES.txt");
+
+/// Show the About dialog (app license + the third-party-software Legal section).
+fn show_about(parent: &impl IsA<gtk::Widget>) {
+    let about = adw::AboutDialog::builder()
+        .application_name("punktfunk")
+        .developer_name("unom")
+        .version(env!("CARGO_PKG_VERSION"))
+        .website("https://git.unom.io/unom/punktfunk")
+        .license_type(gtk::License::Custom)
+        .license(APP_LICENSE)
+        .build();
+    // The native (FFmpeg/GTK/PipeWire/SDL3) components are dynamically linked under their own
+    // (LGPL/Zlib/MIT) licenses; the Rust crate notices are the substantive attribution set.
+    about.add_legal_section(
+        "Third-party software (Rust crates)",
+        None,
+        gtk::License::Custom,
+        Some(THIRD_PARTY_NOTICES),
+    );
+    about.add_legal_section(
+        "Third-party software (system libraries)",
+        None,
+        gtk::License::Custom,
+        Some(
+            "This application dynamically links system libraries under their own licenses, \
+             including FFmpeg (LGPL v2.1+), GTK 4 and libadwaita (LGPL v2.1+), PipeWire (MIT), \
+             and SDL 3 (Zlib). Their full license texts are available from each project.",
+        ),
+    );
+    about.present(Some(parent));
+}
+
 pub fn show(
     parent: &impl IsA<gtk::Widget>,
     settings: Rc<RefCell<Settings>>,
@@ -140,15 +183,39 @@ pub fn show(
     input.add(&inhibit_row);
 
     let audio = adw::PreferencesGroup::builder().title("Audio").build();
+    let surround_row = adw::ComboRow::builder()
+        .title("Audio channels")
+        .subtitle("Request stereo or surround (the host downmixes if its output has fewer)")
+        .model(&gtk::StringList::new(&[
+            "Stereo",
+            "5.1 Surround",
+            "7.1 Surround",
+        ]))
+        .build();
+    audio.add(&surround_row);
     let mic_row = adw::SwitchRow::builder()
         .title("Stream microphone")
         .subtitle("Send the default input device to the host's virtual microphone")
         .build();
     audio.add(&mic_row);
 
+    let about = adw::PreferencesGroup::builder().title("About").build();
+    let licenses_row = adw::ActionRow::builder()
+        .title("Third-party licenses")
+        .subtitle("Open-source software used by punktfunk")
+        .activatable(true)
+        .build();
+    licenses_row.add_suffix(&gtk::Image::from_icon_name("go-next-symbolic"));
+    {
+        let about_parent: gtk::Widget = parent.clone().upcast();
+        licenses_row.connect_activated(move |_| show_about(&about_parent));
+    }
+    about.add(&licenses_row);
+
     page.add(&stream);
     page.add(&input);
     page.add(&audio);
+    page.add(&about);
 
     // Seed from the current settings.
     {
@@ -170,6 +237,11 @@ pub fn show(
         compositor_row.set_selected(comp_i as u32);
         inhibit_row.set_active(s.inhibit_shortcuts);
         mic_row.set_active(s.mic_enabled);
+        surround_row.set_selected(match s.audio_channels {
+            6 => 1,
+            8 => 2,
+            _ => 0,
+        });
     }
 
     let dialog = adw::PreferencesDialog::new();
@@ -186,6 +258,11 @@ pub fn show(
             .to_string();
         s.inhibit_shortcuts = inhibit_row.is_active();
         s.mic_enabled = mic_row.is_active();
+        s.audio_channels = match surround_row.selected() {
+            1 => 6,
+            2 => 8,
+            _ => 2,
+        };
         s.save();
     });
     dialog.present(Some(parent));

clients/linux/tools/screenshots.sh

@@ -0,0 +1,123 @@
+#!/usr/bin/env bash
+# Capture host-free UI screenshots of the native Linux client under a virtual X
+# display. Mirrors the iOS harness (clients/apple/tools/screenshots.sh): one app
+# launch per scene (PUNKTFUNK_SHOT_SCENE), the app renders a mock-populated REAL
+# view and prints `PF_SHOT_READY`, then we grab the X root window. No host, GPU, or
+# live stream — only the chrome scenes (the stream page needs a live connector).
+#
+#   cargo build --release -p punktfunk-client-linux
+#   bash clients/linux/tools/screenshots.sh            # → clients/linux/screenshots/<scene>.png
+#   bash clients/linux/tools/screenshots.sh hosts pair # a subset
+#
+# Env knobs: BIN (client binary), OUT (output dir), GEOMETRY (Xvfb WxHxDepth),
+# SETTLE (extra seconds after PF_SHOT_READY), SHOT_DISPLAY (X display), GSK_RENDERER
+# (gl|ngl|cairo — gl/llvmpipe by default for full libadwaita fidelity).
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)" # clients/linux
+BIN="${BIN:-$here/../../target/release/punktfunk-client}"
+OUT="${OUT:-$here/screenshots}"
+# The client window maps at its 1100x720 default; with no WM under Xvfb it lands at the
+# top-left, so keep the root just larger so the full window (incl. its CSD shadow) is
+# captured by a root grab with only a thin margin to crop.
+GEOMETRY="${GEOMETRY:-1280x800x24}"
+SETTLE="${SETTLE:-1.2}"
+SHOT_DISPLAY="${SHOT_DISPLAY:-:99}"
+
+if [ "$#" -gt 0 ]; then SCENES=("$@"); else SCENES=(hosts settings trust pair); fi
+
+[ -x "$BIN" ] || {
+	echo "client binary not found: $BIN (build it first: cargo build --release -p punktfunk-client-linux)" >&2
+	exit 1
+}
+
+# Isolated scratch HOME: the client generates its identity here on first run, and the
+# saved-hosts grid is read from client-known-hosts.json, so seed mock hosts for the
+# `hosts` scene (the dialogs/settings build their own mock state in-app).
+WORK="$(mktemp -d)"
+export HOME="$WORK"
+mkdir -p "$HOME/.config/punktfunk"
+cat >"$HOME/.config/punktfunk/client-known-hosts.json" <<'JSON'
+{
+  "hosts": [
+    { "name": "Living Room PC", "addr": "192.168.1.42", "port": 9777,
+      "fp_hex": "9f8e7d6c5b4a39281706f5e4d3c2b1a0998877665544332211ffeeddccbbaa00",
+      "paired": true },
+    { "name": "Office", "addr": "192.168.1.50", "port": 9777,
+      "fp_hex": "a1b2c3d4e5f60718293a4b5c6d7e8f90112233445566778899aabbccddeeff00",
+      "paired": false }
+  ]
+}
+JSON
+
+# Software-rendered X session — no GPU/Wayland. GL/llvmpipe runs the real NGL renderer
+# (cairo is documented-incomplete for 3D-transformed content / libadwaita transitions).
+unset WAYLAND_DISPLAY
+export DISPLAY="$SHOT_DISPLAY"
+export GDK_BACKEND=x11
+export LIBGL_ALWAYS_SOFTWARE=1
+export GALLIUM_DRIVER="${GALLIUM_DRIVER:-llvmpipe}"
+export GSK_RENDERER="${GSK_RENDERER:-gl}"
+
+Xvfb "$SHOT_DISPLAY" -screen 0 "$GEOMETRY" -nolisten tcp >"$WORK/xvfb.log" 2>&1 &
+XVFB_PID=$!
+cleanup() {
+	kill "$XVFB_PID" 2>/dev/null || true
+	rm -rf "$WORK"
+}
+trap cleanup EXIT
+
+# Wait for the display to accept connections.
+for _ in $(seq 1 50); do
+	if command -v xdpyinfo >/dev/null 2>&1; then
+		xdpyinfo -display "$SHOT_DISPLAY" >/dev/null 2>&1 && break
+	else
+		[ -e "/tmp/.X11-unix/X${SHOT_DISPLAY#:}" ] && break
+	fi
+	sleep 0.1
+done
+
+capture() {
+	local out="$1"
+	if command -v import >/dev/null 2>&1; then
+		import -silent -window root "$out"
+	elif command -v scrot >/dev/null 2>&1; then
+		scrot -o "$out"
+	else
+		echo "no screenshot tool — install imagemagick or scrot" >&2
+		return 1
+	fi
+}
+
+mkdir -p "$OUT"
+rc=0
+for scene in "${SCENES[@]}"; do
+	: >"$WORK/log"
+	PUNKTFUNK_SHOT_SCENE="$scene" "$BIN" >"$WORK/log" 2>&1 &
+	pid=$!
+	ready=0
+	for _ in $(seq 1 200); do # up to ~20s
+		if grep -q "PF_SHOT_READY" "$WORK/log"; then
+			ready=1
+			break
+		fi
+		if ! kill -0 "$pid" 2>/dev/null; then break; fi
+		sleep 0.1
+	done
+	if [ "$ready" = 1 ]; then
+		sleep "$SETTLE"
+		if capture "$OUT/$scene.png"; then
+			echo "✓ $scene → $OUT/$scene.png"
+		else
+			rc=1
+		fi
+	else
+		echo "✗ $scene: client never signalled PF_SHOT_READY" >&2
+		sed 's/^/    /' "$WORK/log" >&2 || true
+		rc=1
+	fi
+	kill "$pid" 2>/dev/null || true
+	wait "$pid" 2>/dev/null || true
+done
+
+exit "$rc"

clients/probe/Cargo.toml

@@ -18,8 +18,7 @@ tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 # LAN host discovery (`--discover`): browse the native `_punktfunk._udp` mDNS service the host
 # advertises (same crate/version the host advertises with).
 mdns-sd = "0.20"
-
+# Opus: multistream DECODE of the host's audio plane (the surround validator) + `--mic-test`'s
-# Linux-only: --mic-test's Opus encoder (libopus). The mic UPLINK itself is portable —
+# encoder. libopus is already in the graph via `punktfunk-core`'s quic feature; this exposes the
-# only this synthetic-tone test rig needs the encoder.
+# name directly. Cross-platform (cmake-vendored), so the probe builds + validates everywhere.
-[target.'cfg(target_os = "linux")'.dependencies]
 opus = "0.3"

clients/probe/src/main.rs

@@ -78,6 +78,10 @@ struct Args {
     gamepad: GamepadPref,
     /// `--bitrate KBPS` — request this encoder bitrate (kilobits/s); 0 = host default.
     bitrate_kbps: u32,
+    /// `--audio-channels N` — request stereo (2), 5.1 (6) or 7.1 (8) audio; default 2. The probe
+    /// multistream-decodes the host's frames and asserts the per-channel sample count, so it's the
+    /// headless validator for the surround encode path.
+    audio_channels: u8,
     /// `--launch ID` — ask the host to launch a library title in this session (a store-qualified
     /// id from the host's `GET /api/v1/library`, e.g. `steam:570`). Host resolves it; `None` = none.
     launch: Option<String>,
@@ -201,6 +205,11 @@ fn parse_args() -> Args {
         compositor,
         gamepad,
         bitrate_kbps: get("--bitrate").and_then(|s| s.parse().ok()).unwrap_or(0),
+        audio_channels: punktfunk_core::audio::normalize_channels(
+            get("--audio-channels")
+                .and_then(|s| s.parse().ok())
+                .unwrap_or(2),
+        ),
         launch: get("--launch").map(str::to_string),
         speed_test: get("--speed-test").and_then(|s| {
             let (kbps, ms) = s.split_once(':')?;
@@ -385,13 +394,23 @@ async fn session(args: Args) -> Result<()> {
             // `--launch ID` — host resolves it against its own library and runs it this session.
             launch: args.launch.clone(),
             // This headless tool just dumps the bitstream (no decode), so it can always claim
-            // 10-bit support. Gated by env so latency runs stay on the 8-bit baseline:
+            // 10-bit / 4:4:4 support. Gated by env so latency runs stay on the 8-bit 4:2:0 baseline:
-            // PUNKTFUNK_CLIENT_10BIT=1 advertises VIDEO_CAP_10BIT to exercise the host Main10 path.
+            // PUNKTFUNK_CLIENT_10BIT=1 advertises VIDEO_CAP_10BIT (host Main10 path);
-            video_caps: if std::env::var_os("PUNKTFUNK_CLIENT_10BIT").is_some() {
+            // PUNKTFUNK_CLIENT_444=1 advertises VIDEO_CAP_444 (host HEVC 4:4:4 path) — verify the
-                punktfunk_core::quic::VIDEO_CAP_10BIT
+            // resulting chroma with `ffprobe` on the `--out` .h265.
-            } else {
+            video_caps: {
-                0
+                let mut caps = 0u8;
+                if std::env::var_os("PUNKTFUNK_CLIENT_10BIT").is_some() {
+                    caps |= punktfunk_core::quic::VIDEO_CAP_10BIT;
+                }
+                if std::env::var_os("PUNKTFUNK_CLIENT_444").is_some() {
+                    caps |= punktfunk_core::quic::VIDEO_CAP_444;
+                }
+                caps
             },
+            // `--audio-channels` (default stereo); the probe multistream-decodes + validates the
+            // host's frames to exercise the surround encode path headlessly.
+            audio_channels: args.audio_channels,
         }
         .encode(),
     )
@@ -408,6 +427,8 @@ async fn session(args: Args) -> Result<()> {
         bit_depth = welcome.bit_depth,
         color = ?welcome.color,
         hdr = welcome.color.is_hdr(),
+        chroma_444 = welcome.chroma_format == punktfunk_core::quic::CHROMA_IDC_444,
+        chroma_format_idc = welcome.chroma_format,
         "session offer"
     );
 
@@ -830,13 +851,37 @@ async fn session(args: Args) -> Result<()> {
             hidout_pkts.clone(),
         );
         let conn2 = conn.clone();
+        // Build a multistream decoder for the host-RESOLVED layout so the probe actually decodes
+        // the surround stream (not just counts bytes) — the headless validator for the encode path.
+        let audio_channels = welcome.audio_channels;
         tokio::spawn(async move {
             use std::sync::atomic::Ordering::Relaxed;
             let mut hdr_logged = false;
+            let layout = punktfunk_core::audio::layout_for(audio_channels, false);
+            let mut audio_dec =
+                opus::MSDecoder::new(48_000, layout.streams, layout.coupled, layout.mapping).ok();
+            let mut pcm = vec![0f32; 5760 * audio_channels as usize];
+            let mut audio_decoded_logged = false;
             while let Ok(d) = conn2.read_datagram().await {
                 if let Some((_, _, opus)) = punktfunk_core::quic::decode_audio_datagram(&d) {
                     a.fetch_add(1, Relaxed);
                     ab.fetch_add(opus.len() as u64, Relaxed);
+                    // Decode + validate: the per-channel sample count must be a legal Opus frame
+                    // size; log the first success so a loopback test can assert surround decoded.
+                    if let Some(dec) = audio_dec.as_mut() {
+                        match dec.decode_float(opus, &mut pcm, false) {
+                            Ok(samples) if !audio_decoded_logged => {
+                                audio_decoded_logged = true;
+                                tracing::info!(
+                                    channels = audio_channels,
+                                    samples_per_channel = samples,
+                                    "audio decoded (Opus multistream)"
+                                );
+                            }
+                            Ok(_) => {}
+                            Err(e) => tracing::debug!(error = %e, "probe audio decode"),
+                        }
+                    }
                 } else if punktfunk_core::quic::decode_rumble_datagram(&d).is_some() {
                     r.fetch_add(1, Relaxed);
                 } else if let Some(meta) = punktfunk_core::quic::decode_hdr_meta_datagram(&d) {

clients/windows/packaging/pack-msix.ps1

@@ -76,11 +76,29 @@ foreach ($f in $required) {
     Copy-Item $src (Join-Path $layout $f) -Force
 }
 
-# FFmpeg runtime DLLs (the exe link-imports the decode set; copy them all — small and correct)
+# FFmpeg runtime DLLs (the exe link-imports the decode set; copy them all — small and correct).
+# These are unmodified BtbN *lgpl-shared* builds, linked dynamically (replaceable DLLs) — FFmpeg is
+# used under the LGPL v2.1+; the license text + notice ship in licenses\ below.
 $ff = Get-ChildItem -Path $FfmpegBin -Filter *.dll -ErrorAction SilentlyContinue
 if (-not $ff) { throw "no FFmpeg DLLs in $FfmpegBin" }
 $ff | ForEach-Object { Copy-Item $_.FullName (Join-Path $layout $_.Name) -Force }
 
+# license/attribution payload (MSIX has no installer EULA page, so ship them as files): FFmpeg's LGPL
+# notice + license text, the project's own MIT/Apache texts, and the generated third-party notices.
+$licDir = Join-Path $layout 'licenses'
+New-Item -ItemType Directory -Force -Path $licDir | Out-Null
+$repoRoot = (Resolve-Path (Join-Path $PSScriptRoot '..\..\..')).Path
+Copy-Item (Join-Path $repoRoot 'packaging\windows\licenses\FFmpeg-LGPL-NOTICE.txt') $licDir -Force -ErrorAction SilentlyContinue
+foreach ($n in @('THIRD-PARTY-NOTICES.txt', 'LICENSE-MIT', 'LICENSE-APACHE')) {
+    $p = Join-Path $repoRoot $n
+    if (Test-Path $p) { Copy-Item $p $licDir -Force }
+}
+$ffRoot = Split-Path $FfmpegBin -Parent
+foreach ($lic in @('LICENSE.txt', 'LICENSE', 'COPYING.LGPLv2.1', 'COPYING.LGPLv3', 'COPYING.txt')) {
+    $p = Join-Path $ffRoot $lic
+    if (Test-Path $p) { Copy-Item $p $licDir -Force }
+}
+
 # tile/store assets
 Copy-Item (Join-Path $assets '*') (Join-Path $layout 'Assets') -Force
 

clients/windows/src/app.rs

@@ -20,7 +20,9 @@ use crate::video::{DecodedFrame, DecoderPref};
 use punktfunk_core::client::NativeClient;
 use punktfunk_core::config::{CompositorPref, GamepadPref, Mode};
 use std::cell::RefCell;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
+use std::time::Duration;
 use windows_reactor::*;
 
 const RESOLUTIONS: &[(u32, u32)] = &[
@@ -39,13 +41,31 @@ const DECODERS: &[(&str, &str)] = &[
 ];
 /// Bitrate presets in Mb/s; `0` = host default.
 const BITRATES_MBPS: &[u32] = &[0, 10, 20, 30, 50, 80, 150];
+/// Audio channel presets: `(channel count, display label)`. The host clamps to what it can
+/// capture; the resolved count drives the decoder + WASAPI render layout.
+const AUDIO_CHANNELS: &[(u8, &str)] = &[(2, "Stereo"), (6, "5.1 Surround"), (8, "7.1 Surround")];
+
+/// punktfunk's own license (MIT OR Apache-2.0), shown on the Licenses screen.
+const APP_LICENSE: &str = concat!(
+    include_str!("../../../LICENSE-MIT"),
+    "\n\n================================ Apache-2.0 ================================\n\n",
+    include_str!("../../../LICENSE-APACHE"),
+);
+/// Third-party software notices for the linked Rust crates (generated by
+/// scripts/gen-third-party-notices.sh; the MSIX also ships this under licenses/).
+const THIRD_PARTY_NOTICES: &str = include_str!("../../../THIRD-PARTY-NOTICES.txt");
 
 #[derive(Clone, PartialEq)]
 enum Screen {
     Hosts,
     Connecting,
+    /// The no-PIN "request access" wait: an identified connect is in flight, parked by the host
+    /// until the operator approves this device in its console. Cancelable.
+    RequestAccess,
     Stream,
     Settings,
+    /// Open-source / third-party license notices (reached from Settings).
+    Licenses,
     Pair,
 }
 
@@ -129,6 +149,11 @@ struct Shared {
     /// Latest stream stats, written by the session's event loop and mirrored into reactor state
     /// by the stream page's HUD poll thread to drive the overlay.
     stats: Mutex<Stats>,
+    /// Cancel flag for the in-flight "request access" connect. A FRESH flag is installed per
+    /// request: the waiting screen's Cancel button reads it back from here and sets it, and that
+    /// request's event loop (which captured the same `Arc` at spawn) then tears down silently when
+    /// the parked connect finally resolves. `None` outside a request-access flow.
+    cancel: Mutex<Option<Arc<AtomicBool>>>,
 }
 
 pub struct AppCtx {
@@ -373,8 +398,13 @@ fn root(cx: &mut RenderCx, ctx: &Arc<AppCtx>) -> Element {
             .vertical_alignment(VerticalAlignment::Center)
             .into()
         }
+        // request_access_page (like settings_page/Connecting) uses no hooks, so calling it inline
+        // is sound — it only wires a Cancel button to the shared cancel flag + navigation.
+        Screen::RequestAccess => request_access_page(ctx, &set_screen),
         // settings_page uses no hooks (it never touches `cx`), so calling it inline is sound.
         Screen::Settings => settings_page(ctx, &set_screen),
+        // licenses_page is a static text screen (no hooks), so inline is sound.
+        Screen::Licenses => licenses_page(&set_screen),
         Screen::Pair => component(pair_page, svc),
         Screen::Stream => component(stream_page, StreamProps { svc, stats }),
     }
@@ -566,12 +596,61 @@ fn initiate(
     }
 }
 
+/// Tunables that differ between the normal connect and the no-PIN "request access" flow.
+/// `Default` is the normal connect: short handshake budget, persist *unpaired* on TOFU, and the
+/// plain "Connecting" screen.
+struct ConnectOpts {
+    /// Handshake budget. Request-access uses a long one because the host PARKS the connection
+    /// until the operator clicks Approve in its console (see the host's `PENDING_APPROVAL_WAIT`).
+    connect_timeout: Duration,
+    /// Persist the host as *paired* on a successful connect. Set for request-access, where the
+    /// operator's approval IS the pairing, so future connects are silent (rule 1). Normal TOFU
+    /// persists the host *unpaired* (pinned, but not PIN/approval-verified).
+    persist_paired: bool,
+    /// Show the cancelable "waiting for approval" screen instead of "Connecting" (request-access).
+    awaiting_approval: bool,
+    /// Set by the waiting screen's Cancel button. `NativeClient::connect` is blocking with no
+    /// abort, so Cancel returns the UI immediately and leaves the parked connect to resolve/time
+    /// out; this request's event loop then sees the flag and tears down silently (drops the
+    /// connector → closes the connection) without touching a screen a new session may already own.
+    cancel: Option<Arc<AtomicBool>>,
+}
+
+impl Default for ConnectOpts {
+    fn default() -> Self {
+        Self {
+            connect_timeout: Duration::from_secs(15),
+            persist_paired: false,
+            awaiting_approval: false,
+            cancel: None,
+        }
+    }
+}
+
 fn connect(
     ctx: &Arc<AppCtx>,
     target: &Target,
     pin: Option<[u8; 32]>,
     set_screen: &AsyncSetState<Screen>,
     set_status: &AsyncSetState<String>,
+) {
+    connect_with(
+        ctx,
+        target,
+        pin,
+        set_screen,
+        set_status,
+        ConnectOpts::default(),
+    );
+}
+
+fn connect_with(
+    ctx: &Arc<AppCtx>,
+    target: &Target,
+    pin: Option<[u8; 32]>,
+    set_screen: &AsyncSetState<Screen>,
+    set_status: &AsyncSetState<String>,
+    opts: ConnectOpts,
 ) {
     let s = ctx.settings.lock().unwrap().clone();
     let mode = if s.width != 0 && s.refresh_hz != 0 {
@@ -598,34 +677,60 @@ fn connect(
         compositor: CompositorPref::Auto,
         gamepad: gamepad_pref,
         bitrate_kbps: s.bitrate_kbps,
+        audio_channels: s.audio_channels,
         mic_enabled: s.mic_enabled,
         hdr_enabled: s.hdr_enabled,
         decoder: DecoderPref::from_name(&s.decoder),
         pin,
         identity: ctx.identity.clone(),
+        connect_timeout: opts.connect_timeout,
     });
     set_status.call(String::new());
-    set_screen.call(Screen::Connecting);
+    set_screen.call(if opts.awaiting_approval {
+        Screen::RequestAccess
+    } else {
+        Screen::Connecting
+    });
 
     let tofu = pin.is_none();
+    let persist_paired = opts.persist_paired;
+    let cancel = opts.cancel;
     let (shared, gamepad) = (ctx.shared.clone(), ctx.gamepad.clone());
     let (ss, st) = (set_screen.clone(), set_status.clone());
     let target = target.clone();
     std::thread::spawn(move || loop {
-        match handle.events.recv_blocking() {
+        let event = match handle.events.recv_blocking() {
-            Ok(SessionEvent::Connected {
+            Ok(e) => e,
+            Err(_) => {
+                gamepad.detach();
+                ss.call(Screen::Hosts);
+                break;
+            }
+        };
+        // A cancelled request-access connect that resolved late (the host approved or the park
+        // timed out after the user walked away): tear down silently. Cancel already returned the
+        // UI to the host list; dropping `event` (and with it any connector) closes the connection
+        // without popping a stream or a stray error over the screen a new session may own.
+        if cancel.as_ref().is_some_and(|c| c.load(Ordering::SeqCst)) {
+            break;
+        }
+        match event {
+            SessionEvent::Connected {
                 connector,
                 fingerprint,
                 ..
-            }) => {
+            } => {
-                if tofu {
+                if persist_paired || tofu {
+                    // Request-access: the operator approved this device, so record the host as a
+                    // trusted PAIRED host — future connects are then silent (rule 1), exactly like
+                    // after a PIN ceremony. A plain TOFU connect persists it *unpaired* (pinned).
                     let mut k = KnownHosts::load();
                     k.upsert(KnownHost {
                         name: target.name.clone(),
                         addr: target.addr.clone(),
                         port: target.port,
                         fp_hex: trust::hex(&fingerprint),
-                        paired: false,
+                        paired: persist_paired,
                     });
                     let _ = k.save();
                 }
@@ -634,10 +739,10 @@ fn connect(
                 *shared.handoff.lock().unwrap() = Some((connector, handle.frames.clone()));
                 ss.call(Screen::Stream);
             }
-            Ok(SessionEvent::Failed {
+            SessionEvent::Failed {
                 msg,
                 trust_rejected,
-            }) => {
+            } => {
                 st.call(msg);
                 gamepad.detach();
                 if trust_rejected {
@@ -649,22 +754,100 @@ fn connect(
                 }
                 break;
             }
-            Ok(SessionEvent::Ended(err)) => {
+            SessionEvent::Ended(err) => {
                 st.call(err.unwrap_or_else(|| "Session ended".into()));
                 gamepad.detach();
                 ss.call(Screen::Hosts);
                 break;
             }
-            Ok(SessionEvent::Stats(s)) => *shared.stats.lock().unwrap() = s,
+            SessionEvent::Stats(s) => *shared.stats.lock().unwrap() = s,
-            Err(_) => {
-                gamepad.detach();
-                ss.call(Screen::Hosts);
-                break;
-            }
         }
     });
 }
 
+/// The no-PIN "request access" flow: open an identified connect that the host PARKS until the
+/// operator approves this device in its console (or web UI), showing a cancelable "waiting"
+/// screen meanwhile. On approval the SAME connection is admitted (no reconnect) and the host is
+/// saved as paired, so later connects are silent.
+fn request_access(
+    ctx: &Arc<AppCtx>,
+    target: &Target,
+    set_screen: &AsyncSetState<Screen>,
+    set_status: &AsyncSetState<String>,
+) {
+    // Pin the advertised certificate for a discovered host (defence against a host impostor while
+    // we wait); a manually-typed host has no advertised fingerprint, so trust-on-first-use.
+    let pin = target.fp_hex.as_deref().and_then(trust::parse_hex32);
+    // A fresh cancel flag per request, installed where the waiting screen's Cancel button can read
+    // it back; this request's event loop captures the same `Arc` (via ConnectOpts) below.
+    let cancel = Arc::new(AtomicBool::new(false));
+    *ctx.shared.cancel.lock().unwrap() = Some(cancel.clone());
+    connect_with(
+        ctx,
+        target,
+        pin,
+        set_screen,
+        set_status,
+        ConnectOpts {
+            // Must exceed the host's approval window (PENDING_APPROVAL_WAIT) so a slow operator
+            // approval still lands on this connection rather than timing the client out first.
+            connect_timeout: Duration::from_secs(185),
+            persist_paired: true,
+            awaiting_approval: true,
+            cancel: Some(cancel),
+        },
+    );
+}
+
+/// The cancelable "waiting for approval" screen (request-access flow): a spinner + guidance while
+/// the identified connect sits parked on the host, plus a Cancel that returns to the host list and
+/// trips the shared cancel flag so the parked connect tears down silently if it resolves after the
+/// user has walked away. Mirrors the inline `Connecting` screen; uses no hooks.
+fn request_access_page(ctx: &Arc<AppCtx>, set_screen: &AsyncSetState<Screen>) -> Element {
+    let target_name = ctx.shared.target.lock().unwrap().name.clone();
+    let headline = if target_name.is_empty() {
+        "Waiting for approval\u{2026}".to_string()
+    } else {
+        format!("Waiting for {target_name} to approve\u{2026}")
+    };
+    let cancel_btn = {
+        let (ctx, ss) = (ctx.clone(), set_screen.clone());
+        button("Cancel")
+            .icon(SymbolGlyph::Cancel)
+            .on_click(move || {
+                // Return the UI immediately; the parked connect is blocking with no abort, so trip
+                // the flag this request's event loop captured — it then tears down silently when
+                // the connect finally resolves (see ConnectOpts::cancel).
+                if let Some(c) = ctx.shared.cancel.lock().unwrap().as_ref() {
+                    c.store(true, Ordering::SeqCst);
+                }
+                ss.call(Screen::Hosts);
+            })
+            .horizontal_alignment(HorizontalAlignment::Center)
+    };
+    vstack((
+        ProgressRing::indeterminate()
+            .width(48.0)
+            .height(48.0)
+            .horizontal_alignment(HorizontalAlignment::Center),
+        text_block(headline)
+            .font_size(18.0)
+            .semibold()
+            .horizontal_alignment(HorizontalAlignment::Center),
+        text_block(
+            "Approve this device in the host's console or web UI \u{2014} it connects automatically \
+             once you approve it. No PIN needed.",
+        )
+        .foreground(ThemeRef::SecondaryText)
+        .horizontal_alignment(HorizontalAlignment::Center),
+        cancel_btn,
+    ))
+    .spacing(16.0)
+    .horizontal_alignment(HorizontalAlignment::Center)
+    .vertical_alignment(VerticalAlignment::Center)
+    .into()
+}
+
 fn pair_page(props: &Svc, cx: &mut RenderCx) -> Element {
     let ctx = &props.ctx;
     let set_screen = &props.set_screen;
@@ -724,6 +907,20 @@ fn pair_page(props: &Svc, cx: &mut RenderCx) -> Element {
             .icon(SymbolGlyph::Cancel)
             .on_click(move || ss.call(Screen::Hosts))
     };
+    // The no-PIN alternative offered alongside the PIN ceremony: open an identified connect that
+    // the host parks until the operator approves this device in its console (delegated approval).
+    let request_btn = {
+        let (ctx2, ss, st, target2) = (
+            ctx.clone(),
+            set_screen.clone(),
+            set_status.clone(),
+            target.clone(),
+        );
+        button("Request access without a PIN")
+            .icon(SymbolGlyph::Send)
+            .on_click(move || request_access(&ctx2, &target2, &ss, &st))
+            .horizontal_alignment(HorizontalAlignment::Stretch)
+    };
 
     let content = card(vstack((
         grid((
@@ -756,6 +953,13 @@ fn pair_page(props: &Svc, cx: &mut RenderCx) -> Element {
             .font_size(28.0)
             .on_changed(move |s| set_code.call(s)),
         hstack((pair_btn, cancel_btn)).spacing(8.0),
+        text_block(
+            "Don\u{2019}t have a PIN? Request access instead and approve this device on the host \
+             (its console or web UI) \u{2014} no PIN needed.",
+        )
+        .font_size(12.0)
+        .foreground(ThemeRef::SecondaryText),
+        request_btn,
     ))
     .spacing(16.0))
     .max_width(480.0)
@@ -886,6 +1090,23 @@ fn settings_page(ctx: &Arc<AppCtx>, set_screen: &AsyncSetState<Screen>) -> Eleme
                 s.save();
             })
     };
+    let ac_i = AUDIO_CHANNELS
+        .iter()
+        .position(|&(v, _)| v == s.audio_channels)
+        .unwrap_or(0) as i32;
+    let ac_names: Vec<String> = AUDIO_CHANNELS.iter().map(|&(_, l)| l.to_string()).collect();
+    let channels_combo = {
+        let ctx = ctx.clone();
+        ComboBox::new(ac_names)
+            .header("Audio channels")
+            .selected_index(ac_i)
+            .on_selection_changed(move |i: i32| {
+                let (v, _) = AUDIO_CHANNELS[(i.max(0) as usize).min(AUDIO_CHANNELS.len() - 1)];
+                let mut s = ctx.settings.lock().unwrap();
+                s.audio_channels = v;
+                s.save();
+            })
+    };
 
     let header = grid((
         text_block("Settings")
@@ -934,8 +1155,32 @@ fn settings_page(ctx: &Arc<AppCtx>, set_screen: &AsyncSetState<Screen>) -> Eleme
         .spacing(10.0),
     );
 
-    let audio_card =
+    let audio_card = card(
-        card(vstack((text_block("Audio").font_size(15.0).semibold(), mic_toggle)).spacing(10.0));
+        vstack((
+            text_block("Audio").font_size(15.0).semibold(),
+            text_block("Request stereo or surround — the host downmixes if its output has fewer.")
+                .font_size(12.0)
+                .foreground(ThemeRef::SecondaryText),
+            channels_combo,
+            mic_toggle,
+        ))
+        .spacing(10.0),
+    );
+
+    let licenses_button = {
+        let ss = set_screen.clone();
+        button("Third-party licenses").on_click(move || ss.call(Screen::Licenses))
+    };
+    let about_card = card(
+        vstack((
+            text_block("About").font_size(15.0).semibold(),
+            text_block("punktfunk is licensed under MIT OR Apache-2.0.")
+                .font_size(12.0)
+                .foreground(ThemeRef::SecondaryText),
+            licenses_button,
+        ))
+        .spacing(10.0),
+    );
 
     page(vec![
         header.into(),
@@ -945,6 +1190,77 @@ fn settings_page(ctx: &Arc<AppCtx>, set_screen: &AsyncSetState<Screen>) -> Eleme
         video_card.into(),
         section("AUDIO"),
         audio_card.into(),
+        section("ABOUT"),
+        about_card.into(),
+    ])
+}
+
+/// Static screen: the app's own license + the third-party software notices (reached from Settings).
+fn licenses_page(set_screen: &AsyncSetState<Screen>) -> Element {
+    let header = grid((
+        text_block("Third-party licenses")
+            .font_size(30.0)
+            .bold()
+            .grid_column(0)
+            .vertical_alignment(VerticalAlignment::Center),
+        button("Back")
+            .accent()
+            .icon(SymbolGlyph::Back)
+            .on_click({
+                let ss = set_screen.clone();
+                move || ss.call(Screen::Settings)
+            })
+            .grid_column(1)
+            .vertical_alignment(VerticalAlignment::Center),
+    ))
+    .columns([GridLength::Star(1.0), GridLength::Auto])
+    .margin(edges(0.0, 0.0, 0.0, 6.0));
+
+    let app_card = card(
+        vstack((
+            text_block("punktfunk").font_size(15.0).semibold(),
+            text_block("Licensed under MIT OR Apache-2.0, at your option.")
+                .font_size(12.0)
+                .foreground(ThemeRef::SecondaryText),
+            text_block(APP_LICENSE)
+                .font_size(11.0)
+                .foreground(ThemeRef::SecondaryText),
+        ))
+        .spacing(8.0),
+    );
+
+    let natives_card = card(
+        vstack((
+            text_block("Bundled components").font_size(15.0).semibold(),
+            text_block(
+                "FFmpeg is bundled under the LGPL v2.1+ (dynamically linked, replaceable DLLs); its \
+                 license and notice ship in the installed licenses\\ folder. SDL 3 (Zlib) and the \
+                 Windows App SDK (Microsoft) are also linked.",
+            )
+            .font_size(12.0)
+            .foreground(ThemeRef::SecondaryText),
+        ))
+        .spacing(8.0),
+    );
+
+    let notices_card = card(
+        vstack((
+            text_block("Rust crates").font_size(15.0).semibold(),
+            text_block(THIRD_PARTY_NOTICES)
+                .font_size(11.0)
+                .foreground(ThemeRef::SecondaryText),
+        ))
+        .spacing(8.0),
+    );
+
+    page(vec![
+        header.into(),
+        section("PUNKTFUNK"),
+        app_card.into(),
+        section("BUNDLED"),
+        natives_card.into(),
+        section("OPEN SOURCE"),
+        notices_card.into(),
     ])
 }
 

clients/windows/src/audio.rs

@@ -21,9 +21,9 @@ use std::time::Duration;
 use wasapi::{DeviceEnumerator, Direction, SampleType, StreamMode, WaveFormat};
 
 const SAMPLE_RATE: usize = 48_000;
+/// The microphone uplink stays stereo (the host's virtual mic is stereo). The render path is
+/// multichannel — its channel count + block align are runtime, driven by the host-resolved layout.
 const CHANNELS: usize = 2;
-/// 48 kHz stereo f32: 2 channels * 4 bytes = 8 bytes per frame.
-const BLOCK_ALIGN: usize = CHANNELS * 4;
 /// Mic frames are 20 ms (960 samples/channel) — any size ≤ 120 ms is fine host-side.
 const MIC_FRAME: usize = 960;
 
@@ -34,9 +34,10 @@ pub struct AudioPlayer {
 }
 
 impl AudioPlayer {
-    /// Spawn the WASAPI render thread. Failure (no render endpoint on this box) is
+    /// Spawn the WASAPI render thread for `channels` (2/6/8, canonical wire order
-    /// survivable — the caller streams video-only.
+    /// FL FR FC LFE RL RR SL SR). Failure (no render endpoint on this box) is survivable — the
-    pub fn spawn() -> Result<AudioPlayer> {
+    /// caller streams video-only.
+    pub fn spawn(channels: u8) -> Result<AudioPlayer> {
         // 64 × 5 ms = 320 ms of slack between the pump and the WASAPI loop.
         let (pcm_tx, pcm_rx) = std::sync::mpsc::sync_channel::<Vec<f32>>(64);
         let stop = Arc::new(AtomicBool::new(false));
@@ -45,14 +46,14 @@ impl AudioPlayer {
         let thread = std::thread::Builder::new()
             .name("punktfunk-audio".into())
             .spawn(move || {
-                if let Err(e) = render_thread(pcm_rx, stop_t, ready_tx) {
+                if let Err(e) = render_thread(pcm_rx, stop_t, ready_tx, channels) {
                     tracing::warn!(error = format!("{e:#}"), "audio playback thread ended");
                 }
             })
             .context("spawn audio thread")?;
         match ready_rx.recv_timeout(Duration::from_secs(3)) {
             Ok(Ok(())) => {
-                tracing::info!("WASAPI render: 48 kHz stereo f32 (default endpoint)");
+                tracing::info!(channels, "WASAPI render: 48 kHz f32 (default endpoint)");
                 Ok(AudioPlayer {
                     pcm_tx,
                     stop,
@@ -66,8 +67,8 @@ impl AudioPlayer {
         }
     }
 
-    /// Queue one interleaved-stereo f32 chunk. Drops the chunk if the WASAPI side is wedged
+    /// Queue one interleaved f32 chunk (in the session's channel layout). Drops the chunk if the
-    /// (the renderer conceals the gap; never block the session pump).
+    /// WASAPI side is wedged (the renderer conceals the gap; never block the session pump).
     pub fn push(&self, pcm: Vec<f32>) {
         if let Err(TrySendError::Disconnected(_)) = self.pcm_tx.try_send(pcm) {
             // Thread already dead — Drop will reap it; nothing to do per-chunk.
@@ -88,6 +89,7 @@ fn render_thread(
     pcm_rx: Receiver<Vec<f32>>,
     stop: Arc<AtomicBool>,
     ready: SyncSender<Result<()>>,
+    channels: u8,
 ) -> Result<()> {
     if let Err(e) = wasapi::initialize_mta()
         .ok()
@@ -97,12 +99,26 @@ fn render_thread(
         return Ok(());
     }
     let res = (|| -> Result<()> {
+        // F32LE interleaved: channels × 4 bytes/sample. Stereo (channels == 2) is byte-identical
+        // to the old fixed path (mask 0x3, block align 8).
+        let block_align = channels as usize * 4;
         let device = DeviceEnumerator::new()
             .context("DeviceEnumerator")?
             .get_default_device(&Direction::Render)
             .context("default render endpoint")?;
         let mut audio_client = device.get_iaudioclient().context("IAudioClient")?;
-        let desired = WaveFormat::new(32, 32, &SampleType::Float, SAMPLE_RATE, CHANNELS, None);
+        // The explicit dwChannelMask is the wire order (FL FR FC LFE RL RR SL SR); 5.1 = 0x3F,
+        // 7.1 = 0x63F. WASAPI delivers channels in ascending mask-bit order, which equals the wire
+        // order, so the render mapping is the identity — no permute. `autoconvert` (below) lets the
+        // audio engine downmix when the endpoint has fewer speakers.
+        let desired = WaveFormat::new(
+            32,
+            32,
+            &SampleType::Float,
+            SAMPLE_RATE,
+            channels as usize,
+            Some(punktfunk_core::audio::wasapi_channel_mask(channels)),
+        );
         let (default_period, _min_period) =
             audio_client.get_device_period().context("device period")?;
         let mode = StreamMode::EventsShared {
@@ -139,10 +155,10 @@ fn render_thread(
             if avail_frames == 0 {
                 continue;
             }
-            let want_bytes = avail_frames * BLOCK_ALIGN;
+            let want_bytes = avail_frames * block_align;
 
             // Prime to ~3 quanta; cap at ~1 quantum of slack beyond that; re-prime on drain.
-            let target = (3 * want_bytes).clamp(720 * BLOCK_ALIGN, 9600 * BLOCK_ALIGN);
+            let target = (3 * want_bytes).clamp(720 * block_align, 9600 * block_align);
             while ring.len() > target.max(want_bytes) + want_bytes {
                 ring.pop_front();
             }

clients/windows/src/main.rs

@@ -177,11 +177,16 @@ fn run_headless_cli(args: &[String], identity: (String, String)) {
         compositor: CompositorPref::Auto,
         gamepad: GamepadPref::Auto,
         bitrate_kbps,
+        // Headless CLI path (test/scripting) — stereo baseline; the GUI sources this from settings.
+        audio_channels: 2,
         mic_enabled: flag("--mic"),
         hdr_enabled: !flag("--no-hdr"),
         decoder,
         pin,
         identity,
+        // Headless CLI uses the normal (short) handshake budget; the long request-access wait is a
+        // GUI-only flow.
+        connect_timeout: Duration::from_secs(15),
     });
 
     let deadline = Instant::now() + Duration::from_secs(60);

clients/windows/src/session.rs

@@ -23,6 +23,8 @@ pub struct SessionParams {
     pub compositor: CompositorPref,
     pub gamepad: GamepadPref,
     pub bitrate_kbps: u32,
+    /// Requested audio channel count (2/6/8); the host echoes the resolved value.
+    pub audio_channels: u8,
     /// Stream the default microphone to the host's virtual mic source.
     pub mic_enabled: bool,
     /// Advertise 10-bit + HDR10 so the host may upgrade HDR content to a Main10/PQ stream.
@@ -32,6 +34,11 @@ pub struct SessionParams {
     /// Pinned host fingerprint; `None` = trust on first use (caller persists the observed one).
     pub pin: Option<[u8; 32]>,
     pub identity: (String, String),
+    /// How long to wait for the handshake. The normal path uses a short budget; the
+    /// "request access" (delegated-approval) path uses a long one, because the host PARKS the
+    /// connection until the operator clicks Approve in its console (so this must exceed the
+    /// host's approval window — see `PENDING_APPROVAL_WAIT`).
+    pub connect_timeout: Duration,
 }
 
 #[derive(Clone, Copy, Default, PartialEq)]
@@ -94,6 +101,42 @@ fn now_ns() -> u64 {
         .unwrap_or(0)
 }
 
+/// Opus decoder for the audio plane: a plain stereo decoder (the validated path) or a multistream
+/// decoder for 5.1/7.1, both behind one `decode_float`. Built from the host-RESOLVED channel count
+/// via the shared layout table.
+enum AudioDec {
+    Stereo(opus::Decoder),
+    Surround(opus::MSDecoder),
+}
+
+impl AudioDec {
+    fn new(channels: u8) -> Result<AudioDec, opus::Error> {
+        if channels == 2 {
+            Ok(AudioDec::Stereo(opus::Decoder::new(
+                48_000,
+                opus::Channels::Stereo,
+            )?))
+        } else {
+            let l = punktfunk_core::audio::layout_for(channels, false);
+            Ok(AudioDec::Surround(opus::MSDecoder::new(
+                48_000, l.streams, l.coupled, l.mapping,
+            )?))
+        }
+    }
+
+    fn decode_float(
+        &mut self,
+        input: &[u8],
+        out: &mut [f32],
+        fec: bool,
+    ) -> Result<usize, opus::Error> {
+        match self {
+            AudioDec::Stereo(d) => d.decode_float(input, out, fec),
+            AudioDec::Surround(d) => d.decode_float(input, out, fec),
+        }
+    }
+}
+
 fn pump(
     params: SessionParams,
     ev_tx: async_channel::Sender<SessionEvent>,
@@ -122,10 +165,11 @@ fn pump(
             }
             0
         },
+        params.audio_channels,
         None, // launch: the Windows client has no library picker yet
         params.pin,
         Some(params.identity),
-        Duration::from_secs(15),
+        params.connect_timeout,
     ) {
         Ok(c) => Arc::new(c),
         Err(e) => {
@@ -161,11 +205,14 @@ fn pump(
     let mut hardware = decoder.is_hardware();
     let mut hdr = false;
     // Audio is best-effort: a session without it still streams. Gamepads are the
-    // app-lifetime service's job (the UI attaches it on Connected).
+    // app-lifetime service's job (the UI attaches it on Connected). Build the decoder + playback
-    let player = audio::AudioPlayer::spawn()
+    // from the host-RESOLVED channel count (never the request), so an older/clamping host that
+    // resolves stereo is decoded as stereo.
+    let channels = connector.audio_channels;
+    let player = audio::AudioPlayer::spawn(channels)
         .map_err(|e| tracing::warn!(error = %e, "audio disabled"))
         .ok();
-    let mut opus_dec = opus::Decoder::new(48_000, opus::Channels::Stereo)
+    let mut opus_dec = AudioDec::new(channels)
         .map_err(|e| tracing::warn!(error = %e, "opus decoder failed — audio disabled"))
         .ok();
     let _mic = params
@@ -184,7 +231,7 @@ fn pump(
     let mut bytes_n = 0u64;
     let mut decode_us_sum = 0u64;
     let mut lat_us: Vec<u64> = Vec::with_capacity(256);
-    let mut pcm = vec![0f32; 5760 * 2]; // decode scratch: max Opus frame (120 ms stereo)
+    let mut pcm = vec![0f32; 5760 * channels as usize]; // scratch: max Opus frame (120 ms) × channels
                                                         // Loss recovery: watch the host→client unrecoverable-drop count and ask for an IDR when it climbs.
     let mut last_dropped = connector.frames_dropped();
     let mut last_kf_req: Option<Instant> = None;
@@ -253,7 +300,8 @@ fn pump(
         while let Ok(pkt) = connector.next_audio(Duration::ZERO) {
             if let (Some(player), Some(dec)) = (&player, opus_dec.as_mut()) {
                 match dec.decode_float(&pkt.data, &mut pcm, false) {
-                    Ok(samples) => player.push(pcm[..samples * 2].to_vec()),
+                    // `samples` is per-channel; the interleaved frame is `samples * channels`.
+                    Ok(samples) => player.push(pcm[..samples * channels as usize].to_vec()),
                     Err(e) => tracing::debug!(error = %e, "opus decode"),
                 }
             }

clients/windows/src/trust.rs

@@ -130,6 +130,9 @@ pub struct Settings {
     pub inhibit_shortcuts: bool,
     /// Stream the default microphone to the host's virtual mic source.
     pub mic_enabled: bool,
+    /// Requested audio channel count: 2 (stereo), 6 (5.1) or 8 (7.1). The host clamps to what it
+    /// can capture; the resolved count drives the decoder + WASAPI render layout.
+    pub audio_channels: u8,
     /// Advertise 10-bit + HDR10 so the host upgrades HDR content to a Main10/PQ stream (the client
     /// presents it on a 10-bit ST.2084 swapchain). No effect on SDR content.
     pub hdr_enabled: bool,
@@ -148,6 +151,7 @@ impl Default for Settings {
             compositor: "auto".into(),
             inhibit_shortcuts: true,
             mic_enabled: false,
+            audio_channels: 2,
             hdr_enabled: true,
             decoder: "auto".into(),
         }

crates/punktfunk-core/Cargo.toml

@@ -19,7 +19,7 @@ crate-type = ["lib", "cdylib", "staticlib"]
 default = []
 # Control-plane QUIC (pairing, config, reverse audio). tokio is permitted ONLY here,
 # never on the per-frame hot path. Off by default so the core stays runtime-free.
-quic = ["dep:quinn", "dep:tokio", "dep:rustls", "dep:rcgen", "dep:rustls-pki-types", "dep:sha2", "dep:hmac", "dep:spake2"]
+quic = ["dep:quinn", "dep:tokio", "dep:rustls", "dep:rcgen", "dep:rustls-pki-types", "dep:sha2", "dep:hmac", "dep:spake2", "dep:opus"]
 
 [dependencies]
 reed-solomon-simd = "3.1"      # GF(2^16) Leopard-RS, SIMD, O(n log n) — the wall-breaker (P2)
@@ -51,6 +51,12 @@ sha2 = { version = "0.10", optional = true }
 hmac = { version = "0.12", optional = true }
 spake2 = { version = "0.4", optional = true }
 tokio = { version = "1", optional = true, features = ["rt-multi-thread", "net", "sync", "macros"] }
+# In-core Opus (multistream) DECODE for the C-ABI `punktfunk_connection_next_audio_pcm` path —
+# used by embedders without a multistream-capable Opus decoder (Apple's AudioToolbox is
+# stereo-only). The Rust clients link `opus` themselves and decode the raw `next_audio` frames,
+# so this only matters when the connection API (quic) is built. Same libopus the host vendors;
+# cargo unifies the build. Multistream API: `opus::MSDecoder` (lib.rs:1187).
+opus = { version = "0.3", optional = true }
 
 # `libc` for batched UDP syscalls: `sendmmsg`/`recvmmsg` on Linux (the 1 Gbps+ lever) and the
 # `recv(MSG_DONTWAIT)` drain on the other unix (Apple/BSD) targets, which have no `recvmmsg`

crates/punktfunk-core/src/abi.rs

@@ -467,6 +467,23 @@ pub struct PunktfunkConnection {
     last: std::sync::Mutex<Option<crate::session::Frame>>,
     /// Same, for `punktfunk_connection_next_audio` (independent of the video slot).
     last_audio: std::sync::Mutex<Option<crate::client::AudioPacket>>,
+    /// Decode-in-core state for `punktfunk_connection_next_audio_pcm` (Apple / any embedder
+    /// without a multistream Opus decoder). The decoder is built lazily from the negotiated
+    /// `inner.audio_channels`; `pcm` is a fixed-capacity reusable buffer the returned pointer
+    /// borrows until the next PCM call (same contract as `last_audio`).
+    audio_pcm: std::sync::Mutex<AudioPcmState>,
+}
+
+/// Lazily-initialized in-core Opus decode state. A coupled-1-stream multistream decoder is
+/// equivalent to a plain stereo decoder, so one [`opus::MSDecoder`] handles 2/6/8 channels.
+#[cfg(feature = "quic")]
+#[derive(Default)]
+struct AudioPcmState {
+    decoder: Option<opus::MSDecoder>,
+    /// Interleaved f32 PCM, wire channel order. Pre-sized to the largest legal Opus frame
+    /// (120 ms @ 48 kHz = 5760 samples/ch) × 8 channels so decode never reallocates (which would
+    /// dangle the pointer handed to the embedder).
+    pcm: Vec<f32>,
 }
 
 /// `PunktfunkHidOutput::kind` — lightbar RGB (`r`/`g`/`b` valid).
@@ -708,12 +725,18 @@ pub const PUNKTFUNK_VIDEO_CAP_10BIT: u8 = 0x01;
 /// Video-capability bit for [`punktfunk_connect_ex5`] (`video_caps`): the client can present
 /// BT.2020 PQ HDR10 (implies 10-bit). (Mirrors `quic::VIDEO_CAP_HDR`.)
 pub const PUNKTFUNK_VIDEO_CAP_HDR: u8 = 0x02;
+/// Video-capability bit for [`punktfunk_connect_ex5`] (`video_caps`): the client can decode a
+/// full-chroma 4:4:4 HEVC stream (Range Extensions). The host emits 4:4:4 only when this is set,
+/// the host opted in, the codec is HEVC, and the GPU supports it — else the stream stays 4:2:0 and
+/// [`punktfunk_connection_chroma_format`] reports the real value. (Mirrors `quic::VIDEO_CAP_444`.)
+pub const PUNKTFUNK_VIDEO_CAP_444: u8 = 0x04;
 
 // Keep the ABI cap bits in lockstep with the wire constants (compile-time guard against drift).
 #[cfg(feature = "quic")]
 const _: () = {
     assert!(PUNKTFUNK_VIDEO_CAP_10BIT == crate::quic::VIDEO_CAP_10BIT);
     assert!(PUNKTFUNK_VIDEO_CAP_HDR == crate::quic::VIDEO_CAP_HDR);
+    assert!(PUNKTFUNK_VIDEO_CAP_444 == crate::quic::VIDEO_CAP_444);
 };
 
 // Keep the ABI gamepad constants in lockstep with the wire enum (compile-time guard against drift).
@@ -980,6 +1003,58 @@ pub unsafe extern "C" fn punktfunk_connect_ex5(
     client_cert_pem: *const std::os::raw::c_char,
     client_key_pem: *const std::os::raw::c_char,
     timeout_ms: u32,
+) -> *mut PunktfunkConnection {
+    // Delegate to the surround-aware variant requesting stereo (the pre-surround behaviour).
+    unsafe {
+        punktfunk_connect_ex6(
+            host,
+            port,
+            width,
+            height,
+            refresh_hz,
+            compositor,
+            gamepad,
+            bitrate_kbps,
+            video_caps,
+            2, // audio_channels = stereo
+            launch_id,
+            pin_sha256,
+            observed_sha256_out,
+            client_cert_pem,
+            client_key_pem,
+            timeout_ms,
+        )
+    }
+}
+
+/// Like [`punktfunk_connect_ex5`], but additionally requests the audio channel count:
+/// `2` (stereo, the default behaviour of every earlier variant), `6` (5.1) or `8` (7.1). The host
+/// clamps the request to what it can actually capture and echoes the resolved count via
+/// [`punktfunk_connection_audio_channels`]; the `0xC9` audio frames are Opus-(multi)stream encoded
+/// for that layout. A client that wants surround calls this; everything else inherits stereo.
+///
+/// # Safety
+/// Same as [`punktfunk_connect`].
+#[cfg(feature = "quic")]
+#[no_mangle]
+#[allow(clippy::too_many_arguments)]
+pub unsafe extern "C" fn punktfunk_connect_ex6(
+    host: *const std::os::raw::c_char,
+    port: u16,
+    width: u32,
+    height: u32,
+    refresh_hz: u32,
+    compositor: u32,
+    gamepad: u32,
+    bitrate_kbps: u32,
+    video_caps: u8,
+    audio_channels: u8,
+    launch_id: *const std::os::raw::c_char,
+    pin_sha256: *const u8,
+    observed_sha256_out: *mut u8,
+    client_cert_pem: *const std::os::raw::c_char,
+    client_key_pem: *const std::os::raw::c_char,
+    timeout_ms: u32,
 ) -> *mut PunktfunkConnection {
     let r = std::panic::catch_unwind(AssertUnwindSafe(|| {
         if host.is_null() {
@@ -1029,6 +1104,7 @@ pub unsafe extern "C" fn punktfunk_connect_ex5(
             gamepad,
             bitrate_kbps,
             video_caps,
+            crate::audio::normalize_channels(audio_channels),
             launch,
             pin,
             identity,
@@ -1045,6 +1121,7 @@ pub unsafe extern "C" fn punktfunk_connect_ex5(
                     inner: c,
                     last: std::sync::Mutex::new(None),
                     last_audio: std::sync::Mutex::new(None),
+                    audio_pcm: std::sync::Mutex::new(AudioPcmState::default()),
                 }))
             }
             Err(_) => std::ptr::null_mut(),
@@ -1250,6 +1327,121 @@ pub unsafe extern "C" fn punktfunk_connection_next_audio(
     })
 }
 
+/// Read the audio channel count the host resolved for this session (from its Welcome): `2`
+/// (stereo), `6` (5.1) or `8` (7.1). `*out` is filled when non-NULL. The `0xC9` Opus frames are
+/// (multistream-)encoded for this layout; an embedder decoding raw frames itself must build its
+/// decoder from THIS value (see [`crate::audio::layout_for`]) — or use
+/// [`punktfunk_connection_next_audio_pcm`], which decodes in-core. Available immediately after a
+/// successful connect (it doesn't change without a reconfigure).
+///
+/// # Safety
+/// `c` is a valid connection handle; `out` is NULL or writable for one `u8`.
+#[cfg(feature = "quic")]
+#[no_mangle]
+pub unsafe extern "C" fn punktfunk_connection_audio_channels(
+    c: *mut PunktfunkConnection,
+    out: *mut u8,
+) -> PunktfunkStatus {
+    guard(|| {
+        let c = match unsafe { c.as_ref() } {
+            Some(c) => c,
+            None => return PunktfunkStatus::NullPointer,
+        };
+        if !out.is_null() {
+            // SAFETY: `out` is non-null and the caller guarantees it is writable for one `u8`.
+            unsafe { *out = c.inner.audio_channels };
+        }
+        PunktfunkStatus::Ok
+    })
+}
+
+/// One decoded audio frame from [`punktfunk_connection_next_audio_pcm`]: interleaved 32-bit
+/// float PCM at 48 kHz, in the canonical wire channel order `FL FR FC LFE RL RR SL SR` (the
+/// first `channels` of it). `samples` points at `frame_count * channels` floats and borrows
+/// connection memory **until the next PCM call** on this handle.
+#[cfg(feature = "quic")]
+#[repr(C)]
+pub struct PunktfunkAudioPcm {
+    /// Interleaved f32 samples (wire channel order), `frame_count * channels` long.
+    pub samples: *const f32,
+    /// Samples per channel in this frame.
+    pub frame_count: u32,
+    /// Channel count (2/6/8) — the negotiated [`punktfunk_connection_audio_channels`].
+    pub channels: u8,
+    /// Source packet sequence number.
+    pub seq: u32,
+    /// Capture presentation timestamp (ns).
+    pub pts_ns: u64,
+}
+
+/// Pull the next audio frame and **decode it in-core** to interleaved f32 PCM — for embedders
+/// without a multistream-capable Opus decoder (e.g. Apple, whose AudioToolbox Opus path is
+/// stereo-only). The decoder is built once from the negotiated channel count and handles 2/6/8
+/// channels (a 1-coupled-stream multistream decoder is exactly a stereo decoder). Same
+/// timeout/closed semantics as [`punktfunk_connection_next_audio`]; `out->samples` borrows
+/// connection memory until the next PCM call on this handle. Use EITHER this or
+/// [`punktfunk_connection_next_audio`] on a given connection, from one dedicated audio thread —
+/// not both (they share the underlying queue).
+///
+/// # Safety
+/// `c` is a valid connection handle; `out` is writable. At most one thread pulls audio.
+#[cfg(feature = "quic")]
+#[no_mangle]
+pub unsafe extern "C" fn punktfunk_connection_next_audio_pcm(
+    c: *mut PunktfunkConnection,
+    out: *mut PunktfunkAudioPcm,
+    timeout_ms: u32,
+) -> PunktfunkStatus {
+    guard(|| {
+        let c = match unsafe { c.as_ref() } {
+            Some(c) => c,
+            None => return PunktfunkStatus::NullPointer,
+        };
+        if out.is_null() {
+            return PunktfunkStatus::NullPointer;
+        }
+        let channels = crate::audio::normalize_channels(c.inner.audio_channels);
+        let pkt = match c
+            .inner
+            .next_audio(std::time::Duration::from_millis(timeout_ms as u64))
+        {
+            Ok(pkt) => pkt,
+            Err(e) => return e.status(),
+        };
+        let mut state = c.audio_pcm.lock().unwrap();
+        if state.decoder.is_none() {
+            let layout = crate::audio::layout_for(channels, false);
+            match opus::MSDecoder::new(48_000, layout.streams, layout.coupled, layout.mapping) {
+                Ok(d) => {
+                    // Largest legal Opus frame is 120 ms = 5760 samples/ch.
+                    state.pcm = vec![0f32; 5760 * channels as usize];
+                    state.decoder = Some(d);
+                }
+                Err(_) => return PunktfunkStatus::Unsupported,
+            }
+        }
+        let AudioPcmState { decoder, pcm } = &mut *state;
+        let dec = decoder.as_mut().unwrap();
+        // `decode_float` divides the output buffer length by the channel count to get the
+        // per-channel capacity; an empty payload requests packet-loss concealment.
+        match dec.decode_float(&pkt.data, pcm, false) {
+            Ok(frame_count) => {
+                unsafe {
+                    *out = PunktfunkAudioPcm {
+                        samples: pcm.as_ptr(),
+                        frame_count: frame_count as u32,
+                        channels,
+                        seq: pkt.seq,
+                        pts_ns: pkt.pts_ns,
+                    };
+                }
+                PunktfunkStatus::Ok
+            }
+            Err(_) => PunktfunkStatus::BadPacket,
+        }
+    })
+}
+
 /// Pull the next rumble (force-feedback) update, waiting up to `timeout_ms`. Amplitudes
 /// are 0..0xFFFF (`low` = low-frequency motor, `high` = high-frequency), `(0, 0)` = stop.
 /// Same timeout/closed semantics as [`punktfunk_connection_next_audio`].
@@ -1414,6 +1606,33 @@ pub unsafe extern "C" fn punktfunk_connection_color_info(
     })
 }
 
+/// Read the session's resolved chroma subsampling (from the host's Welcome) as the HEVC
+/// `chroma_format_idc`: `1` = 4:2:0 (the default every pre-4:4:4 host produced), `3` = full-chroma
+/// 4:4:4. `*out` is filled when non-NULL. The in-band SPS is authoritative; this lets the embedder
+/// pre-size its decoder / pick a 4:4:4 pixel format up front. Available immediately after a
+/// successful connect (it doesn't change without a reconfigure).
+///
+/// # Safety
+/// `c` is a valid connection handle; `out` is NULL or writable for one `u8`.
+#[cfg(feature = "quic")]
+#[no_mangle]
+pub unsafe extern "C" fn punktfunk_connection_chroma_format(
+    c: *mut PunktfunkConnection,
+    out: *mut u8,
+) -> PunktfunkStatus {
+    guard(|| {
+        let c = match unsafe { c.as_ref() } {
+            Some(c) => c,
+            None => return PunktfunkStatus::NullPointer,
+        };
+        if !out.is_null() {
+            // SAFETY: `out` is non-null and the caller guarantees it is writable for one `u8`.
+            unsafe { *out = c.inner.chroma_format };
+        }
+        PunktfunkStatus::Ok
+    })
+}
+
 /// Send one input event to the host as a QUIC datagram (non-blocking enqueue).
 ///
 /// # Safety

crates/punktfunk-core/src/audio.rs

@@ -0,0 +1,298 @@
+//! Shared audio layout: the single source of truth for Opus (multi)stream surround across the
+//! host, the GameStream compatibility path, and every client decoder.
+//!
+//! **Canonical wire channel order** is `FL FR FC LFE RL RR SL SR` (the GameStream/Moonlight
+//! order, and the PipeWire/PulseAudio default map for 6/8 channels). Every host capturer
+//! delivers PCM in this order and every client decodes into it, so the Opus multistream
+//! `mapping` is the **identity** (`[0, 1, …, channels-1]`) on both ends — punktfunk owns the
+//! encoder and every decoder, so the GFE-style pre-rotation Moonlight needs over SDP
+//! (`gamestream::audio::surround_params`) is a GameStream-only concern and never touches the
+//! native `punktfunk/1` path.
+//!
+//! Channel counts the protocol negotiates: `2` (stereo), `6` (5.1) and `8` (7.1). Anything
+//! else clamps to stereo ([`normalize_channels`]).
+
+/// Canonical wire channel positions; the index is the channel's slot in the interleaved PCM
+/// frame. A count of N uses positions `0..N` (always a prefix of this 8-channel order).
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[repr(u8)]
+pub enum WirePos {
+    FrontLeft = 0,
+    FrontRight = 1,
+    FrontCenter = 2,
+    Lfe = 3,
+    RearLeft = 4,
+    RearRight = 5,
+    SideLeft = 6,
+    SideRight = 7,
+}
+
+/// The full 8-channel wire order; the N-channel order is its first N entries.
+pub const WIRE_ORDER_8: [WirePos; 8] = {
+    use WirePos::*;
+    [
+        FrontLeft,
+        FrontRight,
+        FrontCenter,
+        Lfe,
+        RearLeft,
+        RearRight,
+        SideLeft,
+        SideRight,
+    ]
+};
+
+/// One Opus (multi)stream layout. `mapping` is the libopus multistream mapping we encode AND
+/// decode with — identity, since punktfunk owns both ends. `streams`/`coupled` give the
+/// normal-quality coupling (FL,FR)+(FC,LFE) [+(RL,RR) on 7.1] with the remaining channels as
+/// mono streams; high quality is one mono stream per channel. Bitrates match Sunshine's
+/// per-config values (stereo keeps punktfunk's live-validated 128 kbps).
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct OpusLayout {
+    /// Interleaved channel count (2, 6 or 8).
+    pub channels: u8,
+    /// Number of Opus streams in the multistream packet.
+    pub streams: u8,
+    /// How many of those streams are coupled (stereo) pairs.
+    pub coupled: u8,
+    /// libopus multistream channel mapping — identity `[0, 1, …, channels-1]`.
+    pub mapping: &'static [u8],
+    /// Target Opus bitrate in bits/sec (hard CBR; constant packet size, which GameStream's
+    /// audio FEC relies on).
+    pub bitrate: i32,
+}
+
+/// Stereo: a plain coupled pair. The 128 kbps live-validated config.
+pub const LAYOUT_STEREO: OpusLayout = OpusLayout {
+    channels: 2,
+    streams: 1,
+    coupled: 1,
+    mapping: &[0, 1],
+    bitrate: 128_000,
+};
+/// 5.1 normal quality: (FL,FR)+(FC,LFE) coupled, RL+RR mono.
+pub const LAYOUT_51: OpusLayout = OpusLayout {
+    channels: 6,
+    streams: 4,
+    coupled: 2,
+    mapping: &[0, 1, 2, 3, 4, 5],
+    bitrate: 256_000,
+};
+/// 5.1 high quality: one mono stream per channel.
+pub const LAYOUT_51_HQ: OpusLayout = OpusLayout {
+    channels: 6,
+    streams: 6,
+    coupled: 0,
+    mapping: &[0, 1, 2, 3, 4, 5],
+    bitrate: 1_536_000,
+};
+/// 7.1 normal quality: (FL,FR)+(FC,LFE)+(RL,RR) coupled, SL+SR mono.
+pub const LAYOUT_71: OpusLayout = OpusLayout {
+    channels: 8,
+    streams: 5,
+    coupled: 3,
+    mapping: &[0, 1, 2, 3, 4, 5, 6, 7],
+    bitrate: 450_000,
+};
+/// 7.1 high quality: one mono stream per channel.
+pub const LAYOUT_71_HQ: OpusLayout = OpusLayout {
+    channels: 8,
+    streams: 8,
+    coupled: 0,
+    mapping: &[0, 1, 2, 3, 4, 5, 6, 7],
+    bitrate: 2_048_000,
+};
+
+/// Pick the layout for a negotiated channel count. Unknown counts fall back to stereo (clients
+/// only ever request 2/6/8). `high_quality` selects the uncoupled high-bitrate config.
+pub fn layout_for(channels: u8, high_quality: bool) -> &'static OpusLayout {
+    match (channels, high_quality) {
+        (6, false) => &LAYOUT_51,
+        (6, true) => &LAYOUT_51_HQ,
+        (8, false) => &LAYOUT_71,
+        (8, true) => &LAYOUT_71_HQ,
+        _ => &LAYOUT_STEREO,
+    }
+}
+
+/// Clamp an arbitrary (wire / requested) channel count to one the protocol negotiates. `0`,
+/// absent, or any unsupported value becomes stereo.
+pub fn normalize_channels(requested: u8) -> u8 {
+    match requested {
+        6 => 6,
+        8 => 8,
+        _ => 2,
+    }
+}
+
+// ---- per-platform channel-layout helpers (pure data; no platform deps) --------------------
+
+/// Windows `WAVEFORMATEXTENSIBLE.dwChannelMask` for the wire layout.
+///
+/// NB 7.1 == `0x63F` (FL FR FC LFE **BL BR SL SR**), NOT `0xFF` — `0xFF` selects the
+/// front-of-center pair FLC/FRC, the wrong speakers. WASAPI delivers channels in ascending
+/// mask-bit order, which equals the wire order, so the decoded PCM needs no permutation.
+pub const fn wasapi_channel_mask(channels: u8) -> u32 {
+    const FL: u32 = 0x1;
+    const FR: u32 = 0x2;
+    const FC: u32 = 0x4;
+    const LFE: u32 = 0x8;
+    const BL: u32 = 0x10; // back left  (wire RL)
+    const BR: u32 = 0x20; // back right (wire RR)
+    const SL: u32 = 0x200; // side left
+    const SR: u32 = 0x400; // side right
+    match channels {
+        6 => FL | FR | FC | LFE | BL | BR,           // 0x3F
+        8 => FL | FR | FC | LFE | BL | BR | SL | SR, // 0x63F
+        _ => FL | FR,                                // 0x3 (stereo)
+    }
+}
+
+/// PipeWire / SPA `enum spa_audio_channel` positions in wire order — identical to the host
+/// capture side (`punktfunk-host` `audio::linux::spa_positions`): FL=3 FR=4 FC=5 LFE=6 SL=7
+/// SR=8 RL=12 RR=13. Identity routing: the client sets these on its playback node so PipeWire
+/// maps each wire slot to the matching speaker (and downmixes when the sink has fewer).
+pub fn spa_positions(channels: u8) -> &'static [u32] {
+    const STEREO: [u32; 2] = [3, 4]; // FL FR
+    const C51: [u32; 6] = [3, 4, 5, 6, 12, 13]; // FL FR FC LFE RL RR
+    const C71: [u32; 8] = [3, 4, 5, 6, 12, 13, 7, 8]; // FL FR FC LFE RL RR SL SR
+    match channels {
+        6 => &C51,
+        8 => &C71,
+        _ => &STEREO,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn layout_table_is_consistent() {
+        for l in [
+            &LAYOUT_STEREO,
+            &LAYOUT_51,
+            &LAYOUT_51_HQ,
+            &LAYOUT_71,
+            &LAYOUT_71_HQ,
+        ] {
+            // Mapping is identity and exactly `channels` entries long.
+            assert_eq!(l.mapping.len(), l.channels as usize);
+            for (i, &m) in l.mapping.iter().enumerate() {
+                assert_eq!(m as usize, i, "mapping must be identity for {l:?}");
+            }
+            // libopus invariant: total channels == coupled*2 + (streams - coupled).
+            assert_eq!(
+                l.coupled * 2 + (l.streams - l.coupled),
+                l.channels,
+                "stream/coupled accounting for {l:?}"
+            );
+            assert!(l.coupled <= l.streams);
+            assert!(l.bitrate > 0);
+        }
+    }
+
+    #[test]
+    fn layout_for_picks_expected() {
+        assert_eq!(layout_for(2, false), &LAYOUT_STEREO);
+        assert_eq!(layout_for(6, false), &LAYOUT_51);
+        assert_eq!(layout_for(6, true), &LAYOUT_51_HQ);
+        assert_eq!(layout_for(8, false), &LAYOUT_71);
+        assert_eq!(layout_for(8, true), &LAYOUT_71_HQ);
+        // Unknown / 0 → stereo.
+        assert_eq!(layout_for(0, false), &LAYOUT_STEREO);
+        assert_eq!(layout_for(3, false), &LAYOUT_STEREO);
+        assert_eq!(layout_for(7, true), &LAYOUT_STEREO);
+    }
+
+    #[test]
+    fn normalize_clamps_to_negotiable() {
+        assert_eq!(normalize_channels(2), 2);
+        assert_eq!(normalize_channels(6), 6);
+        assert_eq!(normalize_channels(8), 8);
+        for bad in [0u8, 1, 3, 4, 5, 7, 9, 255] {
+            assert_eq!(normalize_channels(bad), 2, "{bad} must clamp to stereo");
+        }
+    }
+
+    #[test]
+    fn wasapi_masks_are_correct() {
+        assert_eq!(wasapi_channel_mask(2), 0x3);
+        assert_eq!(wasapi_channel_mask(6), 0x3F);
+        assert_eq!(wasapi_channel_mask(8), 0x63F); // NOT 0xFF
+                                                   // Bit count must equal the channel count.
+        assert_eq!(wasapi_channel_mask(2).count_ones(), 2);
+        assert_eq!(wasapi_channel_mask(6).count_ones(), 6);
+        assert_eq!(wasapi_channel_mask(8).count_ones(), 8);
+    }
+
+    #[test]
+    fn spa_positions_match_wire_order() {
+        assert_eq!(spa_positions(2), &[3, 4]);
+        assert_eq!(spa_positions(6), &[3, 4, 5, 6, 12, 13]);
+        assert_eq!(spa_positions(8), &[3, 4, 5, 6, 12, 13, 7, 8]);
+        assert_eq!(spa_positions(2).len(), 2);
+        assert_eq!(spa_positions(6).len(), 6);
+        assert_eq!(spa_positions(8).len(), 8);
+    }
+
+    /// Real-libopus proof that the shared layout round-trips with channel identity: a tone fed
+    /// into wire channel N (host `opus::MSEncoder`) comes back out on channel N (client
+    /// `opus::MSDecoder`), for stereo / 5.1 / 7.1. This is the single guarantee the whole
+    /// feature rests on — encoder layout == decoder layout == identity mapping — so if a layout
+    /// constant is ever wrong, this fails. Gated on `quic` (where `opus` is a dependency).
+    #[cfg(feature = "quic")]
+    #[test]
+    fn multistream_layout_roundtrips_with_channel_identity() {
+        const SR: u32 = 48_000;
+        const SAMPLES: usize = 240; // 5 ms @ 48 kHz
+        for &channels in &[2u8, 6, 8] {
+            let l = layout_for(channels, false);
+            let ch = l.channels as usize;
+            let mut enc = opus::MSEncoder::new(
+                SR,
+                l.streams,
+                l.coupled,
+                l.mapping,
+                opus::Application::LowDelay,
+            )
+            .expect("MSEncoder");
+            enc.set_bitrate(opus::Bitrate::Bits(l.bitrate)).unwrap();
+            enc.set_vbr(false).unwrap();
+            let mut dec =
+                opus::MSDecoder::new(SR, l.streams, l.coupled, l.mapping).expect("MSDecoder");
+
+            for tone_ch in 0..ch {
+                let mut out = vec![0u8; 4000];
+                let mut energy = vec![0f64; ch];
+                // A few frames to clear the codec startup transient before measuring.
+                for f in 0..8 {
+                    let mut frame = vec![0f32; SAMPLES * ch];
+                    for t in 0..SAMPLES {
+                        let phase = (f * SAMPLES + t) as f32 * 440.0 * 2.0 * std::f32::consts::PI
+                            / SR as f32;
+                        frame[t * ch + tone_ch] = 0.5 * phase.sin();
+                    }
+                    let n = enc.encode_float(&frame, &mut out).unwrap();
+                    let mut decoded = vec![0f32; SAMPLES * ch];
+                    let got = dec.decode_float(&out[..n], &mut decoded, false).unwrap();
+                    assert_eq!(got, SAMPLES, "{channels}ch frame size");
+                    if f >= 4 {
+                        for t in 0..SAMPLES {
+                            for (c, e) in energy.iter_mut().enumerate() {
+                                *e += (decoded[t * ch + c] as f64).powi(2);
+                            }
+                        }
+                    }
+                }
+                let loudest = (0..ch)
+                    .max_by(|&a, &b| energy[a].total_cmp(&energy[b]))
+                    .unwrap();
+                assert_eq!(
+                    loudest, tone_ch,
+                    "{channels}ch: tone in channel {tone_ch} must come out on {tone_ch} (energies {energy:?})"
+                );
+            }
+        }
+    }
+}

crates/punktfunk-core/src/client.rs

@@ -40,8 +40,9 @@ enum CtrlRequest {
 /// mode, the host-resolved compositor backend, the host-resolved gamepad backend, the host's
 /// certificate fingerprint, the resolved encoder bitrate (kbps), and the host↔client clock offset
 /// (ns, host minus client; 0 = no skew correction / an old host that didn't answer the handshake).
-/// The trailing `u8` is the resolved encode bit depth (8/10) and [`ColorInfo`] the resolved colour
+/// The trailing `u8`s are the resolved encode bit depth (8/10), the chroma `chroma_format_idc`
-/// signalling, both from the [`Welcome`].
+/// (1 = 4:2:0, 3 = 4:4:4), and the resolved audio channel count (2/6/8), with [`ColorInfo`] the
+/// resolved colour signalling — all from the [`Welcome`].
 type Negotiated = (
     Mode,
     CompositorPref,
@@ -51,6 +52,8 @@ type Negotiated = (
     i64,
     u8,
     ColorInfo,
+    u8,
+    u8,
 );
 
 /// Accumulated state of an in-flight / finished speed test. The data-plane pump mirrors the
@@ -202,6 +205,17 @@ pub struct NativeClient {
     /// decoder/presenter from this. [`ColorInfo::SDR_BT709`] for an older host. The static HDR
     /// mastering metadata (when [`ColorInfo::is_hdr`]) arrives via [`NativeClient::next_hdr_meta`].
     pub color: ColorInfo,
+    /// The chroma subsampling the host resolved for this session ([`Welcome::chroma_format`]), as the
+    /// HEVC `chroma_format_idc`: [`quic::CHROMA_IDC_420`] (4:2:0, the default / older host) or
+    /// [`quic::CHROMA_IDC_444`] (full-chroma 4:4:4). The in-band SPS is authoritative; this lets the
+    /// client pre-size its decoder. `CHROMA_IDC_420` for an older host that didn't report it.
+    pub chroma_format: u8,
+    /// The audio channel count the host resolved for this session ([`Welcome::audio_channels`]):
+    /// `2` (stereo), `6` (5.1) or `8` (7.1). The client MUST build its Opus (multistream) decoder
+    /// from this value (via [`crate::audio::layout_for`]) — never from its own request — so an older
+    /// host that omits it (→ `2`) yields working stereo. The `0xC9` audio frames are encoded with the
+    /// matching layout.
+    pub audio_channels: u8,
 }
 
 /// Pin the calling thread to the user-interactive QoS class on Apple targets.
@@ -246,6 +260,9 @@ impl NativeClient {
         // VIDEO_CAP_HDR) — the host upgrades to a 10-bit / HDR encode only when the matching bit is
         // set. 0 = the 8-bit BT.709 stream every client understands.
         video_caps: u8,
+        // Requested audio channel count (2 = stereo / 6 = 5.1 / 8 = 7.1); the host clamps to what it
+        // can capture and echoes the result in [`NativeClient::audio_channels`].
+        audio_channels: u8,
         launch: Option<String>,
         pin: Option<[u8; 32]>,
         identity: Option<(String, String)>,
@@ -298,6 +315,7 @@ impl NativeClient {
                     gamepad,
                     bitrate_kbps,
                     video_caps,
+                    audio_channels,
                     launch,
                     pin,
                     identity,
@@ -329,6 +347,8 @@ impl NativeClient {
             clock_offset_ns,
             bit_depth,
             color,
+            chroma_format,
+            audio_channels,
         ) = match ready_rx.recv_timeout(timeout) {
             Ok(Ok(t)) => t,
             Ok(Err(e)) => return Err(e),
@@ -360,6 +380,8 @@ impl NativeClient {
             clock_offset_ns,
             bit_depth,
             color,
+            chroma_format,
+            audio_channels,
         })
     }
 
@@ -666,6 +688,7 @@ struct WorkerArgs {
     gamepad: GamepadPref,
     bitrate_kbps: u32,
     video_caps: u8,
+    audio_channels: u8,
     launch: Option<String>,
     pin: Option<[u8; 32]>,
     identity: Option<(String, String)>,
@@ -697,6 +720,7 @@ async fn worker_main(args: WorkerArgs) {
         gamepad,
         bitrate_kbps,
         video_caps,
+        audio_channels,
         launch,
         pin,
         identity,
@@ -763,6 +787,8 @@ async fn worker_main(args: WorkerArgs) {
                 // VIDEO_CAP_10BIT | VIDEO_CAP_HDR). The host only upgrades to a 10-bit / HDR encode
                 // when the matching bit is set, so `0` stays an 8-bit BT.709 stream.
                 video_caps,
+                // Requested surround channel count; the host echoes the resolved value in Welcome.
+                audio_channels,
             }
             .encode(),
         )
@@ -834,6 +860,8 @@ async fn worker_main(args: WorkerArgs) {
             clock_offset_ns,
             welcome.bit_depth,
             welcome.color,
+            welcome.chroma_format,
+            welcome.audio_channels,
         ))
     };
 
@@ -850,6 +878,8 @@ async fn worker_main(args: WorkerArgs) {
         clock_offset_ns,
         bit_depth,
         color,
+        chroma_format,
+        audio_channels,
     ) = match setup.await {
         Ok(t) => t,
         Err(e) => {
@@ -866,6 +896,8 @@ async fn worker_main(args: WorkerArgs) {
         clock_offset_ns,
         bit_depth,
         color,
+        chroma_format,
+        audio_channels,
     )));
 
     // Input task: embedder events → QUIC datagrams.

crates/punktfunk-core/src/lib.rs

@@ -25,6 +25,7 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
 pub mod abi;
+pub mod audio;
 #[cfg(feature = "quic")]
 pub mod client;
 pub mod config;

crates/punktfunk-core/src/quic.rs

@@ -78,12 +78,33 @@ pub struct Hello {
     /// zero-length name/launch placeholder precedes it when those are absent so the offset stays
     /// deterministic. Omitted by older clients (decodes to `0`).
     pub video_caps: u8,
+    /// Requested audio channel count: `2` (stereo, default), `6` (5.1) or `8` (7.1). The host
+    /// resolves it against what it can capture and echoes the final count in
+    /// [`Welcome::audio_channels`], which is what both ends build their Opus (multistream)
+    /// codec from. Appended after `video_caps` as a single trailing byte; when it differs from
+    /// the stereo default the name/launch/video_caps placeholders are forced (0) so it lands at a
+    /// deterministic offset. Omitted by older clients / when `2` (decodes to `2`, i.e. stereo) so
+    /// the stereo wire form stays byte-identical to the pre-surround build.
+    pub audio_channels: u8,
 }
 
 /// [`Hello::video_caps`] bit: the client can decode a 10-bit (Main10) HEVC stream.
 pub const VIDEO_CAP_10BIT: u8 = 0x01;
 /// [`Hello::video_caps`] bit: the client can present BT.2020 PQ HDR10 (implies 10-bit).
 pub const VIDEO_CAP_HDR: u8 = 0x02;
+/// [`Hello::video_caps`] bit: the client can decode a full-chroma **4:4:4** HEVC stream (HEVC
+/// Range Extensions / Rec.ITU-T H.265 `chroma_format_idc = 3`). The host emits 4:4:4 ONLY when this
+/// bit is set, the host opted in (`PUNKTFUNK_444`), the codec is HEVC, **and** the GPU/driver
+/// actually supports a 4:4:4 encode (probed) — otherwise the session stays 4:2:0 and
+/// [`Welcome::chroma_format`] reflects the real resolved value. Independent of 10-bit/HDR (4:4:4 is a
+/// chroma decision, bit depth is a depth decision; the two may combine where the hardware allows).
+pub const VIDEO_CAP_444: u8 = 0x04;
+
+/// HEVC `chroma_format_idc` for 4:2:0 — what every pre-4:4:4 build produced and the back-compat
+/// default when a peer omits [`Welcome::chroma_format`].
+pub const CHROMA_IDC_420: u8 = 1;
+/// HEVC `chroma_format_idc` for full-chroma 4:4:4 (Range Extensions).
+pub const CHROMA_IDC_444: u8 = 3;
 
 /// Per-session colour signalling (CICP / ITU-T H.273 code points) the host resolved for the
 /// encoded video, carried on [`Welcome`]. A client configures its decoder/presenter from these
@@ -198,6 +219,22 @@ pub struct Welcome {
     /// [`ColorInfo::SDR_BT709`]. The client configures its decoder/presenter from this instead of
     /// guessing from the bitstream; the mastering metadata arrives separately on [`HDR_META_MAGIC`].
     pub color: ColorInfo,
+    /// The chroma subsampling the host actually encodes at, as the HEVC `chroma_format_idc`:
+    /// [`CHROMA_IDC_420`] (4:2:0, default / older host) or [`CHROMA_IDC_444`] (full-chroma 4:4:4,
+    /// enabled only when the client advertised [`VIDEO_CAP_444`] *and* the host could open a real
+    /// 4:4:4 encode). The client sizes its decoder/surface pool from this; the in-band SPS carries
+    /// the authoritative value, so this is a hint (and the honest-downgrade channel — if the host
+    /// requested 4:4:4 but the GPU declined, this reads `CHROMA_IDC_420`). Appended after the colour
+    /// bytes as a single trailing byte; an older host that omits it decodes to [`CHROMA_IDC_420`].
+    pub chroma_format: u8,
+    /// The audio channel count the host actually resolved and **will** send on the `0xC9` plane:
+    /// `2` (stereo, default), `6` (5.1) or `8` (7.1). Echoes [`Hello::audio_channels`] clamped to
+    /// what the host can capture (Linux PipeWire always synthesizes the count; Windows WASAPI
+    /// loopback is clamped to the render endpoint's mix-format channels). The client builds its Opus
+    /// (multistream) decoder from THIS value via [`crate::audio::layout_for`] — never from its own
+    /// request — so an older host that omits the byte (→ `2`) always yields working stereo. Appended
+    /// after `chroma_format` as a single trailing byte.
+    pub audio_channels: u8,
 }
 
 /// `client → host`: data plane is bound, begin streaming.
@@ -630,10 +667,11 @@ impl Hello {
                                                                // so a Hello with neither name nor launch stays byte-identical to the bitrate-era form
                                                                // (26 bytes). When `launch` is present we must still emit name's length byte (0 for None)
                                                                // so `launch` lands at a deterministic offset.
-                                                               // `video_caps` is the last trailing field, after `launch`; when it's present (non-zero)
+                                                               // `video_caps`/`audio_channels` are the trailing fields, after `launch`; when either is
-                                                               // the name/launch length bytes must still be emitted (0 for absent) so it lands at a
+                                                               // present (video_caps non-zero / audio_channels not stereo) the name/launch length bytes
+                                                               // AND the video_caps byte must still be emitted (0 / 0) so the later byte lands at a
                                                                // deterministic offset — the same discipline `launch` already imposes on `name`.
-        let need_placeholders = self.video_caps != 0;
+        let need_placeholders = self.video_caps != 0 || self.audio_channels != 2;
         match (&self.name, &self.launch) {
             (None, None) if !need_placeholders => {}
             (name, _) => {
@@ -648,10 +686,15 @@ impl Hello {
             b.push(l.len() as u8);
             b.extend_from_slice(l.as_bytes());
         }
-        // video_caps: single trailing byte. Last field.
+        // video_caps: single trailing byte. Emitted when non-zero OR when audio_channels follows
-        if self.video_caps != 0 {
+        // (so audio_channels lands at a deterministic offset right after it).
+        if self.video_caps != 0 || self.audio_channels != 2 {
             b.push(self.video_caps);
         }
+        // audio_channels: single trailing byte. Last field; omitted when stereo (default).
+        if self.audio_channels != 2 {
+            b.push(self.audio_channels);
+        }
         b
     }
 
@@ -714,6 +757,15 @@ impl Hello {
                 let launch_len = b.get(launch_off).copied().unwrap_or(0) as usize;
                 b.get(launch_off + 1 + launch_len).copied().unwrap_or(0)
             },
+            // Optional trailing audio-channel byte, one past video_caps. Absent on an older client
+            // → stereo. Normalized so a corrupt/unsupported value can't build a bad decoder.
+            audio_channels: {
+                let name_len = b.get(26).copied().unwrap_or(0) as usize;
+                let launch_off = 27 + name_len;
+                let launch_len = b.get(launch_off).copied().unwrap_or(0) as usize;
+                let video_caps_off = launch_off + 1 + launch_len;
+                crate::audio::normalize_channels(b.get(video_caps_off + 1).copied().unwrap_or(2))
+            },
         })
     }
 }
@@ -747,6 +799,10 @@ impl Welcome {
         b.push(self.color.transfer);
         b.push(self.color.matrix);
         b.push(self.color.full_range);
+        // Chroma subsampling at offset 64 — older clients stop before this → 4:2:0 (CHROMA_IDC_420).
+        b.push(self.chroma_format);
+        // Audio channel count at offset 65 — older clients stop before this → stereo (2).
+        b.push(self.audio_channels);
         b
     }
 
@@ -755,7 +811,8 @@ impl Welcome {
         // scheme[22] pct[23] max_data[24..26] shard[26..28] encrypt[28] key[29..45]
         // salt[45..49] frames[49..53] compositor[53] gamepad[54] bitrate_kbps[55..59]
         // bit_depth[59] color.primaries[60] color.transfer[61] color.matrix[62] color.range[63]
-        // (everything from compositor on is an optional trailing byte; an older host stops earlier).
+        // chroma_format[64] audio_channels[65] (everything from compositor on is an optional
+        // trailing byte; an older host stops earlier).
         if b.len() < 53 || &b[0..4] != MAGIC {
             return Err(PunktfunkError::InvalidArg("bad Welcome"));
         }
@@ -812,6 +869,15 @@ impl Welcome {
                 matrix: b.get(62).copied().unwrap_or(ColorInfo::MC_BT709),
                 full_range: b.get(63).copied().unwrap_or(0),
             },
+            // Optional trailing chroma byte — absent on an older host (or an explicit 0 / unknown
+            // value) → 4:2:0. Only `CHROMA_IDC_444` flips the client to a 4:4:4 decode.
+            chroma_format: match b.get(64).copied() {
+                Some(CHROMA_IDC_444) => CHROMA_IDC_444,
+                _ => CHROMA_IDC_420,
+            },
+            // Optional trailing audio-channel byte — absent on an older host → stereo. Any
+            // non-{6,8} value normalizes to stereo so a corrupt byte never builds a bad decoder.
+            audio_channels: crate::audio::normalize_channels(b.get(65).copied().unwrap_or(2)),
         })
     }
 
@@ -1809,6 +1875,8 @@ mod tests {
             bitrate_kbps: 50_000,
             bit_depth: 10,
             color: ColorInfo::HDR10_BT2020_PQ,
+            chroma_format: CHROMA_IDC_444,
+            audio_channels: 2,
         };
         assert_eq!(Welcome::decode(&w.encode()).unwrap(), w);
     }
@@ -1851,6 +1919,7 @@ mod tests {
             name: Some("Test Device".into()),
             launch: Some("steam:570".into()),
             video_caps: VIDEO_CAP_10BIT,
+            audio_channels: 2,
         };
         assert_eq!(Hello::decode(&h.encode()).unwrap(), h);
         let s = Start {
@@ -1930,6 +1999,7 @@ mod tests {
             name: None,
             launch: None,
             video_caps: 0,
+            audio_channels: 2,
         };
         let enc = h.encode();
         assert_eq!(enc.len(), 26);
@@ -1969,9 +2039,11 @@ mod tests {
             bitrate_kbps: 120_000,
             bit_depth: 10,
             color: ColorInfo::HDR10_BT2020_PQ,
+            chroma_format: CHROMA_IDC_444,
+            audio_channels: 6, // 5.1 — exercises the non-default trailing byte
         };
         let wenc = w.encode();
-        assert_eq!(wenc.len(), 64); // 60 base + 4 colour bytes
+        assert_eq!(wenc.len(), 66); // 60 base + 4 colour + 1 chroma + 1 audio-channels byte
         let legacy_w = Welcome::decode(&wenc[..53]).unwrap();
         assert_eq!(legacy_w.compositor, CompositorPref::Auto);
         assert_eq!(legacy_w.gamepad, GamepadPref::Auto);
@@ -1991,13 +2063,29 @@ mod tests {
         let pre_color_w = Welcome::decode(&wenc[..60]).unwrap();
         assert_eq!(pre_color_w.bit_depth, 10);
         assert_eq!(pre_color_w.color, ColorInfo::SDR_BT709);
+        assert_eq!(pre_color_w.chroma_format, CHROMA_IDC_420); // pre-chroma host → 4:2:0
         assert_eq!(legacy_w.color, ColorInfo::SDR_BT709);
+        assert_eq!(legacy_w.chroma_format, CHROMA_IDC_420);
+        // A pre-chroma (64-byte) Welcome carries colour but no chroma/audio bytes → 4:2:0 + stereo.
+        let pre_chroma_w = Welcome::decode(&wenc[..64]).unwrap();
+        assert_eq!(pre_chroma_w.color, ColorInfo::HDR10_BT2020_PQ);
+        assert_eq!(pre_chroma_w.chroma_format, CHROMA_IDC_420);
+        assert_eq!(pre_chroma_w.audio_channels, 2); // audio byte (offset 65) absent → stereo
+                                                    // A pre-audio (65-byte) Welcome carries chroma but no audio byte → 4:4:4 + stereo.
+        let pre_audio_w = Welcome::decode(&wenc[..65]).unwrap();
+        assert_eq!(pre_audio_w.chroma_format, CHROMA_IDC_444);
+        assert_eq!(pre_audio_w.audio_channels, 2);
         assert_eq!(Welcome::decode(&wenc).unwrap().bitrate_kbps, 120_000);
         assert_eq!(Welcome::decode(&wenc).unwrap().bit_depth, 10); // full form carries it
         assert_eq!(
             Welcome::decode(&wenc).unwrap().color,
             ColorInfo::HDR10_BT2020_PQ
         );
+        assert_eq!(
+            Welcome::decode(&wenc).unwrap().chroma_format,
+            CHROMA_IDC_444
+        ); // full form carries 4:4:4
+        assert_eq!(Welcome::decode(&wenc).unwrap().audio_channels, 6); // ...and 5.1
     }
 
     #[test]
@@ -2015,6 +2103,7 @@ mod tests {
             name: Some("Enrico's MacBook".into()),
             launch: None,
             video_caps: 0,
+            audio_channels: 2,
         };
         let enc = base.encode();
         assert_eq!(
@@ -2062,6 +2151,7 @@ mod tests {
             name: None,
             launch: None,
             video_caps: 0,
+            audio_channels: 2,
         };
         // launch alone (no name): a zero-length name placeholder keeps the offset deterministic.
         let with_launch = Hello {
@@ -2268,6 +2358,7 @@ mod tests {
                 name: None,
                 launch: None,
                 video_caps: 0,
+                audio_channels: 2,
             }
             .encode();
             assert!(PairRequest::decode(&h).is_err(), "abi {abi} parsed as pair");

crates/punktfunk-core/tests/c_abi.rs

@@ -13,8 +13,10 @@ use std::process::Command;
 fn native_libs() -> &'static [&'static str] {
     if cfg!(target_os = "macos") {
         // The workspace build unifies features into the staticlib, and `quic` pulls
-        // rustls's platform verifier → Security/CoreFoundation.
+        // rustls's platform verifier → Security/CoreFoundation, plus libopus (the in-core
+        // `next_audio_pcm` decode path) which the `abi.rs` object references.
         &[
+            "-lopus",
             "-liconv",
             "-lm",
             "-framework",
@@ -23,7 +25,17 @@ fn native_libs() -> &'static [&'static str] {
             "CoreFoundation",
         ]
     } else if cfg!(target_os = "linux") {
-        &["-lgcc_s", "-lutil", "-lrt", "-lpthread", "-lm", "-ldl"]
+        // `-lopus`: the `quic` feature pulls in-core Opus decode (`next_audio_pcm`), whose
+        // symbols the linked `abi.rs` object references. Before `-lm` (opus needs libm).
+        &[
+            "-lopus",
+            "-lgcc_s",
+            "-lutil",
+            "-lrt",
+            "-lpthread",
+            "-lm",
+            "-ldl",
+        ]
     } else {
         &[]
     }

crates/punktfunk-host/Cargo.toml

@@ -35,9 +35,11 @@ base64 = "0.22"
 ureq = "2"
 rcgen = { version = "0.13", default-features = false, features = ["aws_lc_rs", "pem"] }
 x509-parser = "0.16"
-axum-server = { version = "0.7", features = ["tls-rustls"] }
+# Only used for the plain-HTTP nvhttp listener (`bind().serve()`); HTTPS/mTLS is hand-rolled over
+# tokio-rustls (axum-server can't surface the peer cert), so we do NOT enable `tls-rustls` — that
+# feature is what pulled the unmaintained `rustls-pemfile` (security-review dep hygiene).
+axum-server = "0.8"
 rustls = "0.23"
-rustls-pemfile = "2"
 # Manual HTTPS+mTLS serve loop for the mgmt API (axum-server can't surface the peer cert): a
 # tokio-rustls handshake exposes the client cert, then hyper serves the axum Router with the
 # verified fingerprint injected as a request extension. Versions match the workspace lock.
@@ -61,9 +63,10 @@ utoipa-scalar = { version = "0.3", features = ["axum"] }
 tower = { version = "0.5", features = ["util"] }
 http-body-util = "0.1"
 
-# Opus stereo encode for the host->client audio plane. The `opus` crate vendors libopus via
+# Opus encode for the host->client audio plane — stereo (`opus::Encoder`) AND 5.1/7.1 surround
-# `audiopus_sys` (cmake-built from source — no system lib, no vcpkg), so it builds on Windows MSVC
+# (`opus::MSEncoder`, the safe multistream API the crate exposes; no `audiopus_sys` needed). The
-# too (needs CMake + NASM, both on the box). Both platforms that have an audio-capture backend.
+# crate vendors libopus (cmake-built from source — no system lib, no vcpkg), so it builds on Windows
+# MSVC too (needs CMake + NASM, both on the box). Both platforms that have an audio-capture backend.
 [target.'cfg(any(target_os = "linux", target_os = "windows"))'.dependencies]
 opus = "0.3"
 
@@ -99,10 +102,6 @@ serde_json = "1"
 rusqlite = { version = "0.40", features = ["bundled"] }
 # Builds/validates the xkb keymap uploaded to the virtual keyboard + tracks modifier state.
 xkbcommon = "0.8"
-# The safe `opus` crate is stereo-only; surround (5.1/7.1) needs the libopus *multistream*
-# encoder (`opus_multistream_encoder_*`). `audiopus_sys` is the sys layer `opus` already
-# vendors (same libopus link), so this adds bindings, not a second copy of the library.
-audiopus_sys = "0.2"
 # libei (EI sender) for the portable input path on KWin/GNOME (RemoteDesktop portal).
 # The `tokio` feature wires reis's event stream into tokio's reactor.
 reis = { version = "0.6.1", features = ["tokio"] }
@@ -220,6 +219,7 @@ bytemuck = { version = "1.19", features = ["derive"] }
 # nvEncodeAPI64.dll) on the linker path. Build the GPU host with `--features nvenc`.
 nvenc = ["dep:nvidia-video-codec-sdk"]
 # AMD/Intel hardware encode on Windows (AMF/QSV via ffmpeg-next). OFF by default: it needs a
-# `FFMPEG_DIR` (BtbN gpl-shared, includes `*_amf`/`*_qsv`) at build time and bundles the FFmpeg
+# `FFMPEG_DIR` (BtbN lgpl-shared — includes `*_amf`/`*_qsv`; the GPL-only x264/x265 are never used,
-# DLLs at runtime. Build the all-vendor GPU host with `--features nvenc,amf-qsv`.
+# so the LGPL build suffices and keeps the bundled DLLs LGPL, not GPL) at build time and bundles the
+# FFmpeg DLLs at runtime. Build the all-vendor GPU host with `--features nvenc,amf-qsv`.
 amf-qsv = ["dep:ffmpeg-next"]

crates/punktfunk-host/src/audio/windows/wasapi_cap.rs

@@ -1,7 +1,9 @@
 //! WASAPI loopback capture of the default render endpoint (system output) — the Windows analogue
-//! of the PipeWire sink-monitor backend. Delivers interleaved f32 PCM at 48 kHz stereo, ready for
+//! of the PipeWire sink-monitor backend. Delivers interleaved f32 PCM at 48 kHz in the requested
-//! the existing Opus path with NO resampling (WASAPI shared-mode autoconvert does any SRC). WASAPI
+//! channel count (stereo / 5.1 / 7.1, canonical wire order FL FR FC LFE RL RR SL SR via the
-//! objects are COM-apartment-bound and not `Send`, so they live on a dedicated thread (mirrors
+//! explicit `dwChannelMask`), ready for the Opus path with NO resampling (WASAPI shared-mode
+//! autoconvert does any SRC + up/downmix to the requested layout). WASAPI objects are
+//! COM-apartment-bound and not `Send`, so they live on a dedicated thread (mirrors
 //! `linux::PwAudioCapturer`); only the channel + stop flag + join handle are in the struct.
 
 use super::{AudioCapturer, SAMPLE_RATE};
@@ -14,9 +16,6 @@ use std::thread::{self, JoinHandle};
 use std::time::Duration;
 use wasapi::{DeviceEnumerator, Direction, SampleType, StreamMode, WaveFormat};
 
-// 48 kHz stereo 32-bit float: 2 channels * 4 bytes = 8 bytes per frame.
-const BLOCK_ALIGN: usize = 2 * 4;
-
 pub struct WasapiLoopbackCapturer {
     chunks: Receiver<Vec<f32>>,
     channels: u32,
@@ -27,8 +26,8 @@ pub struct WasapiLoopbackCapturer {
 impl WasapiLoopbackCapturer {
     pub fn open(channels: u32) -> Result<WasapiLoopbackCapturer> {
         anyhow::ensure!(
-            channels == 2,
+            matches!(channels, 2 | 6 | 8),
-            "WASAPI loopback backend is stereo-only (got {channels})"
+            "WASAPI loopback backend supports 2/6/8 channels (got {channels})"
         );
         let (tx, rx) = sync_channel::<Vec<f32>>(64);
         let stop = Arc::new(AtomicBool::new(false));
@@ -39,7 +38,7 @@ impl WasapiLoopbackCapturer {
         let join = thread::Builder::new()
             .name("punktfunk-wasapi-audio".into())
             .spawn(move || {
-                if let Err(e) = capture_thread(tx, stop_t, ready_tx) {
+                if let Err(e) = capture_thread(tx, stop_t, ready_tx, channels) {
                     tracing::error!(error = format!("{e:#}"), "wasapi loopback thread failed");
                 }
             })
@@ -47,7 +46,8 @@ impl WasapiLoopbackCapturer {
         match ready_rx.recv_timeout(Duration::from_secs(3)) {
             Ok(Ok(())) => {
                 tracing::info!(
-                    "WASAPI loopback capture: 48 kHz stereo f32 (default render endpoint)"
+                    channels,
+                    "WASAPI loopback capture: 48 kHz f32 (default render endpoint)"
                 );
                 Ok(WasapiLoopbackCapturer {
                     chunks: rx,
@@ -95,7 +95,10 @@ fn capture_thread(
     tx: SyncSender<Vec<f32>>,
     stop: Arc<AtomicBool>,
     ready: SyncSender<Result<()>>,
+    channels: u32,
 ) -> Result<()> {
+    // Interleaved f32: channels * 4 bytes per frame.
+    let block_align = channels as usize * 4;
     // COM must be initialized on THIS thread (MTA), before any device call.
     if let Err(e) = wasapi::initialize_mta()
         .ok()
@@ -115,10 +118,20 @@ fn capture_thread(
             .get_default_device(&Direction::Render)
             .context("default render endpoint (loopback needs a render device)")?;
         let mut audio_client = device.get_iaudioclient().context("IAudioClient")?;
-        // 48 kHz stereo f32 interleaved; autoconvert lets WASAPI's shared-mode SRC match the engine
+        // 48 kHz f32 interleaved in the requested channel layout; autoconvert lets WASAPI's
-        // mix format to ours, so we never resample in Rust. Loopback is implied by capturing a
+        // shared-mode SRC match the engine mix format to ours (incl. up/downmix to the requested
-        // RENDER device with Direction::Capture in shared mode (wasapi sets STREAMFLAGS_LOOPBACK).
+        // channel count), so we never resample/remix in Rust. The explicit dwChannelMask pins the
-        let desired = WaveFormat::new(32, 32, &SampleType::Float, SAMPLE_RATE as usize, 2, None);
+        // wire order (FL FR FC LFE RL RR SL SR; 7.1 = 0x63F, not 0xFF). Loopback is implied by
+        // capturing a RENDER device with Direction::Capture in shared mode (STREAMFLAGS_LOOPBACK).
+        let mask = punktfunk_core::audio::wasapi_channel_mask(channels as u8);
+        let desired = WaveFormat::new(
+            32,
+            32,
+            &SampleType::Float,
+            SAMPLE_RATE as usize,
+            channels as usize,
+            Some(mask),
+        );
         let (default_period, _min_period) =
             audio_client.get_device_period().context("device period")?;
         let mode = StreamMode::EventsShared {
@@ -154,7 +167,7 @@ fn capture_thread(
                     Err(e) => return Err(anyhow!("get_next_packet_size: {e}")),
                 }
             }
-            let whole = (bytes.len() / BLOCK_ALIGN) * BLOCK_ALIGN;
+            let whole = (bytes.len() / block_align) * block_align;
             if whole == 0 {
                 continue;
             }

crates/punktfunk-host/src/capture.rs

@@ -62,6 +62,11 @@ pub struct OutputFormat {
     /// HDR: the capturer converts to 10-bit (IDD-push FP16 → `Rgb10a2`; the DDA secure-desktop HDR hint).
     /// `false` = 8-bit SDR.
     pub hdr: bool,
+    /// Full-chroma 4:4:4 session: the capturer must keep full chroma — deliver packed **RGB**
+    /// (`Bgra` / `Rgb10a2`), NOT the subsampled `Nv12`/`P010` the Windows video-engine path produces by
+    /// default — because 4:4:4 can only be recovered from a full-chroma source. NVENC then does the
+    /// RGB→YUV444 CSC at encode (chroma_format_idc=3). `false` on every 4:2:0 session.
+    pub chroma_444: bool,
 }
 
 impl OutputFormat {
@@ -73,6 +78,8 @@ impl OutputFormat {
         OutputFormat {
             gpu: gpu_encode(),
             hdr,
+            // The GameStream + spike paths are always 4:2:0 (4:4:4 is punktfunk/1-native only).
+            chroma_444: false,
         }
     }
 }
@@ -361,13 +368,16 @@ pub fn open_portal_monitor() -> Result<Box<dyn Capturer>> {
 #[cfg(target_os = "linux")]
 pub fn capture_virtual_output(
     vout: crate::vdisplay::VirtualOutput,
-    _want: OutputFormat,
+    want: OutputFormat,
     _capture: crate::session_plan::CaptureBackend,
 ) -> Result<Box<dyn Capturer>> {
-    // The Linux host stays 8-bit (HDR is blocked upstream) and the portal negotiates its own format, so
+    // The Linux host stays 8-bit (HDR is blocked upstream) and the portal negotiates its own pixel
-    // the `OutputFormat` is unused here; the capture backend is always the portal (the `CaptureBackend`
+    // format, so only `want.gpu` is honored here: it gates GPU zero-copy capture (the capture backend
-    // arg is a Windows-only dispatch — ignored here).
+    // is always the portal — the `CaptureBackend` arg is a Windows-only dispatch). `gpu = false`
-    linux::PortalCapturer::from_virtual_output(vout).map(|c| Box::new(c) as Box<dyn Capturer>)
+    // (a 4:4:4 NVENC session) forces the CPU mmap path so the encoder gets CPU-resident RGB to swscale
+    // into YUV444P — otherwise it would receive CUDA frames and bail.
+    linux::PortalCapturer::from_virtual_output(vout, want.gpu)
+        .map(|c| Box::new(c) as Box<dyn Capturer>)
 }
 
 /// `PUNKTFUNK_NO_WGC=1` forces the pure single-process DDA (Desktop Duplication) path everywhere: it
@@ -394,6 +404,14 @@ pub fn capture_virtual_output(
     })?;
     let pref = vout.preferred_mode;
     let keep = vout.keepalive;
+    // Full-chroma 4:4:4 needs a full-chroma RGB source. The IDD-push and WGC paths emit subsampled
+    // NV12/P010 by default, which can't reconstruct 4:4:4; route a 4:4:4 session to DDA, which delivers
+    // RGB (Bgra) when its `chroma_444` flag is set. (IDD-push/WGC 4:4:4 capture is a follow-up.)
+    if want.chroma_444 && capture != CaptureBackend::Dda {
+        tracing::info!("4:4:4 session — using DDA capture (RGB source) instead of {capture:?}");
+        return dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false, want.chroma_444)
+            .map(|c| Box::new(c) as Box<dyn Capturer>);
+    }
     // P2 direct frame push (kill DDA): consume frames straight from the pf-vdisplay driver's shared
     // ring — no Desktop Duplication, no win32u reparenting hook. Resolved once in the `SessionPlan`
     // (was re-derived from `config().idd_push` here); `IddPush` takes the keepalive (owns the virtual
@@ -414,7 +432,14 @@ pub fn capture_virtual_output(
                     error = %format!("{e:#}"),
                     "IDD-push open/attach failed — falling back to DDA"
                 );
-                return dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false)
+                return dxgi::DuplCapturer::open(
+                    target,
+                    pref,
+                    keep,
+                    want.gpu,
+                    false,
+                    want.chroma_444,
+                )
                 .map(|c| Box::new(c) as Box<dyn Capturer>);
             }
         }
@@ -426,7 +451,7 @@ pub fn capture_virtual_output(
     // chosen backend (it owns the SudoVDA keepalive), so there's no open-time auto-fallback. The
     // backend choice (`dda`/`dxgi`/`PUNKTFUNK_NO_WGC` → DDA, else WGC) is now resolved once in the plan.
     if capture == CaptureBackend::Dda {
-        return dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false)
+        return dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false, want.chroma_444)
             .map(|c| Box::new(c) as Box<dyn Capturer>);
     }
     // WGC default, with a watchdog'd DDA fallback. WGC's Direct3D11CaptureFramePool::CreateFreeThreaded
@@ -461,12 +486,12 @@ pub fn capture_virtual_output(
         }
         Ok(Err(e)) => {
             tracing::warn!(error = %format!("{e:#}"), "WGC open failed — falling back to DDA");
-            dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false)
+            dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false, want.chroma_444)
                 .map(|c| Box::new(c) as Box<dyn Capturer>)
         }
         Err(_) => {
             tracing::warn!("WGC open timed out (CreateFreeThreaded hang on the virtual display) — falling back to DDA");
-            dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false)
+            dxgi::DuplCapturer::open(target, pref, keep, want.gpu, false, want.chroma_444)
                 .map(|c| Box::new(c) as Box<dyn Capturer>)
         }
     }

crates/punktfunk-host/src/capture/linux/mod.rs

@@ -89,21 +89,29 @@ impl PortalCapturer {
             node_id,
             "ScreenCast portal session started; connecting PipeWire"
         );
-        Ok(spawn_pipewire(Some(fd), node_id, None)?.into_capturer(node_id, None))
+        // This portal path (GameStream / monitor capture) is always 4:2:0, so allow zero-copy as before.
+        Ok(spawn_pipewire(Some(fd), node_id, None, true)?.into_capturer(node_id, None))
     }
 
     /// Build a capturer from an already-created virtual output ([`crate::vdisplay::VirtualOutput`]):
     /// connect PipeWire to its node (`remote_fd` selects portal-remote vs. default-daemon) and
     /// take ownership of its keepalive so the output lives exactly as long as this capturer. This
     /// is how the client's requested resolution becomes the captured resolution without scaling.
-    pub fn from_virtual_output(vout: crate::vdisplay::VirtualOutput) -> Result<PortalCapturer> {
+    /// `allow_zerocopy` mirrors [`OutputFormat::gpu`](crate::capture::OutputFormat): `false` forces the
+    /// CPU mmap path (a 4:4:4 NVENC session needs CPU-resident RGB), `true` keeps the GPU zero-copy
+    /// path subject to `PUNKTFUNK_ZEROCOPY`.
+    pub fn from_virtual_output(
+        vout: crate::vdisplay::VirtualOutput,
+        allow_zerocopy: bool,
+    ) -> Result<PortalCapturer> {
         tracing::info!(
             node_id = vout.node_id,
+            allow_zerocopy,
             "connecting PipeWire to virtual output"
         );
         let node_id = vout.node_id;
         Ok(
-            spawn_pipewire(vout.remote_fd, node_id, vout.preferred_mode)?
+            spawn_pipewire(vout.remote_fd, node_id, vout.preferred_mode, allow_zerocopy)?
                 .into_capturer(node_id, Some(vout.keepalive)),
         )
     }
@@ -146,6 +154,12 @@ fn spawn_pipewire(
     fd: Option<OwnedFd>,
     node_id: u32,
     preferred: Option<(u32, u32, u32)>,
+    // Allow GPU zero-copy capture (dmabuf→CUDA/VA). `false` forces the CPU mmap path even when
+    // `PUNKTFUNK_ZEROCOPY` is set — a 4:4:4 NVENC session needs CPU-resident RGB (the encoder
+    // swscales RGB→YUV444P; `hevc_nvenc` can't 4:4:4 from a CUDA RGB surface), so the session plan
+    // passes `gpu = false` for it. Without this, a 4:4:4 session under `PUNKTFUNK_ZEROCOPY=1` would
+    // get CUDA frames and the encoder would bail (`want_444 && cuda`).
+    allow_zerocopy: bool,
 ) -> Result<PwHandles> {
     // Frames flow from the pipewire thread over a small bounded channel.
     let (frame_tx, frame_rx) = sync_channel::<CapturedFrame>(8);
@@ -159,7 +173,7 @@ fn spawn_pipewire(
     // sender lives on the capturer and fires in its `Drop`. Absolute `::pipewire` path — the
     // inner `mod pipewire` shadows the crate name at this scope.
     let (quit_tx, quit_rx) = ::pipewire::channel::channel::<()>();
-    let zerocopy = crate::zerocopy::enabled();
+    let zerocopy = allow_zerocopy && crate::zerocopy::enabled();
     let join = thread::Builder::new()
         .name("punktfunk-pipewire".into())
         .spawn(move || {

crates/punktfunk-host/src/capture/windows/dxgi.rs

@@ -188,7 +188,8 @@ pub(crate) unsafe fn make_device(
     let device = device.context("null D3D11 device")?;
     let context = context.context("null D3D11 context")?;
 
-    // Apollo-style GPU scheduling hardening (Sunshine display_base.cpp:599-709). Our capture+encode
+    // GPU scheduling hardening — the same approach Sunshine/Apollo use, reimplemented here via the
+    // documented D3DKMT/DXGI APIs (no GPL source copied). Our capture+encode
     // shares the GPU with the streamed game; when the game saturates the GPU our process is starved of
     // GPU time slices, so NVENC sits near-idle yet `lock_bitstream` waits ~20 ms for our context to be
     // scheduled — capping the stream (~47 fps measured at 5K@240) and stuttering. Per-frame copy/convert
@@ -197,7 +198,7 @@ pub(crate) unsafe fn make_device(
     // GPU thread priority and a 1-frame latency cap.
     elevate_process_gpu_priority();
     if let Ok(dxgi_dev) = device.cast::<IDXGIDevice>() {
-        // Apollo's absolute max GPU thread priority (0x4000001E); fall back to relative +7.
+        // The absolute max GPU thread priority (0x4000001E; the same value Sunshine/Apollo use); fall back to relative +7.
         if dxgi_dev.SetGPUThreadPriority(0x4000_001E).is_err()
             && dxgi_dev.SetGPUThreadPriority(7).is_err()
         {
@@ -291,7 +292,8 @@ unsafe fn d3dkmt_set_scheduling_priority_class(
     Some(f(process, prio))
 }
 
-/// Apollo-style GPU scheduling-priority hardening (Sunshine `display_base.cpp:599-709`). On a
+/// GPU scheduling-priority hardening — the same approach as Sunshine/Apollo, independently
+/// implemented via the documented D3DKMT APIs (no GPL source copied). On a
 /// GPU-saturated game our capture+encode process is starved of GPU time slices — NVENC sits ~idle but
 /// `lock_bitstream` waits ~20 ms for our context to be scheduled. Elevating the PROCESS GPU scheduling
 /// priority class (the strong cross-process lever — far more effective than `SetGPUThreadPriority`
@@ -532,7 +534,9 @@ const ES_DISPLAY_REQUIRED: u32 = 0x0000_0002;
 
 /// Replacement for `win32u.dll!NtGdiDdDDIGetCachedHybridQueryValue`: always report
 /// `D3DKMT_GPU_PREFERENCE_STATE_UNSPECIFIED` (3). We fully replace the function (never call the
-/// original), so no trampoline is needed. (Ported verbatim from Apollo's MinHook hook.)
+/// original), so no trampoline is needed. (Independent reimplementation of the same technique Apollo
+/// uses: Apollo installs its hook via the MinHook library; this is an original inline byte-patch and
+/// copies no Apollo/GPL source.)
 unsafe extern "system" fn hybrid_query_hook(gpu_preference: *mut u32) -> i32 {
     HYBRID_HOOK_HITS.fetch_add(1, Ordering::Relaxed);
     if gpu_preference.is_null() {
@@ -542,7 +546,8 @@ unsafe extern "system" fn hybrid_query_hook(gpu_preference: *mut u32) -> i32 {
     0 // STATUS_SUCCESS
 }
 
-/// Apollo's win32u GPU-preference hook, ported. On a HYBRID-GPU box DXGI resolves a GPU preference
+/// The win32u GPU-preference hook (the same technique Apollo applies, reimplemented here from the
+/// documented DDI — no GPL source copied). On a HYBRID-GPU box DXGI resolves a GPU preference
 /// (registry + power settings + the hybrid-adapter DDI) and REPARENTS outputs onto the chosen render
 /// GPU — which constantly invalidates Desktop Duplication (DXGI_ERROR_ACCESS_LOST 0x887A0026, the
 /// freeze/churn observed on the RTX 4090 + AMD iGPU box; `SET_RENDER_ADAPTER` is ignored there). Faking
@@ -555,7 +560,7 @@ pub(crate) fn install_gpu_pref_hook() {
     // SAFETY: this one-time hook install only touches a region it has just validated.
     // `LoadLibraryA("win32u.dll")` + `GetProcAddress("NtGdiDdDDIGetCachedHybridQueryValue")` yield the
     // live base of the real exported function, so `target` is a valid executable code pointer to at
-    // least the 12 bytes the patch overwrites (an x64 prologue, per Apollo's verified hook). The two
+    // least the 12 bytes the patch overwrites (an x64 prologue). The two
     // `ptr::copy_nonoverlapping`s each move exactly 12 bytes between the 12-byte stack arrays
     // (`patch`/`readback`) and `target`, which `VirtualProtect(target, 12, PAGE_EXECUTE_READWRITE, …)`
     // has just made writable (and is restored to `old` after) — source and dest never overlap (stack
@@ -2010,6 +2015,10 @@ pub struct DuplCapturer {
     /// first, retried (legacy DuplicateOutput can't capture HDR). Set for the secure-desktop DDA leg
     /// when the SudoVDA is in HDR; threaded into every (re)duplication incl. ACCESS_LOST recovery.
     want_hdr: bool,
+    /// Full-chroma 4:4:4 session: deliver packed RGB (`Bgra` SDR / `Rgb10a2` HDR) and SKIP the
+    /// video-engine RGB→YUV (NV12/P010) conversion — NVENC reconstructs 4:4:4 only from a full-chroma
+    /// source, so we hand it the RGB texture and it CSCs to YUV444 at encode (chroma_format_idc=3).
+    chroma_444: bool,
     /// HDR (scRGB FP16) capture state. Set when the duplication surface is `R16G16B16A16_FLOAT`
     /// (the desktop has HDR on). The frame can't be `CopyResource`d into a BGRA target, so the HDR
     /// path copies it into an FP16 SRV texture, composites the cursor, then runs [`HdrConverter`] to
@@ -2087,6 +2096,8 @@ impl DuplCapturer {
         // stage 5) so the capturer never re-derives the encode backend itself.
         gpu: bool,
         want_hdr: bool,
+        // 4:4:4 session → deliver RGB, skip the NV12/P010 video-engine conversion (see the field doc).
+        chroma_444: bool,
     ) -> Result<Self> {
         // SAFETY: runs on the capture thread that will own this `DuplCapturer`. `install_gpu_pref_hook()`
         // and the DPI-context calls take by-value handles / no args and touch only thread/process state;
@@ -2311,6 +2322,7 @@ impl DuplCapturer {
                 gpu_copy: None,
                 last_present: None,
                 want_hdr,
+                chroma_444,
                 hdr_fp16: is_hdr_init,
                 hdr_meta: hdr_meta_init,
                 fp16_src: None,
@@ -3088,7 +3100,10 @@ impl DuplCapturer {
                                                     // Video-engine path: scRGB FP16 → BT.2020 PQ P010 on the VIDEO engine (no 3D shader, and
                                                     // NVENC encodes P010 natively). Fall back to the HdrConverter pixel shader (3D) only if the
                                                     // video processor is unavailable.
-            if let Some(p010) = self.convert_to_yuv(&src, true) {
+            if let Some(p010) = (!self.chroma_444)
+                .then(|| self.convert_to_yuv(&src, true))
+                .flatten()
+            {
                 self.last_present = Some((p010.clone(), PixelFormat::P010));
                 return Ok(CapturedFrame {
                     width: self.width,
@@ -3148,7 +3163,10 @@ impl DuplCapturer {
             // conversion AND NVENC's encode stay OFF the 3D engine — the only way to keep up when a
             // game pins the 3D engine at ~100%. Fall back to handing NVENC the BGRA texture (it then
             // does RGB→YUV internally on the 3D/compute engine).
-            if let Some(nv12) = self.convert_to_yuv(&gpu, false) {
+            if let Some(nv12) = (!self.chroma_444)
+                .then(|| self.convert_to_yuv(&gpu, false))
+                .flatten()
+            {
                 self.last_present = Some((nv12.clone(), PixelFormat::Nv12));
                 return Ok(CapturedFrame {
                     width: self.width,

crates/punktfunk-host/src/config.rs

@@ -7,7 +7,7 @@
 //! **Goal-1 stages 1–2** (`design/windows-host-rewrite.md` §2.2): stage 1 stood this up; stage 2 migrated the
 //! genuinely-constant operator/dispatch knobs onto it (the dispatch-disagreement bug class: `idd_push`,
 //! `capture_backend`, `encoder_pref`, `render_adapter`, `no_wgc`, the vdisplay backend select — plus the
-//! plan-named `secure_dda`/`idd_depth`/`zerocopy`/`ten_bit` and the multi-site `perf`/`compositor`/
+//! plan-named `secure_dda`/`idd_depth`/`zerocopy`/`ten_bit`/`four_four_four` and the multi-site `perf`/`compositor`/
 //! `video_source`/`gamepad`). `SessionPlan` (stage 3) consumes it as the single owner of the
 //! capture/topology/encoder decision.
 //!
@@ -63,6 +63,10 @@ pub struct HostConfig {
     pub zerocopy: bool,
     /// `PUNKTFUNK_10BIT` — host policy gate for HEVC Main10 (only honored when the client also advertised 10-bit).
     pub ten_bit: bool,
+    /// `PUNKTFUNK_444` — host policy gate for full-chroma HEVC 4:4:4 (Range Extensions). Honored only
+    /// when the client also advertised 4:4:4, the codec is HEVC, and the GPU/driver supports a 4:4:4
+    /// encode (probed) — otherwise the session stays 4:2:0. Independent of `ten_bit` (chroma vs depth).
+    pub four_four_four: bool,
     /// `PUNKTFUNK_PERF` — per-stage timing instrumentation.
     pub perf: bool,
     /// `PUNKTFUNK_VIDEO_SOURCE` — GameStream video source select (`virtual` / `portal` / unset → synthetic).
@@ -112,6 +116,7 @@ impl HostConfig {
                 .unwrap_or(2),
             zerocopy: flag("PUNKTFUNK_ZEROCOPY"),
             ten_bit: flag("PUNKTFUNK_10BIT"),
+            four_four_four: flag("PUNKTFUNK_444"),
             perf: flag("PUNKTFUNK_PERF"),
             video_source: val("PUNKTFUNK_VIDEO_SOURCE"),
             compositor: val("PUNKTFUNK_COMPOSITOR"),

crates/punktfunk-host/src/encode.rs

@@ -29,6 +29,33 @@ pub enum Codec {
     Av1,
 }
 
+/// Chroma subsampling the encoder emits, negotiated with the client (the `PUNKTFUNK_444` gate + the
+/// client's `VIDEO_CAP_444` + a GPU probe). `Yuv420` is the universal default; `Yuv444` is HEVC-only,
+/// native-protocol-only (GameStream stays 4:2:0), and the host only ever passes it after
+/// [`can_encode_444`] confirmed the active backend supports it.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
+pub enum ChromaFormat {
+    #[default]
+    Yuv420,
+    Yuv444,
+}
+
+impl ChromaFormat {
+    /// The HEVC `chroma_format_idc` this maps to: `1` (4:2:0) or `3` (4:4:4). Also the wire value
+    /// echoed in [`punktfunk_core::quic::Welcome::chroma_format`].
+    pub fn idc(self) -> u8 {
+        match self {
+            ChromaFormat::Yuv420 => punktfunk_core::quic::CHROMA_IDC_420,
+            ChromaFormat::Yuv444 => punktfunk_core::quic::CHROMA_IDC_444,
+        }
+    }
+
+    /// True for full-chroma 4:4:4.
+    pub fn is_444(self) -> bool {
+        matches!(self, ChromaFormat::Yuv444)
+    }
+}
+
 impl Codec {
     /// The FFmpeg NVENC encoder name (selected by name, not codec id — the latter would
     /// pick the software encoder).
@@ -89,6 +116,13 @@ pub struct EncoderCaps {
     /// When `false`, `set_hdr_meta` is a no-op and no in-band grade reaches the client. Only the
     /// Windows direct-NVENC path attaches it today.
     pub supports_hdr_metadata: bool,
+    /// The opened encoder is actually producing a full-chroma 4:4:4 (`chroma_format_idc = 3`) stream.
+    /// `false` on every 4:2:0 session (the default) and on a backend that declined 4:4:4. Set by the
+    /// NVENC backends (Linux + Windows). The chroma is committed to the wire (`Welcome::chroma_format`)
+    /// from the pre-open probe, so this is a *post-open cross-check*: the session glue logs loudly if
+    /// the encoder's real chroma disagrees with what was negotiated (the in-band SPS is authoritative
+    /// for the decoder either way).
+    pub chroma_444: bool,
 }
 
 /// A hardware encoder. One per session; runs on the encode thread.
@@ -193,8 +227,29 @@ pub fn open_video(
     bitrate_bps: u64,
     cuda: bool,
     bit_depth: u8,
+    chroma: ChromaFormat,
 ) -> Result<Box<dyn Encoder>> {
     validate_dimensions(codec, width, height)?;
+    // Refresh/fps must be positive and sane: fps feeds the encoder time_base (`Rational(1, fps)`)
+    // and the pts→ns conversion (`pts * 1e9 / fps`), so 0 builds a 1/0 rational / divides by zero.
+    // The mid-stream Reconfigure path already guards `refresh_hz > 0`; enforcing it at this single
+    // open chokepoint makes EVERY path (initial Hello, GameStream ANNOUNCE, Reconfigure) safe
+    // regardless of which backend opens (security-review 2026-06-28 S5).
+    if fps == 0 || fps > 1000 {
+        anyhow::bail!("invalid refresh/fps {fps}: must be 1..=1000 Hz");
+    }
+    // 4:4:4 is HEVC-only. The negotiator should never pass `Yuv444` for another codec (it gates on
+    // `codec == H265`), but defend the contract here so a future caller can't silently emit a stream
+    // no decoder expects: a non-HEVC 4:4:4 request degrades to 4:2:0 with a warning.
+    let chroma = if chroma.is_444() && codec != Codec::H265 {
+        tracing::warn!(
+            ?codec,
+            "4:4:4 requested for a non-HEVC codec — encoding 4:2:0"
+        );
+        ChromaFormat::Yuv420
+    } else {
+        chroma
+    };
     #[cfg(target_os = "linux")]
     {
         // Pick the GPU encode backend. NVIDIA → NVENC/CUDA (the original path, unchanged);
@@ -203,7 +258,16 @@ pub fn open_video(
         // its errors crisply instead of silently trying the other).
         let pref = crate::config::config().encoder_pref.as_str();
         let open_vaapi = || -> Result<Box<dyn Encoder>> {
-            vaapi::VaapiEncoder::open(codec, format, width, height, fps, bitrate_bps, bit_depth)
+            vaapi::VaapiEncoder::open(
+                codec,
+                format,
+                width,
+                height,
+                fps,
+                bitrate_bps,
+                bit_depth,
+                chroma,
+            )
             .map(|e| Box::new(e) as Box<dyn Encoder>)
         };
         match pref {
@@ -216,6 +280,7 @@ pub fn open_video(
                 bitrate_bps,
                 cuda,
                 bit_depth,
+                chroma,
             ),
             "vaapi" | "amd" | "intel" => open_vaapi(),
             "auto" | "" => {
@@ -231,6 +296,7 @@ pub fn open_video(
                         bitrate_bps,
                         cuda,
                         bit_depth,
+                        chroma,
                     )
                 } else {
                     open_vaapi()
@@ -260,6 +326,7 @@ pub fn open_video(
                         fps,
                         bitrate_bps,
                         bit_depth,
+                        chroma,
                     )
                     .map(|e| Box::new(e) as Box<dyn Encoder>)
                 }
@@ -289,6 +356,7 @@ pub fn open_video(
                         fps,
                         bitrate_bps,
                         bit_depth,
+                        chroma,
                     )
                     .map(|e| Box::new(e) as Box<dyn Encoder>)
                 }
@@ -333,6 +401,7 @@ pub fn open_video(
             bitrate_bps,
             cuda,
             bit_depth,
+            chroma,
         );
         anyhow::bail!("video encode requires Linux or Windows")
     }
@@ -355,6 +424,7 @@ fn open_nvenc_probed(
     bitrate_bps: u64,
     cuda: bool,
     bit_depth: u8,
+    chroma: ChromaFormat,
 ) -> Result<Box<dyn Encoder>> {
     const MIN_PROBE_BPS: u64 = 50_000_000;
     let mut candidates = vec![bitrate_bps];
@@ -369,7 +439,9 @@ fn open_nvenc_probed(
     }
     let mut last: Option<anyhow::Error> = None;
     for (i, &b) in candidates.iter().enumerate() {
-        match linux::NvencEncoder::open(codec, format, width, height, fps, b, cuda, bit_depth) {
+        match linux::NvencEncoder::open(
+            codec, format, width, height, fps, b, cuda, bit_depth, chroma,
+        ) {
             Ok(enc) => {
                 if i > 0 {
                     tracing::warn!(
@@ -446,6 +518,65 @@ pub fn vaapi_codec_support() -> CodecSupport {
     })
 }
 
+/// Whether the active GPU encode backend can actually produce a full-chroma **4:4:4** HEVC stream.
+/// Resolved (and cached, once) *before* the Welcome so the host advertises the chroma it will really
+/// encode — the honest-downgrade channel. 4:4:4 is HEVC-only; the probe opens a tiny encoder on the
+/// active backend (NVENC FREXT is broad on NVIDIA, but VAAPI / AMF / QSV 4:4:4 is hardware-specific,
+/// so it must be probed, never assumed). Non-HEVC codecs are always `false`.
+#[cfg(any(target_os = "linux", target_os = "windows"))]
+pub fn can_encode_444(codec: Codec) -> bool {
+    use std::sync::OnceLock;
+    if codec != Codec::H265 {
+        return false;
+    }
+    static CACHE: OnceLock<bool> = OnceLock::new();
+    *CACHE.get_or_init(|| {
+        let supported = {
+            #[cfg(target_os = "linux")]
+            {
+                // Mirror open_video's backend dispatch: VAAPI (AMD/Intel) vs NVENC (NVIDIA).
+                if linux_zero_copy_is_vaapi() {
+                    vaapi::probe_can_encode_444(codec)
+                } else {
+                    linux::probe_can_encode_444(codec)
+                }
+            }
+            #[cfg(target_os = "windows")]
+            {
+                match windows_resolved_backend() {
+                    WindowsBackend::Nvenc => {
+                        #[cfg(feature = "nvenc")]
+                        {
+                            nvenc::probe_can_encode_444(codec)
+                        }
+                        #[cfg(not(feature = "nvenc"))]
+                        {
+                            false
+                        }
+                    }
+                    WindowsBackend::Amf | WindowsBackend::Qsv => {
+                        #[cfg(feature = "amf-qsv")]
+                        {
+                            let vendor = match windows_resolved_backend() {
+                                WindowsBackend::Qsv => ffmpeg_win::WinVendor::Qsv,
+                                _ => ffmpeg_win::WinVendor::Amf,
+                            };
+                            ffmpeg_win::probe_can_encode_444(vendor, codec)
+                        }
+                        #[cfg(not(feature = "amf-qsv"))]
+                        {
+                            false
+                        }
+                    }
+                    WindowsBackend::Software => false,
+                }
+            }
+        };
+        tracing::info!(supported, "HEVC 4:4:4 encode capability probed");
+        supported
+    })
+}
+
 // ---------------------------------------------------------------------------------------------
 // Windows backend selection (the analogue of the Linux nvidia_present / linux_zero_copy_is_vaapi
 // logic). NVIDIA → NVENC, AMD → AMF, Intel → QSV; `auto` (default) reads the DXGI adapter vendor.

crates/punktfunk-host/src/encode/linux/mod.rs

@@ -11,7 +11,7 @@
 // Every `unsafe` block in this file carries a `// SAFETY:` proof; enforce it (unsafe-proof program).
 #![deny(clippy::undocumented_unsafe_blocks)]
 
-use super::{Codec, EncodedFrame, Encoder};
+use super::{ChromaFormat, Codec, EncodedFrame, Encoder};
 use crate::capture::{CapturedFrame, FramePayload, PixelFormat};
 use anyhow::{anyhow, bail, Context, Result};
 use ffmpeg::format::Pixel;
@@ -19,9 +19,33 @@ use ffmpeg::util::frame::Video as VideoFrame;
 use ffmpeg::{codec, encoder, Dictionary, Packet, Rational};
 use ffmpeg_next as ffmpeg;
 use std::os::raw::c_int;
+use std::ptr;
 
 use ffmpeg::ffi; // = ffmpeg_sys_next
 
+/// swscale: nearest-neighbour scaler flag (`SWS_POINT`). We never rescale (src dims == dst dims), so
+/// the resampler choice only governs the colour-conversion path; POINT is the cheapest.
+const SWS_POINT: c_int = 0x10;
+/// swscale colorspace id for ITU-R BT.709 (`SWS_CS_ITU709`) — the CSC coefficients for our RGB→YUV.
+const SWS_CS_ITU709: c_int = 1;
+
+/// The swscale *source* pixel format for a captured packed RGB/BGR layout (the real byte order, not
+/// the NVENC-padded `*0` form). Used by the 4:4:4 RGB→YUV444P conversion path. Mirrors the VAAPI
+/// CPU-input mapping; YUV/10-bit inputs can't feed this path (the 4:4:4 session forces packed RGB).
+fn sws_src_pixel(format: PixelFormat) -> Result<Pixel> {
+    Ok(match format {
+        PixelFormat::Bgrx => Pixel::BGRZ, // bgr0
+        PixelFormat::Rgbx => Pixel::RGBZ, // rgb0
+        PixelFormat::Bgra => Pixel::BGRA,
+        PixelFormat::Rgba => Pixel::RGBA,
+        PixelFormat::Rgb => Pixel::RGB24,
+        PixelFormat::Bgr => Pixel::BGR24,
+        PixelFormat::Nv12 | PixelFormat::P010 | PixelFormat::Rgb10a2 => {
+            bail!("NVENC 4:4:4 CPU-input path supports packed RGB/BGR only; got {format:?}")
+        }
+    })
+}
+
 /// `AVCUDADeviceContext` (libavutil/hwcontext_cuda.h) — not in the ffmpeg-sys bindings (the
 /// crate doesn't allowlist that header), so mirror its stable 3-pointer layout. We set the
 /// first field to *our* `CUcontext` so NVENC shares the context the EGL importer maps into.
@@ -131,6 +155,10 @@ pub struct NvencEncoder {
     frame: Option<VideoFrame>,
     /// Zero-copy path: CUDA hwdevice/hwframes contexts (the encoder takes `AV_PIX_FMT_CUDA`).
     cuda: Option<CudaHw>,
+    /// 4:4:4 path only: swscale context converting the captured packed RGB/BGR → planar YUV444P
+    /// (BT.709 limited) into [`Self::frame`], because `hevc_nvenc` only emits 4:4:4 from a YUV444
+    /// *input* (RGB-in is always 4:2:0). `None` on the ordinary 4:2:0 RGB path. Freed in `Drop`.
+    sws_444: Option<*mut ffi::SwsContext>,
     src_format: PixelFormat,
     expand: bool,
     width: u32,
@@ -142,10 +170,12 @@ pub struct NvencEncoder {
     force_kf: bool,
 }
 
-// `CudaHw` holds raw `AVBufferRef`s; the encoder lives on a single thread. The CPU encoder is
+// `CudaHw` holds raw `AVBufferRef`s and `sws_444` a raw `SwsContext`; the encoder lives on a single
-// already `Send` via ffmpeg-next; assert it for the CUDA fields too.
+// thread. The CPU encoder is already `Send` via ffmpeg-next; assert it for the raw fields too.
 // SAFETY: `NvencEncoder` owns an ffmpeg-next `Encoder`/`VideoFrame` (already `Send`) plus a `CudaHw`
-// holding raw `AVBufferRef`s, which are not `Send` by default. The encoder is owned and driven by
+// holding raw `AVBufferRef`s and an optional raw `SwsContext`, none of which are `Send` by default.
+// The `SwsContext` is a self-contained swscale state object with no thread affinity, touched only
+// through `&mut self` on the one encode thread. The encoder is owned and driven by
 // exactly ONE thread — the per-session encode thread it is moved to — and is only touched through
 // `&mut self` methods, so it is never aliased or accessed concurrently. The wrapped libav contexts
 // (and the shared `CUcontext` the `CudaHw` references) have no thread affinity, so transferring
@@ -164,6 +194,7 @@ impl NvencEncoder {
         bitrate_bps: u64,
         cuda: bool,
         bit_depth: u8,
+        chroma: ChromaFormat,
     ) -> Result<Self> {
         // TODO(hdr): Linux 10-bit parity. Unlike the Windows raw-SDK path (which upconverts 8-bit
         // ARGB → Main10 via pixelBitDepthMinus8), libavcodec hevc_nvenc needs a 10-bit input pixel
@@ -175,6 +206,18 @@ impl NvencEncoder {
                 "Linux NVENC 10-bit not yet wired — encoding 8-bit"
             );
         }
+        // Full-chroma 4:4:4 (HEVC Range Extensions). `hevc_nvenc` only emits 4:4:4 from a YUV444
+        // *input* frame — feeding RGB always subsamples to 4:2:0 regardless of profile (verified on
+        // the RTX 5070 Ti). So a 4:4:4 session swscales the captured RGB → YUV444P (BT.709 limited)
+        // and feeds that with `profile=rext`. The negotiator gates this to HEVC + the single-process
+        // CPU-capture topology, so `cuda` must be false here; defend the contract.
+        let want_444 = chroma.is_444() && codec == Codec::H265;
+        if want_444 && cuda {
+            bail!(
+                "NVENC 4:4:4 needs CPU RGB frames (the session forces non-zero-copy capture for \
+                 4:4:4); got a CUDA frame — capture/encoder negotiation mismatch"
+            );
+        }
         ffmpeg::init().context("ffmpeg init")?;
         if std::env::var_os("PUNKTFUNK_FFMPEG_DEBUG").is_some() {
             // SAFETY: `av_log_set_level` sets libav's global integer log level; `48` (= AV_LOG_DEBUG)
@@ -185,7 +228,14 @@ impl NvencEncoder {
         let name = codec.nvenc_name();
         let av_codec = encoder::find_by_name(name)
             .ok_or_else(|| anyhow!("{name} not built into libavcodec"))?;
-        let (nvenc_pixel, expand) = nvenc_input(format);
+        let (rgb_pixel, rgb_expand) = nvenc_input(format);
+        // 4:4:4 feeds NVENC a planar YUV444P frame we produce by swscale; the ordinary path feeds the
+        // captured RGB straight in and lets NVENC's internal CSC subsample to 4:2:0.
+        let (nvenc_pixel, expand) = if want_444 {
+            (Pixel::YUV444P, false)
+        } else {
+            (rgb_pixel, rgb_expand)
+        };
 
         let mut video = codec::context::Context::new_with_codec(av_codec)
             .encoder()
@@ -234,12 +284,12 @@ impl NvencEncoder {
             (*video.as_mut_ptr()).gop_size = -1;
         }
 
-        // NV12 path: we did the RGB→YUV conversion ourselves as BT.709 *limited* range, so signal
+        // NV12 / 4:4:4 paths: we do the RGB→YUV conversion ourselves as BT.709 *limited* range
-        // that in the bitstream VUI (colorspace/range/primaries/transfer) — otherwise the client
+        // (swscale), so signal that in the bitstream VUI (colorspace/range/primaries/transfer) —
-        // decoder assumes a default and the picture comes out washed-out / wrong-contrast. The
+        // otherwise the client decoder assumes a default and the picture comes out washed-out /
-        // RGB-input paths leave these unset (NVENC's internal CSC writes its own VUI). Matches the
+        // wrong-contrast. The RGB-input 4:2:0 path leaves these unset (NVENC's internal CSC writes
-        // Windows NV12 path's BT.709 limited-range signalling.
+        // its own VUI). Matches the Windows NV12 path's BT.709 limited-range signalling.
-        if matches!(format, PixelFormat::Nv12) {
+        if matches!(format, PixelFormat::Nv12) || want_444 {
             // SAFETY: same `video` builder — `raw = video.as_mut_ptr()` is the non-null, properly-
             // aligned, sole-owned, not-yet-opened `AVCodecContext`. We set its four VUI colour enum
             // fields to valid `AVColorSpace`/`AVColorRange`/`AVColorPrimaries`/`AVColorTransfer-
@@ -280,6 +330,45 @@ impl NvencEncoder {
             None
         };
 
+        // 4:4:4: build the RGB→YUV444P swscale (BT.709 limited, no rescale). Mirrors the VAAPI CPU
+        // path's RGB→NV12 scaler, but the dst is full-chroma planar 4:4:4.
+        let sws_444 = if want_444 {
+            let src_av = pixel_to_av(sws_src_pixel(format)?);
+            // SAFETY: `sws_getContext` allocates a swscale context for the given src/dst dims + pixel
+            // formats. Both dims are the encoder's positive `width`/`height` as `c_int`; `src_av` is a
+            // valid `AVPixelFormat` (from the `sws_src_pixel`-validated, packed-RGB-only source), the
+            // dst is YUV444P. The trailing filter/param pointers are null = "use defaults" (documented
+            // as accepted). No Rust memory is borrowed; the returned pointer is null-checked below.
+            let sws = unsafe {
+                ffi::sws_getContext(
+                    width as c_int,
+                    height as c_int,
+                    src_av,
+                    width as c_int,
+                    height as c_int,
+                    ffi::AVPixelFormat::AV_PIX_FMT_YUV444P,
+                    SWS_POINT,
+                    ptr::null_mut(),
+                    ptr::null_mut(),
+                    ptr::null(),
+                )
+            };
+            if sws.is_null() {
+                bail!("sws_getContext(RGB→YUV444P) failed");
+            }
+            // SAFETY: `sws` is the non-null context from the call above (null-checked). The ITU-709
+            // coefficient table from `sws_getCoefficients` is a process-lifetime libswscale static,
+            // reused for src+dst matrices; `sws_setColorspaceDetails` only reads it and writes scalar
+            // CSC settings into `sws` (limited-range dst: dstRange = 0). No Rust memory is passed.
+            unsafe {
+                let cs709 = ffi::sws_getCoefficients(SWS_CS_ITU709);
+                ffi::sws_setColorspaceDetails(sws, cs709, 1, cs709, 0, 0, 1 << 16, 1 << 16);
+            }
+            Some(sws)
+        } else {
+            None
+        };
+
         // Low-latency NVENC tuning (plan §7 / linux-setup doc).
         let mut opts = Dictionary::new();
         opts.set("preset", "p1"); // fastest
@@ -288,6 +377,12 @@ impl NvencEncoder {
         opts.set("bf", "0");
         opts.set("delay", "0");
         opts.set("forced-idr", "1"); // RFI/request_keyframe → real IDR under the infinite GOP
+        if want_444 {
+            // HEVC Range Extensions — the profile that carries chroma_format_idc=3. With a YUV444P
+            // input `hevc_nvenc` auto-selects it, but pin it explicitly so the chroma is never silently
+            // dropped on a future libavcodec.
+            opts.set("profile", "rext");
+        }
 
         // Split-frame encode across both NVENC engines (GB203 has 2) when the pixel rate exceeds
         // a single engine's HEVC capacity (~1 Gpix/s); e.g. 5120x1440@240 = 1.77 Gpix/s needs it,
@@ -321,6 +416,7 @@ impl NvencEncoder {
             enc,
             frame,
             cuda: cuda_hw,
+            sws_444,
             src_format: format,
             expand,
             width,
@@ -333,6 +429,15 @@ impl NvencEncoder {
 }
 
 impl Encoder for NvencEncoder {
+    fn caps(&self) -> super::EncoderCaps {
+        super::EncoderCaps {
+            // 4:4:4 iff this session opened the RGB→YUV444P swscale path (FREXT). RFI/HDR-SEI stay
+            // unsupported on libavcodec NVENC (the trait defaults).
+            chroma_444: self.sws_444.is_some(),
+            ..super::EncoderCaps::default()
+        }
+    }
+
     fn submit(&mut self, captured: &CapturedFrame) -> Result<()> {
         anyhow::ensure!(
             captured.width == self.width && captured.height == self.height,
@@ -411,6 +516,47 @@ impl NvencEncoder {
             bytes.len(),
             src_row * h
         );
+        // 4:4:4: swscale the packed RGB straight into the planar YUV444P input frame (BT.709 limited),
+        // then send it — no byte-expand. The 4:2:0 RGB path (below) feeds NVENC packed RGB directly.
+        if let Some(sws) = self.sws_444 {
+            let frame = self
+                .frame
+                .as_mut()
+                .context("CPU frame missing (encoder opened in CUDA mode)")?;
+            // SAFETY: `format == self.src_format` and `bytes.len() >= src_row * h` (the `ensure!`s
+            // above), so `sws_scale` reads `h` rows of `src_row` bytes from `src_data[0] = bytes`
+            // (packed RGB is single-plane; the other src planes are null/0) — all in bounds. `sws` is
+            // the non-null context built in `open`. The dst is `frame`'s underlying `AVFrame`: its
+            // `data`/`linesize` in-struct arrays were sized for YUV444P by `VideoFrame::new`, and the
+            // 3 planes are each `width`×`height`. All pointers are live locals for this synchronous
+            // call; the encoder runs only on this thread (`unsafe impl Send`), so no aliasing/race.
+            unsafe {
+                let dst_av = frame.as_mut_ptr();
+                let src_data: [*const u8; 4] =
+                    [bytes.as_ptr(), ptr::null(), ptr::null(), ptr::null()];
+                let src_stride: [c_int; 4] = [src_row as c_int, 0, 0, 0];
+                let r = ffi::sws_scale(
+                    sws,
+                    src_data.as_ptr(),
+                    src_stride.as_ptr(),
+                    0,
+                    h as c_int,
+                    (*dst_av).data.as_ptr(),
+                    (*dst_av).linesize.as_ptr(),
+                );
+                if r < 0 {
+                    bail!("sws_scale(RGB→YUV444P) failed ({r})");
+                }
+            }
+            frame.set_pts(Some(pts));
+            frame.set_kind(if idr {
+                ffmpeg::picture::Type::I
+            } else {
+                ffmpeg::picture::Type::None
+            });
+            self.enc.send_frame(frame).context("send_frame(444)")?;
+            return Ok(());
+        }
         let frame = self
             .frame
             .as_mut()
@@ -526,3 +672,51 @@ impl NvencEncoder {
         Ok(())
     }
 }
+
+impl Drop for NvencEncoder {
+    fn drop(&mut self) {
+        if let Some(sws) = self.sws_444.take() {
+            // SAFETY: `sws` is the non-null `SwsContext` allocated by `sws_getContext` in `open` and
+            // owned exclusively by this encoder (taken out of the field so it can't be freed twice).
+            // `sws_freeContext` frees it; nothing else references it after this single-threaded drop.
+            unsafe { ffi::sws_freeContext(sws) };
+        }
+    }
+}
+
+/// Probe whether this NVIDIA GPU + driver + libavcodec can actually encode HEVC **4:4:4** (Range
+/// Extensions). Opens a tiny real `hevc_nvenc` 4:4:4 session — the exact path [`NvencEncoder::open`]
+/// takes for a live 4:4:4 stream — and reports whether it succeeded. HEVC-only; the result is cached
+/// by the caller ([`crate::encode::can_encode_444`]). A GPU/driver/ffmpeg without RExt 4:4:4 fails
+/// the open here, so the host resolves the session to 4:2:0 before the Welcome (honest downgrade).
+pub fn probe_can_encode_444(codec: Codec) -> bool {
+    if codec != Codec::H265 {
+        return false;
+    }
+    if ffmpeg::init().is_err() {
+        return false;
+    }
+    // Quiet ffmpeg's open error on a GPU that lacks 4:4:4 — the probe failing is an expected outcome.
+    // SAFETY: libav initialized above; `av_log_{get,set}_level` only read/write the global int level
+    // (no pointer args) and are always sound post-init.
+    let prev = unsafe {
+        let p = ffi::av_log_get_level();
+        ffi::av_log_set_level(ffi::AV_LOG_FATAL);
+        p
+    };
+    let ok = NvencEncoder::open(
+        codec,
+        PixelFormat::Bgra,
+        640,
+        480,
+        30,
+        2_000_000,
+        false, // CPU input (the 4:4:4 path never uses CUDA)
+        8,
+        ChromaFormat::Yuv444,
+    )
+    .is_ok();
+    // SAFETY: restore the saved global log level (scalar arg, no pointers).
+    unsafe { ffi::av_log_set_level(prev) };
+    ok
+}

crates/punktfunk-host/src/encode/linux/vaapi.rs

@@ -160,6 +160,18 @@ pub fn probe_can_encode(codec: Codec) -> bool {
     }
 }
 
+/// Whether the active VAAPI GPU can encode HEVC **4:4:4** (Range Extensions). **Deferred in v1 —
+/// always `false`.** VAAPI HEVC 4:4:4 encode is narrow and vendor-specific (the lab's AMD Phoenix1 /
+/// RDNA3 exposes only `VAProfileHEVCMain`/`Main10` `EncSlice`, no `Main444`), and there is no
+/// validated hardware to build + verify the 4:4:4 surface/profile path against. Returning `false`
+/// keeps the negotiation honest: a VAAPI host resolves every session to 4:2:0 before the Welcome, so
+/// the client never builds a 4:4:4 decoder it would only get 4:2:0 frames for. (Follow-up: implement
+/// and validate on an Intel Arc / RDNA4-class box that advertises a HEVC 4:4:4 encode entrypoint.)
+pub fn probe_can_encode_444(_codec: Codec) -> bool {
+    tracing::info!("VAAPI HEVC 4:4:4 encode is not implemented yet — declining (encoding 4:2:0)");
+    false
+}
+
 /// Drain the encoder for one packet (shared poll logic).
 fn poll_encoder(enc: &mut encoder::video::Encoder, fps: u32) -> Result<Option<EncodedFrame>> {
     let mut pkt = Packet::empty();
@@ -848,6 +860,7 @@ pub struct VaapiEncoder {
 unsafe impl Send for VaapiEncoder {}
 
 impl VaapiEncoder {
+    #[allow(clippy::too_many_arguments)]
     pub fn open(
         codec: Codec,
         format: PixelFormat,
@@ -856,10 +869,18 @@ impl VaapiEncoder {
         fps: u32,
         bitrate_bps: u64,
         bit_depth: u8,
+        chroma: super::ChromaFormat,
     ) -> Result<Self> {
         if bit_depth != 8 {
             tracing::warn!(bit_depth, "VAAPI 10-bit not yet wired — encoding 8-bit");
         }
+        // VAAPI 4:4:4 is deferred (see `probe_can_encode_444`): no validated AMD/Intel hardware in the
+        // lab exposes a HEVC 4:4:4 encode entrypoint, and the probe returns false so the host never
+        // negotiates 4:4:4 for a VAAPI session. If a request slips through, fall back to 4:2:0 rather
+        // than emit an unverified stream — the host signalled 4:2:0 in the Welcome anyway.
+        if chroma.is_444() {
+            tracing::warn!("VAAPI 4:4:4 encode not implemented — encoding 4:2:0");
+        }
         ffmpeg::init().context("ffmpeg init")?;
         if std::env::var_os("PUNKTFUNK_FFMPEG_DEBUG").is_some() {
             // SAFETY: `av_log_set_level` sets libav's global integer log level; `48` (= AV_LOG_DEBUG)

crates/punktfunk-host/src/encode/windows/ffmpeg_win.rs

@@ -31,7 +31,7 @@
 // Every `unsafe` block in this file carries a `// SAFETY:` proof; enforce it (unsafe-proof program).
 #![deny(clippy::undocumented_unsafe_blocks)]
 
-use super::{Codec, EncodedFrame, Encoder};
+use super::{ChromaFormat, Codec, EncodedFrame, Encoder};
 use crate::capture::{dxgi::D3d11Frame, CapturedFrame, FramePayload, PixelFormat};
 use anyhow::{anyhow, bail, Context, Result};
 use ffmpeg::format::Pixel;
@@ -241,6 +241,18 @@ unsafe fn open_win_encoder(
 /// driver/runtime rejects codecs the video engine can't do (AV1 on pre-RDNA3 AMD / pre-Arc Intel,
 /// or HEVC on a very old part). Used to build the GameStream codec advertisement so a client never
 /// negotiates a codec the encoder can't open. Torn down immediately.
+/// Whether the active AMD (AMF) / Intel (QSV) GPU can encode HEVC **4:4:4**. **Deferred in v1 —
+/// always `false`.** AMF/QSV HEVC 4:4:4 encode is narrow (AMD RDNA3+, Intel Arc/Xe2+) and the
+/// libavcodec profile/pixel-format incantation is vendor- and driver-specific — a wrong profile
+/// `avcodec_open2` *silently* falls back to 4:2:0, so a positive probe would need a verify-by-frame,
+/// and there is no AMD/Intel Windows box in the lab to build + validate that against. Returning
+/// `false` keeps the negotiation honest: an AMF/QSV host resolves every session to 4:2:0 before the
+/// Welcome. (Follow-up: implement + validate on an RDNA3+/Arc Windows box.)
+pub fn probe_can_encode_444(_vendor: WinVendor, _codec: Codec) -> bool {
+    tracing::info!("AMF/QSV HEVC 4:4:4 encode is not implemented yet — declining (encoding 4:2:0)");
+    false
+}
+
 pub fn probe_can_encode(vendor: WinVendor, codec: Codec) -> bool {
     if ffmpeg::init().is_err() {
         return false;
@@ -1096,6 +1108,7 @@ pub struct FfmpegWinEncoder {
 unsafe impl Send for FfmpegWinEncoder {}
 
 impl FfmpegWinEncoder {
+    #[allow(clippy::too_many_arguments)]
     #[allow(clippy::too_many_arguments)]
     pub fn open(
         vendor: WinVendor,
@@ -1106,7 +1119,15 @@ impl FfmpegWinEncoder {
         fps: u32,
         bitrate_bps: u64,
         bit_depth: u8,
+        chroma: ChromaFormat,
     ) -> Result<Self> {
+        // AMF/QSV 4:4:4 is deferred (see `probe_can_encode_444`): no validated AMD/Intel Windows
+        // hardware in the lab, and the AMF/QSV HEVC 4:4:4 profile/format incantations are vendor- and
+        // driver-specific (a wrong profile silently encodes 4:2:0). The probe returns false so the host
+        // never negotiates 4:4:4 for an AMF/QSV session; if a request slips through, fall back to 4:2:0.
+        if chroma.is_444() {
+            tracing::warn!("AMF/QSV 4:4:4 encode not implemented — encoding 4:2:0");
+        }
         ffmpeg::init().context("ffmpeg init")?;
         if std::env::var_os("PUNKTFUNK_FFMPEG_DEBUG").is_some() {
             // SAFETY: `ffmpeg::init()` ran on the line above, so libav is initialised; `av_log_set_level`

crates/punktfunk-host/src/encode/windows/nvenc.rs

@@ -16,7 +16,7 @@
 // Every `unsafe` block / impl in this file carries a `// SAFETY:` proof; enforce it.
 #![deny(clippy::undocumented_unsafe_blocks)]
 
-use super::{Codec, EncodedFrame, Encoder, EncoderCaps};
+use super::{ChromaFormat, Codec, EncodedFrame, Encoder, EncoderCaps};
 use crate::capture::{CapturedFrame, FramePayload, PixelFormat};
 use anyhow::{anyhow, bail, Context, Result};
 use std::collections::{HashMap, VecDeque};
@@ -57,6 +57,15 @@ pub struct NvencD3d11Encoder {
     buffer_fmt: nv::NV_ENC_BUFFER_FORMAT,
     /// Encoded bit depth (8 or 10). 10 → HEVC Main10 (NVENC upconverts the 8-bit ARGB input).
     bit_depth: u8,
+    /// Full-chroma 4:4:4 (HEVC Range Extensions, `chroma_format_idc = 3`) requested for this session.
+    /// NVENC ingests the RGB (ARGB/ABGR10) input and CSCs it to YUV444 internally; the `FREXT` profile
+    /// and `chromaFormatIDC = 3` in the encode config carry the chroma. Gated on the GPU's
+    /// `NV_ENC_CAPS_SUPPORT_YUV444_ENCODE` (cleared in `query_caps` on a card that lacks it) and on an
+    /// RGB input format (NV12/P010 capture can't reconstruct 4:4:4). HEVC-only.
+    chroma_444: bool,
+    /// `NV_ENC_CAPS_SUPPORT_YUV444_ENCODE` from the caps probe — whether this GPU can 4:4:4 encode at
+    /// all. `chroma_444` is forced off when this is false (graceful downgrade to 4:2:0).
+    yuv444_supported: bool,
     /// HDR: the capturer is delivering BT.2020 PQ 10-bit (`PixelFormat::Rgb10a2`) frames. Sets the
     /// `ABGR10` input format + the BT.2020/PQ colour VUI. Derived per-frame from the capture format
     /// (HDR can toggle mid-session); a change re-inits the session.
@@ -103,6 +112,7 @@ pub struct NvencD3d11Encoder {
 unsafe impl Send for NvencD3d11Encoder {}
 
 impl NvencD3d11Encoder {
+    #[allow(clippy::too_many_arguments)]
     pub fn open(
         codec: Codec,
         _format: PixelFormat,
@@ -111,6 +121,7 @@ impl NvencD3d11Encoder {
         fps: u32,
         bitrate_bps: u64,
         bit_depth: u8,
+        chroma: ChromaFormat,
     ) -> Result<Self> {
         Ok(Self {
             encoder: ptr::null_mut(),
@@ -122,6 +133,9 @@ impl NvencD3d11Encoder {
             bitrate_bps,
             buffer_fmt: nv::NV_ENC_BUFFER_FORMAT::NV_ENC_BUFFER_FORMAT_ARGB,
             bit_depth,
+            // 4:4:4 is HEVC-only; the GPU-support gate is applied in `query_caps`.
+            chroma_444: chroma.is_444() && codec == Codec::H265,
+            yuv444_supported: false,
             hdr: false,
             hdr_meta: None,
             regs: HashMap::new(),
@@ -209,6 +223,7 @@ impl NvencD3d11Encoder {
         let wmax = self.get_cap(enc, nv::NV_ENC_CAPS::NV_ENC_CAPS_WIDTH_MAX);
         let hmax = self.get_cap(enc, nv::NV_ENC_CAPS::NV_ENC_CAPS_HEIGHT_MAX);
         let ten_bit = self.get_cap(enc, nv::NV_ENC_CAPS::NV_ENC_CAPS_SUPPORT_10BIT_ENCODE);
+        let yuv444 = self.get_cap(enc, nv::NV_ENC_CAPS::NV_ENC_CAPS_SUPPORT_YUV444_ENCODE);
         let rfi = self.get_cap(
             enc,
             nv::NV_ENC_CAPS::NV_ENC_CAPS_SUPPORT_REF_PIC_INVALIDATION,
@@ -235,6 +250,13 @@ impl NvencD3d11Encoder {
             self.bit_depth = 8;
             self.hdr = false;
         }
+        // Same for 4:4:4: a card without YUV444 encode falls back to 4:2:0. (The host already probed
+        // this via `probe_can_encode_444` before the Welcome, so this is a belt-and-braces guard.)
+        self.yuv444_supported = yuv444 != 0;
+        if self.chroma_444 && !self.yuv444_supported {
+            tracing::warn!("NVENC: this GPU can't 4:4:4 encode — falling back to 4:2:0");
+            self.chroma_444 = false;
+        }
         self.rfi_supported = rfi != 0;
         self.custom_vbv = custom_vbv != 0;
         tracing::info!(
@@ -313,9 +335,31 @@ impl NvencD3d11Encoder {
         cfg.encodeCodecConfig.hevcConfig.tier = 1;
         cfg.encodeCodecConfig.hevcConfig.level = 0;
 
+        // Chroma + bit depth. Full-chroma 4:4:4 (HEVC Range Extensions) takes precedence and composes
+        // with 10-bit (Main 4:4:4 10): NVENC ingests the RGB input (ARGB / ABGR10) and CSCs it to
+        // YUV444 internally when `chromaFormatIDC = 3` under the FREXT profile. Only valid on an RGB
+        // input — a subsampled NV12/P010 source can't reconstruct full chroma (so the capturer is
+        // forced to RGB for a 4:4:4 session, and we guard on the input format here too).
+        //
+        // ON-GLASS TODO (RTX box): confirm ARGB + chromaFormatIDC=3 + FREXT yields a *true* 4:4:4
+        // stream. NVENC's RGB→YUV CSC is documented to honor chromaFormatIDC (unlike libavcodec's
+        // wrapper, which always subsamples RGB to 4:2:0 — hence the Linux path feeds planar YUV444
+        // instead). If on-glass shows 4:2:0, the follow-up is a BGRA→AYUV shader feeding the native
+        // `NV_ENC_BUFFER_FORMAT_AYUV` 4:4:4 input format.
+        let rgb_input = matches!(
+            self.buffer_fmt,
+            nv::NV_ENC_BUFFER_FORMAT::NV_ENC_BUFFER_FORMAT_ARGB
+                | nv::NV_ENC_BUFFER_FORMAT::NV_ENC_BUFFER_FORMAT_ABGR10
+        );
+        if self.chroma_444 && rgb_input {
+            cfg.profileGUID = nv::NV_ENC_HEVC_PROFILE_FREXT_GUID;
+            cfg.encodeCodecConfig.hevcConfig.set_chromaFormatIDC(3);
+            if self.bit_depth == 10 {
+                cfg.encodeCodecConfig.hevcConfig.set_pixelBitDepthMinus8(2); // Main 4:4:4 10
+            }
+        } else if self.bit_depth == 10 {
             // 10-bit HEVC Main10 (HDR foundation): NVENC upconverts the 8-bit input; 8-bit leaves the
             // preset default (Main) untouched.
-        if self.bit_depth == 10 {
             cfg.profileGUID = nv::NV_ENC_HEVC_PROFILE_MAIN10_GUID;
             cfg.encodeCodecConfig.hevcConfig.set_pixelBitDepthMinus8(2); // 10 - 8
         }
@@ -787,6 +831,9 @@ impl Encoder for NvencD3d11Encoder {
         EncoderCaps {
             supports_rfi: self.rfi_supported,
             supports_hdr_metadata: self.hdr,
+            // Reflects what the session actually configured (cleared in `query_caps` if the GPU lacks
+            // YUV444 encode), so the glue can confirm 4:4:4 vs the negotiated request.
+            chroma_444: self.chroma_444,
         }
     }
 
@@ -904,3 +951,69 @@ impl Drop for NvencD3d11Encoder {
         unsafe { self.teardown() };
     }
 }
+
+/// Probe whether the active NVIDIA GPU can encode HEVC **4:4:4** (`NV_ENC_CAPS_SUPPORT_YUV444_ENCODE`).
+/// Creates a throwaway hardware D3D11 device + NVENC session, queries the cap, and tears down. HEVC-only;
+/// the result is cached by the caller ([`crate::encode::can_encode_444`]) and read *before* the Welcome
+/// so the host advertises the chroma it can really encode (honest downgrade to 4:2:0 on a card without it).
+pub fn probe_can_encode_444(codec: Codec) -> bool {
+    use windows::Win32::Foundation::HMODULE;
+    use windows::Win32::Graphics::Direct3D::{D3D_DRIVER_TYPE_HARDWARE, D3D_FEATURE_LEVEL_11_0};
+    use windows::Win32::Graphics::Direct3D11::{
+        D3D11CreateDevice, D3D11_CREATE_DEVICE_BGRA_SUPPORT, D3D11_SDK_VERSION,
+    };
+    if codec != Codec::H265 {
+        return false;
+    }
+    // SAFETY: a self-contained probe owning every handle it creates. `D3D11CreateDevice` (HARDWARE
+    // driver, NULL adapter) fills `device` or returns Err (→ false). `open_encode_session_ex` opens an
+    // NVENC session against that device's raw pointer (valid while `device` is held) or errors (→ false,
+    // tearing nothing down). `get_encode_caps` reads one scalar cap into `val` via the loaded API table.
+    // `destroy_encoder` frees the session exactly once; `device`/its context drop with the COM wrappers.
+    // No handle escapes this call and nothing runs concurrently.
+    unsafe {
+        let mut device: Option<ID3D11Device> = None;
+        if D3D11CreateDevice(
+            None,
+            D3D_DRIVER_TYPE_HARDWARE,
+            HMODULE::default(),
+            D3D11_CREATE_DEVICE_BGRA_SUPPORT,
+            Some(&[D3D_FEATURE_LEVEL_11_0]),
+            D3D11_SDK_VERSION,
+            Some(&mut device),
+            None,
+            None,
+        )
+        .is_err()
+        {
+            return false;
+        }
+        let Some(device) = device else { return false };
+        let mut params = nv::NV_ENC_OPEN_ENCODE_SESSION_EX_PARAMS {
+            version: nv::NV_ENC_OPEN_ENCODE_SESSION_EX_PARAMS_VER,
+            deviceType: nv::NV_ENC_DEVICE_TYPE::NV_ENC_DEVICE_TYPE_DIRECTX,
+            device: device.as_raw(),
+            apiVersion: nv::NVENCAPI_VERSION,
+            ..Default::default()
+        };
+        let mut enc: *mut c_void = ptr::null_mut();
+        if (API.open_encode_session_ex)(&mut params, &mut enc)
+            .result_without_string()
+            .is_err()
+        {
+            return false;
+        }
+        let mut param = nv::NV_ENC_CAPS_PARAM {
+            version: nv::NV_ENC_CAPS_PARAM_VER,
+            capsToQuery: nv::NV_ENC_CAPS::NV_ENC_CAPS_SUPPORT_YUV444_ENCODE,
+            reserved: [0; 62],
+        };
+        let mut val: i32 = 0;
+        let ok = (API.get_encode_caps)(enc, nv::NV_ENC_CODEC_HEVC_GUID, &mut param, &mut val)
+            .result_without_string()
+            .is_ok()
+            && val != 0;
+        let _ = (API.destroy_encoder)(enc);
+        ok
+    }
+}

crates/punktfunk-host/src/gamestream/audio.rs

@@ -41,8 +41,6 @@ type Aes128CbcEnc = cbc::Encryptor<aes::Aes128>;
 /// `RTP_PAYLOAD_TYPE_FEC  127`).
 const AUDIO_PACKET_TYPE: u8 = 97;
 const AUDIO_FEC_PACKET_TYPE: u8 = 127;
-/// Stereo Opus bitrate (unchanged from the live-validated stereo path).
-const OPUS_BITRATE: i32 = 128_000;
 
 /// Audio FEC geometry (moonlight-common-c `RtpAudioQueue.h`: `RTPA_DATA_SHARDS 4`,
 /// `RTPA_FEC_SHARDS 2`). Blocks are aligned: the client synthesizes the block base as
@@ -82,67 +80,20 @@ impl Default for AudioParams {
     }
 }
 
-/// One Opus (multi)stream layout. Channel order is the GameStream/Moonlight order
+// The Opus surround layout table (channel order FL FR FC LFE RL RR [SL SR], identity mapping,
-/// FL FR FC LFE RL RR [SL SR]; `mapping` is the libopus multistream mapping we *encode*
+// Sunshine's per-config bitrates) now lives in `punktfunk_core::audio`, shared with the native
-/// with — identical to Sunshine's `audio.cpp stream_configs` (verified verbatim 2026-06-10):
+// `punktfunk/1` path and every client decoder. Re-export the pieces the GameStream module + its
-/// identity mapping, so normal quality couples (FL,FR) and (FC,LFE) [+ (RL,RR) on 7.1] with
+// RTSP SDP (`rtsp.rs`) reference; the GFE-specific `surround_params` SDP rotation stays below.
-/// the remaining channels as mono streams; high quality is one mono stream per channel.
+pub use punktfunk_core::audio::{
-/// Bitrates are Sunshine's per-config values (stereo keeps punktfunk's existing 128 kbps).
+    OpusLayout, LAYOUT_51, LAYOUT_51_HQ, LAYOUT_71, LAYOUT_71_HQ, LAYOUT_STEREO,
-pub struct OpusLayout {
-    pub channels: u8,
-    pub streams: u8,
-    pub coupled: u8,
-    pub mapping: &'static [u8],
-    pub bitrate: i32,
-}
-
-pub const LAYOUT_STEREO: OpusLayout = OpusLayout {
-    channels: 2,
-    streams: 1,
-    coupled: 1,
-    mapping: &[0, 1],
-    bitrate: OPUS_BITRATE,
-};
-pub const LAYOUT_51: OpusLayout = OpusLayout {
-    channels: 6,
-    streams: 4,
-    coupled: 2,
-    mapping: &[0, 1, 2, 3, 4, 5],
-    bitrate: 256_000,
-};
-pub const LAYOUT_51_HQ: OpusLayout = OpusLayout {
-    channels: 6,
-    streams: 6,
-    coupled: 0,
-    mapping: &[0, 1, 2, 3, 4, 5],
-    bitrate: 1_536_000,
-};
-pub const LAYOUT_71: OpusLayout = OpusLayout {
-    channels: 8,
-    streams: 5,
-    coupled: 3,
-    mapping: &[0, 1, 2, 3, 4, 5, 6, 7],
-    bitrate: 450_000,
-};
-pub const LAYOUT_71_HQ: OpusLayout = OpusLayout {
-    channels: 8,
-    streams: 8,
-    coupled: 0,
-    mapping: &[0, 1, 2, 3, 4, 5, 6, 7],
-    bitrate: 2_048_000,
 };
 
-/// Pick the encoder layout for the negotiated session parameters. Unknown channel counts
+/// Pick the encoder layout for the negotiated session parameters. Thin wrapper over the shared
-/// fall back to stereo (the client can only request 2/6/8 — `AUDIO_CONFIGURATION_*` in
+/// [`punktfunk_core::audio::layout_for`] keyed on this module's [`AudioParams`] (unknown channel
+/// counts fall back to stereo; the client can only request 2/6/8 — `AUDIO_CONFIGURATION_*` in
 /// Limelight.h).
 pub fn layout_for(params: &AudioParams) -> &'static OpusLayout {
-    match (params.channels, params.high_quality) {
+    punktfunk_core::audio::layout_for(params.channels, params.high_quality)
-        (6, false) => &LAYOUT_51,
-        (6, true) => &LAYOUT_51_HQ,
-        (8, false) => &LAYOUT_71,
-        (8, true) => &LAYOUT_71_HQ,
-        _ => &LAYOUT_STEREO,
-    }
 }
 
 /// The `a=fmtp:97 surround-params=` digit string for a layout: channelCount, streams,
@@ -345,21 +296,21 @@ fn run(
 }
 
 /// Opus encoder for one session: the plain stereo encoder (the live-validated path, byte
-/// identical) or a libopus multistream encoder for 5.1/7.1.
+/// identical) or the safe `opus::MSEncoder` multistream encoder for 5.1/7.1. Both are
+/// cross-platform (Linux + Windows) — surround no longer needs `audiopus_sys`.
 #[cfg(any(target_os = "linux", target_os = "windows"))]
 enum SessionEncoder {
     Stereo(opus::Encoder),
-    // Surround needs the libopus *multistream* encoder via `audiopus_sys` (Linux-only dep).
+    Surround(opus::MSEncoder),
-    #[cfg(target_os = "linux")]
-    Surround(MsEncoder),
 }
 
 #[cfg(any(target_os = "linux", target_os = "windows"))]
 impl SessionEncoder {
     fn new(layout: &'static OpusLayout) -> Result<SessionEncoder> {
+        // RESTRICTED_LOWDELAY (`opus::Application::LowDelay`) + hard CBR, matching Sunshine — CBR
+        // keeps the Opus packet size constant, which the GameStream audio FEC (equal-length shards)
+        // relies on, and the client asserts a constant per-stream TOC.
         if layout.channels == 2 {
-            // RESTRICTED_LOWDELAY + CBR, matching Sunshine — CBR keeps the Opus TOC byte
-            // constant, which the client asserts per stream.
             let mut enc = opus::Encoder::new(
                 SAMPLE_RATE,
                 opus::Channels::Stereo,
@@ -370,138 +321,32 @@ impl SessionEncoder {
             enc.set_vbr(false).ok();
             Ok(SessionEncoder::Stereo(enc))
         } else {
-            #[cfg(target_os = "linux")]
+            let mut enc = opus::MSEncoder::new(
-            {
+                SAMPLE_RATE,
-                Ok(SessionEncoder::Surround(MsEncoder::new(layout)?))
+                layout.streams,
-            }
+                layout.coupled,
-            #[cfg(not(target_os = "linux"))]
+                layout.mapping,
-            {
+                opus::Application::LowDelay,
-                anyhow::bail!(
-                    "surround audio ({} ch) needs the libopus multistream encoder (Linux only) — \
-                     use a stereo session",
-                    layout.channels
             )
-            }
+            .map_err(|e| anyhow::anyhow!("create Opus multistream encoder: {e}"))?;
+            enc.set_bitrate(opus::Bitrate::Bits(layout.bitrate)).ok();
+            enc.set_vbr(false).ok();
+            Ok(SessionEncoder::Surround(enc))
         }
     }
 
-    /// Encode one interleaved frame (`samples_per_channel * channels` f32s) into `out`,
+    /// Encode one interleaved frame into `out`, returning the packet length. Both encoders infer
-    /// returning the packet length.
+    /// the per-channel sample count from `frame.len()` and their channel count.
-    fn encode_float(
+    fn encode_float(&mut self, frame: &[f32], out: &mut [u8]) -> Result<usize> {
-        &mut self,
-        frame: &[f32],
-        samples_per_channel: usize,
-        out: &mut [u8],
-    ) -> Result<usize> {
-        // `samples_per_channel` only feeds the multistream (surround) encoder; stereo infers it.
-        #[cfg(not(target_os = "linux"))]
-        let _ = samples_per_channel;
         match self {
             SessionEncoder::Stereo(enc) => enc.encode_float(frame, out).context("opus encode"),
-            #[cfg(target_os = "linux")]
+            SessionEncoder::Surround(enc) => enc
-            SessionEncoder::Surround(enc) => enc.encode_float(frame, samples_per_channel, out),
+                .encode_float(frame, out)
+                .context("opus multistream encode"),
         }
     }
 }
 
-/// RAII wrapper for `OpusMSEncoder` (the safe `opus` crate is stereo-only; the multistream
-/// API comes from `audiopus_sys`, the same libopus the crate already links). Configured like
-/// the stereo path: RESTRICTED_LOWDELAY, hard CBR, per-layout bitrate.
-#[cfg(target_os = "linux")]
-struct MsEncoder {
-    st: std::ptr::NonNull<audiopus_sys::OpusMSEncoder>,
-}
-
-// SAFETY: `MsEncoder` owns a unique `OpusMSEncoder` via `NonNull` (it is neither `Clone` nor
-// `Sync`, so the pointer is never aliased). libopus's multistream encoder state is a self-contained
-// heap allocation with no thread-local or thread-affine state, so moving ownership to another thread
-// is sound; every method takes `&mut self`, keeping access single-threaded at any instant.
-#[cfg(target_os = "linux")]
-unsafe impl Send for MsEncoder {}
-
-#[cfg(target_os = "linux")]
-impl MsEncoder {
-    fn new(layout: &OpusLayout) -> Result<MsEncoder> {
-        use std::os::raw::c_int;
-        let mut err: c_int = 0;
-        // SAFETY: every scalar arg is a valid libopus input (sample rate, channel/stream/coupled
-        // counts, the RESTRICTED_LOWDELAY application constant). `layout.mapping.as_ptr()` addresses
-        // a 'static slice of exactly `layout.channels` bytes (every `OpusLayout` constant upholds
-        // that), which is the element count `opus_multistream_encoder_create` reads through it, and
-        // `&mut err` is a live local the call writes its status into. libopus copies the mapping into
-        // its own allocation, so the pointer need only be valid for the call; the returned pointer is
-        // null/`OPUS_OK`-checked below before any use.
-        let st = unsafe {
-            audiopus_sys::opus_multistream_encoder_create(
-                SAMPLE_RATE as i32,
-                layout.channels as c_int,
-                layout.streams as c_int,
-                layout.coupled as c_int,
-                layout.mapping.as_ptr(),
-                audiopus_sys::OPUS_APPLICATION_RESTRICTED_LOWDELAY,
-                &mut err,
-            )
-        };
-        let st = std::ptr::NonNull::new(st)
-            .filter(|_| err == audiopus_sys::OPUS_OK)
-            .ok_or_else(|| anyhow::anyhow!("opus_multistream_encoder_create failed ({err})"))?;
-        // SAFETY: `st` is the non-null encoder `opus_multistream_encoder_create` just returned, owned
-        // exclusively here. Each `opus_multistream_encoder_ctl` call passes a valid request constant
-        // with the single by-value `c_int` argument that request's variadic ABI expects
-        // (`OPUS_SET_BITRATE_REQUEST` → bitrate, `OPUS_SET_VBR_REQUEST` → 0). No pointer escapes the
-        // call and the encoder outlives it.
-        unsafe {
-            audiopus_sys::opus_multistream_encoder_ctl(
-                st.as_ptr(),
-                audiopus_sys::OPUS_SET_BITRATE_REQUEST,
-                layout.bitrate as c_int,
-            );
-            audiopus_sys::opus_multistream_encoder_ctl(
-                st.as_ptr(),
-                audiopus_sys::OPUS_SET_VBR_REQUEST,
-                0 as c_int, // hard CBR (constant packet size — also what audio FEC relies on)
-            );
-        }
-        Ok(MsEncoder { st })
-    }
-
-    fn encode_float(
-        &mut self,
-        frame: &[f32],
-        samples_per_channel: usize,
-        out: &mut [u8],
-    ) -> Result<usize> {
-        // SAFETY: `self.st` is the live encoder from `new`. libopus reads `samples_per_channel *
-        // channels` f32s through `frame.as_ptr()`; every caller passes a `frame` of exactly that
-        // length together with the matching `samples_per_channel` (`audio_body`'s `frame_len =
-        // samples_per_channel * layout.channels`; the round-trip tests size identically), so the read
-        // stays in bounds. `out.as_mut_ptr()` is written for at most `out.len()` bytes, which is
-        // passed as the capacity bound. Both buffers are live locals outliving this synchronous call;
-        // the return value is range-checked before being used as a length.
-        let n = unsafe {
-            audiopus_sys::opus_multistream_encode_float(
-                self.st.as_ptr(),
-                frame.as_ptr(),
-                samples_per_channel as std::os::raw::c_int,
-                out.as_mut_ptr(),
-                out.len() as i32,
-            )
-        };
-        anyhow::ensure!(n > 0, "opus_multistream_encode_float failed ({n})");
-        Ok(n as usize)
-    }
-}
-
-#[cfg(target_os = "linux")]
-impl Drop for MsEncoder {
-    fn drop(&mut self) {
-        // SAFETY: `self.st` is the encoder `opus_multistream_encoder_create` returned; this
-        // `MsEncoder` owns it uniquely and `drop` runs exactly once, so the destroy frees it once
-        // with no subsequent use.
-        unsafe { audiopus_sys::opus_multistream_encoder_destroy(self.st.as_ptr()) }
-    }
-}
-
 #[cfg(any(target_os = "linux", target_os = "windows"))]
 fn audio_body(
     cap: &mut dyn AudioCapturer,
@@ -565,7 +410,7 @@ fn audio_body(
                     *s = (*s * gain).clamp(-1.0, 1.0);
                 }
             }
-            let n = enc.encode_float(&frame, samples_per_channel, &mut out)?;
+            let n = enc.encode_float(&frame, &mut out)?;
             // AES-128-CBC the Opus payload (RTP header stays plaintext). Per-packet IV =
             // BE32(rikeyid + seq) in [0..4], zero elsewhere; PKCS7 padding.
             let iv_seq = (rikeyid as u32).wrapping_add(seq as u32);
@@ -775,41 +620,33 @@ mod tests {
     /// Real-codec proof of the 5.1 mapping math: encode with our encoder layout, decode with
     /// the mapping a stock Moonlight client derives from our advertised surround-params
     /// (parse → GFE swap), and verify a tone fed into each input channel comes out on the
-    /// same output channel.
+    /// same output channel. Cross-platform via the safe `opus` crate — this also guards the
-    #[cfg(target_os = "linux")]
+    /// (now un-gated) Windows GameStream surround build.
     #[test]
     fn multistream_51_roundtrip_channel_identity() {
         let layout = &LAYOUT_51;
         let samples = 240; // 5 ms
         let ch = layout.channels as usize;
 
-        // Client-side decoder mapping derived exactly as moonlight-common-c does.
+        // Client-side decoder mapping derived exactly as moonlight-common-c does (GFE swap).
         let s = surround_params(layout, false);
         let digits: Vec<u8> = s.bytes().map(|b| b - b'0').collect();
         let client_mapping = client_swap(&digits[3..]);
 
-        let mut err = 0i32;
+        let mut dec =
-        // SAFETY: scalar args are valid libopus inputs. `client_mapping.as_ptr()` addresses a
+            opus::MSDecoder::new(SAMPLE_RATE, layout.streams, layout.coupled, &client_mapping)
-        // `Vec<u8>` of exactly `ch` entries (derived from the advertised surround-params), which is
+                .expect("multistream decoder");
-        // the element count the decoder reads through it, and `&mut err` is a live local the call
-        // writes. The returned pointer is `OPUS_OK`/non-null-checked immediately below before use.
-        let dec = unsafe {
-            audiopus_sys::opus_multistream_decoder_create(
-                SAMPLE_RATE as i32,
-                ch as i32,
-                layout.streams as i32,
-                layout.coupled as i32,
-                client_mapping.as_ptr(),
-                &mut err,
-            )
-        };
-        assert_eq!(err, audiopus_sys::OPUS_OK);
-        assert!(!dec.is_null());
 
         for tone_ch in 0..ch {
-            let mut enc = MsEncoder::new(layout).unwrap();
+            let mut enc = opus::MSEncoder::new(
+                SAMPLE_RATE,
+                layout.streams,
+                layout.coupled,
+                layout.mapping,
+                opus::Application::LowDelay,
+            )
+            .expect("multistream encoder");
             let mut out = vec![0u8; 1400];
-            let mut decoded = vec![0f32; samples * ch];
             let mut energy = vec![0f64; ch];
             // A few frames so the codec converges past its startup transient.
             for f in 0..8 {
@@ -819,28 +656,15 @@ mod tests {
                         / SAMPLE_RATE as f32;
                     frame[t * ch + tone_ch] = 0.5 * phase.sin();
                 }
-                let n = enc.encode_float(&frame, samples, &mut out).unwrap();
+                let n = enc.encode_float(&frame, &mut out).unwrap();
                 assert!(n > 0);
-                // SAFETY: `dec` is the non-null decoder asserted above. `out.as_ptr()` is read for
+                let mut decoded = vec![0f32; samples * ch];
-                // the `n` encoded bytes just produced by `encode_float`; `decoded.as_mut_ptr()` is
+                let got = dec.decode_float(&out[..n], &mut decoded, false).unwrap();
-                // written for up to `samples * ch` f32s and `decoded` is exactly that long; `samples`
+                assert_eq!(got, samples);
-                // is the per-channel frame size. All buffers are live locals outliving the call; the
-                // return is checked to equal `samples`.
-                let got = unsafe {
-                    audiopus_sys::opus_multistream_decode_float(
-                        dec,
-                        out.as_ptr(),
-                        n as i32,
-                        decoded.as_mut_ptr(),
-                        samples as i32,
-                        0,
-                    )
-                };
-                assert_eq!(got as usize, samples);
                 if f >= 4 {
                     for t in 0..samples {
-                        for c in 0..ch {
+                        for (c, e) in energy.iter_mut().enumerate() {
-                            energy[c] += (decoded[t * ch + c] as f64).powi(2);
+                            *e += (decoded[t * ch + c] as f64).powi(2);
                         }
                     }
                 }
@@ -854,9 +678,6 @@ mod tests {
                  (energies: {energy:?})"
             );
         }
-        // SAFETY: `dec` is the decoder `opus_multistream_decoder_create` returned; the test owns it
-        // and destroys it exactly once here, after the final decode — no later use, no double free.
-        unsafe { audiopus_sys::opus_multistream_decoder_destroy(dec) };
     }
 
     /// Live 5.1 capture → multistream encode → decode, against a real PipeWire session.
@@ -869,7 +690,15 @@ mod tests {
     fn surround_capture_live() {
         let mut cap = crate::audio::open_audio_capture(6).expect("open 6ch capture");
         let layout = &LAYOUT_51;
-        let mut enc = MsEncoder::new(layout).unwrap();
+        let mut enc = opus::MSEncoder::new(
+            SAMPLE_RATE,
+            layout.streams,
+            layout.coupled,
+            layout.mapping,
+            opus::Application::LowDelay,
+        )
+        .unwrap();
+        enc.set_vbr(false).ok(); // hard CBR so packet sizes are constant (audio FEC relies on it)
         let mut out = vec![0u8; 1400];
         let mut acc: Vec<f32> = Vec::new();
         let frame_len = 240 * 6;
@@ -880,49 +709,24 @@ mod tests {
             acc.extend_from_slice(&chunk);
             while acc.len() >= frame_len && packets < 100 {
                 let frame: Vec<f32> = acc.drain(..frame_len).collect();
-                let n = enc.encode_float(&frame, 240, &mut out).unwrap();
+                let n = enc.encode_float(&frame, &mut out).unwrap();
                 sizes.insert(n);
                 packets += 1;
             }
         }
         // Hard CBR: every multistream packet must be the same size (audio FEC relies on it).
         assert_eq!(sizes.len(), 1, "CBR sizes: {sizes:?}");
-        // And a stock client's decoder must accept them.
+        // And a stock client's GFE-derived decoder must accept them.
         let s = surround_params(layout, false);
         let digits: Vec<u8> = s.bytes().map(|b| b - b'0').collect();
         let client_mapping = client_swap(&digits[3..]);
-        let mut err = 0i32;
+        let mut dec =
-        // SAFETY: scalar args are valid; `client_mapping.as_ptr()` addresses a 6-entry `Vec<u8>`
+            opus::MSDecoder::new(SAMPLE_RATE, layout.streams, layout.coupled, &client_mapping)
-        // (matches the 6-channel layout the decoder reads through it), alive past the call, and
+                .unwrap();
-        // `&mut err` is a live local. The pointer is `OPUS_OK`-checked before use.
-        let dec = unsafe {
-            audiopus_sys::opus_multistream_decoder_create(
-                48000,
-                6,
-                layout.streams as i32,
-                layout.coupled as i32,
-                client_mapping.as_ptr(),
-                &mut err,
-            )
-        };
-        assert_eq!(err, audiopus_sys::OPUS_OK);
         let mut pcm = vec![0f32; 240 * 6];
-        // SAFETY: `dec` is the non-null decoder from create. `out.as_ptr()` is read for the CBR
+        let got = dec
-        // packet length passed in (`*sizes.first()`, a real encoded packet size in `out`);
+            .decode_float(&out[..*sizes.first().unwrap()], &mut pcm, false)
-        // `pcm.as_mut_ptr()` is written for up to `240 * 6` f32s and `pcm` is exactly that long;
+            .unwrap();
-        // `240` is the per-channel frame size. All buffers are live locals outliving the call.
-        let got = unsafe {
-            audiopus_sys::opus_multistream_decode_float(
-                dec,
-                out.as_ptr(),
-                *sizes.first().unwrap() as i32,
-                pcm.as_mut_ptr(),
-                240,
-                0,
-            )
-        };
-        // SAFETY: `dec` is owned by the test; destroyed exactly once here after the final decode.
-        unsafe { audiopus_sys::opus_multistream_decoder_destroy(dec) };
         assert_eq!(got, 240);
     }
 }

crates/punktfunk-host/src/gamestream/control.rs

@@ -56,6 +56,9 @@ pub fn spawn(state: Arc<AppState>) -> Result<()> {
         .spawn(move || {
             // GCM scheme detected from the first authenticating packet; reused thereafter.
             let mut detected: Option<Scheme> = None;
+            // Consecutive control-decrypt failures for this peer — throttles the warn log so a
+            // junk-packet flood can't spam unbounded lines (security-review 2026-06-28 #10).
+            let mut decrypt_fails: u64 = 0;
             // Decoded keyboard/mouse is forwarded to a dedicated host-lifetime injector thread —
             // NEVER injected inline, so a slow Wayland/libei/SendInput call can't head-block ENet
             // keepalive/retransmit servicing on this thread. The injector owns non-Send compositor
@@ -77,6 +80,7 @@ pub fn spawn(state: Arc<AppState>) -> Result<()> {
                             Event::Disconnect { .. } => {
                                 tracing::info!("control: client disconnected");
                                 detected = None;
+                                decrypt_fails = 0;
                                 peer = None;
                                 // Unplug the session's virtual pads.
                                 pads = GamepadManager::new();
@@ -89,6 +93,7 @@ pub fn spawn(state: Arc<AppState>) -> Result<()> {
                                     channel_id,
                                     packet.data(),
                                     &mut detected,
+                                    &mut decrypt_fails,
                                     &inj_tx,
                                     &mut pads,
                                 );
@@ -163,6 +168,7 @@ fn on_receive(
     _channel_id: u8,
     d: &[u8],
     detected: &mut Option<Scheme>,
+    decrypt_fails: &mut u64,
     inj_tx: &Sender<InputEvent>,
     pads: &mut GamepadManager,
 ) {
@@ -180,10 +186,20 @@ fn on_receive(
                 tracing::info!(?scheme, "control: GCM scheme locked in");
             }
             *detected = Some(scheme);
+            *decrypt_fails = 0;
             pt
         }
         None => {
-            tracing::warn!(len = d.len(), "control: GCM decrypt failed");
+            // Throttle: a junk-packet flood must not spam one warn line per packet. Log the first
+            // failure, then only at exponentially-spaced counts (1, 2, 4, 8, …).
+            *decrypt_fails += 1;
+            if decrypt_fails.is_power_of_two() {
+                tracing::warn!(
+                    len = d.len(),
+                    fails = *decrypt_fails,
+                    "control: GCM decrypt failed"
+                );
+            }
             return;
         }
     };

crates/punktfunk-host/src/gamestream/mod.rs

@@ -90,6 +90,11 @@ pub struct LaunchSession {
     pub fps: u32,
     /// `/launch?appid=N` — selects the app-catalog entry (session recipe).
     pub appid: u32,
+    /// Source IP of the paired HTTPS client that issued `/launch`. The unauthenticated RTSP/UDP
+    /// media plane binds to this so only the launching peer can start/own the stream — an
+    /// unpaired RTSP peer cannot ride a paired client's launch (security-review 2026-06-28 #4).
+    /// `None` if the address could not be captured (then RTSP falls back to launch-present only).
+    pub peer_ip: Option<std::net::IpAddr>,
 }
 
 /// Shared control-plane state used as the axum app state.
@@ -262,9 +267,10 @@ pub(crate) fn config_dir() -> PathBuf {
 }
 
 /// Create `dir` (and parents) owner-private — **0700** on Unix (so the host's secrets aren't readable
-/// by other local users via a traversable config path). Best-effort on Windows: the dir inherits the
+/// by other local users via a traversable config path). On Windows, applies a restrictive DACL
-/// (Users-readable) `%ProgramData%` ACL, so secret *files* are individually locked down by
+/// ([`restrict_dir_to_system_admins`]) so a local unprivileged user can't pre-create / plant files in
-/// [`write_secret_file`]. Tightens an already-existing dir too.
+/// the config tree (the default `%ProgramData%` ACL grants Users *create*; security-review
+/// 2026-06-28 #3/#11). Tightens (and re-owns) an already-existing dir too.
 pub(crate) fn create_private_dir(dir: &std::path::Path) -> std::io::Result<()> {
     #[cfg(unix)]
     {
@@ -281,7 +287,60 @@ pub(crate) fn create_private_dir(dir: &std::path::Path) -> std::io::Result<()> {
     }
     #[cfg(not(unix))]
     {
-        std::fs::create_dir_all(dir)
+        let r = std::fs::create_dir_all(dir);
+        #[cfg(windows)]
+        restrict_dir_to_system_admins(dir);
+        r
+    }
+}
+
+/// Best-effort Windows DACL lockdown of the config *directory* (the companion to
+/// [`restrict_to_system_admins`] for files). The default `%ProgramData%` ACL lets `BUILTIN\Users`
+/// create subfolders/files (and become `CREATOR OWNER`), so a non-admin could pre-create the
+/// `punktfunk` dir or plant a `host.env`/`apps.json` that the privileged SYSTEM service then trusts
+/// (LPE; security-review 2026-06-28 #3). This re-owns the dir to Administrators (defeating a
+/// pre-creation), strips inheritance, and sets an explicit DACL: SYSTEM/Administrators/OWNER full
+/// (object+container inherit so child files/dirs inherit it), and Users **read-only** (so existing
+/// reads of non-secret config keep working but a local user can no longer write/plant). Secret files
+/// are additionally locked to SYSTEM/Admins by [`write_secret_file`]. Hard-coded SIDs
+/// (locale-independent) via the absolute `%SystemRoot%` path; never fatal.
+#[cfg(windows)]
+fn restrict_dir_to_system_admins(dir: &std::path::Path) {
+    let icacls = std::env::var("SystemRoot")
+        .map(|r| format!("{r}\\System32\\icacls.exe"))
+        .unwrap_or_else(|_| "icacls".to_string());
+    // Reset ownership of the directory object to Administrators first, so a dir a non-admin may have
+    // pre-created can't keep OWNER control (an owner can always rewrite the DACL). No `/T` — re-owning
+    // the dir itself is what defeats the pre-creation; recursing a large captures tree each call is
+    // needless churn (secret files are individually owner-locked by `write_secret_file`).
+    let _ = std::process::Command::new(&icacls)
+        .arg(dir.as_os_str())
+        .args(["/setowner", "*S-1-5-32-544"]) // BUILTIN\Administrators
+        .stdout(std::process::Stdio::null())
+        .stderr(std::process::Stdio::null())
+        .status();
+    let status = std::process::Command::new(&icacls)
+        .arg(dir.as_os_str())
+        .args([
+            "/inheritance:r",
+            "/grant:r",
+            "*S-1-5-18:(OI)(CI)(F)", // NT AUTHORITY\SYSTEM
+            "/grant:r",
+            "*S-1-5-32-544:(OI)(CI)(F)", // BUILTIN\Administrators
+            "/grant:r",
+            "*S-1-3-4:(OI)(CI)(F)", // OWNER RIGHTS
+            "/grant:r",
+            "*S-1-5-32-545:(OI)(CI)(RX)", // BUILTIN\Users — read-only (no create/write → no plant)
+        ])
+        .stdout(std::process::Stdio::null())
+        .stderr(std::process::Stdio::null())
+        .status();
+    match status {
+        Ok(s) if s.success() => {}
+        _ => tracing::warn!(
+            dir = %dir.display(),
+            "config-dir DACL hardening did not fully succeed — a local user may be able to plant config files"
+        ),
     }
 }
 

crates/punktfunk-host/src/gamestream/nvhttp.rs

@@ -1,9 +1,14 @@
 //! The nvhttp servers: plain HTTP on 47989 and mutual-TLS on 47984. Serves `/serverinfo`,
-//! the `/pair` flow, `/applist`, and `/launch`/`/resume`/`/cancel`, plus a punktfunk-only
+//! the `/pair` flow, `/applist`, and `/launch`/`/resume`/`/cancel`. Over HTTPS the client is
-//! `/pin` endpoint to deliver the Moonlight-displayed PIN. Over HTTPS the client is
 //! mutual-TLS-authenticated, so `/serverinfo` reports `PairStatus=1` there.
+//!
+//! The pairing PIN is delivered out-of-band ONLY through the bearer-authenticated management
+//! API (`POST /api/v1/pair/pin`): the operator reads the PIN off the Moonlight client and
+//! types it into the host console. There is deliberately NO unauthenticated nvhttp PIN
+//! endpoint — one would let a network client submit its own displayed PIN and drive the whole
+//! ceremony to a pinned cert with no operator consent (security-review 2026-06-28 #1).
 
-use super::tls::PeerCertFingerprint;
+use super::tls::{PeerAddr, PeerCertFingerprint};
 use super::{serverinfo, AppState, LaunchSession, HTTPS_PORT, HTTP_PORT, RTSP_PORT};
 use anyhow::{anyhow, Context, Result};
 use axum::{
@@ -58,7 +63,6 @@ fn router(state: Arc<AppState>, https: bool) -> Router {
     Router::new()
         .route("/serverinfo", get(h_serverinfo))
         .route("/pair", get(h_pair))
-        .route("/pin", get(h_pin))
         .route("/applist", get(h_applist))
         .route("/launch", get(h_launch))
         .route("/resume", get(h_resume))
@@ -82,19 +86,6 @@ async fn h_serverinfo(
     xml(serverinfo::serverinfo_xml(&st.host, https, paired))
 }
 
-async fn h_pin(
-    State(st): State<Arc<AppState>>,
-    Query(q): Query<HashMap<String, String>>,
-) -> impl IntoResponse {
-    match q.get("pin").filter(|p| !p.is_empty()) {
-        Some(pin) => {
-            st.pairing.pin.submit(pin.clone());
-            "PIN accepted\n".to_string()
-        }
-        None => "usage: GET /pin?pin=NNNN\n".to_string(),
-    }
-}
-
 async fn h_applist(
     State(st): State<Arc<AppState>>,
     peer: Option<Extension<PeerCertFingerprint>>,
@@ -110,6 +101,7 @@ async fn h_applist(
 async fn h_launch(
     State(st): State<Arc<AppState>>,
     peer: Option<Extension<PeerCertFingerprint>>,
+    addr: Option<Extension<PeerAddr>>,
     Query(q): Query<HashMap<String, String>>,
 ) -> impl IntoResponse {
     if !peer_is_paired(&peer, &st) {
@@ -117,7 +109,9 @@ async fn h_launch(
         return xml(error_xml());
     }
     match launch(&st, &q) {
-        Ok(session) => {
+        Ok(mut session) => {
+            // Bind the (unauthenticated) RTSP/UDP media plane to this paired client's source IP.
+            session.peer_ip = addr.map(|Extension(PeerAddr(a))| a.ip());
             *st.launch.lock().unwrap() = Some(session);
             tracing::info!(
                 w = session.width,
@@ -193,6 +187,7 @@ fn launch(_st: &AppState, q: &HashMap<String, String>) -> Result<LaunchSession>
         height,
         fps,
         appid,
+        peer_ip: None, // set by `h_launch` from the verified HTTPS peer address
     })
 }
 

crates/punktfunk-host/src/gamestream/pairing.rs

@@ -17,9 +17,14 @@ use std::sync::Mutex;
 use std::time::Duration;
 use tokio::sync::Notify;
 
-/// Out-of-band PIN delivery. Moonlight generates + displays a PIN; the user submits it
+/// Out-of-band PIN delivery. Moonlight generates + displays a PIN; the operator submits it
-/// (via the management API's `POST /api/v1/pair/pin` or nvhttp's `GET /pin?pin=NNNN`).
+/// via the bearer-authenticated management API (`POST /api/v1/pair/pin`) only — there is no
-/// `getservercert` parks until a PIN arrives.
+/// unauthenticated nvhttp delivery path (a network client must never be able to submit its
+/// own PIN; security-review 2026-06-28 #1). `getservercert` parks until a PIN arrives.
+/// Max pairing handshakes parked in [`PinGate::take`] at once (each holds a slot for up to
+/// 300s), bounding a pre-auth waiter flood. Real pairing is one operator-driven client at a time.
+const MAX_PARKED_WAITERS: usize = 4;
+
 pub struct PinGate {
     pin: Mutex<Option<String>>,
     notify: Notify,
@@ -48,7 +53,20 @@ impl PinGate {
     }
 
     async fn take(&self, timeout: Duration) -> Option<String> {
-        self.waiters.fetch_add(1, Ordering::SeqCst);
+        // Bound the number of pairing handshakes parked at once: each `getservercert` is
+        // pre-auth and parks for up to 300s, so without a cap an unpaired LAN peer could pin
+        // unbounded tasks + keep `awaiting_pin` asserted (security-review 2026-06-28 #12).
+        // Reserve a slot atomically; refuse (treated as "no PIN") once the cap is reached.
+        if self
+            .waiters
+            .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |n| {
+                (n < MAX_PARKED_WAITERS).then_some(n + 1)
+            })
+            .is_err()
+        {
+            tracing::warn!("pairing: too many handshakes awaiting a PIN — refusing");
+            return None;
+        }
         // Decrement on every exit path (PIN delivered, timeout, or future cancellation).
         struct WaiterGuard<'a>(&'a AtomicUsize);
         impl Drop for WaiterGuard<'_> {
@@ -117,7 +135,8 @@ impl Pairing {
 
         tracing::info!(
             uniqueid,
-            "pairing phase 1 (getservercert) — awaiting PIN: submit `GET /pin?pin=NNNN`"
+            "pairing phase 1 (getservercert) — awaiting PIN: deliver it via the management \
+             API `POST /api/v1/pair/pin` (operator reads the PIN off the Moonlight client)"
         );
         let pin = self
             .pin
@@ -304,4 +323,28 @@ mod tests {
         assert_eq!(pairing.pin.take(Duration::from_millis(10)).await, None);
         assert!(!pairing.pin.awaiting_pin());
     }
+
+    /// A pre-auth peer flood can park at most `MAX_PARKED_WAITERS` pairing handshakes; the next
+    /// `take` is refused immediately (returns `None` without parking), bounding the 300s-waiter DoS
+    /// (security-review 2026-06-28 #12).
+    #[tokio::test]
+    async fn pin_gate_caps_parked_waiters() {
+        let pairing = Arc::new(Pairing::new());
+        let mut handles = Vec::new();
+        for _ in 0..MAX_PARKED_WAITERS {
+            let p = pairing.clone();
+            handles.push(tokio::spawn(async move {
+                p.pin.take(Duration::from_secs(5)).await
+            }));
+        }
+        // Wait until all the slots are taken.
+        while pairing.pin.waiters.load(Ordering::SeqCst) < MAX_PARKED_WAITERS {
+            tokio::time::sleep(Duration::from_millis(2)).await;
+        }
+        // One more is refused right away (no parking), even with a long timeout.
+        assert_eq!(pairing.pin.take(Duration::from_secs(5)).await, None);
+        for h in handles {
+            h.abort();
+        }
+    }
 }

crates/punktfunk-host/src/gamestream/rtsp.rs

@@ -14,7 +14,7 @@ use crate::encode::Codec;
 use anyhow::{Context, Result};
 use std::collections::HashMap;
 use std::io::{Read, Write};
-use std::net::{TcpListener, TcpStream};
+use std::net::{SocketAddr, TcpListener, TcpStream};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 use std::time::Duration;
@@ -102,13 +102,12 @@ fn handle_conn(mut stream: TcpStream, state: Arc<AppState>) -> Result<()> {
             "RTSP {} | {}", req.head.replace("\r\n", " | "),
             if req.body.is_empty() { String::new() } else { format!("body: {}", req.body.replace("\r\n", " | ")) }
         );
-        let resp = handle_request(&req, &state);
+        let resp = handle_request(&req, &state, peer);
         stream.write_all(resp.as_bytes()).context("RTSP write")?;
         stream.flush().ok();
         // Close (FIN after the flushed response) so the client detects end-of-response.
         let _ = stream.shutdown(std::net::Shutdown::Both);
     }
-    let _ = peer;
     Ok(())
 }
 
@@ -171,7 +170,7 @@ fn parse_request(head: &str, body: String) -> Request {
     }
 }
 
-fn handle_request(req: &Request, state: &AppState) -> String {
+fn handle_request(req: &Request, state: &AppState, peer: Option<SocketAddr>) -> String {
     match req.method.as_str() {
         "OPTIONS" => response(
             &req.cseq,
@@ -216,16 +215,30 @@ fn handle_request(req: &Request, state: &AppState) -> String {
             response(&req.cseq, &[], None)
         }
         "PLAY" => {
+            // The RTSP/UDP media plane is UNAUTHENTICATED. A stream may start only for the paired
+            // client that completed the pairing-gated `/launch` (which set `state.launch`), and —
+            // when the launching IP is known — only from that same source IP. So an unpaired RTSP
+            // peer can neither start a stream on an idle host nor ride a paired client's active
+            // launch (security-review 2026-06-28 #4). `nvhttp` gates `/launch` on a pinned cert.
+            let launch = *state.launch.lock().unwrap();
+            let Some(ls) = launch else {
+                tracing::warn!(?peer, "RTSP PLAY — refused: no paired `/launch` session");
+                return response_status("401 Unauthorized", &req.cseq, &[], None);
+            };
+            if let (Some(want), Some(got)) = (ls.peer_ip, peer.map(|p| p.ip())) {
+                if want != got {
+                    tracing::warn!(
+                        %want, %got,
+                        "RTSP PLAY — refused: peer IP does not match the launching client"
+                    );
+                    return response_status("401 Unauthorized", &req.cseq, &[], None);
+                }
+            }
             let cfg = *state.stream.lock().unwrap();
             match cfg {
                 Some(cfg) if !state.streaming.swap(true, Ordering::SeqCst) => {
                     // Resolve the launched catalog entry (session recipe) for the stream.
-                    let app = state
+                    let app = super::apps::by_id(ls.appid);
-                        .launch
-                        .lock()
-                        .unwrap()
-                        .map(|l| l.appid)
-                        .and_then(super::apps::by_id);
                     tracing::info!(app = ?app.as_ref().map(|a| &a.title), "RTSP PLAY — starting video stream");
                     stream::start(
                         cfg,
@@ -243,8 +256,6 @@ fn handle_request(req: &Request, state: &AppState) -> String {
             // Audio runs independently (Opus on UDP 48000, stereo or 5.1/7.1 multistream per
             // the ANNOUNCE); it needs the launch key for the AES-CBC payload encryption the
             // client expects.
-            let launch = *state.launch.lock().unwrap();
-            if let Some(ls) = launch {
             if !state.audio_streaming.swap(true, Ordering::SeqCst) {
                 tracing::info!("RTSP PLAY — starting audio stream");
                 audio::start(
@@ -255,7 +266,6 @@ fn handle_request(req: &Request, state: &AppState) -> String {
                     state.audio_cap.clone(),
                 );
             }
-            }
             response(&req.cseq, &[("Session", "DEADBEEFCAFE;timeout = 90")], None)
         }
         "TEARDOWN" => {

crates/punktfunk-host/src/gamestream/stream.rs

@@ -431,6 +431,9 @@ fn stream_body(
         cfg.bitrate_kbps as u64 * 1000,
         frame.is_cuda(),
         8, // GameStream/Moonlight path: 8-bit (its own codec negotiation)
+        // GameStream/Moonlight stays 4:2:0 — stock Moonlight clients can't decode 4:4:4, and the
+        // protocol has no chroma negotiation. 4:4:4 is punktfunk/1-native only.
+        encode::ChromaFormat::Yuv420,
     )
     .context("open video encoder for stream")?;
     // FEC overhead percent (Sunshine default 20). Override with PUNKTFUNK_FEC_PCT (0 = data-only).
@@ -560,6 +563,7 @@ fn stream_body(
                     cfg.bitrate_kbps as u64 * 1000,
                     frame.is_cuda(),
                     8,
+                    encode::ChromaFormat::Yuv420, // GameStream stays 4:2:0
                 )
                 .context("reopen encoder after rebuild")?;
                 supports_rfi = enc.caps().supports_rfi;

crates/punktfunk-host/src/gamestream/tls.rs

@@ -7,11 +7,12 @@
 //! fingerprint ([`PeerCertFingerprint`]) to each request, and the nvhttp/mgmt handlers reject
 //! callers whose fingerprint is not pinned (mirroring Apollo's post-handshake `get_verified_cert`).
 
-use anyhow::{anyhow, Context, Result};
+use anyhow::{Context, Result};
 use axum::Router;
 use rustls::client::danger::HandshakeSignatureValid;
 use rustls::crypto::{verify_tls12_signature, verify_tls13_signature, CryptoProvider};
-use rustls::pki_types::{CertificateDer, UnixTime};
+use rustls::pki_types::pem::PemObject;
+use rustls::pki_types::{CertificateDer, PrivateKeyDer, UnixTime};
 use rustls::server::danger::{ClientCertVerified, ClientCertVerifier};
 use rustls::{DigitallySignedStruct, DistinguishedName, ServerConfig, SignatureScheme};
 use std::net::SocketAddr;
@@ -24,6 +25,12 @@ use std::sync::Arc;
 #[derive(Clone)]
 pub(crate) struct PeerCertFingerprint(pub Option<String>);
 
+/// The TCP source address of an HTTPS request, injected per-connection by [`serve_https`]. Used by
+/// `/launch` to record which paired client owns the session so the unauthenticated RTSP/UDP media
+/// plane can bind to that peer's IP (security-review 2026-06-28 #4).
+#[derive(Clone, Copy)]
+pub(crate) struct PeerAddr(pub SocketAddr);
+
 /// HTTPS server that surfaces the verified client cert to handlers. `axum_server` can't expose the
 /// peer cert, so this runs the rustls handshake itself (tokio-rustls), reads the peer certificate,
 /// and serves the axum `Router` over hyper with the peer's fingerprint attached to every request as
@@ -39,7 +46,7 @@ pub(crate) async fn serve_https(
         .await
         .with_context(|| format!("bind HTTPS {bind}"))?;
     loop {
-        let (tcp, _peer) = match listener.accept().await {
+        let (tcp, peer) = match listener.accept().await {
             Ok(v) => v,
             Err(e) => {
                 tracing::warn!(error = %e, "HTTPS accept failed");
@@ -63,14 +70,16 @@ pub(crate) async fn serve_https(
                 .peer_certificates()
                 .and_then(|c| c.first())
                 .map(|c| hex::encode(punktfunk_core::quic::endpoint::cert_fingerprint(c.as_ref())));
-            let peer = PeerCertFingerprint(fp);
+            let fp = PeerCertFingerprint(fp);
+            let addr = PeerAddr(peer);
             let svc =
                 hyper::service::service_fn(move |req: hyper::Request<hyper::body::Incoming>| {
                     let app = app.clone();
-                    let peer = peer.clone();
+                    let fp = fp.clone();
                     async move {
                         let mut req = req.map(axum::body::Body::new);
-                        req.extensions_mut().insert(peer);
+                        req.extensions_mut().insert(fp);
+                        req.extensions_mut().insert(addr);
                         app.oneshot(req).await // Router error is Infallible
                     }
                 });
@@ -169,12 +178,12 @@ fn build_server_config(
     mandatory: bool,
 ) -> Result<Arc<ServerConfig>> {
     let provider = Arc::new(rustls::crypto::aws_lc_rs::default_provider());
-    let certs = rustls_pemfile::certs(&mut cert_pem.as_bytes())
+    // PEM parsing via rustls-pki-types (the same `PemObject` path punktfunk-core/quic.rs uses),
+    // so we don't pull the unmaintained `rustls-pemfile`.
+    let certs = CertificateDer::pem_slice_iter(cert_pem.as_bytes())
         .collect::<std::result::Result<Vec<_>, _>>()
         .context("parse host cert PEM")?;
-    let key = rustls_pemfile::private_key(&mut key_pem.as_bytes())
+    let key = PrivateKeyDer::from_pem_slice(key_pem.as_bytes()).context("parse host key PEM")?;
-        .context("parse host key PEM")?
-        .ok_or_else(|| anyhow!("no private key in host key PEM"))?;
 
     let verifier = Arc::new(AcceptAnyClientCert {
         provider: provider.clone(),

crates/punktfunk-host/src/inject.rs

@@ -76,9 +76,7 @@ pub fn open(backend: Backend) -> Result<Box<dyn InputInjector>> {
             #[cfg(target_os = "linux")]
             {
                 Ok(Box::new(libei::LibeiInjector::open_with(
-                    libei::EiSource::SocketPathFile(
+                    libei::EiSource::SocketPathFile(crate::vdisplay::gamescope_ei_socket_file()),
-                        crate::vdisplay::gamescope_ei_socket_file().into(),
-                    ),
                 )?))
             }
             #[cfg(not(target_os = "linux"))]

crates/punktfunk-host/src/inject/linux/libei.rs

@@ -305,6 +305,19 @@ async fn connect_socket_file(file: &std::path::Path) -> Result<UnixStream> {
     let deadline = std::time::Instant::now() + Duration::from_secs(15);
     let mut logged = String::new();
     loop {
+        // Defense-in-depth: never follow a symlinked relay file. It lives under `$XDG_RUNTIME_DIR`
+        // (per-user 0700) so a cross-user plant is already blocked, but refuse a symlink outright
+        // rather than read through one to an attacker-chosen target (a rogue EIS server would
+        // keylog/deny the session's input; security-review 2026-06-28 #6).
+        if std::fs::symlink_metadata(file)
+            .map(|m| m.file_type().is_symlink())
+            .unwrap_or(false)
+        {
+            return Err(anyhow!(
+                "EIS relay file {} is a symlink — refusing to follow it",
+                file.display()
+            ));
+        }
         if let Ok(s) = std::fs::read_to_string(file) {
             let name = s.trim();
             if !name.is_empty() {

crates/punktfunk-host/src/library.rs

@@ -577,10 +577,11 @@ impl LibraryProvider for EpicProvider {
             if p.extension().and_then(|e| e.to_str()) != Some("item") {
                 continue;
             }
-            let Ok(text) = std::fs::read_to_string(&p) else {
+            // `.item` manifests are small JSON; cap the read so a planted giant can't OOM the host.
+            let Some(bytes) = read_capped(&p, 1024 * 1024) else {
                 continue;
             };
-            let Ok(v) = serde_json::from_str::<serde_json::Value>(&text) else {
+            let Ok(v) = serde_json::from_slice::<serde_json::Value>(&bytes) else {
                 continue;
             };
             if let Some(g) = epic_entry(&v, &art) {
@@ -650,6 +651,23 @@ fn epic_entry(
     })
 }
 
+/// Read a launcher cache/manifest with a hard size cap, so a local unprivileged user can't plant a
+/// multi-GB file under the launcher's (Users-writable) data dir that OOMs the privileged host when
+/// it's loaded — then base64/JSON-decoded into further copies — during library enumeration
+/// (security-review 2026-06-28 S4). Returns `None` if missing, empty, or over `max`. Mirrors the
+/// Linux lutris-art reader's 1 MiB cap.
+#[cfg(windows)]
+fn read_capped(path: &Path, max: u64) -> Option<Vec<u8>> {
+    let meta = std::fs::metadata(path).ok()?;
+    if meta.len() == 0 || meta.len() > max {
+        if meta.len() > max {
+            tracing::warn!(path = %path.display(), len = meta.len(), max, "launcher cache exceeds size cap — skipping");
+        }
+        return None;
+    }
+    std::fs::read(path).ok()
+}
+
 /// Best-effort parse of `catcache.bin` (base64-encoded JSON array of catalog items) into
 /// catalogItemId → [`Artwork`] from each item's `keyImages`. Empty map on any read/decode failure
 /// (the format is community-reverse-engineered + can lag a fresh install → titles just show no art).
@@ -657,7 +675,8 @@ fn epic_entry(
 fn epic_art_index(catcache: &Path) -> std::collections::HashMap<String, Artwork> {
     use base64::Engine as _;
     let mut map = std::collections::HashMap::new();
-    let Ok(raw) = std::fs::read(catcache) else {
+    // 32 MiB cap: comfortably fits a real catalog cache, blocks a planted giant (S4).
+    let Some(raw) = read_capped(catcache, 32 * 1024 * 1024) else {
         return map;
     };
     let Ok(decoded) = base64::engine::general_purpose::STANDARD.decode(raw) else {

crates/punktfunk-host/src/main.rs

@@ -121,7 +121,8 @@ fn real_main() -> Result<()> {
         punktfunk_core::ABI_VERSION
     );
 
-    // Install Apollo's win32u GPU-preference hook BEFORE anything touches DXGI (the SudoVDA
+    // Install the win32u GPU-preference hook (same technique as Apollo, reimplemented — no GPL source
+    // copied) BEFORE anything touches DXGI (the virtual-display
     // render-adapter selection creates a DXGI factory during virtual-display setup, well before
     // capture). On a hybrid-GPU box this stops DXGI from reparenting the virtual output off the
     // capture GPU — the ACCESS_LOST churn fix. Idempotent (Once); harmless on non-hybrid boxes.

crates/punktfunk-host/src/mgmt.rs

@@ -1680,6 +1680,7 @@ mod tests {
             height: 1440,
             fps: 120,
             appid: 1,
+            peer_ip: None,
         });
         state.streaming.store(true, Ordering::SeqCst);
 
@@ -1805,6 +1806,7 @@ mod tests {
             height: 1080,
             fps: 60,
             appid: 1,
+            peer_ip: None,
         });
 
         let del = axum::http::Request::delete("/api/v1/session")

crates/punktfunk-host/src/mgmt_token.rs

@@ -11,9 +11,6 @@
 use anyhow::{Context, Result};
 use rand::RngCore;
 use std::fs;
-use std::io::Write;
-#[cfg(unix)]
-use std::os::unix::fs::{OpenOptionsExt, PermissionsExt};
 use std::path::Path;
 
 const ENV_VAR: &str = "PUNKTFUNK_MGMT_TOKEN";
@@ -38,9 +35,11 @@ pub fn load_or_generate() -> Result<String> {
     rand::thread_rng().fill_bytes(&mut buf);
     let token = hex::encode(buf);
     let dir = crate::gamestream::config_dir();
-    fs::create_dir_all(&dir).with_context(|| format!("create {}", dir.display()))?;
+    // Owner-private dir (0700 Unix / DACL-locked Windows) so the token can't leak via the config path.
+    crate::gamestream::create_private_dir(&dir)
+        .with_context(|| format!("create {}", dir.display()))?;
     write_token(&path, &token)?;
-    tracing::info!(path = %path.display(), "generated and persisted management API token (0600)");
+    tracing::info!(path = %path.display(), "generated and persisted management API token (owner-only)");
     Ok(token)
 }
 
@@ -55,19 +54,15 @@ fn parse_token(contents: &str) -> Option<String> {
     (!tok.is_empty()).then(|| tok.to_string())
 }
 
-/// Write `PUNKTFUNK_MGMT_TOKEN=<token>` to `path`, mode 0600 (never briefly world-readable).
+/// Write `PUNKTFUNK_MGMT_TOKEN=<token>` to `path` as an owner-only secret — 0600 on Unix AND
+/// DACL-locked to SYSTEM/Administrators on Windows. Routes through the shared `write_secret_file` so
+/// the mgmt bearer token (full admin authority) gets the SAME Windows lockdown as the host key; the
+/// bespoke `cfg(unix)`-only writer used to leave it readable by any local user (security-review
+/// 2026-06-28 #2).
 fn write_token(path: &Path, token: &str) -> Result<()> {
-    let mut opts = fs::OpenOptions::new();
+    let line = format!("PUNKTFUNK_MGMT_TOKEN={token}\n");
-    opts.write(true).create(true).truncate(true);
+    crate::gamestream::write_secret_file(path, line.as_bytes())
-    #[cfg(unix)]
+        .with_context(|| format!("write {}", path.display()))
-    opts.mode(0o600);
-    let mut f = opts
-        .open(path)
-        .with_context(|| format!("write {}", path.display()))?;
-    writeln!(f, "PUNKTFUNK_MGMT_TOKEN={token}")?;
-    #[cfg(unix)]
-    let _ = fs::set_permissions(path, fs::Permissions::from_mode(0o600));
-    Ok(())
 }
 
 #[cfg(test)]
@@ -95,6 +90,7 @@ mod tests {
         assert_eq!(parse_token(&read).as_deref(), Some("cafef00d"));
         #[cfg(unix)]
         {
+            use std::os::unix::fs::PermissionsExt;
             let mode = fs::metadata(&path).unwrap().permissions().mode() & 0o777;
             assert_eq!(mode, 0o600);
         }

crates/punktfunk-host/src/native_pairing.rs

@@ -11,6 +11,7 @@ use anyhow::Result;
 use std::path::PathBuf;
 use std::sync::Mutex;
 use std::time::{Duration, Instant};
+use tokio::sync::Notify;
 
 /// The host's paired punktfunk/1 clients: `~/.config/punktfunk/punktfunk1-paired.json`.
 /// (Separate from GameStream pairing, which has its own store and ceremony.)
@@ -76,6 +77,18 @@ pub struct PendingRequest {
     pub age_secs: u64,
 }
 
+/// The outcome of [`NativePairing::wait_for_decision`] — what an operator did with a parked,
+/// unpaired knock (delegated approval, roadmap §8b-1).
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum PairingDecision {
+    /// The operator clicked Approve (the fingerprint is now paired) — admit the session.
+    Approved,
+    /// The operator denied, or the pending entry was otherwise dropped without pairing — reject.
+    Denied,
+    /// No decision within the wait window — reject; the device can knock again.
+    TimedOut,
+}
+
 /// Pending knocks older than this are dropped (the device retries; a stale entry shouldn't be
 /// approvable days later when the operator no longer remembers the context).
 const PENDING_TTL: Duration = Duration::from_secs(10 * 60);
@@ -88,6 +101,11 @@ pub struct NativePairing {
     arm: Mutex<Armed>,
     paired: Mutex<PairedState>,
     pending: Mutex<PendingState>,
+    /// Notified whenever the trust/pending state changes (a fingerprint paired, or a pending knock
+    /// denied/dropped), so a QUIC connection parked in [`NativePairing::wait_for_decision`] wakes
+    /// the instant an operator acts in the console — the substrate for delegated approval admitting
+    /// a session with no client reconnect.
+    changed: Notify,
 }
 
 /// A snapshot for the management API / web console.
@@ -199,6 +217,7 @@ impl NativePairing {
             arm: Mutex::new(arm),
             paired: Mutex::new(PairedState { path, clients }),
             pending: Mutex::new(PendingState::default()),
+            changed: Notify::new(),
         })
     }
 
@@ -276,10 +295,17 @@ impl NativePairing {
             }
         }
         // A device that knocked and is now paired shouldn't linger in the approval list.
+        {
             let mut pending = self.pending.lock().unwrap();
             pending
                 .items
                 .retain(|p| !p.fp_hex.eq_ignore_ascii_case(fp_hex));
+        }
+        // Wake any connection parked in `wait_for_decision` for this fingerprint: pairing just
+        // completed (console approve or the PIN ceremony), so it can admit the session with no
+        // reconnect. Notified AFTER the pin AND the pending-clear so a woken waiter observes the
+        // fully settled state (paired = true, no longer pending) — see `wait_for_decision`.
+        self.changed.notify_waiters();
         Ok(())
     }
 
@@ -372,6 +398,17 @@ impl NativePairing {
             .collect()
     }
 
+    /// Is a knock for this fingerprint still awaiting approval? (Expired entries are dropped
+    /// first, so this also reports whether a parked knock is still live.)
+    pub fn pending_contains(&self, fp_hex: &str) -> bool {
+        let mut pending = self.pending.lock().unwrap();
+        Self::expire_pending(&mut pending);
+        pending
+            .items
+            .iter()
+            .any(|p| p.fp_hex.eq_ignore_ascii_case(fp_hex))
+    }
+
     /// Approve a pending knock: pair its fingerprint (under `name_override` if the operator
     /// labeled it, else the knock's own name) and drop it from the queue. `Ok(None)` = no such
     /// (or expired) id.
@@ -380,29 +417,78 @@ impl NativePairing {
         id: u32,
         name_override: Option<&str>,
     ) -> Result<Option<PairedClient>> {
-        let entry = {
+        // Read (do NOT pre-remove) the entry: `add()` pins the fingerprint and THEN clears its
+        // pending entry — an order `wait_for_decision` relies on so a parked waiter never observes
+        // the device as "neither pending nor paired" (which would read as a denial). Removing here
+        // first would open exactly that window.
+        let (knock_name, fp_hex) = {
             let mut pending = self.pending.lock().unwrap();
             Self::expire_pending(&mut pending);
-            let Some(at) = pending.items.iter().position(|p| p.id == id) else {
+            match pending.items.iter().find(|p| p.id == id) {
-                return Ok(None);
+                Some(p) => (p.name.clone(), p.fp_hex.clone()),
-            };
+                None => return Ok(None),
-            pending.items.remove(at)
+            }
-        }; // pending lock released — add() takes the paired lock
+        }; // pending lock released — add() takes the paired then pending locks
-        let name = name_override.unwrap_or(&entry.name);
+        let name = name_override.unwrap_or(&knock_name).to_string();
-        self.add(name, &entry.fp_hex)?;
+        self.add(&name, &fp_hex)?; // pins, clears the pending entry, and notifies waiters
         Ok(Some(PairedClient {
-            name: name.to_string(),
+            name,
-            fingerprint: entry.fp_hex,
+            fingerprint: fp_hex,
         }))
     }
 
     /// Deny (drop) a pending knock. Returns whether one was removed. The device's next knock
     /// re-creates an entry — deny is "not now", not a blocklist.
     pub fn deny_pending(&self, id: u32) -> bool {
+        let removed = {
             let mut pending = self.pending.lock().unwrap();
             let before = pending.items.len();
             pending.items.retain(|p| p.id != id);
             pending.items.len() != before
+        };
+        if removed {
+            // Wake a parked waiter so it returns `Denied` at once instead of holding the
+            // connection open until the approval window lapses.
+            self.changed.notify_waiters();
+        }
+        removed
+    }
+
+    /// Park (async) until an operator decides on a knock identified by `fp_hex`, up to `timeout`.
+    /// Returns [`PairingDecision::Approved`] the instant the fingerprint is paired (console
+    /// approve or a concurrent PIN ceremony), [`PairingDecision::Denied`] if its pending entry is
+    /// dropped without pairing, or [`PairingDecision::TimedOut`] if the window lapses. Holds no
+    /// lock across the await. The QUIC accept path calls this right after [`Self::note_pending`]
+    /// to keep the knocking connection open until a human clicks Approve — so the device pairs and
+    /// streams with no reconnect (delegated approval, roadmap §8b-1).
+    pub async fn wait_for_decision(&self, fp_hex: &str, timeout: Duration) -> PairingDecision {
+        let deadline = tokio::time::Instant::now() + timeout;
+        loop {
+            // Arm the wakeup BEFORE re-reading state, and `enable()` it, so an approve/deny that
+            // lands between the state check and the await still wakes us (no lost notification).
+            let notified = self.changed.notified();
+            tokio::pin!(notified);
+            notified.as_mut().enable();
+
+            if self.is_paired(fp_hex) {
+                return PairingDecision::Approved;
+            }
+            if !self.pending_contains(fp_hex) {
+                // Neither pending nor paired. This is almost always a denial — but it can also be
+                // the tiny interval inside `add()` between pinning and clearing the pending entry.
+                // Re-check `is_paired` once: because `add()` pins BEFORE it clears pending, a
+                // cleared-pending observation that is really an approval will now read as paired.
+                if self.is_paired(fp_hex) {
+                    return PairingDecision::Approved;
+                }
+                return PairingDecision::Denied;
+            }
+
+            tokio::select! {
+                _ = &mut notified => {}
+                _ = tokio::time::sleep_until(deadline) => return PairingDecision::TimedOut,
+            }
+        }
     }
 }
 
@@ -561,4 +647,60 @@ mod tests {
         assert!(np.current_pin().is_none());
         let _ = std::fs::remove_file(&p);
     }
+
+    #[tokio::test]
+    async fn wait_for_decision_approve_deny_timeout() {
+        use std::sync::Arc;
+        let p = temp();
+        let _ = std::fs::remove_file(&p);
+        let np = Arc::new(NativePairing::load_with(Some(p.clone()), None, false).unwrap());
+
+        // TimedOut: a parked knock with no decision returns TimedOut; the entry survives.
+        np.note_pending("Knocker", "ab01");
+        let d = np
+            .wait_for_decision("ab01", Duration::from_millis(80))
+            .await;
+        assert_eq!(d, PairingDecision::TimedOut);
+        assert!(np.pending_contains("ab01"));
+
+        // Approved: approving WHILE parked wakes the waiter with Approved.
+        let np2 = np.clone();
+        let waiter =
+            tokio::spawn(
+                async move { np2.wait_for_decision("ab01", Duration::from_secs(5)).await },
+            );
+        tokio::time::sleep(Duration::from_millis(30)).await;
+        let id = np
+            .pending()
+            .into_iter()
+            .find(|x| x.fingerprint == "ab01")
+            .unwrap()
+            .id;
+        np.approve_pending(id, Some("Approved")).unwrap().unwrap();
+        assert_eq!(waiter.await.unwrap(), PairingDecision::Approved);
+        assert!(np.is_paired("ab01"));
+
+        // Denied: denying WHILE parked wakes the waiter with Denied (not held until timeout).
+        np.note_pending("Knock2", "cd02");
+        let np3 = np.clone();
+        let waiter =
+            tokio::spawn(
+                async move { np3.wait_for_decision("cd02", Duration::from_secs(5)).await },
+            );
+        tokio::time::sleep(Duration::from_millis(30)).await;
+        let id = np
+            .pending()
+            .into_iter()
+            .find(|x| x.fingerprint == "cd02")
+            .unwrap()
+            .id;
+        assert!(np.deny_pending(id));
+        assert_eq!(waiter.await.unwrap(), PairingDecision::Denied);
+        assert!(!np.is_paired("cd02"));
+
+        // Already paired before the call → immediate Approved (no waiting).
+        let d = np.wait_for_decision("ab01", Duration::from_secs(5)).await;
+        assert_eq!(d, PairingDecision::Approved);
+        let _ = std::fs::remove_file(&p);
+    }
 }

crates/punktfunk-host/src/punktfunk1.rs

@@ -78,7 +78,7 @@ pub struct Punktfunk1Options {
 }
 
 /// The native (punktfunk/1) trust store + on-demand arming PIN, shared with the management API.
-use crate::native_pairing::NativePairing;
+use crate::native_pairing::{NativePairing, PairingDecision};
 /// The shared streaming-stats recorder (web-console capture/graph), shared with the management API
 /// and the GameStream loop; threaded into each session's `SessionContext`.
 use crate::stats_recorder::StatsRecorder;
@@ -290,8 +290,11 @@ pub(crate) async fn serve(
         let stats = stats.clone();
         let inj_tx = injector.sender();
         let mic_tx = mic_service.sender();
+        // The session permit + the pool it came from are handed to serve_session, which owns the
+        // permit's lifetime: it's released while a knock is parked for delegated approval and
+        // re-acquired on approval, so the hold is no longer a simple closure-scoped binding.
+        let sem_session = sem.clone();
         sessions.spawn(async move {
-            let _permit = permit; // held for the session's lifetime; frees a slot on completion
             match serve_session(
                 conn,
                 &opts,
@@ -302,6 +305,8 @@ pub(crate) async fn serve(
                 &np,
                 &last_pairing,
                 stats,
+                permit,
+                sem_session,
             )
             .await
             {
@@ -355,6 +360,15 @@ fn resolve_bitrate_kbps(requested: u32) -> u32 {
     }
 }
 
+/// Resolve the audio channel count the session will capture + encode from the client's request.
+/// Normalizes to one of 2 (stereo) / 6 (5.1) / 8 (7.1); anything else (older client, garbage)
+/// becomes stereo. Both backends can produce the requested count (PipeWire pads/upmixes positions,
+/// WASAPI loopback up/downmixes via AUTOCONVERTPCM), so no capability clamp is needed here — the
+/// surround channels just carry up/downmixed content when the host's sink has fewer real channels.
+fn resolve_audio_channels(requested: u8) -> u8 {
+    punktfunk_core::audio::normalize_channels(requested)
+}
+
 /// Static FEC override: `PUNKTFUNK_FEC_PCT`, when set, PINS the recovery percent and DISABLES
 /// adaptive FEC — so a speed test / measurement keeps a fixed, known overhead. `None` ⇒ adaptive
 /// FEC (the host sizes recovery to the loss the client reports). `0` disables FEC entirely.
@@ -401,6 +415,14 @@ type AudioCapSlot = Arc<std::sync::Mutex<Option<Box<dyn crate::audio::AudioCaptu
 /// client), so its budget is far larger than the machine-speed session handshake.
 const PAIRING_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(60);
 
+/// How long the host keeps an unpaired knock PARKED — connection held open — waiting for the
+/// operator to click Approve in the console (delegated approval, roadmap §8b-1). The QUIC
+/// keep-alive (4 s, under the 8 s idle timeout) holds the path warm meanwhile, so on approval the
+/// device pairs and streams with NO reconnect. Bounded well under the pending entry's TTL (10 min);
+/// the client uses a comparable connect timeout, and a client that gives up first closes the
+/// connection (the host stops waiting at once).
+const PENDING_APPROVAL_WAIT: std::time::Duration = std::time::Duration::from_secs(180);
+
 /// The host side of the SPAKE2 pairing ceremony (see `punktfunk_core::quic::pake`):
 /// generate + display a PIN, run SPAKE2 as B binding both cert fingerprints, verify the
 /// client's key-confirmation MAC (its single online guess), and persist the client's
@@ -488,11 +510,16 @@ async fn serve_session(
     opts: &Punktfunk1Options,
     audio_cap: &AudioCapSlot,
     inj_tx: std::sync::mpsc::Sender<InputEvent>,
-    mic_tx: std::sync::mpsc::Sender<Vec<u8>>,
+    mic_tx: std::sync::mpsc::SyncSender<Vec<u8>>,
     host_fp: &[u8; 32],
     np: &NativePairing,
     last_pairing: &std::sync::Mutex<Option<std::time::Instant>>,
     stats: Arc<StatsRecorder>,
+    // The session slot. Owned here (not just held by the spawning task) because an unpaired knock
+    // RELEASES it while parked for delegated approval, then RE-ACQUIRES one on approval — so a
+    // parked knock can't hold a streaming slot. `sem` is the pool it re-acquires from.
+    mut permit: tokio::sync::OwnedSemaphorePermit,
+    sem: Arc<tokio::sync::Semaphore>,
 ) -> Result<()> {
     let peer = conn.remote_address();
 
@@ -522,6 +549,79 @@ async fn serve_session(
         return pair_ceremony(&conn, send, recv, req, host_fp, np, &pin).await;
     }
 
+    // Pairing gate for a session Hello (a PairRequest was handled above). Lifted OUT of the
+    // `handshake` future below for two reasons: (1) the approval wait must not be bound by the
+    // short HANDSHAKE_TIMEOUT — a human reads the console and clicks Approve; (2) the NVENC session
+    // permit is released while parked, so a knock awaiting approval can't hold a streaming slot.
+    // On approval the device is now paired, so the handshake proceeds and the session starts with
+    // NO client reconnect (delegated approval, roadmap §8b-1).
+    if opts.require_pairing {
+        // Decode just enough to gate (the Hello carries the device name for the pending label);
+        // the `handshake` future re-decodes for the real session — a few dozen bytes, negligible.
+        let gate_hello = Hello::decode(&first).map_err(|e| anyhow!("Hello decode: {e:?}"))?;
+        anyhow::ensure!(
+            gate_hello.abi_version == punktfunk_core::ABI_VERSION,
+            "ABI mismatch: client {} host {}",
+            gate_hello.abi_version,
+            punktfunk_core::ABI_VERSION
+        );
+        let fp = endpoint::peer_fingerprint(&conn);
+        let known = fp
+            .as_ref()
+            .map(|fp| np.is_paired(&fingerprint_hex(fp)))
+            .unwrap_or(false);
+        if !known {
+            // An anonymous client (no certificate) has no identity to approve — reject outright
+            // (the PIN ceremony is its way in). Mirrors the prior behavior for anonymous knocks.
+            let Some(fp) = fp else {
+                anyhow::bail!(
+                    "unpaired anonymous client rejected (this host requires pairing — present a \
+                     client identity and approve it in the console, or run the PIN ceremony)"
+                );
+            };
+            let fp_hex = fingerprint_hex(&fp);
+            // Sanitize the wire-supplied name before it reaches the log / console (untrusted: an
+            // unpaired device could embed terminal escapes / bidi overrides); note_pending stores
+            // the same sanitized form and derives a fingerprint label when empty.
+            let label = crate::native_pairing::sanitize_device_name(
+                gate_hello.name.as_deref().unwrap_or(""),
+                &fp_hex,
+            );
+            tracing::info!(name = %label, fingerprint = %fp_hex,
+                "unpaired device knocked — parking connection for delegated approval in the console");
+            np.note_pending(&label, &fp_hex);
+            // Free the session slot while a human decides — a parked knock must not hold an NVENC
+            // permit (a handful of parked knocks would otherwise block every real session).
+            drop(permit);
+            let decision = tokio::select! {
+                d = np.wait_for_decision(&fp_hex, PENDING_APPROVAL_WAIT) => d,
+                // The client gave up (closed the connection) before a decision — stop waiting.
+                _ = conn.closed() => anyhow::bail!("client disconnected before pairing approval"),
+            };
+            match decision {
+                PairingDecision::Approved => {
+                    tracing::info!(name = %label, fingerprint = %fp_hex,
+                        "device approved in console — admitting session (no reconnect)");
+                }
+                PairingDecision::Denied => anyhow::bail!("pairing request denied in the console"),
+                PairingDecision::TimedOut => anyhow::bail!(
+                    "pairing request not approved within {PENDING_APPROVAL_WAIT:?} \
+                     — the device can knock again"
+                ),
+            }
+            // Re-acquire a session slot for the now-approved session (waits if all slots are busy,
+            // exactly like any freshly accepted client).
+            permit = sem
+                .clone()
+                .acquire_owned()
+                .await
+                .expect("session semaphore is never closed");
+        }
+    }
+    // Held for the rest of the session (RAII frees the slot on return). For an already-paired
+    // client this is the original permit; for a just-approved knock it's the re-acquired one.
+    let _permit = permit;
+
     let source = opts.source;
     let frames = opts.frames;
     let handshake = async {
@@ -532,36 +632,8 @@ async fn serve_session(
             hello.abi_version,
             punktfunk_core::ABI_VERSION
         );
-        if opts.require_pairing {
+        // The pairing gate (require_pairing → paired? else park for delegated approval) ran above,
-            let fp = endpoint::peer_fingerprint(&conn);
+        // before this future, so a client reaching here is paired (or the host is `--open`).
-            let known = fp
-                .as_ref()
-                .map(|fp| np.is_paired(&fingerprint_hex(fp)))
-                .unwrap_or(false);
-            if !known {
-                // Delegated approval (§8b-1): an identified-but-unpaired knock becomes a pending
-                // request the operator can approve from the console — no PIN fetched out of band.
-                // The label is the client's Hello name, else fingerprint-derived. An anonymous
-                // client (no certificate) has no identity to approve, so nothing is recorded.
-                if let Some(fp) = &fp {
-                    let fp_hex = fingerprint_hex(fp);
-                    // Sanitize the wire-supplied name before it reaches the log (untrusted: an
-                    // unpaired device could embed terminal escapes / bidi overrides); note_pending
-                    // stores the same sanitized form and derives a fingerprint label when empty.
-                    let label = crate::native_pairing::sanitize_device_name(
-                        hello.name.as_deref().unwrap_or(""),
-                        &fp_hex,
-                    );
-                    tracing::info!(name = %label, fingerprint = %fp_hex,
-                        "unpaired device knocked — held for approval in the console");
-                    np.note_pending(&label, &fp_hex);
-                }
-                anyhow::bail!(
-                    "unpaired client rejected (this host requires pairing — approve the device \
-                     in the console, or run the PIN ceremony)"
-                );
-            }
-        }
         crate::encode::validate_dimensions(
             crate::encode::Codec::H265,
             hello.mode.width,
@@ -588,9 +660,11 @@ async fn serve_session(
         // we look it up in OUR library so a client can't inject a command). The bare-spawn gamescope
         // backend picks this up via the `PUNKTFUNK_GAMESCOPE_APP` env fallback in `spawn` (on a shared
         // desktop / attach-to-existing session it's a harmless no-op). This is the process-global env
-        // path — safe under today's ONE-session-at-a-time model; when concurrent native sessions land
+        // path; the write is serialized via `vdisplay::with_env_lock` so concurrent native-session
-        // (`what's left` §3), resolve the command into the per-session VirtualDisplay via
+        // handshakes can't race the `set_var` (security-review 2026-06-28 #7). The remaining
-        // `set_launch_command` (as the GameStream path now does) so sessions can't stomp each other.
+        // cross-session *value* confusion (B's launch id stomping A's pending gamescope spawn) wants
+        // the command resolved into the per-session VirtualDisplay via `set_launch_command` (as the
+        // GameStream path does) — a follow-up; the data-race UB is closed here.
         if let Some(id) = hello.launch.as_deref() {
             // Linux: resolve the id to a gamescope-nested command and stash it in the env the
             // gamescope backend reads. Windows has no gamescope to nest into — the data plane launches
@@ -600,7 +674,9 @@ async fn serve_session(
             match crate::library::launch_command(id) {
                 Some(cmd) => {
                     tracing::info!(launch_id = id, command = %cmd, "launching library title");
-                    std::env::set_var("PUNKTFUNK_GAMESCOPE_APP", &cmd);
+                    crate::vdisplay::with_env_lock(|| {
+                        std::env::set_var("PUNKTFUNK_GAMESCOPE_APP", &cmd)
+                    });
                 }
                 None => tracing::warn!(
                     launch_id = id,
@@ -623,6 +699,17 @@ async fn serve_session(
             "encoder bitrate"
         );
 
+        // Resolve the audio channel count (client request → stereo / 5.1 / 7.1). The capturer opens
+        // at this count: PipeWire synthesizes the requested positions (padding with silence when the
+        // sink has fewer), WASAPI loopback up/downmixes via AUTOCONVERTPCM — so a client always gets
+        // the channels it asked for, and the Welcome echoes the value the audio thread will encode.
+        let audio_channels = resolve_audio_channels(hello.audio_channels);
+        tracing::info!(
+            requested = hello.audio_channels,
+            resolved = audio_channels,
+            "audio channels"
+        );
+
         // Resolve the encode bit depth: HEVC Main10 only when the client advertised it AND the host
         // opted in (PUNKTFUNK_10BIT). A client that can't decode 10-bit (caps bit clear, or an older
         // client) always gets the 8-bit stream. PUNKTFUNK_10BIT is the host policy gate until a
@@ -642,6 +729,44 @@ async fn serve_session(
             "encode bit depth"
         );
 
+        // Resolve the chroma subsampling: full-chroma HEVC 4:4:4 only when ALL of — the host opted in
+        // (PUNKTFUNK_444), the client advertised VIDEO_CAP_444, the session is single-process (the
+        // two-process WGC relay encodes 4:2:0 in v1), and the active GPU/driver actually supports a
+        // 4:4:4 encode (probed, cached). The native path always encodes HEVC. We resolve this BEFORE
+        // the Welcome so `chroma_format` reflects what we'll really emit — the honest-downgrade
+        // channel: if any gate fails the client is told 4:2:0 before it builds its decoder. The probe
+        // opens a tiny encoder; it runs only when both opt-ins are set and is cached after the first.
+        let host_wants_444 = crate::config::config().four_four_four;
+        let client_supports_444 = hello.video_caps & punktfunk_core::quic::VIDEO_CAP_444 != 0;
+        let single_process = crate::session_plan::resolve_topology()
+            == crate::session_plan::SessionTopology::SingleProcess;
+        // The GPU probe opens a real (tiny) encoder on first use, so run it off the reactor like the
+        // compositor probe above (blocking probes → spawn_blocking). Short-circuit so it only runs when
+        // the cheap gates already pass. The result is cached process-wide (a negative latches until
+        // restart — acceptable: a GPU either supports HEVC 4:4:4 or it doesn't, and a transient open
+        // failure here is rare since the session's own encoder isn't open yet).
+        let gpu_supports_444 = if host_wants_444 && client_supports_444 && single_process {
+            tokio::task::spawn_blocking(|| {
+                crate::encode::can_encode_444(crate::encode::Codec::H265)
+            })
+            .await
+            .context("4:4:4 capability probe task")?
+        } else {
+            false
+        };
+        let chroma = if gpu_supports_444 {
+            crate::encode::ChromaFormat::Yuv444
+        } else {
+            crate::encode::ChromaFormat::Yuv420
+        };
+        tracing::info!(
+            chroma = ?chroma,
+            host_wants_444,
+            client_supports_444,
+            single_process,
+            "encode chroma"
+        );
+
         // Reserve a UDP port for the data plane (bind, read it back, rebind in UdpTransport).
         let probe = std::net::UdpSocket::bind("0.0.0.0:0")?;
         let udp_port = probe.local_addr()?.port();
@@ -691,6 +816,12 @@ async fn serve_session(
             } else {
                 ColorInfo::SDR_BT709
             },
+            // The chroma the encoder will actually emit (resolved + GPU-probed above) — 4:4:4 only
+            // when every gate passed, else 4:2:0. The client sizes its decoder from this.
+            chroma_format: chroma.idc(),
+            // The resolved audio channel count the audio thread will capture + Opus-(multi)stream
+            // encode (2/6/8). The client builds its decoder from this echoed value.
+            audio_channels,
         };
         io::write_msg(&mut send, &welcome.encode()).await?;
 
@@ -843,8 +974,9 @@ async fn serve_session(
         while let Ok(d) = input_conn.read_datagram().await {
             if let Some((_seq, _pts, opus)) = punktfunk_core::quic::decode_mic_datagram(&d) {
                 mic_count += 1;
-                // Host-lifetime mic service; a send error just means the host is shutting down.
+                // Host-lifetime mic service (bounded queue): `try_send` drops the frame when the
-                let _ = mic_tx.send(opus.to_vec());
+                // service is full or gone, never blocking this datagram loop (security-review S6).
+                let _ = mic_tx.try_send(opus.to_vec());
             } else if let Some(rich) = punktfunk_core::quic::RichInput::decode(&d) {
                 rich_count += 1;
                 if rich_tx.send(rich).is_err() {
@@ -884,9 +1016,10 @@ async fn serve_session(
         let conn = conn.clone();
         let stop = stop.clone();
         let cap = audio_cap.clone();
+        let channels = welcome.audio_channels;
         std::thread::Builder::new()
             .name("punktfunk1-audio".into())
-            .spawn(move || audio_thread(conn, stop, cap))
+            .spawn(move || audio_thread(conn, stop, cap, channels))
             .map_err(|e| tracing::error!(error = %e, "audio thread spawn failed — session continues without audio"))
             .ok()
     } else {
@@ -946,6 +1079,13 @@ async fn serve_session(
     let launch_for_dp = hello.launch.clone();
     let bitrate_kbps = welcome.bitrate_kbps; // resolved encoder bitrate (Hello clamped, or default)
     let bit_depth = welcome.bit_depth; // resolved encode bit depth (8, or 10 when negotiated)
+                                       // Resolved chroma — derive the typed value back from the wire byte the Welcome carried (so the
+                                       // session uses exactly what the client was told). `Yuv444` only when the handshake gate passed.
+    let chroma = if welcome.chroma_format == punktfunk_core::quic::CHROMA_IDC_444 {
+        crate::encode::ChromaFormat::Yuv444
+    } else {
+        crate::encode::ChromaFormat::Yuv420
+    };
     let stop_stream = stop.clone();
     let fec_target_dp = fec_target.clone(); // data-plane handle to the adaptive-FEC target
     let conn_stream = conn.clone(); // for sending the source's real HDR metadata (0xCE) mid-stream
@@ -1005,6 +1145,7 @@ async fn serve_session(
                         compositor,
                         bitrate_kbps,
                         bit_depth,
+                        chroma,
                         probe_rx,
                         probe_result_tx,
                         fec_target: fec_target_dp,
@@ -1112,6 +1253,8 @@ const INJECTOR_REOPEN_BACKOFF: std::time::Duration = std::time::Duration::from_s
 
 /// Mic is 48 kHz stereo — matches the Opus stereo decoder and the host→client audio layout.
 const MIC_CHANNELS: u32 = 2;
+/// Bound for the shared mic frame queue (drop-newest when full). See [`MicService::start`].
+const MIC_QUEUE_CAP: usize = 64;
 
 /// Host-lifetime virtual microphone, shared across punktfunk/1 sessions (mirror of
 /// [`InjectorService`]). One thread owns the PipeWire `Audio/Source` + an Opus decoder; sessions
@@ -1119,12 +1262,16 @@ const MIC_CHANNELS: u32 = 2;
 /// feeds the source. Opened lazily on the first frame, the source node persists across sessions
 /// (no per-session registration churn), and reopens after a backoff if the source/decoder fails.
 struct MicService {
-    tx: std::sync::mpsc::Sender<Vec<u8>>,
+    tx: std::sync::mpsc::SyncSender<Vec<u8>>,
 }
 
 impl MicService {
     fn start() -> MicService {
-        let (tx, rx) = std::sync::mpsc::channel::<Vec<u8>>();
+        // Bounded so the host-lifetime mic queue (shared across all concurrent sessions) can't grow
+        // without limit under a near-line-rate flood; the producer drops the newest frame when full
+        // (audio is lossy by design) rather than buffering unboundedly (security-review 2026-06-28
+        // S6). 64 × 5–10 ms frames ≈ 0.3–0.6 s of slack, far more than the decode loop ever lags.
+        let (tx, rx) = std::sync::mpsc::sync_channel::<Vec<u8>>(MIC_QUEUE_CAP);
         if let Err(e) = std::thread::Builder::new()
             .name("punktfunk1-mic".into())
             .spawn(move || mic_service_thread(rx))
@@ -1136,7 +1283,7 @@ impl MicService {
 
     /// A sender a session forwards the client's Opus mic frames to. Cloned per session; dropping a
     /// clone does NOT stop the service (it holds the original sender for the host life).
-    fn sender(&self) -> std::sync::mpsc::Sender<Vec<u8>> {
+    fn sender(&self) -> std::sync::mpsc::SyncSender<Vec<u8>> {
         self.tx.clone()
     }
 }
@@ -1151,14 +1298,17 @@ fn mic_service_thread(rx: std::sync::mpsc::Receiver<Vec<u8>>) {
 
 /// The host-lifetime mic worker: lazily open the virtual mic + decoder, then Opus-decode each
 /// forwarded frame and push the PCM into the source. Reopen (after [`INJECTOR_REOPEN_BACKOFF`])
-/// on open failure or a decode error. Exits when every session sender and the service's own
+/// only on a backend OPEN failure; a per-frame Opus DECODE error is just a dropped frame (it must
-/// sender drop (host shutdown), tearing the virtual mic down. Linux = PipeWire `Audio/Source`;
+/// not tear down this mic, which is shared across every concurrent session — otherwise one paired
-/// Windows = a virtual audio device's render endpoint (see `audio::wasapi_mic`).
+/// client's junk frames would deny everyone's mic; security-review 2026-06-28 S2). Exits when every
+/// session sender and the service's own sender drop (host shutdown), tearing the virtual mic down.
+/// Linux = PipeWire `Audio/Source`; Windows = a virtual audio device's render endpoint.
 #[cfg(any(target_os = "linux", target_os = "windows"))]
 fn mic_service_thread(rx: std::sync::mpsc::Receiver<Vec<u8>>) {
     let mut mic: Option<Box<dyn crate::audio::VirtualMic>> = None;
     let mut decoder: Option<opus::Decoder> = None;
     let mut last_failed: Option<std::time::Instant> = None;
+    let mut decode_fails: u64 = 0;
     let mut pcm = vec![0f32; 5760 * MIC_CHANNELS as usize]; // up to 120 ms scratch
     for opus_frame in rx {
         if opus_frame.is_empty() {
@@ -1194,12 +1344,16 @@ fn mic_service_thread(rx: std::sync::mpsc::Receiver<Vec<u8>>) {
             Ok(samples_per_ch) => {
                 let total = (samples_per_ch * MIC_CHANNELS as usize).min(pcm.len());
                 m.push(&pcm[..total]);
+                decode_fails = 0;
             }
             Err(e) => {
-                tracing::warn!(error = %e, "mic opus decode failed — reopening");
+                // Malformed/garbage frame: drop it and keep the (shared) mic + decoder open. The
-                mic = None;
+                // next valid frame decodes normally; only a backend OPEN failure reopens. Throttle
-                decoder = None;
+                // the log (1, 2, 4, … fails) so a junk flood can't spam.
-                last_failed = Some(std::time::Instant::now());
+                decode_fails += 1;
+                if decode_fails.is_power_of_two() {
+                    tracing::warn!(error = %e, fails = decode_fails, "mic opus decode failed — dropping frame");
+                }
             }
         }
     }
@@ -1381,8 +1535,14 @@ fn input_thread(
     // left-button-down then turns every later click into a drag: windows move, but clicking buttons
     // and text inputs does nothing). We synthesize the matching up-events when this session ends —
     // see the release loop after the `break`.
-    let mut held_buttons: Vec<u32> = Vec::new();
+    // Sets (not Vecs) so the presence test is O(1), not O(n) per event, and bounded by `MAX_HELD`
-    let mut held_keys: Vec<u32> = Vec::new();
+    // so a client flooding distinct never-released codes can't grow the tracking state or spike the
+    // input thread (security-review 2026-06-28 S3). A real keyboard+mouse holds far fewer at once;
+    // codes past the cap simply aren't tracked for end-of-session release (worst case: one unreleased
+    // key on a pathological disconnect, which the injector's own state still bounds).
+    const MAX_HELD: usize = 256;
+    let mut held_buttons: std::collections::HashSet<u32> = std::collections::HashSet::new();
+    let mut held_keys: std::collections::HashSet<u32> = std::collections::HashSet::new();
     loop {
         match rx.recv_timeout(std::time::Duration::from_millis(4)) {
             Ok(ev) => match ev.kind {
@@ -1400,14 +1560,18 @@ fn input_thread(
                 _ => {
                     // Track press/release so a mid-press disconnect can be undone below.
                     match ev.kind {
-                        InputKind::MouseButtonDown if !held_buttons.contains(&ev.code) => {
+                        InputKind::MouseButtonDown if held_buttons.len() < MAX_HELD => {
-                            held_buttons.push(ev.code)
+                            held_buttons.insert(ev.code);
                         }
-                        InputKind::MouseButtonUp => held_buttons.retain(|&c| c != ev.code),
+                        InputKind::MouseButtonUp => {
-                        InputKind::KeyDown if !held_keys.contains(&ev.code) => {
+                            held_buttons.remove(&ev.code);
-                            held_keys.push(ev.code)
+                        }
+                        InputKind::KeyDown if held_keys.len() < MAX_HELD => {
+                            held_keys.insert(ev.code);
+                        }
+                        InputKind::KeyUp => {
+                            held_keys.remove(&ev.code);
                         }
-                        InputKind::KeyUp => held_keys.retain(|&c| c != ev.code),
                         _ => {}
                     }
                     // Pointer/keyboard → the host-lifetime injector service (one persistent
@@ -1493,33 +1657,88 @@ fn input_thread(
     }
 }
 
-/// The audio thread: desktop capture → Opus (48 kHz stereo, 5 ms, CBR — same tuning as the
+/// Opus encoder for the native audio plane: a plain stereo encoder (the live-validated,
-/// GameStream path) → `AUDIO_MAGIC` datagrams. QUIC already encrypts; no extra layer.
+/// byte-identical path) or a libopus *multistream* encoder for 5.1/7.1, both behind one
-/// The capturer comes from (and returns to) the persistent slot — see [`AudioCapSlot`].
+/// `encode_float`. Surround uses the safe `opus::MSEncoder` (no `audiopus_sys`).
 #[cfg(any(target_os = "linux", target_os = "windows"))]
-fn audio_thread(conn: quinn::Connection, stop: Arc<AtomicBool>, audio_cap: AudioCapSlot) {
+enum NativeAudioEnc {
-    use crate::audio::{CHANNELS, SAMPLE_RATE};
+    Stereo(opus::Encoder),
+    Surround(opus::MSEncoder),
+}
+
+#[cfg(any(target_os = "linux", target_os = "windows"))]
+impl NativeAudioEnc {
+    /// Build the encoder for `channels` (2/6/8), hard-CBR + RESTRICTED_LOWDELAY like the
+    /// GameStream path; bitrate from the shared layout table (stereo keeps the validated 128 kbps).
+    fn new(channels: u8) -> Result<NativeAudioEnc, opus::Error> {
+        if channels == 2 {
+            let mut e = opus::Encoder::new(
+                crate::audio::SAMPLE_RATE,
+                opus::Channels::Stereo,
+                opus::Application::LowDelay,
+            )?;
+            e.set_bitrate(opus::Bitrate::Bits(128_000)).ok();
+            e.set_vbr(false).ok();
+            Ok(NativeAudioEnc::Stereo(e))
+        } else {
+            let l = punktfunk_core::audio::layout_for(channels, false);
+            let mut e = opus::MSEncoder::new(
+                crate::audio::SAMPLE_RATE,
+                l.streams,
+                l.coupled,
+                l.mapping,
+                opus::Application::LowDelay,
+            )?;
+            e.set_bitrate(opus::Bitrate::Bits(l.bitrate)).ok();
+            e.set_vbr(false).ok();
+            Ok(NativeAudioEnc::Surround(e))
+        }
+    }
+
+    fn encode_float(&mut self, frame: &[f32], out: &mut [u8]) -> Result<usize, opus::Error> {
+        match self {
+            NativeAudioEnc::Stereo(e) => e.encode_float(frame, out),
+            NativeAudioEnc::Surround(e) => e.encode_float(frame, out),
+        }
+    }
+}
+
+/// The audio thread: desktop capture → Opus (48 kHz, 5 ms, CBR — same tuning as the GameStream
+/// path) → `AUDIO_MAGIC` datagrams, at the negotiated `channels` (2 stereo / 6 = 5.1 / 8 = 7.1,
+/// canonical wire order FL FR FC LFE RL RR SL SR). QUIC already encrypts; no extra layer. The
+/// capturer comes from (and returns to) the persistent slot — see [`AudioCapSlot`].
+#[cfg(any(target_os = "linux", target_os = "windows"))]
+fn audio_thread(
+    conn: quinn::Connection,
+    stop: Arc<AtomicBool>,
+    audio_cap: AudioCapSlot,
+    channels: u8,
+) {
+    use crate::audio::SAMPLE_RATE;
     const FRAME_MS: usize = 5;
     const SAMPLES_PER_FRAME: usize = SAMPLE_RATE as usize * FRAME_MS / 1000; // 240
+    let want = punktfunk_core::audio::normalize_channels(channels);
 
+    // Reuse the cached capturer ONLY when its channel count matches this session's; a stereo
+    // capturer left by a prior session must not feed a 5.1/7.1 session (the encoder + the client's
+    // decoder are sized for `want`, so a mismatched capturer would garble/desync the audio).
     let capturer = match audio_cap.lock().unwrap().take() {
-        Some(mut c) => {
+        Some(mut c) if c.channels() == want as u32 => {
             c.drain(); // discard audio captured between sessions
             c
         }
-        None => match crate::audio::open_audio_capture(CHANNELS as u32) {
+        prev => {
+            drop(prev); // wrong channel count (or none): clean teardown, open fresh at `want`
+            match crate::audio::open_audio_capture(want as u32) {
                 Ok(c) => c,
                 Err(e) => {
                     tracing::warn!(error = %format!("{e:#}"), "punktfunk/1 audio unavailable — session continues without it");
                     return;
                 }
-        },
+            }
+        }
     };
-    let mut enc = match opus::Encoder::new(
+    let mut enc = match NativeAudioEnc::new(want) {
-        SAMPLE_RATE,
-        opus::Channels::Stereo,
-        opus::Application::LowDelay,
-    ) {
         Ok(e) => e,
         Err(e) => {
             tracing::error!(error = %e, "opus encoder");
@@ -1527,12 +1746,11 @@ fn audio_thread(conn: quinn::Connection, stop: Arc<AtomicBool>, audio_cap: Audio
             return;
         }
     };
-    enc.set_bitrate(opus::Bitrate::Bits(128_000)).ok();
-    enc.set_vbr(false).ok();
 
-    let frame_len = SAMPLES_PER_FRAME * CHANNELS;
+    let frame_len = SAMPLES_PER_FRAME * want as usize;
     let mut acc: Vec<f32> = Vec::with_capacity(frame_len * 4);
-    let mut opus_buf = vec![0u8; 1500];
+    // Sized for the largest surround frame (7.1 HQ ≈ 1.3 KB at 5 ms); ample for normal quality.
+    let mut opus_buf = vec![0u8; 4096];
     let mut seq: u32 = 0;
     // Reopen-with-backoff: hold the capturer in an Option so a mid-session capture-thread death
     // (device unplug, daemon restart) reopens instead of muting the rest of a multi-hour session.
@@ -1542,14 +1760,17 @@ fn audio_thread(conn: quinn::Connection, stop: Arc<AtomicBool>, audio_cap: Audio
     // restart). The first open already happened above; failing THAT still ends the session quietly.
     let mut capturer = Some(capturer);
     let mut last_failed: Option<std::time::Instant> = None;
-    tracing::info!("punktfunk/1 audio streaming (Opus 48 kHz stereo, 5 ms datagrams)");
+    tracing::info!(
+        channels = want,
+        "punktfunk/1 audio streaming (Opus 48 kHz, 5 ms datagrams)"
+    );
     'session: while !stop.load(Ordering::SeqCst) {
         if capturer.is_none() {
             if last_failed.is_some_and(|t| t.elapsed() < INJECTOR_REOPEN_BACKOFF) {
                 std::thread::sleep(std::time::Duration::from_millis(200));
                 continue;
             }
-            match crate::audio::open_audio_capture(CHANNELS as u32) {
+            match crate::audio::open_audio_capture(want as u32) {
                 Ok(c) => {
                     tracing::info!("punktfunk/1 audio capture reopened");
                     capturer = Some(c);
@@ -1599,7 +1820,12 @@ fn audio_thread(conn: quinn::Connection, stop: Arc<AtomicBool>, audio_cap: Audio
 /// Stub — punktfunk/1 audio needs Linux (PipeWire capture + libopus); non-Linux dev builds
 /// run sessions without it, same as when the capturer fails to open.
 #[cfg(not(any(target_os = "linux", target_os = "windows")))]
-fn audio_thread(_conn: quinn::Connection, _stop: Arc<AtomicBool>, _audio_cap: AudioCapSlot) {
+fn audio_thread(
+    _conn: quinn::Connection,
+    _stop: Arc<AtomicBool>,
+    _audio_cap: AudioCapSlot,
+    _channels: u8,
+) {
     tracing::warn!("punktfunk/1 audio requires Linux or Windows — session continues without it");
 }
 
@@ -2368,6 +2594,8 @@ struct SessionContext {
     bitrate_kbps: u32,
     /// Negotiated encode bit depth (8, or 10 = HEVC Main10).
     bit_depth: u8,
+    /// Negotiated chroma subsampling (4:2:0, or 4:4:4 when the client + host + GPU all support it).
+    chroma: crate::encode::ChromaFormat,
     /// Speed-test burst requests (see [`service_probes`]).
     probe_rx: std::sync::mpsc::Receiver<ProbeRequest>,
     /// Speed-test results back to the control task.
@@ -2398,7 +2626,7 @@ fn virtual_stream(ctx: SessionContext) -> Result<()> {
     // path now reads this typed `SessionPlan` instead of re-deriving from config at each dispatch site
     // (the latent "capture and encode disagree on the backend" hazard, plan §2.4). `bit_depth` is the
     // only per-session input — capture/topology/encoder are otherwise pure functions of `HostConfig`.
-    let plan = crate::session_plan::SessionPlan::resolve(ctx.bit_depth);
+    let plan = crate::session_plan::SessionPlan::resolve(ctx.bit_depth, ctx.chroma);
     tracing::info!(?plan, "resolved session plan");
     // Windows two-process secure-desktop path: when the host runs as SYSTEM (required for the secure
     // desktop + SendInput), WGC can't activate in-process, so we capture the normal desktop via a
@@ -2420,6 +2648,8 @@ fn virtual_stream(ctx: SessionContext) -> Result<()> {
         compositor,
         bitrate_kbps,
         bit_depth,
+        // The resolved chroma is already captured in `plan` (above); ignore the duplicate here.
+        chroma: _,
         probe_rx,
         probe_result_tx,
         fec_target,
@@ -2969,6 +3199,9 @@ fn virtual_stream_relay(ctx: SessionContext) -> Result<()> {
         compositor,
         bitrate_kbps,
         bit_depth,
+        // The two-process WGC relay encodes 4:2:0 in v1 — the handshake's `single_process` gate already
+        // forced `chroma` to Yuv420 for this topology, so the helper + secure-desktop DDA stay 4:2:0.
+        chroma: _,
         probe_rx,
         probe_result_tx,
         fec_target,
@@ -3079,6 +3312,7 @@ fn virtual_stream_relay(ctx: SessionContext) -> Result<()> {
                 // stage 5) so the DDA capturer doesn't re-derive it.
                 crate::capture::gpu_encode(),
                 hdr,
+                false, // the two-process relay path is 4:2:0 in v1
             )
             .context("open DDA for secure desktop")?;
             cap.set_active(true);
@@ -3092,6 +3326,8 @@ fn virtual_stream_relay(ctx: SessionContext) -> Result<()> {
                 bitrate_kbps as u64 * 1000,
                 frame.is_cuda(),
                 bit_depth,
+                // Secure-desktop DDA on the two-process relay path: 4:2:0 in v1 (matches the helper).
+                crate::encode::ChromaFormat::Yuv420,
             )
             .context("open video encoder for DDA")?;
             Ok(DdaPipe {
@@ -3491,6 +3727,9 @@ fn is_permanent_build_error(chain: &str) -> bool {
         "could not find output", // KWin < 6.5.6: createVirtualOutput unsupported
         "must be a node id",     // PUNKTFUNK_GAMESCOPE_NODE not an integer
         "is it installed",       // gamescope / kscreen-doctor not on PATH
+        // 4:4:4 NVENC got a CUDA frame — should never happen now the Linux capturer honors gpu=false,
+        // but fail fast instead of 8× retry (~90 s) rather than wedge the session if it ever recurs.
+        "capture/encoder negotiation mismatch",
     ];
     let lower = chain.to_ascii_lowercase();
     PERMANENT.iter().any(|p| lower.contains(p))
@@ -3540,8 +3779,20 @@ fn build_pipeline(
         bitrate_kbps as u64 * 1000,
         frame.is_cuda(),
         bit_depth,
+        plan.chroma,
     )
     .context("open video encoder")?;
+    // Post-open cross-check: the Welcome already committed `chroma_format` from the pre-open probe, so
+    // warn loudly if the encoder actually opened a different chroma than negotiated (the in-band SPS is
+    // authoritative for the decoder, but a mismatch means the probe and the live open disagreed).
+    let opened_444 = enc.caps().chroma_444;
+    if opened_444 != plan.chroma.is_444() {
+        tracing::warn!(
+            negotiated_444 = plan.chroma.is_444(),
+            opened_444,
+            "encoder chroma disagrees with the negotiated Welcome — the client was told the other value"
+        );
+    }
     let interval = std::time::Duration::from_secs_f64(1.0 / effective_hz.max(1) as f64);
     Ok((capturer, enc, frame, interval))
 }
@@ -3922,10 +4173,11 @@ mod tests {
         std::env::temp_dir().join(format!("punktfunk-paired-test-{}.json", std::process::id()))
     }
 
-    /// Delegated approval (§8b-1) end to end in-process: an identified-but-unpaired client's
+    /// Delegated approval (§8b-1) end to end in-process, the SEAMLESS flow: an
-    /// knock on a pairing-required host is held as a pending request (fingerprint-derived label —
+    /// identified-but-unpaired client's knock on a pairing-required host is PARKED (connection held
-    /// the connector sends no Hello name); approving it pairs the fingerprint, and the same
+    /// open) and shows up as a pending request (fingerprint-derived label — the connector sends no
-    /// identity then gets a session with no PIN ceremony.
+    /// Hello name); the operator approves it WHILE the client waits, and the SAME connection is
+    /// admitted to a session with no PIN and no reconnect.
     #[test]
     fn delegated_approval_admits_after_knock() {
         use punktfunk_core::client::NativeClient;
@@ -3948,7 +4200,7 @@ mod tests {
                     source: Punktfunk1Source::Synthetic,
                     seconds: 0,
                     frames: 25,
-                    max_sessions: 2, // the knock + the post-approval session
+                    max_sessions: 1, // the single parked-then-approved session (no reconnect)
                     max_concurrent: 1,
                     require_pairing: true,
                     allow_pairing: false,
@@ -3962,48 +4214,47 @@ mod tests {
             ))
         });
         std::thread::sleep(std::time::Duration::from_millis(500));
-        let timeout = std::time::Duration::from_secs(10);
         let (cert, key) = endpoint::generate_identity().unwrap();
+        let expected_fp = fingerprint_hex(&endpoint::fingerprint_of_pem(&cert).unwrap());
         let mode = punktfunk_core::Mode {
             width: 1280,
             height: 720,
             refresh_hz: 60,
         };
 
-        // 1: the knock — an identified-but-unpaired connect is rejected, but lands in pending.
+        // Approver thread: wait for the parked knock to register, assert its label, then APPROVE it
+        // WHILE the client is still parked — the console "click accept" flow.
+        let np_approve = np.clone();
+        let expect_fp = expected_fp.clone();
+        let approver = std::thread::spawn(move || {
+            let deadline = std::time::Instant::now() + std::time::Duration::from_secs(8);
+            let pend = loop {
+                if let Some(p) = np_approve
+                    .pending()
+                    .into_iter()
+                    .find(|p| p.fingerprint == expect_fp)
+                {
+                    break p;
+                }
                 assert!(
-            NativeClient::connect(
+                    std::time::Instant::now() < deadline,
-                "127.0.0.1",
+                    "the knock must register while the client is parked"
-                19779,
-                mode,
-                CompositorPref::Auto,
-                GamepadPref::Auto,
-                0,
-                0,    // video_caps
-                None, // launch
-                None,
-                Some((cert.clone(), key.clone())),
-                timeout
-            )
-            .is_err(),
-            "unpaired knock must still be rejected"
                 );
-        let expected_fp = fingerprint_hex(&endpoint::fingerprint_of_pem(&cert).unwrap());
+                std::thread::sleep(std::time::Duration::from_millis(40));
-        let pend = np.pending();
+            };
-        assert_eq!(pend.len(), 1, "the knock must be held for approval");
-        assert_eq!(pend[0].fingerprint, expected_fp);
             assert!(
-            pend[0].name.starts_with("device "),
+                pend.name.starts_with("device "),
                 "no Hello name → fingerprint-derived label, got {:?}",
-            pend[0].name
+                pend.name
             );
-
+            np_approve
-        // 2: approve (with an operator label) → the same identity now gets a session, no PIN.
+                .approve_pending(pend.id, Some("Approved Device"))
-        let approved = np
-            .approve_pending(pend[0].id, Some("Approved Device"))
                 .unwrap()
                 .expect("pending id must approve");
-        assert_eq!(approved.fingerprint, expected_fp);
+        });
+
+        // The knock: a SINGLE connect that parks until approved, then streams — no reconnect. The
+        // timeout is generous (it covers the park + the approver's poll latency).
         let client = NativeClient::connect(
             "127.0.0.1",
             19779,
@@ -4012,12 +4263,19 @@ mod tests {
             GamepadPref::Auto,
             0,
             0,    // video_caps
+            2,    // audio_channels (stereo)
             None, // launch
-            None,
+            None, // pin: TOFU — the operator's approval (not a PIN) authorizes this client
             Some((cert, key)),
-            timeout,
+            std::time::Duration::from_secs(15),
         )
-        .expect("approved identity gets a session");
+        .expect("approved mid-park → session admitted with no reconnect");
+        approver.join().unwrap();
+        assert!(
+            np.is_paired(&expected_fp),
+            "approval must pin the knocking fingerprint"
+        );
+        assert_eq!(np.list()[0].name, "Approved Device");
         drop(client);
         let _ = std::fs::remove_file(&store);
         host.join().unwrap().unwrap();
@@ -4065,6 +4323,7 @@ mod tests {
                 GamepadPref::Auto,
                 0,
                 0,    // video_caps
+                2,    // audio_channels (stereo)
                 None, // launch
                 None,
                 None,
@@ -4090,6 +4349,7 @@ mod tests {
             GamepadPref::Auto,
             0,
             0,    // video_caps
+            2,    // audio_channels (stereo)
             None, // launch
             Some(host_fp),
             Some((cert.clone(), key.clone())),

crates/punktfunk-host/src/session_plan.rs

@@ -106,17 +106,22 @@ pub struct SessionPlan {
     /// The IDD-push HDR hint (`bit_depth >= 10`) — the want-HDR flag the capturer was passed before.
     /// Non-IDD-push Windows backends ignore it and auto-detect HDR from the monitor; Linux is 8-bit.
     pub hdr: bool,
+    /// Handshake-negotiated chroma subsampling (4:2:0, or full-chroma 4:4:4 when the client + host +
+    /// GPU all support it). Resolved before the Welcome; `Yuv420` on every backend that declined it.
+    pub chroma: crate::encode::ChromaFormat,
 }
 
 impl SessionPlan {
-    /// Resolve the whole plan once from [`config`](crate::config) + the negotiated `bit_depth`.
+    /// Resolve the whole plan once from [`config`](crate::config) + the negotiated `bit_depth` and
-    pub fn resolve(bit_depth: u8) -> Self {
+    /// `chroma`.
+    pub fn resolve(bit_depth: u8, chroma: crate::encode::ChromaFormat) -> Self {
         SessionPlan {
             capture: CaptureBackend::resolve(),
             topology: resolve_topology(),
             encoder: resolve_encoder(),
             bit_depth,
             hdr: bit_depth >= 10,
+            chroma,
         }
     }
 
@@ -124,9 +129,24 @@ impl SessionPlan {
     /// (no second backend probe), `hdr` from the plan. Handed into `capture::capture_virtual_output` so the
     /// capturer never re-derives the encode backend.
     pub fn output_format(&self) -> crate::capture::OutputFormat {
+        let gpu = self.encoder.is_gpu();
+        // Linux NVENC 4:4:4: libavcodec `hevc_nvenc` only emits 4:4:4 from a YUV444 *input* frame —
+        // RGB-in is always subsampled to 4:2:0 (verified on the RTX 5070 Ti). So the encoder does an
+        // RGB→YUV444P swscale and needs CPU-resident RGB frames; force the zero-copy GPU capture off
+        // for a 4:4:4 NVENC session. (VAAPI 4:4:4, where the hardware supports it, keeps its dmabuf
+        // path via `scale_vaapi`; Windows NVENC ingests ARGB directly and stays GPU.)
+        #[cfg(target_os = "linux")]
+        let gpu = {
+            let force_cpu_for_nvenc_444 =
+                self.chroma.is_444() && !crate::encode::linux_zero_copy_is_vaapi();
+            gpu && !force_cpu_for_nvenc_444
+        };
         crate::capture::OutputFormat {
-            gpu: self.encoder.is_gpu(),
+            gpu,
             hdr: self.hdr,
+            // 4:4:4 needs a full-chroma source: on Windows this keeps the capturer on RGB (not the
+            // default NV12/P010 video-engine output) so NVENC can CSC to 4:4:4.
+            chroma_444: self.chroma.is_444(),
         }
     }
 }
@@ -134,7 +154,7 @@ impl SessionPlan {
 /// Process topology. On Windows this is the former `punktfunk1::should_use_helper` logic verbatim; on
 /// every other platform the session is always single-process.
 #[cfg(target_os = "windows")]
-fn resolve_topology() -> SessionTopology {
+pub(crate) fn resolve_topology() -> SessionTopology {
     let cfg = crate::config::config();
     // `NO_HELPER`/`NO_WGC` force single-process; IDD-push captures in-process in Session 0 (no helper);
     // otherwise the helper runs when forced or when we're SYSTEM (in-process WGC can't activate there).
@@ -151,7 +171,7 @@ fn resolve_topology() -> SessionTopology {
 }
 
 #[cfg(not(target_os = "windows"))]
-fn resolve_topology() -> SessionTopology {
+pub(crate) fn resolve_topology() -> SessionTopology {
     SessionTopology::SingleProcess
 }