fix(vdisplay/kwin): the streamed output declares it mirrors nothing, so a stored replicationSource can't clone a panel into the stream

KWin stores output configuration per *setup* — the exact set of connected
outputs, matched by EDID/connector — in `kwinoutputconfig.json`, and
`replicationSource` is one of the fields it saves and restores
(`OutputConfigurationStore::storeConfig` / `setupToConfig`). Our virtual output
carries a STABLE name on purpose, so once any setup has an entry making
`Virtual-punktfunk` a mirror of a physical head, KWin re-applies it to OUR
output on every session that reproduces that same monitor set — and only that
set, which is why the failure looks environment-dependent: a field report has
the stream cloning the panel whenever exactly one monitor is live, and behaving
normally the moment the others come back (a different setup key, a different
stored entry).

A mirroring output is not a desktop. KWin's `applyMirroring` overrides its scale
and render offset to the source's, so the stream carries the physical screen's
viewport at the physical screen's size instead of the mode the client
negotiated. The protocol says the rest out loud on `priority`: "an output may
not be in the output order if it's disabled or mirroring another screen" — so
the primary assertion this module works so hard to verify silently stops meaning
anything too.

Nothing we sent ever contradicted the stored value. The topology config enabled
our output, took priority 1 and disabled the others, but never stated the one
property that decides whether the thing is its own screen. Now it does:
`set_replication_source(ours, "")` rides along in the config we already build
(free, idempotent — an empty source is exactly what KWin resolves to "mirrors
nothing"), gated on management v13 where the request appeared, since wayland-rs
does not range-check requests and an out-of-range opcode would kill the
connection.

`extend`/`auto` issue no topology calls by design — the streamed output is meant
to join the desk without rearranging it — but a mirror is not an arrangement, it
is a broken source under every topology. So they get `clear_replication_source`,
which enumerates and applies ONLY when our output really is mirroring.

The device's `replication_source` event is now read, so the state is visible: a
mirrored streamed output names its source in a warn instead of leaving "the
stream just shows my monitor" as something only the reporter can see.

Verified on 192.168.1.25 (Ubuntu, cargo 1.96): `cargo test -p pf-vdisplay` 128
pass (7 in `kwin_output_mgmt`), `cargo clippy -p pf-vdisplay --all-targets
--locked -D warnings` clean, `scripts/xcheck.sh linux` clean, fmt clean. NOT yet
on-glass — no KDE box here reproduces a stored mirror; the reporter's setup is
the real test.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/android-promote.yml

@@ -0,0 +1,95 @@
+# Move a versionCode that is ALREADY on Google Play between tracks — no rebuild.
+#
+# Why this is separate from android.yml: promotion must not rebuild. A rebuild produces a fresh
+# versionCode (github.run_number) from possibly-newer sources, so it ships something nobody tested;
+# promoting assigns the byte-identical artifact the testers already ran. Bolting this onto
+# android.yml would mean an `if:` on all ten of its build steps.
+#
+# What it is for:
+#   * promote a tested build up a track (alpha -> production)
+#   * roll production back by re-pointing it at an older versionCode (to_track=production,
+#     version_code=<the good one>, from_track blank)
+#   * halt a rollout (status=halted)
+#
+# Defaults are deliberately the safe ones: dry_run starts TRUE, so a mis-typed versionCode
+# validates and deletes the edit instead of publishing. Flip it to false only when the dry run
+# printed what you meant.
+name: android-promote
+
+# Two concurrent promotions would race on the same Play edit; the loser fails with a stale-edit
+# error. One at a time, and never cancel one mid-flight — a half-applied track change is worse
+# than a queued one.
+concurrency:
+  group: android-promote
+  cancel-in-progress: false
+
+on:
+  workflow_dispatch:
+    inputs:
+      version_code:
+        description: 'versionCode already on Play (e.g. 10816)'
+        required: true
+      to_track:
+        description: 'destination track'
+        required: true
+        default: 'production'
+      from_track:
+        description: 'track to verify it is on, then clear (blank = touch nothing else)'
+        required: false
+        default: 'alpha'
+      notes_tag:
+        description: "tag whose docs/releases/whatsnew/<tag>.txt to attach, e.g. v0.23.0 (blank = none)"
+        required: false
+        default: ''
+      status:
+        description: 'completed (100%) | inProgress (needs user_fraction) | halted | draft'
+        required: true
+        default: 'completed'
+      user_fraction:
+        description: 'staged rollout fraction for inProgress, e.g. 0.2 (blank otherwise)'
+        required: false
+        default: ''
+      dry_run:
+        description: 'validate only, publish nothing'
+        required: true
+        default: 'true'
+
+jobs:
+  promote:
+    runs-on: ubuntu-24.04
+    # Same image as android.yml purely for python3 + openssl (play-upload.py's only deps); it is
+    # already warm on the runner. Nothing here builds.
+    container:
+      image: 192.168.1.58:5010/punktfunk-android-ci:latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Promote
+        env:
+          SERVICE_ACCOUNT_JSON: ${{ secrets.SERVICE_ACCOUNT_JSON }}
+          VERSION_CODE: ${{ inputs.version_code }}
+          TO_TRACK: ${{ inputs.to_track }}
+          FROM_TRACK: ${{ inputs.from_track }}
+          NOTES_TAG: ${{ inputs.notes_tag }}
+          STATUS: ${{ inputs.status }}
+          USER_FRACTION: ${{ inputs.user_fraction }}
+          DRY_RUN: ${{ inputs.dry_run }}
+        run: |
+          set -- --package io.unom.punktfunk \
+                 --promote "$VERSION_CODE" \
+                 --track "$TO_TRACK" --status "$STATUS"
+          # Explicit `if`, not `[ ] && …`: under `sh -e` a false AND-OR list that ends up LAST in
+          # the script aborts the step, and these get reordered.
+          if [ -n "$FROM_TRACK" ]; then set -- "$@" --promote-from "$FROM_TRACK"; fi
+          if [ -n "$USER_FRACTION" ]; then set -- "$@" --user-fraction "$USER_FRACTION"; fi
+          if [ -n "$NOTES_TAG" ]; then
+            NOTES="docs/releases/whatsnew/${NOTES_TAG}.txt"
+            # Fail loudly rather than silently publishing with the PREVIOUS release's text still
+            # showing on the store listing.
+            [ -f "$NOTES" ] || { echo "ERROR: no such notes file: $NOTES"; exit 1; }
+            set -- "$@" --release-notes-file "$NOTES"
+          fi
+          if [ "$DRY_RUN" = "true" ]; then set -- "$@" --no-commit; fi
+          echo "promoting versionCode=$VERSION_CODE -> $TO_TRACK (dry_run=$DRY_RUN)"
+          python3 clients/android/ci/play-upload.py "$@"

.gitea/workflows/android.yml

@@ -34,9 +34,10 @@ on:
       - 'rust-toolchain.toml'
       - 'scripts/ci/**'
       - '.gitea/workflows/android.yml'
-    # Single project version: a `vX.Y.Z` tag is THE release (uploads to Play's `alpha` closed
-    # track for manual promotion + attaches the .aab/.apk to the unified Gitea Release). A main
-    # push is canary (Play `internal`).
+    # Single project version: a `vX.Y.Z` tag is THE release (publishes to Play `production` at
+    # 100% + attaches the .aab/.apk to the unified Gitea Release). A main push is canary
+    # (Play `internal`). Production access was granted 2026-08-01; before that a tag could only
+    # reach `alpha` and someone had to promote it by hand in the Console.
     tags: ['v*']
   pull_request:
     paths:
@@ -75,6 +76,56 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      # FIRST, because it costs a second and everything after it costs ten minutes.
+      #
+      # A release tag MUST carry its own Play "What's new". If the file is absent Play does not
+      # show nothing — it carries the PREVIOUS release's text onto this version, so production
+      # users read notes for a build they are not getting. That is the same defect the v0.22.3
+      # notes shipped (see docs/releases/README.md), and it is invisible until someone reads the
+      # store listing. Failing here also means a missing file cannot leave a half-published
+      # release: nothing is built, nothing is attached to the Gitea release, nothing reaches Play.
+      #
+      # Canary is exempt on purpose: it has no curated notes, and Play reusing text for internal
+      # testers costs nothing.
+      - name: Play release notes gate (tags only)
+        if: startsWith(github.ref, 'refs/tags/v')
+        run: |
+          NOTES="docs/releases/whatsnew/${GITHUB_REF_NAME}.txt"
+          if [ ! -f "$NOTES" ]; then
+            echo "ERROR: $NOTES does not exist."
+            echo "A production release needs its own Play 'What's new' (<=500 chars, written for"
+            echo "phone/TV users). Without it Play reuses the previous release's text."
+            echo "See docs/releases/README.md; copy docs/releases/whatsnew/TEMPLATE.txt."
+            exit 1
+          fi
+          # A verbatim copy of another release's file is the same bug wearing a hat: the store
+          # listing still describes the wrong build. Cheap to check, and only ever trips on an
+          # actual copy-paste that was never edited.
+          for other in docs/releases/whatsnew/*.txt; do
+            if [ "$other" != "$NOTES" ] && [ "$other" != "docs/releases/whatsnew/TEMPLATE.txt" ]; then
+              if cmp -s "$NOTES" "$other"; then
+                echo "ERROR: $NOTES is byte-identical to $other."
+                echo "Write notes describing THIS release, not the one before it."
+                exit 1
+              fi
+            fi
+          done
+          # Length is checked here as well as in play-upload.py. Not redundant: the uploader is
+          # the last line of defence (and the only one android-promote.yml gets), but it runs at
+          # step 9 — this catches an unedited TEMPLATE copy at step 1 instead of after the build.
+          # Must count CHARACTERS, not bytes: Play's cap is 500 chars and `•` is 3 bytes in UTF-8,
+          # so `wc -c` would reject a file that is comfortably legal.
+          python3 - "$NOTES" <<'PY'
+          import sys
+          path = sys.argv[1]
+          text = open(path, encoding="utf-8").read().strip()
+          if not text:
+              sys.exit(f"ERROR: {path} is empty.")
+          if len(text) > 500:
+              sys.exit(f"ERROR: {path} is {len(text)} chars; Play allows 500. Trim it.")
+          print(f"Play release notes OK: {path} ({len(text)}/500 chars)")
+          PY
+
       # Everything below the checkout used to be four download steps (JDK, SDK,
       # NDK+CMake, cargo-ndk — the flakiest, heaviest part of the job); it is all baked
       # into the image now. This guard only re-asserts the Android targets so a
@@ -122,11 +173,20 @@ jobs:
         run: |
           eval "$(bash scripts/ci/pf-version.sh)"   # -> PF_BASE (one minor ahead of the latest stable tag)
           case "$GITHUB_REF" in
-            refs/tags/v*) VN="${GITHUB_REF_NAME#v}"; TRACK="alpha" ;;   # alpha = built-in closed testing
+            refs/tags/v*) VN="${GITHUB_REF_NAME#v}"; TRACK="production" ;;
             *)            VN="${PF_BASE}-ci${GITHUB_RUN_NUMBER}"; TRACK="internal" ;;
           esac
           echo "VERSION_NAME=$VN" >> "$GITHUB_ENV"
           echo "PLAY_TRACK=$TRACK" >> "$GITHUB_ENV"
+          # Play's own "What's new" (500-char cap, its own file — the vX.Y.Z.md body is ~34 KB).
+          # On a tag the gate step above already proved this exists, so the else branch is only
+          # ever the canary path. See docs/releases/README.md.
+          NOTES="docs/releases/whatsnew/${GITHUB_REF_NAME}.txt"
+          if [ -f "$NOTES" ]; then
+            echo "PLAY_NOTES=$NOTES" >> "$GITHUB_ENV"
+          else
+            echo "no Play release notes at $NOTES (canary — Play keeps the previous text)"
+          fi
           echo "android version $VN -> Play track '$TRACK'"
 
       - name: Build Release (signed AAB + universal APK)
@@ -199,15 +259,21 @@ jobs:
       # Direct Publishing-API upload instead of r0adkll/upload-google-play — that action hides the
       # real API error behind "Unknown error occurred."; this prints it. stdlib + openssl only (no
       # pip), reuses SERVICE_ACCOUNT_JSON (raw JSON or base64), auto-handles changesNotSentForReview.
-      # Track: canary main -> `internal`; a vX.Y.Z release -> `alpha` (closed testing) for manual
-      # promotion to production in the Play console.
+      # Track: canary main -> `internal`; a vX.Y.Z release -> `production` at 100% (`completed`).
+      #
+      # A tag therefore ships to real users with no further click. Two things keep that honest:
+      # the tag is only pushed once every platform is green, and Play reviews each production
+      # release before it reaches anyone. To ramp instead of going straight to 100%, this is
+      # `--status inProgress --user-fraction 0.2`; to undo a bad one, halt or roll back from the
+      # Console (or `android-promote.yml`, which can re-point production at an older versionCode).
       - name: Upload to Google Play
         if: github.event_name == 'push' && (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v'))
         env:
           SERVICE_ACCOUNT_JSON: ${{ secrets.SERVICE_ACCOUNT_JSON }}
         run: |
           echo "uploading to Play track '$PLAY_TRACK'"
-          python3 clients/android/ci/play-upload.py \
-            --package io.unom.punktfunk \
-            --aab clients/android/app/build/outputs/bundle/release/app-release.aab \
-            --track "$PLAY_TRACK" --status completed
+          set -- --package io.unom.punktfunk \
+                 --aab clients/android/app/build/outputs/bundle/release/app-release.aab \
+                 --track "$PLAY_TRACK" --status completed
+          if [ -n "${PLAY_NOTES:-}" ]; then set -- "$@" --release-notes-file "$PLAY_NOTES"; fi
+          python3 clients/android/ci/play-upload.py "$@"

clients/android/ci/play-upload.py

@@ -6,13 +6,23 @@ Why hand-rolled: stdlib + `openssl` only (no pip on the runner), and it prints G
 error at the stage it fails instead of a catch-all. Reuses the SERVICE_ACCOUNT_JSON secret and
 tolerates it being raw JSON *or* base64-encoded JSON.
 
-Usage:
+Usage (upload a new build):
   SERVICE_ACCOUNT_JSON='<raw-or-base64 SA key>' \
     python3 play-upload.py --package io.unom.punktfunk \
       --aab path/to/app-release.aab --track internal --status completed [--no-commit]
 
---no-commit: do insert -> upload -> track-update -> validate, then delete the edit (publishes
-nothing). Use it to dry-run the credentials/AAB without touching the live track.
+Usage (promote a build that is already on Play, no rebuild):
+  python3 play-upload.py --package io.unom.punktfunk \
+      --promote 10816 --promote-from alpha --track production
+
+Promotion assigns an EXISTING versionCode to another track, so what ships to production is the
+byte-identical artifact the testers ran — rebuilding would burn a fresh versionCode and ship
+something nobody has tested. --promote-from additionally asserts the code really is on that track
+(catches a typo'd versionCode before it reaches production) and empties it in the SAME edit, so
+the move is atomic: testers are never left pinned to a code that production also serves.
+
+--no-commit: do insert -> upload/assign -> track-update -> validate, then delete the edit
+(publishes nothing). Use it to dry-run the credentials/AAB/notes without touching the live track.
 """
 import argparse, base64, json, os, subprocess, sys, tempfile, time
 import urllib.request, urllib.parse, urllib.error
@@ -104,18 +114,79 @@ def access_token(sa) -> str:
     return tok["access_token"]
 
 
+# Play's "What's new" is capped at 500 characters per language. The cap lives in the Console
+# (the REST reference does not state it) and the API rejects longer text at commit — i.e. AFTER
+# the AAB has uploaded — so check it up front and print the actual count.
+NOTES_MAX = 500
+
+
+def load_release_notes(path, language):
+    with open(path, encoding="utf-8") as f:
+        text = f.read().strip()
+    if not text:
+        sys.exit(f"ERROR: release-notes file is empty: {path}")
+    if len(text) > NOTES_MAX:
+        sys.exit(f"ERROR: release notes are {len(text)} chars, Play allows {NOTES_MAX}: {path}")
+    print(f"release notes: {len(text)}/{NOTES_MAX} chars ({language})")
+    return [{"language": language, "text": text}]
+
+
+def put_track(app, edit, tok, track, version_codes, status, user_fraction=None, notes=None):
+    """PUT one track. An empty version_codes list clears the track (what promotion does to the
+    track it promoted OUT of)."""
+    release = {"status": status, "versionCodes": [str(v) for v in version_codes]}
+    if user_fraction is not None:
+        release["userFraction"] = user_fraction
+    if notes:
+        release["releaseNotes"] = notes
+    # Clearing a track means "no active releases", not "an empty release".
+    body = {"track": track, "releases": [release] if version_codes else []}
+    call("PUT", f"{app}/edits/{edit}/tracks/{track}", token=tok,
+         data=json.dumps(body).encode(), content_type="application/json")
+
+
+def assert_on_track(app, edit, tok, track, vc):
+    """Fail before anything is written if --promote names a versionCode that is not actually on
+    the track we claim to be promoting out of."""
+    got = call("GET", f"{app}/edits/{edit}/tracks/{track}", token=tok)
+    live = [c for r in got.get("releases", []) for c in r.get("versionCodes", [])]
+    if str(vc) not in live:
+        sys.exit(f"ERROR: versionCode {vc} is not on track '{track}' (it has: {live or 'nothing'})")
+    print(f"verified versionCode={vc} is live on '{track}'")
+
+
 def main():
     ap = argparse.ArgumentParser()
     ap.add_argument("--package", required=True)
-    ap.add_argument("--aab", required=True)
+    ap.add_argument("--aab", help="upload this bundle (mutually exclusive with --promote)")
+    ap.add_argument("--promote", type=int, metavar="VERSIONCODE",
+                    help="assign an already-uploaded versionCode instead of uploading")
+    ap.add_argument("--promote-from", metavar="TRACK",
+                    help="with --promote: assert the code is on TRACK, then clear TRACK")
     ap.add_argument("--track", default="internal")
     ap.add_argument("--status", default="completed")
+    ap.add_argument("--user-fraction", type=float,
+                    help="staged rollout fraction, 0<f<1; required by --status inProgress")
+    ap.add_argument("--release-notes-file", help="Play 'What's new' text (<=500 chars)")
+    ap.add_argument("--release-notes-language", default="en-US")
     ap.add_argument("--no-commit", action="store_true")
     a = ap.parse_args()
 
-    if not os.path.isfile(a.aab):
+    if bool(a.aab) == bool(a.promote):
+        sys.exit("ERROR: pass exactly one of --aab (upload) or --promote (assign an existing code)")
+    if a.promote_from and not a.promote:
+        sys.exit("ERROR: --promote-from only applies to --promote")
+    # inProgress without a fraction is an API error; halted/completed with one is also rejected.
+    if a.status == "inProgress" and a.user_fraction is None:
+        sys.exit("ERROR: --status inProgress requires --user-fraction")
+    if a.user_fraction is not None and not (0 < a.user_fraction < 1):
+        sys.exit(f"ERROR: --user-fraction must be strictly between 0 and 1 (got {a.user_fraction})")
+    if a.aab and not os.path.isfile(a.aab):
         sys.exit(f"ERROR: AAB not found: {a.aab}")
 
+    notes = load_release_notes(a.release_notes_file, a.release_notes_language) \
+        if a.release_notes_file else None
+
     sa = load_sa()
     tok = access_token(sa)
     print(f"authenticated as {sa['client_email']} (project {sa.get('project_id')})")
@@ -123,17 +194,25 @@ def main():
 
     try:
         edit = call("POST", f"{app}/edits", token=tok)["id"]
-        with open(a.aab, "rb") as f:
-            blob = f.read()
-        print(f"uploading {a.aab} ({len(blob)} bytes) ...")
-        vc = call("POST", f"{UPLOAD}/{a.package}/edits/{edit}/bundles?uploadType=media",
-                  token=tok, data=blob, content_type="application/octet-stream")["versionCode"]
-        print(f"uploaded versionCode={vc}")
-        call("PUT", f"{app}/edits/{edit}/tracks/{a.track}", token=tok,
-             data=json.dumps({"track": a.track,
-                              "releases": [{"status": a.status, "versionCodes": [str(vc)]}]}).encode(),
-             content_type="application/json")
-        print(f"assigned versionCode={vc} -> track={a.track} status={a.status}")
+        if a.promote:
+            vc = a.promote
+            if a.promote_from:
+                assert_on_track(app, edit, tok, a.promote_from, vc)
+        else:
+            with open(a.aab, "rb") as f:
+                blob = f.read()
+            print(f"uploading {a.aab} ({len(blob)} bytes) ...")
+            vc = call("POST", f"{UPLOAD}/{a.package}/edits/{edit}/bundles?uploadType=media",
+                      token=tok, data=blob, content_type="application/octet-stream")["versionCode"]
+            print(f"uploaded versionCode={vc}")
+
+        put_track(app, edit, tok, a.track, [vc], a.status, a.user_fraction, notes)
+        print(f"assigned versionCode={vc} -> track={a.track} status={a.status}"
+              + (f" userFraction={a.user_fraction}" if a.user_fraction is not None else ""))
+        # Same edit as the assignment above, so the code is never active on both tracks at once.
+        if a.promote_from:
+            put_track(app, edit, tok, a.promote_from, [], a.status)
+            print(f"cleared track '{a.promote_from}'")
 
         if a.no_commit:
             call("POST", f"{app}/edits/{edit}:validate", token=tok)

clients/session/README.md

@@ -61,6 +61,7 @@ default ≈1000 nits). The host still gates the upgrade behind its `PUNKTFUNK_10
 policy.
 
 Debug/bisect knobs: `PUNKTFUNK_DECODER=vulkan|vaapi|d3d11va|software`, `PUNKTFUNK_PRESENT_MODE=
-mailbox|immediate` (default FIFO), `PUNKTFUNK_VK_DEVICE=<index>` (multi-GPU), and
+mailbox|fifo|immediate|fifo_relaxed` (default MAILBOX, FIFO where the surface offers no
+MAILBOX — AMD on Windows), `PUNKTFUNK_VK_DEVICE=<index>` (multi-GPU), and
 `PUNKTFUNK_HW_FAULT=import` (fault every VAAPI dmabuf import — proves the three-strike
 demotion to software on healthy hardware).

crates/pf-capture/src/windows/idd_push.rs

@@ -1670,6 +1670,22 @@ impl IddPushCapturer {
             // the running correlated/total tally — lives on `StallWatch` (sweep Phase 5.4). It was
             // ~65 lines of log prose inside `try_consume`, which is the hot loop, and its two
             // counters were capturer fields that nothing else touched.
+            // One ETW read serves both evidence fields: the prose summary spans the gap plus
+            // the same 300 ms lead-in the report's OS-event correlation uses (the disturbance
+            // that CAUSED the hole lands just before it), while the discriminator counts span
+            // the GAP ONLY — no lead-in: presents from the healthy flow right before the hole
+            // would falsely acquit the content (the stall-ending frame's own present lands at
+            // the window edge and stays well under the acquit bar). Both halves must come from
+            // the same ring snapshot under the same clock anchor, or the prose and the verdict
+            // can disagree about the same hole.
+            let (etw, etw_counts) = self
+                .etw
+                .as_ref()
+                .and_then(|w| {
+                    now.checked_sub(stall.gap)
+                        .map(|from| w.window_report(from, now, Duration::from_millis(300)))
+                })
+                .unzip();
             let evidence = StallEvidence {
                 // A publisher re-attach restarts `offered_total` near zero; a ring recreate resets
                 // the stall watch before that can matter, but guard the delta anyway (a restarted
@@ -1682,24 +1698,14 @@ impl IddPushCapturer {
                     }
                 }),
                 max_heartbeat_age_ms: self.max_hb_age_us / 1_000,
-                // The probe + ETW reads span the same window the report's OS-event correlation
-                // uses (the gap plus a lead-in for the disturbance that CAUSED it).
+                // The probe read spans the same window the report's OS-event correlation uses
+                // (the gap plus a lead-in for the disturbance that CAUSED it).
                 probes: now
                     .checked_sub(stall.gap + Duration::from_millis(300))
                     .zip(self.probes.as_deref())
                     .map(|(from, p)| p.window(from, now)),
-                etw: self.etw.as_ref().and_then(|w| {
-                    now.checked_sub(stall.gap + Duration::from_millis(300))
-                        .map(|from| w.summary(from, now))
-                }),
-                // The discriminator counts span the GAP ONLY — no lead-in: presents from the
-                // healthy flow right before the hole would falsely acquit the content. The
-                // stall-ending frame's own present lands at the window edge and stays well
-                // under the acquit bar.
-                etw_counts: self.etw.as_ref().and_then(|w| {
-                    now.checked_sub(stall.gap)
-                        .map(|from| w.window_counts(from, now))
-                }),
+                etw,
+                etw_counts,
             };
             self.stall_watch.report(&stall, now, &evidence);
         }
@@ -2453,6 +2459,18 @@ mod tests {
             ),
             StallClass::ContentSilence
         );
+        // A LIVE witness (history true = it demonstrably worked just before the hole) reading
+        // an exact zero is the strongest content conviction — the zero is a measurement, not
+        // an absence.
+        assert_eq!(
+            classify(
+                gap,
+                &StallVerdict::ComposeSilence,
+                Some(&probes(Some(16_000), Some(20_000), Some(30_000))),
+                Some(&counts(0, 0))
+            ),
+            StallClass::ContentSilence
+        );
         // The present witness does NOT overrule the driver's own verdicts or the harder
         // classes — it only refines compose-silence.
         assert_eq!(

crates/pf-capture/src/windows/idd_push/dxgkrnl_etw.rs

@@ -18,7 +18,7 @@
 //! A second provider rides the same session: `Microsoft-Windows-DXGI` (user-mode), filtered to
 //! `Present`/`PresentMultiplaneOverlay` starts (ids 42/55) — one event per swapchain present,
 //! stamped with the PRESENTING process id. Together they are the compose-silence discriminator
-//! ([`EtwWatch::window_counts`]): DXGI presents flowing while `BltQueueAddEntry` gaps = the OS
+//! ([`EtwWatch::window_report`]): DXGI presents flowing while `BltQueueAddEntry` gaps = the OS
 //! display path dropped composed frames (the real display-path bug); BOTH silent = the content
 //! stopped presenting (benign pause — menus/loading/game hitch). The predecessor witnesses are
 //! retired for cause: DxgKrnl id 184 `Present` never fires on the modern redirected path, and
@@ -48,7 +48,8 @@ use windows::Win32::System::Diagnostics::Etw::{
     EVENT_CONTROL_CODE_ENABLE_PROVIDER, EVENT_FILTER_DESCRIPTOR, EVENT_FILTER_TYPE_EVENT_ID,
     EVENT_RECORD, EVENT_TRACE_CONTROL_STOP, EVENT_TRACE_LOGFILEW, EVENT_TRACE_PROPERTIES,
     EVENT_TRACE_REAL_TIME_MODE, PROCESSTRACE_HANDLE, PROCESS_TRACE_MODE_EVENT_RECORD,
-    PROCESS_TRACE_MODE_REAL_TIME, TRACE_LEVEL_INFORMATION, WNODE_FLAG_TRACED_GUID,
+    PROCESS_TRACE_MODE_RAW_TIMESTAMP, PROCESS_TRACE_MODE_REAL_TIME, TRACE_LEVEL_INFORMATION,
+    WNODE_FLAG_TRACED_GUID,
 };
 use windows::Win32::System::Performance::{QueryPerformanceCounter, QueryPerformanceFrequency};
 use windows::Win32::System::Threading::{
@@ -122,8 +123,13 @@ fn qpc_freq() -> i64 {
     })
 }
 
-/// The consumer's per-event callback — record id + QPC timestamp (the session's `ClientContext`
-/// is 1, so `TimeStamp` IS a QPC value) and return; runs on the consumer thread.
+/// The consumer's per-event callback — record id + timestamp + pid into the ring and return;
+/// runs on the consumer thread. `TimeStamp` is a raw QPC value only because BOTH halves of the
+/// clock contract hold: `ClientContext = 1` makes QPC the session clock, and the consumer is
+/// opened with `PROCESS_TRACE_MODE_RAW_TIMESTAMP`, which is what stops ProcessTrace converting
+/// every event's timestamp to FILETIME (100 ns units since 1601) on delivery. Without the flag
+/// the conversion happens REGARDLESS of the session clock, and every `ts <= to_q` comparison
+/// downstream is against the wrong clock — never true, a witness that silently reads empty.
 unsafe extern "system" fn on_event(record: *mut EVENT_RECORD) {
     if record.is_null() {
         return;
@@ -150,10 +156,10 @@ pub(super) struct EtwWatch {
 }
 
 // SAFETY: both fields are plain kernel handle VALUES (u64 wrappers) owned by this watch; every
-// operation on them (summary reads the static ring; Drop stops/closes) is thread-safe by the ETW
-// API contract, and the singleton hands out only `Arc<EtwWatch>`.
+// operation on them (window_report reads the static ring; Drop stops/closes) is thread-safe by
+// the ETW API contract, and the singleton hands out only `Arc<EtwWatch>`.
 unsafe impl Send for EtwWatch {}
-// SAFETY: as above — `&EtwWatch` exposes only `summary` (static-ring reads).
+// SAFETY: as above — `&EtwWatch` exposes only `window_report` (static-ring reads).
 unsafe impl Sync for EtwWatch {}
 
 static WATCH: Mutex<Weak<EtwWatch>> = Mutex::new(Weak::new());
@@ -201,8 +207,10 @@ impl EtwWatch {
         let mut session = CONTROLTRACE_HANDLE::default();
         // SAFETY: `buf` is a live, zeroed allocation of base + name bytes; every write below is a
         // field of the properties struct at its head; `LoggerNameOffset = base` points at the
-        // appended name space (ETW copies the name there itself). ClientContext 1 = QPC clock —
-        // what makes event timestamps comparable to our probe windows.
+        // appended name space (ETW copies the name there itself). ClientContext 1 selects QPC as
+        // the SESSION clock — necessary but not sufficient for QPC comparisons: ProcessTrace
+        // still converts every event's timestamp to FILETIME on delivery unless the consumer is
+        // opened with PROCESS_TRACE_MODE_RAW_TIMESTAMP (set below).
         let rc = unsafe {
             let props = buf.as_mut_ptr().cast::<EVENT_TRACE_PROPERTIES>();
             (*props).Wnode.BufferSize = buf.len() as u32;
@@ -224,6 +232,11 @@ impl EtwWatch {
             );
             return None;
         }
+        // A fresh session gets a fresh ring: the static [`RING`] outlives any `EtwWatch`, so
+        // whatever is in it belongs to a DEAD session — leaking it forward would let a previous
+        // session's presents pose as this session's witness history. Race-free here: the
+        // consumer thread that repopulates it is spawned below.
+        RING.lock().unwrap().clear();
 
         // Enable DxgKrnl with a kernel-side event-id filter — the whole point: the provider's
         // vblank/DPC keywords never reach us. Fatal on failure (the DDI families + queue
@@ -240,7 +253,7 @@ impl EtwWatch {
             return None;
         }
         // The DXGI (user-mode) present witness rides the same session. Degraded-not-fatal: a
-        // refusal only costs the per-process present counts — `window_counts` then reports
+        // refusal only costs the per-process present counts — `window_report` then reports
         // no present history and classification stays honest (Unattributed, never a guess).
         if !enable_provider(session, &DXGI, &DXGI_FILTER_IDS) {
             tracing::debug!(
@@ -252,8 +265,12 @@ impl EtwWatch {
             LoggerName: PWSTR(name.as_ptr() as *mut _),
             ..Default::default()
         };
-        log.Anonymous1.ProcessTraceMode =
-            PROCESS_TRACE_MODE_REAL_TIME | PROCESS_TRACE_MODE_EVENT_RECORD;
+        // RAW_TIMESTAMP is load-bearing: it stops ProcessTrace converting `EVENT_HEADER.TimeStamp`
+        // to FILETIME on delivery, so events arrive stamped in the session clock (QPC, per the
+        // ClientContext above) — the only clock the window edges are computed in.
+        log.Anonymous1.ProcessTraceMode = PROCESS_TRACE_MODE_REAL_TIME
+            | PROCESS_TRACE_MODE_EVENT_RECORD
+            | PROCESS_TRACE_MODE_RAW_TIMESTAMP;
         log.Anonymous2.EventRecordCallback = Some(on_event);
         // SAFETY: `log` is a fully-initialized local; `name` outlives the call (OpenTrace copies
         // what it needs before returning).
@@ -303,14 +320,34 @@ impl EtwWatch {
         Some(Self { session, consumer })
     }
 
-    /// Summarize the DDI activity inside `[from, to]` — the correlation line a stall report
-    /// carries. Brackets that merely SPAN the window count too (a freeze-long `SetPowerState`
-    /// has both edges outside the hole it caused). `"none"` when the window is clean.
-    pub(super) fn summary(&self, from: Instant, to: Instant) -> String {
-        // Instant → QPC: anchor both clocks now and offset backwards.
+    /// One stall window's ETW evidence, both halves from a SINGLE ring snapshot under a SINGLE
+    /// `(Instant::now(), qpc_now())` anchor: the DDI/present prose summary a stall report
+    /// carries, and the structured discriminator counts the classifier folds in. The summary
+    /// covers `[hole_from - lead_in, hole_to]` — the disturbance that CAUSED a hole lands just
+    /// before DWM stops delivering, so the prose needs the lead-in. The counts cover
+    /// `[hole_from, hole_to]` ONLY — presents from the healthy flow inside the lead-in would
+    /// falsely acquit the content. Two separate reads (two locks, two anchors, syscalls in
+    /// between) would let events arriving between them make the prose and the verdict disagree
+    /// about the same hole — hence one method returning both.
+    ///
+    /// Brackets that merely SPAN the summary window count too (a freeze-long `SetPowerState`
+    /// has both edges outside the hole it caused). The summary reads `"none"` when the window
+    /// is clean.
+    pub(super) fn window_report(
+        &self,
+        hole_from: Instant,
+        hole_to: Instant,
+        lead_in: Duration,
+    ) -> (String, EtwWindowCounts) {
+        // Instant → QPC: anchor both clocks once and offset backwards; every window edge below
+        // derives from this one anchor.
         let (now_i, now_q, freq) = (Instant::now(), qpc_now(), qpc_freq());
-        let to_q = now_q - duration_qpc(now_i.saturating_duration_since(to), freq);
-        let from_q = now_q - duration_qpc(now_i.saturating_duration_since(from), freq);
+        let to_q = now_q - duration_qpc(now_i.saturating_duration_since(hole_to), freq);
+        let from_q = now_q - duration_qpc(now_i.saturating_duration_since(hole_from), freq);
+        let summary_from_q = from_q - duration_qpc(lead_in, freq);
+        // One snapshot, then the lock drops: everything below — including the OpenProcess
+        // syscalls behind `process_name` — runs off the copy, so the consumer callback never
+        // queues behind a stall report.
         let events: Vec<(i64, u16, u32)> = {
             let ring = RING.lock().unwrap();
             ring.iter()
@@ -318,6 +355,7 @@ impl EtwWatch {
                 .copied()
                 .collect()
         };
+        let counts = count_window(&events, from_q, to_q, duration_qpc(LOOKBACK, freq));
         let ms = |dq: i64| dq.max(0) * 1_000 / freq;
         let mut parts = Vec::new();
         for (start_id, stop_id, label) in [
@@ -335,7 +373,7 @@ impl EtwWatch {
                 } else if id == stop_id {
                     if let Some(s) = open.take() {
                         // The bracket [s, ts] counts when it intersects the window.
-                        if s <= to_q && ts >= from_q {
+                        if s <= to_q && ts >= summary_from_q {
                             count += 1;
                             max_ms = max_ms.max(ms(ts - s));
                         }
@@ -362,43 +400,34 @@ impl EtwWatch {
         ] {
             let count = events
                 .iter()
-                .filter(|(ts, i, _)| *i == id && *ts >= from_q && *ts <= to_q)
+                .filter(|(ts, i, _)| *i == id && *ts >= summary_from_q && *ts <= to_q)
                 .count();
             if count > 0 {
                 parts.push(format!("{label}×{count}"));
             }
         }
         // Present + queue accounting (DXGI 42/55 + BltQueueAddEntry/Complete): total presents
-        // inside the window plus the top presenters, NAMED — the line that splits a
+        // inside the summary window plus the top presenters, NAMED — the line that splits a
         // compose-silence hole into "the content stopped presenting" (no presents anywhere)
         // versus "presents flowed and the display path dropped them" (presents at rate while
-        // the queue starves). "Present×0" is printed explicitly when the stream has history
-        // but the window is empty — silence is a finding, not an absence.
+        // the queue starves). "Present×0" is printed explicitly when the witness was LIVE
+        // before the hole ([`LOOKBACK`]) but the window is empty — silence is a finding, not
+        // an absence; a dead witness's window prints nothing rather than a fake zero.
         let mut per_pid: Vec<(u32, u32)> = Vec::new();
-        let mut have_present_history = false;
         let (mut adds, mut completes) = (0u32, 0u32);
-        let mut have_queue_history = false;
         for &(ts, id, pid) in &events {
+            if ts < summary_from_q || ts > to_q {
+                continue;
+            }
             match id {
                 DXGI_PRESENT_ID | DXGI_PRESENT_MPO_ID => {
-                    have_present_history = true;
-                    if ts >= from_q && ts <= to_q {
-                        match per_pid.iter_mut().find(|(p, _)| *p == pid) {
-                            Some((_, c)) => *c += 1,
-                            None => per_pid.push((pid, 1)),
-                        }
-                    }
-                }
-                BLT_ADD_ID | BLT_COMPLETE_ID => {
-                    have_queue_history = true;
-                    if ts >= from_q && ts <= to_q {
-                        if id == BLT_ADD_ID {
-                            adds += 1;
-                        } else {
-                            completes += 1;
-                        }
+                    match per_pid.iter_mut().find(|(p, _)| *p == pid) {
+                        Some((_, c)) => *c += 1,
+                        None => per_pid.push((pid, 1)),
                     }
                 }
+                BLT_ADD_ID => adds += 1,
+                BLT_COMPLETE_ID => completes += 1,
                 _ => {}
             }
         }
@@ -415,61 +444,80 @@ impl EtwWatch {
                 .collect::<Vec<_>>()
                 .join(",");
             parts.push(format!("Present×{total}({top})"));
-        } else if have_present_history {
+        } else if counts.present_history {
             parts.push("Present×0".to_string());
         }
-        if have_queue_history {
+        if counts.queue_history || adds > 0 || completes > 0 {
             parts.push(format!("blt-queue add×{adds} complete×{completes}"));
         }
-        if parts.is_empty() {
+        let summary = if parts.is_empty() {
             "none".to_string()
         } else {
             parts.join(" ")
-        }
-    }
-
-    /// The structured discriminator read for `[from, to]` (the stall classifier's evidence):
-    /// how many swapchain presents (DXGI 42/55, any process) and how many virtual-display
-    /// queue entries (`BltQueueAddEntry`) landed in the window, plus whether each stream has
-    /// EVER produced an event (distinguishing a true zero from a witness that is not working —
-    /// e.g. the DXGI enable was refused, or an OS build renumbered the BltQueue events).
-    pub(super) fn window_counts(&self, from: Instant, to: Instant) -> EtwWindowCounts {
-        let (now_i, now_q, freq) = (Instant::now(), qpc_now(), qpc_freq());
-        let to_q = now_q - duration_qpc(now_i.saturating_duration_since(to), freq);
-        let from_q = now_q - duration_qpc(now_i.saturating_duration_since(from), freq);
-        let ring = RING.lock().unwrap();
-        let mut out = EtwWindowCounts::default();
-        for &(ts, id, _) in ring.iter() {
-            match id {
-                DXGI_PRESENT_ID | DXGI_PRESENT_MPO_ID => {
-                    out.present_history = true;
-                    if ts >= from_q && ts <= to_q {
-                        out.presents += 1;
-                    }
-                }
-                BLT_ADD_ID => {
-                    out.queue_history = true;
-                    if ts >= from_q && ts <= to_q {
-                        out.queue_adds += 1;
-                    }
-                }
-                _ => {}
-            }
-        }
-        out
+        };
+        (summary, counts)
     }
 }
 
-/// [`EtwWatch::window_counts`]'s read: the compose-silence discriminator's structured evidence.
+/// Witness-liveness lookback: the [`EtwWindowCounts`] history flags are true only when the
+/// stream produced at least one event inside the `LOOKBACK` window ENDING at the hole's start.
+/// "Ever produced an event" would be wrong in both directions: an event that arrived only AFTER
+/// the hole (the resume burst, the stall-ending frame) proves nothing about whether the witness
+/// was working DURING it, and a provider that died mid-session (or whose events aged out of the
+/// ring) would keep flying a stale known-working flag forever. Demonstrated life immediately
+/// BEFORE the hole is the claim the classifier actually needs; 5 s is far longer than any
+/// pre-stall active-flow gate, so a genuinely working witness cannot blink false across a
+/// frame-time lull.
+const LOOKBACK: Duration = Duration::from_secs(5);
+
+/// The discriminator's windowing math, factored pure (plain i64 QPC-tick arithmetic, no ETW,
+/// no clock reads) so the ring→counts contract is unit-testable without a session: presents
+/// (DXGI 42/55, any process) and queue entries (`BltQueueAddEntry`) inside `[from_q, to_q]`,
+/// witness liveness from `[from_q - lookback_q, from_q]` (see [`LOOKBACK`]). A
+/// `BltQueueCompleteIndirectPresent` proves the queue witness works exactly as an add does —
+/// both ride the same provider enable — so either satisfies `queue_history`.
+fn count_window(
+    events: &[(i64, u16, u32)],
+    from_q: i64,
+    to_q: i64,
+    lookback_q: i64,
+) -> EtwWindowCounts {
+    let mut out = EtwWindowCounts::default();
+    for &(ts, id, _) in events {
+        let in_window = ts >= from_q && ts <= to_q;
+        let in_lookback = ts >= from_q.saturating_sub(lookback_q) && ts <= from_q;
+        match id {
+            DXGI_PRESENT_ID | DXGI_PRESENT_MPO_ID => {
+                out.present_history |= in_lookback;
+                if in_window {
+                    out.presents += 1;
+                }
+            }
+            BLT_ADD_ID => {
+                out.queue_history |= in_lookback;
+                if in_window {
+                    out.queue_adds += 1;
+                }
+            }
+            BLT_COMPLETE_ID => out.queue_history |= in_lookback,
+            _ => {}
+        }
+    }
+    out
+}
+
+/// [`EtwWatch::window_report`]'s structured half: the compose-silence discriminator's evidence.
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
 pub(super) struct EtwWindowCounts {
     /// Swapchain presents (any process — the game AND dwm both count) inside the window.
     pub(super) presents: u32,
     /// `BltQueueAddEntry` events (frames entering the virtual display's kernel queue) inside it.
     pub(super) queue_adds: u32,
-    /// The present stream has produced at least one event EVER (witness known-working).
+    /// The present stream demonstrated liveness inside [`LOOKBACK`] BEFORE the hole opened — a
+    /// working witness whose in-window zero is a reading, not a dead one whose zero is noise.
     pub(super) present_history: bool,
-    /// The queue stream has produced at least one event EVER (witness known-working).
+    /// Queue-stream liveness inside [`LOOKBACK`] before the hole (`BltQueueAddEntry` or
+    /// `BltQueueCompleteIndirectPresent` — either proves the witness works).
     pub(super) queue_history: bool,
 }
 
@@ -561,3 +609,72 @@ impl Drop for EtwWatch {
         }
     }
 }
+
+// The module only compiles on Windows (lib.rs gates `mod windows`), so plain `cfg(test)` here
+// already means "Windows tests" — and [`count_window`] itself is pure tick math, no session.
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// [`count_window`]'s contract: counts come from the hole window `[from, to]`; liveness
+    /// comes ONLY from the lookback window ending at the hole's start. An event after the hole
+    /// (the resume burst) or older than the lookback (a dead provider's leftovers) must not fly
+    /// the known-working flag — those are exactly the shapes that used to convict every
+    /// compose-silence hole as content.
+    #[test]
+    fn count_window_liveness_and_windowing() {
+        // Hole [1000, 2000], lookback 500 → liveness window [500, 1000]. Plain ticks.
+        let (from, to, lb) = (1_000i64, 2_000i64, 500i64);
+        let ev = |ts: i64, id: u16| (ts, id, 42u32);
+
+        // The healthy shape: liveness demonstrated before the hole, activity inside it.
+        let events = [
+            ev(600, DXGI_PRESENT_ID),       // lookback → present witness live
+            ev(700, BLT_COMPLETE_ID),       // lookback → queue witness live (completes count)
+            ev(1_100, DXGI_PRESENT_ID),     // in-window present
+            ev(1_200, DXGI_PRESENT_MPO_ID), // in-window present (MPO path)
+            ev(1_300, BLT_ADD_ID),          // in-window queue add
+            ev(1_400, 430),                 // non-witness id: never counted here
+        ];
+        assert_eq!(
+            count_window(&events, from, to, lb),
+            EtwWindowCounts {
+                presents: 2,
+                queue_adds: 1,
+                present_history: true,
+                queue_history: true,
+            }
+        );
+
+        // In-window events count but do NOT confer liveness — the witness must have worked
+        // BEFORE the hole for its zeros elsewhere to mean anything.
+        let window_only = [ev(1_500, DXGI_PRESENT_ID), ev(1_600, BLT_ADD_ID)];
+        let c = count_window(&window_only, from, to, lb);
+        assert_eq!((c.presents, c.queue_adds), (1, 1));
+        assert!(!c.present_history && !c.queue_history);
+
+        // An event only AFTER the hole proves nothing about the witness during it.
+        let after_only = [ev(2_100, DXGI_PRESENT_ID), ev(2_200, BLT_ADD_ID)];
+        assert_eq!(
+            count_window(&after_only, from, to, lb),
+            EtwWindowCounts::default()
+        );
+
+        // Events that aged past the lookback (a previous session's leftovers) don't either.
+        let stale = [ev(499, DXGI_PRESENT_ID), ev(1, BLT_ADD_ID)];
+        assert_eq!(
+            count_window(&stale, from, to, lb),
+            EtwWindowCounts::default()
+        );
+
+        // Both lookback edges are inclusive; the hole-start event is both liveness and count.
+        let edges = [ev(500, DXGI_PRESENT_ID), ev(1_000, BLT_ADD_ID)];
+        let c = count_window(&edges, from, to, lb);
+        assert!(c.present_history && c.queue_history);
+        assert_eq!((c.presents, c.queue_adds), (0, 1));
+
+        // A lookback reaching below tick 0 saturates instead of wrapping.
+        let c = count_window(&[ev(0, DXGI_PRESENT_ID)], 3, to, i64::MAX);
+        assert!(c.present_history);
+    }
+}

crates/pf-capture/src/windows/idd_push/stall.rs

@@ -57,7 +57,7 @@ pub(super) struct StallEvidence {
     /// The DxgKrnl DDI activity inside the window (Phase A.3 ETW summary); `None` when the
     /// session is unavailable (non-admin dev run).
     pub(super) etw: Option<String>,
-    /// The structured present-vs-queue counts for the window ([`EtwWatch::window_counts`]) —
+    /// The structured present-vs-queue counts for the window ([`EtwWatch::window_report`]) —
     /// the compose-silence discriminator: presents flowing while the queue starves = the OS
     /// display path dropped composed frames; both silent = the content stopped presenting.
     /// `None` when the ETW session is unavailable.

crates/pf-client-core/src/session.rs

@@ -424,11 +424,31 @@ fn pump(
     // Build the decoder for the codec the host resolved (never assume HEVC), honoring the
     // Settings backend preference (auto/vaapi/software).
     let codec_id = crate::video::ffmpeg_codec_id(connector.codec);
-    tracing::info!(
-        ?codec_id,
-        welcome_codec = connector.codec,
-        "negotiated video codec"
-    );
+    // The WIRE codec is the negotiated truth; the FFmpeg id is meaningful only where
+    // FFmpeg decodes it. `ffmpeg_codec_id`'s fallthrough maps every unknown wire bit —
+    // PyroWave included — to HEVC, so logging it unconditionally claimed
+    // `codec_id=HEVC` for wavelet sessions that never touch FFmpeg at all.
+    let codec = match connector.codec {
+        punktfunk_core::quic::CODEC_H264 => "H264",
+        punktfunk_core::quic::CODEC_HEVC => "HEVC",
+        punktfunk_core::quic::CODEC_AV1 => "AV1",
+        punktfunk_core::quic::CODEC_PYROWAVE => "PyroWave",
+        _ => "unknown",
+    };
+    if connector.codec == punktfunk_core::quic::CODEC_PYROWAVE {
+        tracing::info!(
+            codec,
+            welcome_codec = connector.codec,
+            "negotiated video codec"
+        );
+    } else {
+        tracing::info!(
+            codec,
+            ?codec_id,
+            welcome_codec = connector.codec,
+            "negotiated video codec"
+        );
+    }
     // A negotiated PyroWave session decodes on the presenter's device, no FFmpeg —
     // reachable only through the explicit preference above (resolve_codec never
     // auto-picks the bit), so failing loudly here is failing an opted-in experiment.

crates/pf-client-core/src/video.rs

@@ -321,6 +321,88 @@ pub fn ffmpeg_codec_id(wire: u8) -> ffmpeg::codec::Id {
     }
 }
 
+/// Select a decoder for `codec_id` that can actually drive `hw_pix_fmt` through
+/// `hw_device_ctx` — the open-time capability check every hardware backend needs.
+///
+/// `avcodec_find_decoder(id)` is NOT that: it returns the registry's FIRST decoder for
+/// the id, and upstream orders the native `av1` decoder LAST on purpose ("hwaccel hooks
+/// only, so prefer external decoders" — allcodecs.c), behind libdav1d/libaom. The ID
+/// lookup therefore hands every AV1 session a pure software decoder that silently
+/// ignores `hw_device_ctx` and never calls `get_format`; each frame then fails the
+/// backend's hw-format guard and the session burns the demotion ladder MID-STREAM
+/// (~1 s per rung — field-logged as 68 Vulkan fails → D3D11VA → 102 fails → software,
+/// ~3 s of black) instead of failing here at open in milliseconds. H.264/HEVC never hit
+/// this only because their native decoders happen to be registered first.
+///
+/// The walk mirrors what `avcodec_find_decoder` would do, restricted to decoders whose
+/// `avcodec_get_hw_config` advertises the wanted surface via
+/// `AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX` — registry order still wins among those,
+/// so H.264/HEVC keep selecting exactly the decoder they always did. The error names
+/// the decoders that WERE found, so a log reader can tell "this build has no AV1
+/// hwaccel at all" from "no AV1 decoder exists, period".
+pub(crate) fn find_hw_decoder(
+    codec_id: ffmpeg::codec::Id,
+    hw_pix_fmt: ffmpeg::ffi::AVPixelFormat,
+) -> Result<*const ffmpeg::ffi::AVCodec> {
+    use ffmpeg::ffi;
+    let want: ffi::AVCodecID = codec_id.into();
+    let mut found: Vec<String> = Vec::new();
+    // SAFETY: `av_codec_iterate` walks libav's static codec registry (`opaque` is its
+    // cursor) and returns static `AVCodec`s; `avcodec_get_hw_config` only reads the
+    // codec's own static hw-config table, NULL-terminated by returning null past the end.
+    unsafe {
+        let mut opaque = std::ptr::null_mut();
+        loop {
+            let codec = ffi::av_codec_iterate(&mut opaque);
+            if codec.is_null() {
+                break;
+            }
+            if (*codec).id != want || ffi::av_codec_is_decoder(codec) == 0 {
+                continue;
+            }
+            for i in 0.. {
+                let cfg = ffi::avcodec_get_hw_config(codec, i);
+                if cfg.is_null() {
+                    break;
+                }
+                if (*cfg).methods & ffi::AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX as i32 != 0
+                    && (*cfg).pix_fmt == hw_pix_fmt
+                {
+                    return Ok(codec);
+                }
+            }
+            found.push(
+                std::ffi::CStr::from_ptr((*codec).name)
+                    .to_string_lossy()
+                    .into_owned(),
+            );
+        }
+    }
+    if found.is_empty() {
+        bail!("no {codec_id:?} decoder in this FFmpeg build");
+    }
+    bail!(
+        "no {codec_id:?} decoder in this FFmpeg build can drive {hw_pix_fmt:?} via \
+         hw_device_ctx (found: {})",
+        found.join(", ")
+    );
+}
+
+/// The name of a registry `AVCodec` (`(*codec).name`), owned — the field every decode
+/// log carries so `decoder="av1"` vs `decoder="libdav1d"` is one glance, not a debugger.
+///
+/// # Safety
+/// `codec` must point to a registered `AVCodec` (their `name` is a static NUL-terminated
+/// string, valid for the process).
+pub(crate) unsafe fn codec_name(codec: *const ffmpeg::ffi::AVCodec) -> String {
+    // SAFETY: caller guarantees a registered AVCodec; `name` is its static C string.
+    unsafe {
+        std::ffi::CStr::from_ptr((*codec).name)
+            .to_string_lossy()
+            .into_owned()
+    }
+}
+
 /// The `quic` codec bitfield this client can decode — whatever FFmpeg has a decoder for (HEVC/H.264
 /// always; AV1 when built in). Advertised to the host so it never emits a codec we can't decode.
 pub fn decodable_codecs() -> u8 {
@@ -435,7 +517,11 @@ impl Decoder {
             vaapi_tried = true;
             match VaapiDecoder::new(codec_id) {
                 Ok(v) => {
-                    tracing::info!(?codec_id, "VAAPI hardware decode active (zero-copy dmabuf)");
+                    tracing::info!(
+                        ?codec_id,
+                        decoder = v.name(),
+                        "VAAPI hardware decode active (zero-copy dmabuf)"
+                    );
                     return done(Backend::Vaapi(v));
                 }
                 Err(e) => {
@@ -470,6 +556,7 @@ impl Decoder {
                     Ok(d) => {
                         tracing::info!(
                             ?codec_id,
+                            decoder = d.name(),
                             "D3D11VA hardware decode active (shared-texture hand-off)"
                         );
                         return done(Backend::D3d11va(d));
@@ -490,6 +577,7 @@ impl Decoder {
                     Ok(v) => {
                         tracing::info!(
                             ?codec_id,
+                            decoder = v.name(),
                             "Vulkan Video hardware decode active (presenter-shared device)"
                         );
                         return done(Backend::Vulkan(v));
@@ -520,7 +608,11 @@ impl Decoder {
         if choice != "software" && choice != "vulkan" && !vaapi_tried {
             match VaapiDecoder::new(codec_id) {
                 Ok(v) => {
-                    tracing::info!(?codec_id, "VAAPI hardware decode active (zero-copy dmabuf)");
+                    tracing::info!(
+                        ?codec_id,
+                        decoder = v.name(),
+                        "VAAPI hardware decode active (zero-copy dmabuf)"
+                    );
                     return done(Backend::Vaapi(v));
                 }
                 Err(e) => {
@@ -548,6 +640,7 @@ impl Decoder {
                         Ok(d) => {
                             tracing::info!(
                                 ?codec_id,
+                                decoder = d.name(),
                                 "D3D11VA hardware decode active (shared-texture hand-off)"
                             );
                             return done(Backend::D3d11va(d));
@@ -724,6 +817,7 @@ impl Decoder {
                         match VaapiDecoder::new(self.codec_id) {
                             Ok(v) => {
                                 tracing::warn!(error = %e, fails = self.vaapi_fails,
+                                    decoder = v.name(),
                                     "Vulkan Video decode failing repeatedly — demoting to VAAPI");
                                 self.backend = Backend::Vaapi(v);
                                 self.vaapi_fails = 0;
@@ -745,6 +839,7 @@ impl Decoder {
                         ) {
                             Ok(d) => {
                                 tracing::warn!(error = %e, fails = self.vaapi_fails,
+                                    decoder = d.name(),
                                     "Vulkan Video decode failing repeatedly — demoting to D3D11VA");
                                 self.backend = Backend::D3d11va(d);
                                 self.vaapi_fails = 0;

crates/pf-client-core/src/video_d3d11.rs

@@ -552,6 +552,10 @@ pub(crate) struct D3d11vaDecoder {
     /// ([`crate::video::VulkanDecodeDevice::d3d11_hdr10`]) — PQ streams get the HDR
     /// pass-through ring; without it they keep the tonemap-to-sRGB ring.
     hdr10_out: bool,
+    /// The selected decoder's registry name (`(*codec).name`) — `"av1"` vs `"libdav1d"`
+    /// is the difference between hardware decode and a silent CPU fallback, so every
+    /// log a field report leans on carries it.
+    name: String,
 }
 
 // SAFETY: the libav pointers are this decoder's own allocations (freed once in `Drop`) and the COM
@@ -609,10 +613,16 @@ impl D3d11vaDecoder {
             if !d3d11va_decode_supported(hw_device.as_ptr()) {
                 bail!("GPU can't create the D3D11VA decode surface pool");
             }
-            let codec = ffi::avcodec_find_decoder(codec_id.into());
-            if codec.is_null() {
-                bail!("no {codec_id:?} decoder");
-            }
+            // NOT `avcodec_find_decoder`: the ID lookup returns the registry's FIRST
+            // decoder, and for AV1 that is libdav1d (upstream orders the hwaccel-only
+            // native decoder last) — a software decoder that silently ignores
+            // `hw_device_ctx` and fails every frame's D3D11-format guard mid-stream,
+            // even when the DXVA profile + pool probes above all passed. Select by
+            // capability instead: the first decoder that can drive AV_PIX_FMT_D3D11
+            // via hw_device_ctx, or fail here at open.
+            let codec =
+                crate::video::find_hw_decoder(codec_id, ffi::AVPixelFormat::AV_PIX_FMT_D3D11)?;
+            let name = crate::video::codec_name(codec);
             let ctx = ffi::avcodec_alloc_context3(codec);
             (*ctx).hw_device_ctx = ffi::av_buffer_ref(hw_device.as_ptr());
             (*ctx).get_format = Some(get_format_d3d11);
@@ -638,10 +648,16 @@ impl D3d11vaDecoder {
                 video_context1,
                 ring: None,
                 hdr10_out,
+                name,
             })
         }
     }
 
+    /// The selected decoder's registry name (e.g. `"av1"`) — see the field doc.
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
     pub(crate) fn decode(&mut self, au: &[u8]) -> Result<Option<D3d11Frame>> {
         use ffmpeg::ffi;
         // SAFETY: `packet`/`frame`/`ctx` are this decoder's own allocations, live for its whole
@@ -830,6 +846,7 @@ impl D3d11vaDecoder {
                 src_desc.Height,
                 index,
                 color.is_pq(),
+                &self.name,
             );
             Ok(D3d11Frame {
                 width,
@@ -883,7 +900,15 @@ impl Drop for D3d11vaDecoder {
 /// One-time dump of the first decoded surface's layout — the forensics for a new GPU/driver.
 /// `tex_*` is the DXVA-aligned decode surface (>= the frame); the gap is the padding the
 /// stream source rect excludes.
-fn log_layout_once(width: u32, height: u32, tex_w: u32, tex_h: u32, index: u32, pq: bool) {
+fn log_layout_once(
+    width: u32,
+    height: u32,
+    tex_w: u32,
+    tex_h: u32,
+    index: u32,
+    pq: bool,
+    decoder: &str,
+) {
     use std::sync::atomic::{AtomicBool, Ordering};
     static ONCE: AtomicBool = AtomicBool::new(true);
     if ONCE.swap(false, Ordering::Relaxed) {
@@ -894,6 +919,7 @@ fn log_layout_once(width: u32, height: u32, tex_w: u32, tex_h: u32, index: u32,
             tex_h,
             slice = index,
             pq,
+            decoder,
             "D3D11VA first frame"
         );
     }

crates/pf-client-core/src/video_software.rs

@@ -34,6 +34,12 @@ impl SoftwareDecoder {
             (*raw).thread_count = 0; // auto
         }
         let decoder = ctx.decoder().video().context("open video decoder")?;
+        // Every construction site (session open, preference, mid-stream demotion) says
+        // which decoder actually opened: for AV1 the ID lookup means libdav1d here —
+        // deliberately (fastest CPU path; the native `av1` decoder has no software
+        // path at all) — and the name in the log is what keeps that distinguishable
+        // from the hardware lanes' capability-selected decoders.
+        tracing::info!(?codec_id, decoder = codec.name(), "software decoder opened");
         Ok(SoftwareDecoder { decoder, sws: None })
     }
 

crates/pf-client-core/src/video_vaapi.rs

@@ -46,6 +46,10 @@ pub(crate) struct VaapiDecoder {
     hw_device: AvBuffer,
     packet: *mut ffmpeg::ffi::AVPacket,
     frame: *mut ffmpeg::ffi::AVFrame,
+    /// The selected decoder's registry name (`(*codec).name`) — `"av1"` vs `"libdav1d"`
+    /// is the difference between hardware decode and a silent CPU fallback, so every
+    /// log a field report leans on carries it.
+    name: String,
 }
 
 // SAFETY: the three raw pointers (`ctx`, `packet`, `frame`) are allocations this decoder makes in
@@ -80,11 +84,15 @@ impl VaapiDecoder {
             // Owned from here: every `bail!` below drops it, so none of them unref by hand.
             let hw_device = AvBuffer::from_raw(hw_device)
                 .context("av_hwdevice_ctx_create(VAAPI) gave no device")?;
-            // The negotiated codec's decoder id (av_codec_id maps 1:1 from ffmpeg::codec::Id).
-            let codec = ffi::avcodec_find_decoder(codec_id.into());
-            if codec.is_null() {
-                bail!("no {codec_id:?} decoder");
-            }
+            // NOT `avcodec_find_decoder`: the ID lookup returns the registry's FIRST
+            // decoder, and for AV1 that is libdav1d (upstream orders the hwaccel-only
+            // native decoder last) — a software decoder that silently ignores
+            // `hw_device_ctx` and fails every frame's VAAPI-format guard mid-stream.
+            // Select by capability instead: the first decoder that can drive
+            // AV_PIX_FMT_VAAPI via hw_device_ctx, or fail here at open.
+            let codec =
+                crate::video::find_hw_decoder(codec_id, ffi::AVPixelFormat::AV_PIX_FMT_VAAPI)?;
+            let name = crate::video::codec_name(codec);
             let ctx = ffi::avcodec_alloc_context3(codec);
             (*ctx).hw_device_ctx = ffi::av_buffer_ref(hw_device.as_ptr());
             (*ctx).get_format = Some(pick_vaapi);
@@ -109,10 +117,16 @@ impl VaapiDecoder {
                 hw_device,
                 packet: ffi::av_packet_alloc(),
                 frame: ffi::av_frame_alloc(),
+                name,
             })
         }
     }
 
+    /// The selected decoder's registry name (e.g. `"av1"`) — see the field doc.
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
     pub(crate) fn decode(&mut self, au: &[u8]) -> Result<Option<DmabufFrame>> {
         use ffmpeg::ffi;
         // SAFETY: `packet`/`frame`/`ctx` are this decoder's own allocations, live for its whole
@@ -207,7 +221,7 @@ impl VaapiDecoder {
             // a single modifier for the texture.
             let modifier = d.objects[0].format_modifier;
 
-            log_descriptor_once(d, sw_format, fourcc, modifier);
+            log_descriptor_once(d, sw_format, fourcc, modifier, &self.name);
 
             Ok(DmabufFrame {
                 width: (*self.frame).width as u32,
@@ -233,6 +247,7 @@ fn log_descriptor_once(
     sw: ffmpeg_next::ffi::AVPixelFormat,
     fourcc: u32,
     modifier: u64,
+    decoder: &str,
 ) {
     use std::sync::atomic::{AtomicBool, Ordering};
     static ONCE: AtomicBool = AtomicBool::new(true);
@@ -250,6 +265,7 @@ fn log_descriptor_once(
         nb_layers = d.nb_layers,
         ?layers,
         modifier = format_args!("{:#018x}", modifier),
+        decoder,
         "VAAPI dmabuf descriptor layout (first frame)"
     );
 }

crates/pf-client-core/src/video_vulkan.rs

@@ -33,6 +33,10 @@ pub(crate) struct VulkanDecoder {
     /// (resolved through the same get_proc_addr chain FFmpeg uses).
     wait_semaphores: pf_ffvk::PFN_vkWaitSemaphores,
     vk_device: pf_ffvk::VkDevice,
+    /// The selected decoder's registry name (`(*codec).name`) — `"av1"` vs `"libdav1d"`
+    /// is the difference between hardware decode and a silent CPU fallback, so every
+    /// log a field report leans on carries it.
+    name: String,
     /// Storage `AVVulkanDeviceContext` points into (extension string arrays + the
     /// feature chain) — FFmpeg reads the extension lists past init (frames-context
     /// setup keys code paths off them), so this lives exactly as long as `hw_device`.
@@ -245,10 +249,15 @@ impl VulkanDecoder {
             }
             let vk_device = (*hwctx).act_dev;
 
-            let codec = ffi::avcodec_find_decoder(codec_id.into());
-            if codec.is_null() {
-                bail!("no {codec_id:?} decoder");
-            }
+            // NOT `avcodec_find_decoder`: the ID lookup returns the registry's FIRST
+            // decoder, and for AV1 that is libdav1d (upstream orders the hwaccel-only
+            // native decoder last) — a software decoder that silently ignores
+            // `hw_device_ctx` and fails every frame's Vulkan-format guard mid-stream.
+            // Select by capability instead: the first decoder that can drive
+            // AV_PIX_FMT_VULKAN via hw_device_ctx, or fail here at open.
+            let codec =
+                crate::video::find_hw_decoder(codec_id, ffi::AVPixelFormat::AV_PIX_FMT_VULKAN)?;
+            let name = crate::video::codec_name(codec);
             let ctx = ffi::avcodec_alloc_context3(codec);
             (*ctx).hw_device_ctx = ffi::av_buffer_ref(hw_device.as_ptr());
             (*ctx).get_format = Some(pick_vulkan);
@@ -270,11 +279,17 @@ impl VulkanDecoder {
                 frame: ffi::av_frame_alloc(),
                 wait_semaphores,
                 vk_device,
+                name,
                 _ctx_storage: store,
             })
         }
     }
 
+    /// The selected decoder's registry name (e.g. `"av1"`) — see the field doc.
+    pub(crate) fn name(&self) -> &str {
+        &self.name
+    }
+
     pub(crate) fn decode(&mut self, au: &[u8]) -> Result<Option<VkVideoFrame>> {
         use ffmpeg::ffi;
         // SAFETY: `packet`/`frame`/`ctx` are this decoder's own allocations, live for its whole
@@ -388,6 +403,7 @@ impl VulkanDecoder {
                 (*fc).width,
                 (*fc).height,
                 sw,
+                &self.name,
             );
             Ok(VkVideoFrame {
                 vkframe: vkf as usize,
@@ -423,6 +439,7 @@ fn log_layout_once(
     pool_w: i32,
     pool_h: i32,
     sw: ffmpeg::ffi::AVPixelFormat,
+    decoder: &str,
 ) {
     use std::sync::atomic::{AtomicBool, Ordering};
     static ONCE: AtomicBool = AtomicBool::new(true);
@@ -433,6 +450,7 @@ fn log_layout_once(
             pool_w,
             pool_h,
             ?sw,
+            decoder,
             "Vulkan Video first frame"
         );
     }

crates/pf-console-ui/src/screens/settings.rs

@@ -365,7 +365,8 @@ fn detail(id: RowId) -> &'static str {
         }
         RowId::Chroma444 => {
             "Full-colour video: crisp small text and thin lines, at more bandwidth. \
-             HEVC only, and only where the host can encode it."
+             Needs an NVIDIA host (NVENC) or the PyroWave codec — other encoders \
+             stream 4:2:0 and the session falls back silently."
         }
         RowId::Audio => "The speaker layout requested from the host.",
         RowId::Mic => {

crates/pf-inject/src/inject/proto/dualsense_proto.rs

@@ -35,10 +35,14 @@ pub const DS_FEATURE_PAIRING: &[u8] = &[ // report 0x09 (pairing info: MAC at by
     0x00, 0x00, 0x00, 0x00,
 ];
 #[rustfmt::skip]
-pub const DS_FEATURE_FIRMWARE: &[u8] = &[ // report 0x20 (firmware info / build date)
+pub const DS_FEATURE_FIRMWARE: &[u8] = &[ // report 0x20 (firmware info / build date); bytes 44..46
+    // = update version, kept ABOVE Sony's real releases (0x0630 as of 2026-08) — an older value
+    // makes PlayStation Accessories and libScePad titles demand a firmware update the virtual pad
+    // cannot take ("can't complete the update"), and ≥ 0x0224 is what puts writers on the
+    // COMPATIBLE_VIBRATION2 convention parse_ds_output accepts alongside flag0.
     0x20, 0x4A, 0x75, 0x6E, 0x20, 0x31, 0x39, 0x20, 0x32, 0x30, 0x32, 0x33, 0x31, 0x34, 0x3A, 0x34,
     0x37, 0x3A, 0x33, 0x34, 0x03, 0x00, 0x44, 0x00, 0x08, 0x02, 0x00, 0x01, 0x36, 0x00, 0x00, 0x01,
-    0xC1, 0xC8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x54, 0x01, 0x00, 0x00,
+    0xC1, 0xC8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x99, 0x09, 0x00, 0x00,
     0x14, 0x00, 0x00, 0x00, 0x0B, 0x00, 0x01, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 ];
 
@@ -494,10 +498,13 @@ pub fn parse_ds_output(pad: u8, data: &[u8], fb: &mut DsFeedback) {
                          // data[4]. Scale 0..255 → 0..0xFFFF, same (low, high) convention as the uinput pad's mixer,
                          // and route to the universal rumble plane (0xCA).
                          // Writers on firmware ≥ 2.24 signal rumble via COMPATIBLE_VIBRATION2 in valid_flag2
-                         // (data[39] BIT2) instead of flag0 BIT0. Our feature report advertises 0x0154 so the
-                         // kernel and SDL stay on the flag0 convention, but a writer that hardcodes v2 would
-                         // otherwise have its rumble — including stops — silently ignored, and a missed stop
-                         // buzzes for the rest of the session (the 500 ms refresh re-sends stale state forever).
+                         // (data[39] BIT2) instead of flag0 BIT0. Our feature report advertises a version
+                         // above 2.24 (DS_FEATURE_FIRMWARE bytes 44..46, chosen to keep Sony's updater
+                         // quiet), so the kernel and SDL write the v2 flag — while older writers, and any
+                         // that never read the version, stay on flag0. Both conventions must land here: a
+                         // rumble dropped on either — including stops — is silently ignored, and a missed
+                         // stop buzzes for the rest of the session (the 500 ms refresh re-sends stale state
+                         // forever).
     if flag0 & 0x03 != 0 || data[39] & 0x04 != 0 {
         let high = (data[3] as u16) << 8;
         let low = (data[4] as u16) << 8;

crates/pf-presenter/src/run.rs

@@ -204,6 +204,11 @@ struct StreamState {
     /// mid-stream re-syncs keep the end-to-end number honest after an NTP step / drift.
     clock_offset: Option<Arc<std::sync::atomic::AtomicI64>>,
     hdr: bool,
+    /// The presented lane was the CPU/software one, where a PQ stream is shown RAW — the
+    /// software path has no tone-map pass at all (the presenter uploads swscale RGBA
+    /// as-is; the CSC mode-1 tonemap is hardware-lane only) — so the OSD badge reads
+    /// `HDR→SDR (raw)` there instead of claiming a tone-map that never ran.
+    hdr_untonemapped: bool,
     // Presenter-side 1 s window (design/stats-unification.md): end-to-end
     // capture→displayed (host-clock corrected) p50+p95, display = decoded→displayed p50.
     win_e2e_us: Vec<u64>,
@@ -308,6 +313,7 @@ impl StreamState {
             latch_grid,
             clock_offset: None,
             hdr: false,
+            hdr_untonemapped: false,
             win_e2e_us: Vec::with_capacity(256),
             win_disp_us: Vec::with_capacity(256),
             win_start: Instant::now(),
@@ -1103,6 +1109,7 @@ fn run_inner(mut opts: SessionOpts, mut mode: ModeCtl) -> Result<Option<Outcome>
                         &st.presented,
                         st.hdr,
                         presenter.hdr_active(),
+                        st.hdr_untonemapped,
                         st.profile.as_deref(),
                     );
                     if stats_verbosity != StatsVerbosity::Off {
@@ -1115,6 +1122,7 @@ fn run_inner(mut opts: SessionOpts, mut mode: ModeCtl) -> Result<Option<Outcome>
                             &st.presented,
                             st.hdr,
                             presenter.hdr_active(),
+                            st.hdr_untonemapped,
                             st.profile.as_deref(),
                         );
                         println!("stats: {}", full.replace('\n', " | "));
@@ -1296,6 +1304,7 @@ fn run_inner(mut opts: SessionOpts, mut mode: ModeCtl) -> Result<Option<Outcome>
                         // HDR (PQ) pyrowave session presents through the HDR10 path exactly
                         // like the H.26x codecs (design/pyrowave-444-hdr.md Phase 3).
                         st.hdr = f.color.is_pq();
+                        st.hdr_untonemapped = false;
                         match presenter.present(
                             &window,
                             FrameInput::PyroWave(f),
@@ -1323,6 +1332,9 @@ fn run_inner(mut opts: SessionOpts, mut mode: ModeCtl) -> Result<Option<Outcome>
                     }
                     DecodedImage::Cpu(c) => {
                         st.hdr = c.color.is_pq();
+                        // The software lane shows PQ raw (no tone-map pass exists there)
+                        // — the OSD badge must not claim `HDR→SDR` for it.
+                        st.hdr_untonemapped = true;
                         presenter.present(&window, FrameInput::Cpu(&c), overlay_frame.as_ref())?
                     }
                     #[cfg(target_os = "linux")]
@@ -1330,6 +1342,7 @@ fn run_inner(mut opts: SessionOpts, mut mode: ModeCtl) -> Result<Option<Outcome>
                         if presenter.supports_dmabuf() && !st.dmabuf_demoted =>
                     {
                         st.hdr = d.color.is_pq();
+                        st.hdr_untonemapped = false;
                         match presenter.present(
                             &window,
                             FrameInput::Dmabuf(d),
@@ -1380,6 +1393,7 @@ fn run_inner(mut opts: SessionOpts, mut mode: ModeCtl) -> Result<Option<Outcome>
                     #[cfg(windows)]
                     DecodedImage::D3d11(d) if presenter.supports_d3d11() && !st.dmabuf_demoted => {
                         st.hdr = d.color.is_pq();
+                        st.hdr_untonemapped = false;
                         match presenter.present(
                             &window,
                             FrameInput::D3d11(d),
@@ -1426,6 +1440,7 @@ fn run_inner(mut opts: SessionOpts, mut mode: ModeCtl) -> Result<Option<Outcome>
                     // demotion contract as the dmabuf path.
                     DecodedImage::VkFrame(v) if !st.dmabuf_demoted => {
                         st.hdr = v.color.is_pq();
+                        st.hdr_untonemapped = false;
                         match presenter.present(
                             &window,
                             FrameInput::VkFrame(v),
@@ -1910,6 +1925,7 @@ fn bump_stats_tier(
                 &st.presented,
                 st.hdr,
                 presenter.hdr_active(),
+                st.hdr_untonemapped,
                 st.profile.as_deref(),
             ),
             None => String::new(),
@@ -2007,11 +2023,15 @@ const HINT_WITH_PAD: &str = "Click the stream to capture input · Ctrl+Alt+Shift
 ///
 /// The HDR tag is honest about the display path: `HDR` only when the swapchain actually
 /// runs HDR10 (`hdr_display`); a PQ stream tone-mapped onto an SDR surface (no HDR10
-/// format offered, HDR off in the compositor) shows `HDR→SDR` instead.
+/// format offered, HDR off in the compositor) shows `HDR→SDR`; and a PQ stream on the
+/// software-decode lane (`hdr_untonemapped`) shows `HDR→SDR (raw)` — that lane has no
+/// tone-map pass at all, so the washed-out picture is named for what it is rather than
+/// passed off as a tone-map.
 ///
 /// `profile` (the session's settings profile, `None` for the global defaults) closes the
 /// first line at every tier — the cheapest possible answer to "which profile am I on?"
 /// (design/client-settings-profiles.md §5.2).
+#[allow(clippy::too_many_arguments)]
 fn stats_text(
     verbosity: StatsVerbosity,
     mode_line: &str,
@@ -2019,6 +2039,7 @@ fn stats_text(
     p: &PresentedWindow,
     hdr_stream: bool,
     hdr_display: bool,
+    hdr_untonemapped: bool,
     profile: Option<&str>,
 ) -> String {
     let profile_tag = profile.map(|n| format!(" · {n}")).unwrap_or_default();
@@ -2068,6 +2089,7 @@ fn stats_text(
             if s.decoder.is_empty() { "-" } else { s.decoder },
             match (hdr_stream, hdr_display) {
                 (true, true) => " · HDR",
+                (true, false) if hdr_untonemapped => " · HDR→SDR (raw)",
                 (true, false) => " · HDR→SDR",
                 _ => "",
             },
@@ -2380,7 +2402,7 @@ mod tests {
     #[test]
     fn stats_text_tiers() {
         let (s, p) = sample();
-        let text = |v| stats_text(v, "1920×1080@120", &s, &p, true, false, None);
+        let text = |v| stats_text(v, "1920×1080@120", &s, &p, true, false, false, None);
 
         assert_eq!(text(StatsVerbosity::Off), "");
 
@@ -2397,6 +2419,10 @@ mod tests {
 
         let detailed = text(StatsVerbosity::Detailed);
         assert!(detailed.contains("vulkan · HDR→SDR"));
+        assert!(
+            !detailed.contains("(raw)"),
+            "the hardware lane tone-maps — no raw tag"
+        );
         assert!(detailed.contains("host 1.2 · net 0.9 · decode 1.8 · display 1.1 ms"));
         assert!(detailed.contains("host: queue 0.3 · encode 0.5 · xfer 0.1 · pace 0.3 ms"));
         assert!(detailed.contains("lost 3 (0.4%)"));
@@ -2406,6 +2432,32 @@ mod tests {
         );
     }
 
+    /// The honest HDR badges: a PQ stream on the software-decode lane is shown WITHOUT
+    /// tone-mapping (that lane has no PQ→sRGB pass), so its badge must not read as the
+    /// hardware lane's `HDR→SDR` tone-map — and an HDR10 swapchain shows plain `HDR`
+    /// whatever the lane claims (a CPU frame forces the swapchain to SDR anyway).
+    #[test]
+    fn hdr_badge_names_the_untonemapped_cpu_lane() {
+        let (s, p) = sample();
+        let badge = |hdr_display, raw| {
+            stats_text(
+                StatsVerbosity::Detailed,
+                "m",
+                &s,
+                &p,
+                true,
+                hdr_display,
+                raw,
+                None,
+            )
+        };
+        assert!(badge(false, true).contains(" · HDR→SDR (raw)"));
+        assert!(!badge(false, false).contains("(raw)"));
+        assert!(badge(false, false).contains(" · HDR→SDR"));
+        assert!(badge(true, false).contains(" · HDR"));
+        assert!(!badge(true, false).contains("HDR→SDR"));
+    }
+
     /// Detailed shows the negotiated encoder target next to the measured rate — the
     /// figure whose absence let the settings-drop bug ship four releases — tagged
     /// `(auto)` when the ABR owns it, plus the honest chroma tag when 4:4:4 was asked.
@@ -2413,7 +2465,7 @@ mod tests {
     fn detailed_shows_target_and_chroma_resolution() {
         let (mut s, p) = sample();
         let line1 = |s: &Stats, v| {
-            stats_text(v, "m", s, &p, false, false, None)
+            stats_text(v, "m", s, &p, false, false, false, None)
                 .lines()
                 .next()
                 .unwrap()
@@ -2446,7 +2498,7 @@ mod tests {
     #[test]
     fn stats_text_mic_line() {
         let (mut s, p) = sample();
-        let text = |s: &Stats, v| stats_text(v, "m", s, &p, false, false, None);
+        let text = |s: &Stats, v| stats_text(v, "m", s, &p, false, false, false, None);
         assert!(
             !text(&s, StatsVerbosity::Detailed).contains("mic"),
             "no mic line while the mic is off"
@@ -2473,7 +2525,16 @@ mod tests {
         s.lost = 0;
         let p = PresentedWindow::default();
         assert_eq!(
-            stats_text(StatsVerbosity::Compact, "m", &s, &p, false, false, None),
+            stats_text(
+                StatsVerbosity::Compact,
+                "m",
+                &s,
+                &p,
+                false,
+                false,
+                false,
+                None
+            ),
             "120 fps · 24 Mb/s"
         );
     }
@@ -2491,6 +2552,7 @@ mod tests {
                 &p,
                 false,
                 false,
+                false,
                 Some("Game")
             ),
             "120 fps · 6.4 ms · 24 Mb/s · lost 3 · Game"
@@ -2502,6 +2564,7 @@ mod tests {
             &p,
             false,
             false,
+            false,
             Some("Work"),
         );
         assert_eq!(
@@ -2515,13 +2578,22 @@ mod tests {
             &p,
             true,
             true,
+            false,
             Some("Work"),
         );
         assert!(detailed.lines().next().unwrap().ends_with("· HDR · Work"));
         // No profile → the line is exactly what it always was.
-        assert!(
-            !stats_text(StatsVerbosity::Normal, "m", &s, &p, false, false, None).contains(" ·  ")
-        );
+        assert!(!stats_text(
+            StatsVerbosity::Normal,
+            "m",
+            &s,
+            &p,
+            false,
+            false,
+            false,
+            None
+        )
+        .contains(" ·  "));
     }
 
     #[test]

crates/pf-presenter/src/vk/present.rs

@@ -40,7 +40,27 @@ impl Presenter {
         // PQ→sRGB pass.
         let frame_pq = match &input {
             FrameInput::Redraw => None,
-            FrameInput::Cpu(_) => Some(false),
+            FrameInput::Cpu(f) => {
+                // The swapchain answer stays `false` (above) — but a PQ stream on this
+                // lane is then shown RAW: no PQ→sRGB pass exists here (the CSC mode-1
+                // tonemap is hardware-lane only; CPU frames are a straight RGBA upload),
+                // so the picture is washed out and the pq-downgrade warn below never
+                // fires. Say so once, or the only trace is an OSD badge. (A process-once
+                // latch, same idiom as the decoders' first-frame layout dumps — the
+                // condition is a property of the lane, not of one Presenter.)
+                if f.color.is_pq() {
+                    use std::sync::atomic::{AtomicBool, Ordering};
+                    static WARNED: AtomicBool = AtomicBool::new(false);
+                    if !WARNED.swap(true, Ordering::Relaxed) {
+                        tracing::warn!(
+                            "HDR10 (PQ) stream on the software-decode lane — it has no \
+                             PQ→sRGB pass, so the picture is shown untonemapped (washed \
+                             out). Hardware decode restores correct colour."
+                        );
+                    }
+                }
+                Some(false)
+            }
             #[cfg(target_os = "linux")]
             FrameInput::Dmabuf(d) => Some(d.color.is_pq()),
             FrameInput::VkFrame(v) => Some(v.color.is_pq()),

crates/pf-presenter/src/vk/setup.rs

@@ -731,12 +731,17 @@ pub(super) fn pick_formats(
 }
 
 /// MAILBOX when the surface offers it, FIFO otherwise (`PUNKTFUNK_PRESENT_MODE=
-/// fifo|mailbox|immediate` overrides). Both are tear-free, but an arrival-paced
-/// presenter must not block in FIFO's present queue: when the compositor holds images
-/// for a vblank pass (gamescope's composite path) or arrival cadence drifts against
-/// refresh, `acquire_next_image` stalls most of a refresh — a standing 11-13 ms added
-/// to every frame at 60 Hz. MAILBOX never queues more than the newest frame, so the
+/// fifo|mailbox|immediate|fifo_relaxed` overrides). Both defaults are tear-free, but an
+/// arrival-paced presenter must not block in FIFO's present queue: when the compositor
+/// holds images for a vblank pass (gamescope's composite path) or arrival cadence drifts
+/// against refresh, `acquire_next_image` stalls most of a refresh — a standing 11-13 ms
+/// added to every frame at 60 Hz. MAILBOX never queues more than the newest frame, so the
 /// pipeline stays at decode latency and a late frame is replaced, not waited for.
+///
+/// AMD's Windows driver offers no MAILBOX (NVIDIA does), so those clients land on FIFO —
+/// expected, not a client misconfiguration. FIFO_RELAXED is opt-in only: it tears exactly
+/// when a stream frame misses the vblank it was pacing for, which on a drifting arrival
+/// cadence is often — a trade the user must choose, never a silent fallback.
 fn pick_present_mode(
     surface_i: &ash::khr::surface::Instance,
     pdev: vk::PhysicalDevice,
@@ -748,7 +753,15 @@ fn pick_present_mode(
     let want = match std::env::var("PUNKTFUNK_PRESENT_MODE").ok().as_deref() {
         Some("fifo") => vk::PresentModeKHR::FIFO,
         Some("immediate") => vk::PresentModeKHR::IMMEDIATE,
-        _ => vk::PresentModeKHR::MAILBOX,
+        Some("fifo_relaxed") => vk::PresentModeKHR::FIFO_RELAXED,
+        Some("mailbox") | None => vk::PresentModeKHR::MAILBOX,
+        Some(other) => {
+            tracing::warn!(
+                value = other,
+                "unknown PUNKTFUNK_PRESENT_MODE (expected fifo|mailbox|immediate|fifo_relaxed) — using mailbox"
+            );
+            vk::PresentModeKHR::MAILBOX
+        }
     };
     Ok(if modes.contains(&want) {
         want

crates/pf-vdisplay/src/vdisplay/linux/kwin.rs

@@ -138,7 +138,14 @@ impl KwinDisplay {
         let kind = match topology {
             Topology::Exclusive => TopologyKind::Exclusive,
             Topology::Primary => TopologyKind::Primary,
-            Topology::Extend | Topology::Auto => return Vec::new(),
+            Topology::Extend | Topology::Auto => {
+                // No topology to apply — but the output must still be its OWN desktop rather than a
+                // mirror of someone's panel, and KWin restores a stored `replicationSource` onto our
+                // (stable) output name for whatever monitor set it was saved under. Applies only if
+                // it really is mirroring; nothing else about the user's arrangement is touched.
+                crate::kwin_output_mgmt::clear_replication_source(our_prefix, dims.0, dims.1);
+                return Vec::new();
+            }
         };
         // In-process over Wayland — immune to whatever wedges the standalone kscreen-doctor.
         let outcome = crate::kwin_output_mgmt::apply_topology(our_prefix, dims.0, dims.1, kind);

crates/pf-vdisplay/src/vdisplay/linux/kwin_output_mgmt.rs

@@ -112,6 +112,34 @@ const POLL_MS: i32 = 100;
 /// asked — matches `kwin::CVT_H_GRANULARITY`. Used when matching the generated mode back.
 const CVT_H_GRANULARITY: u32 = 8;
 
+/// `kde_output_management_v2.set_replication_source` (and the device's `replication_source` event)
+/// arrived in v13. wayland-rs does not range-check requests, so sending one to a lower-version bind
+/// would be a protocol error that kills the connection — every call site gates on this.
+const REPLICATION_SOURCE_SINCE: u32 = 13;
+
+/// The `source` value that means "this output mirrors nothing" — KWin's `applyMirroring` looks the
+/// source UUID up among the enabled outputs and treats an EMPTY string as no replication at all.
+const NO_REPLICATION_SOURCE: &str = "";
+
+/// Is this output currently a MIRROR of another one?
+///
+/// KWin persists output config per *setup* — the exact set of connected outputs, matched by
+/// EDID/connector — in `kwinoutputconfig.json`, and `replicationSource` is one of the fields it
+/// stores and restores (`OutputConfigurationStore::storeConfig` / `setupToConfig`). Our virtual
+/// output carries a STABLE name across sessions (that is deliberate — KWin keys per-output scale by
+/// it), so a stored `replicationSource` for that name is re-applied to OUR output on every session
+/// that reproduces the same monitor set. The output then shows the source's viewport instead of
+/// being its own desktop, which is the whole point of creating it — and per the protocol's own note
+/// on `priority`, "an output may not be in the output order if it's disabled **or mirroring another
+/// screen**", so the primary assertion silently stops meaning anything too.
+///
+/// The event carries an empty string for the ordinary case, so `Some("")` must read as "not
+/// mirroring" — treating the mere presence of the event as a mirror would de-mirror every output on
+/// every apply.
+fn is_mirroring(replication_source: Option<&str>) -> bool {
+    replication_source.is_some_and(|s| !s.is_empty())
+}
+
 /// Which topology to apply once our output is resolved.
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub(crate) enum TopologyKind {
@@ -154,6 +182,9 @@ struct DeviceState {
     scale: Option<f64>,
     /// KWin's output priority; 1 is the primary. `None` until the `priority` event (device ≥ v18).
     priority: Option<u32>,
+    /// UUID of the output this one MIRRORS, from the `replication_source` event (device ≥ v13).
+    /// Empty / `None` ⇒ it is its own desktop. See [`is_mirroring`] for why this matters to us.
+    replication_source: Option<String>,
     /// The `current_mode` object id; its size is looked up in [`State::mode_dims`].
     current_mode: Option<ObjectId>,
     /// Every mode this output advertised, in announce order — `(mode object id, proxy)` — so restore
@@ -307,6 +338,7 @@ impl Dispatch<OutputDevice, u32> for State {
             DeviceEvent::Scale { factor } => entry.scale = Some(factor),
             DeviceEvent::Enabled { enabled } => entry.enabled = enabled != 0,
             DeviceEvent::Priority { priority } => entry.priority = Some(priority),
+            DeviceEvent::ReplicationSource { source } => entry.replication_source = Some(source),
             DeviceEvent::CurrentMode { mode } => entry.current_mode = Some(mode.id()),
             DeviceEvent::Mode { mode } => entry.modes.push((mode.id(), mode)),
             DeviceEvent::Done => entry.seen_done = true,
@@ -626,6 +658,17 @@ pub(crate) fn apply_topology(
     };
     let our_uuid = ours.uuid.clone();
     let our_id = ours.proxy.as_ref().map(|p| p.id());
+    if is_mirroring(ours.replication_source.as_deref()) {
+        // Worth a line of its own: this is the state a user experiences as "the stream just shows my
+        // monitor", and it comes from KWin's stored config for THIS monitor set, so it reproduces
+        // every session until something clears it. The config below does.
+        tracing::warn!(
+            source_uuid = ?ours.replication_source,
+            our_prefix,
+            "KWin had our streamed output MIRRORING another screen (a stored kwinoutputconfig.json \
+             replicationSource for this monitor set) — clearing it so the output is its own desktop"
+        );
+    }
 
     // First-slot-wins (§6.1): don't steal primary if another managed sibling already holds it
     // (priority 1) — a 2nd exclusive session joins as a secondary of the shared desktop. A
@@ -681,6 +724,17 @@ pub(crate) fn apply_topology(
     let config = sess.new_config();
     if let Some(proxy) = ours.proxy.as_ref() {
         config.enable(proxy, 1);
+        // State that ours is its OWN desktop, not a replica of somebody's panel. A stored
+        // `replicationSource` for our (stable) output name is re-applied by KWin on every session
+        // that reproduces the same monitor set, and it survives everything else this config says:
+        // enabling and prioritising a mirror still leaves it showing the source's viewport, scaled
+        // to the source's size (`OutputConfigurationStore::applyMirroring`). See [`is_mirroring`].
+        // Unconditional rather than conditional on what we enumerated: KWin may apply the stored
+        // setup config between our enumerate and this apply, and clearing a source that is already
+        // empty is exactly what KWin does for a non-mirroring output anyway.
+        if mgmt_version >= REPLICATION_SOURCE_SINCE {
+            config.set_replication_source(proxy, NO_REPLICATION_SOURCE.to_string());
+        }
         if !sibling_is_primary {
             config.set_primary_output(proxy);
             if mgmt_version >= 3 {
@@ -781,6 +835,68 @@ pub(crate) fn apply_topology(
     }
 }
 
+/// De-mirror the just-created virtual output (name starts with `our_prefix`, current size
+/// `our_w`×`our_h`) **without touching the rest of the topology** — the `Extend`/`Auto` counterpart
+/// to the clear [`apply_topology`] folds into its own config.
+///
+/// Those topologies deliberately issue no output-management calls: the streamed output is meant to
+/// join the desk as one more head, and re-arranging the user's screens would be the rudeness the
+/// setting exists to avoid. But a stored `replicationSource` (see [`is_mirroring`]) is not an
+/// arrangement — it makes our output show a *physical panel's* viewport instead of its own desktop,
+/// which is broken under every topology equally. So this reads the state and applies **only** when
+/// our output really is mirroring; the ordinary session pays one bounded enumerate and no apply.
+pub(crate) fn clear_replication_source(our_prefix: &str, our_w: u32, our_h: u32) {
+    let Some(mut sess) = Session::open() else {
+        return;
+    };
+    let deadline = Instant::now() + OP_BUDGET;
+    let mgmt_version = sess
+        .state
+        .mgmt_name_version
+        .map(|(_, v)| v)
+        .unwrap_or_default();
+    if mgmt_version < REPLICATION_SOURCE_SINCE {
+        return;
+    }
+    // Same resolve as `apply_topology`: managed-prefix name AND the birth size, newest global wins.
+    let Some(ours) = sess
+        .state
+        .devices
+        .values()
+        .filter(|d| {
+            d.name.as_deref().is_some_and(|n| n.starts_with(our_prefix))
+                && sess.current_dims(d).map(|(w, h, _)| (w, h)) == Some((our_w, our_h))
+        })
+        .max_by_key(|d| d.global)
+        .cloned()
+    else {
+        return;
+    };
+    if !is_mirroring(ours.replication_source.as_deref()) {
+        return;
+    }
+    let Some(proxy) = ours.proxy.as_ref() else {
+        return;
+    };
+    tracing::warn!(
+        source_uuid = ?ours.replication_source,
+        our_prefix,
+        "KWin had our streamed output MIRRORING another screen (a stored kwinoutputconfig.json \
+         replicationSource for this monitor set) — clearing it so the output is its own desktop"
+    );
+    let config = sess.new_config();
+    config.set_replication_source(proxy, NO_REPLICATION_SOURCE.to_string());
+    let ok = sess.apply(&config, deadline);
+    config.destroy();
+    if !ok {
+        tracing::warn!(
+            reason = ?sess.state.failure_reason,
+            "KWin output management: could not clear the streamed output's replication source — \
+             the stream will show the mirrored screen's content"
+        );
+    }
+}
+
 /// Install + select a `want_w`×`want_h`@`want_hz` custom mode on the just-created virtual output
 /// (name starts with `our_prefix`, currently at its sacrificial birth size `birth_w`×`birth_h`) —
 /// entirely over `kde_output_management_v2`, the in-process replacement for the `kscreen-doctor`
@@ -1010,6 +1126,37 @@ fn find_mode(sess: &Session, dev: &DeviceState, spec: &str) -> Option<DeviceMode
 mod tests {
     use super::*;
 
+    /// KWin sends `replication_source` with an EMPTY string for the ordinary, non-mirroring output.
+    /// Reading the event's mere presence as "mirroring" would make every apply issue a pointless
+    /// de-mirror — and, worse, would make the warn fire on every healthy session.
+    #[test]
+    fn an_empty_replication_source_is_not_mirroring() {
+        assert!(!is_mirroring(None));
+        assert!(!is_mirroring(Some("")));
+    }
+
+    /// A real source UUID is the state the field report describes: the streamed output shows a
+    /// physical panel's viewport instead of its own desktop.
+    #[test]
+    fn a_uuid_replication_source_is_mirroring() {
+        assert!(is_mirroring(Some("f7a3c1e2-0b44-4c19-9a1d-6f2b8e0c5d31")));
+    }
+
+    /// The clear we send must be the value KWin reads as "mirrors nothing" — an empty source, which
+    /// its `applyMirroring` fails to resolve to any enabled output and so treats as no replication.
+    #[test]
+    fn the_clear_value_is_the_empty_source() {
+        assert!(!is_mirroring(Some(NO_REPLICATION_SOURCE)));
+    }
+
+    /// The request/event pair is `since 13`; wayland-rs does not range-check requests, so a bind
+    /// below this must never reach `set_replication_source` (it would be a fatal protocol error).
+    #[test]
+    fn replication_source_version_gate_matches_the_protocol() {
+        assert_eq!(REPLICATION_SOURCE_SINCE, 13);
+        const { assert!(MGMT_MAX >= REPLICATION_SOURCE_SINCE) };
+    }
+
     /// The `WxH@Hz` capture rounds mHz to whole Hz — the shape teardown parses back.
     #[test]
     fn mode_spec_rounds_millihertz() {

crates/punktfunk-core/src/abi.rs

@@ -4116,7 +4116,11 @@ pub struct PunktfunkProbeResult {
     /// Application goodput bytes / access units the host offered.
     pub host_bytes: u64,
     pub host_packets: u32,
-    /// The host's measured burst duration, milliseconds (the throughput denominator).
+    /// The throughput denominator, milliseconds: the client-measured burst receive interval
+    /// (first → last probe-packet arrival) once `done`; the host's measured send-window
+    /// duration when fewer than two probe packets arrived (no interval to measure from). The
+    /// host duration alone overstates throughput — its window closes while the bottleneck
+    /// queue is still draining toward the client.
     pub elapsed_ms: u32,
     /// Delivered wire throughput = `recv_bytes * 8 / elapsed_ms` (kilobits/second).
     pub throughput_kbps: u32,
@@ -4130,7 +4134,7 @@ pub struct PunktfunkProbeResult {
 }
 
 /// Start a bandwidth speed test: ask the host to burst filler over the data plane at
-/// `target_kbps` of goodput for `duration_ms` (each clamped host-side to ≤ 3 Gbps / ≤ 5 s),
+/// `target_kbps` of goodput for `duration_ms` (each clamped host-side to ≤ 10 Gbps / ≤ 5 s),
 /// *briefly pausing video*. Non-blocking — poll [`punktfunk_connection_probe_result`] until its
 /// `done` field is 1. Starting a probe resets any prior measurement.
 ///

crates/punktfunk-core/src/abr.rs

@@ -31,6 +31,10 @@
 //! after ~4.5 s clean, ceilinged). Changes are rate-limited (each one costs the IDR the host's
 //! rebuilt encoder opens with) and the whole controller disables itself against a host that never
 //! answers [`crate::quic::BitrateChanged`] (an older build that ignores unknown control messages).
+//! Standing limits are LEARNED rather than re-poked: two identical short host acks latch the
+//! encoder's ceiling (`host_cap_kbps`), two consecutive decode-severe backoffs at a similar rate
+//! latch the client decoder's knee (`decode_cap_kbps`) — and both re-probe slowly
+//! ([`CAP_REPROBE_WINDOWS`]) so neither latch outlives the condition that taught it.
 //!
 //! Climbs are additionally **evidence-gated**. The target is only a *promise* to the encoder —
 //! how many bits it actually emits depends on the content — so on calm content (a menu, an idle
@@ -129,7 +133,16 @@ const ENCODE_SEVERE_US: i64 = 12_000;
 /// evidence, not a spec limit — without a re-probe, one heavy scene would cap the whole
 /// session. A still-standing limit just re-teaches itself in two short acks, which the host
 /// pre-clamps without touching the encoder — the re-probe costs no rebuild, no IDR.
+/// The [`decode cap`](BitrateController::decode_cap_kbps) re-probes on the same clock for the
+/// same reason: the decoder's knee moves with content and thermals, so its latch must not be
+/// permanent either.
 const CAP_REPROBE_WINDOWS: u32 = 80;
+/// Two consecutive decode-driven backoffs latch the
+/// [`decode cap`](BitrateController::decode_cap_kbps) only when their pre-backoff rates agree
+/// within ±1/8: the decoder's knee is a RATE, so repeated chokes at the same rate are its
+/// signature — two unrelated events (a Wi-Fi flush at 300 Mbps, a decode spike at 500) share
+/// no knee and must not teach one.
+const DECODE_CAP_SIMILAR_DIV: u32 = 8;
 /// Rolling window (in 750 ms report windows, ~30 s) whose minimum mean is the OWD baseline.
 /// Long enough to remember the uncongested floor, short enough to follow genuine path changes.
 const BASELINE_WINDOWS: usize = 40;
@@ -137,6 +150,23 @@ const BASELINE_WINDOWS: usize = 40;
 /// predates bitrate renegotiation and going quiet for the rest of the session.
 const MAX_UNACKED: u32 = 3;
 
+/// Operator escape hatch: `PUNKTFUNK_ABR_MAX_MBPS` (megabits/second, the
+/// `PUNKTFUNK_PYROWAVE_MAX_MBPS` convention) caps the climb ceiling however it is learned.
+/// The startup link-capacity probe MEASURES the ceiling, and
+/// [`set_ceiling`](BitrateController::set_ceiling)'s deliberate monotonicity makes an inflated
+/// measurement permanent for the session — a link that mis-measures (a bursty middlebox, a
+/// queue-flattered interval) needs a knob that binds regardless of what any probe claims.
+/// `PUNKTFUNK_ABR_PROBE_KBPS` is NOT that knob: it only shrinks the burst target, not what the
+/// measurement may conclude. Unset/0/garbage → no cap. Read once per controller, at
+/// construction.
+fn ceiling_cap_from_env() -> Option<u32> {
+    std::env::var("PUNKTFUNK_ABR_MAX_MBPS")
+        .ok()
+        .and_then(|v| v.trim().parse::<u32>().ok())
+        .filter(|&m| m > 0)
+        .map(|m| m.saturating_mul(1_000))
+}
+
 /// One decision per report window; `Some(kbps)` = send a [`crate::quic::SetBitrate`].
 pub(crate) struct BitrateController {
     /// `false` = permanently off (explicit user bitrate, an old host, or ack silence).
@@ -147,6 +177,10 @@ pub(crate) struct BitrateController {
     /// raises it via [`set_ceiling`](Self::set_ceiling) — that measurement is what lets an
     /// Automatic session scale past its conservative start.
     ceiling_kbps: u32,
+    /// The `PUNKTFUNK_ABR_MAX_MBPS` cap in kbps (see [`ceiling_cap_from_env`]), injected at
+    /// construction so tests exercise the clamp without touching the process environment.
+    /// `None` = no cap.
+    ceiling_cap_kbps: Option<u32>,
     floor_kbps: u32,
     /// Slow start: true until the first congestion signal — clean windows DOUBLE the rate
     /// (cooldown-paced) instead of the +6 % additive step.
@@ -178,6 +212,24 @@ pub(crate) struct BitrateController {
     short_acks: u32,
     /// Clean windows spent parked at the learned cap (the re-probe clock).
     cap_probe_windows: u32,
+    /// The client-decoder rate cap, mirroring [`host_cap_kbps`](Self::host_cap_kbps) for the
+    /// OTHER end of the pipe: latched when two CONSECUTIVE backoffs carried decode-severe
+    /// evidence (a deep decode-latency excursion, or a jump-to-live flush — in the
+    /// decoder-saturation regime the flushed backlog formed BEHIND a decoder that stopped
+    /// keeping up) at a similar pre-backoff rate. Without it a decoder knee below the link
+    /// ceiling is a permanent 30–60 s sawtooth: every ×0.7 backoff re-climbs toward a ceiling
+    /// the decoder can't hold, and each cycle costs a flush plus a dropped-frame burst (the
+    /// 1440p120 HEVC field case: knee ~490 Mbps under a ~658 Mbps ceiling). Slowly re-probed
+    /// on the [`CAP_REPROBE_WINDOWS`] clock, exactly like the host cap, so a decoder that
+    /// recovers (lighter content, thermal headroom) climbs again — the latch is never
+    /// permanent.
+    decode_cap_kbps: Option<u32>,
+    /// The previous decode-driven backoff's pre-backoff rate (0 = the last backoff wasn't
+    /// decode-driven): the reference the next one must land near ([`DECODE_CAP_SIMILAR_DIV`])
+    /// to latch the cap — one spurious flush teaches nothing.
+    decode_backoff_kbps: u32,
+    /// Clean windows spent parked at the learned decode cap (its re-probe clock).
+    decode_cap_probe_windows: u32,
     /// Proven throughput: the session's highest windowed ACTUAL delivered rate seen with flat
     /// decode latency — the known-good high-water mark climbs are bounded against. Never decays;
     /// shrinking capacity (thermals, a heavier scene) is the reactive decode signal's job. On
@@ -196,10 +248,17 @@ impl BitrateController {
     /// to build a permanently-disabled controller (explicit bitrate / an old host that didn't
     /// echo one — no known ceiling to work against).
     pub(crate) fn new(start_kbps: u32) -> Self {
+        Self::with_ceiling_cap(start_kbps, ceiling_cap_from_env())
+    }
+
+    /// [`new`](Self::new) with the `PUNKTFUNK_ABR_MAX_MBPS` cap injected — the seam the unit
+    /// tests use so the clamp's behavior never depends on the test process's environment.
+    fn with_ceiling_cap(start_kbps: u32, ceiling_cap_kbps: Option<u32>) -> Self {
         BitrateController {
             enabled: start_kbps > 0,
             current_kbps: start_kbps,
             ceiling_kbps: start_kbps,
+            ceiling_cap_kbps,
             floor_kbps: FLOOR_KBPS.min(start_kbps.max(1)),
             probing: true,
             owd_means: VecDeque::with_capacity(BASELINE_WINDOWS),
@@ -210,6 +269,9 @@ impl BitrateController {
             short_ack_kbps: 0,
             short_acks: 0,
             cap_probe_windows: 0,
+            decode_cap_kbps: None,
+            decode_backoff_kbps: 0,
+            decode_cap_probe_windows: 0,
             proven_kbps: 0,
             bad_windows: 0,
             clean_windows: 0,
@@ -222,8 +284,12 @@ impl BitrateController {
     /// delivered throughput with headroom already subtracted by the caller). Without this call
     /// the ceiling stays the negotiated start rate — exactly the old behavior. Never lowers:
     /// a congested-moment measurement must not shrink authority below what was negotiated
-    /// (descent is the congestion signals' job).
+    /// (descent is the congestion signals' job). The `PUNKTFUNK_ABR_MAX_MBPS` cap clamps HERE
+    /// — the one funnel every learned ceiling passes through — so it binds no matter how the
+    /// ceiling was learned; monotonicity is precisely why the user needs it (one inflated
+    /// measurement is otherwise permanent for the session).
     pub(crate) fn set_ceiling(&mut self, kbps: u32) {
+        let kbps = kbps.min(self.ceiling_cap_kbps.unwrap_or(u32::MAX));
         if self.enabled && kbps > self.ceiling_kbps {
             self.ceiling_kbps = kbps;
         }
@@ -274,11 +340,16 @@ impl BitrateController {
 
     /// An accepted mode switch: the encoder's ceiling and compute knee are properties of the
     /// MODE (4K120 caps where 1080p60 never would) — drop the mode-scoped learned state. The
-    /// probe-measured `ceiling_kbps` (a LINK property) survives.
+    /// decoder's knee is just as mode-scoped (pixel rate drives both ends of the codec), so
+    /// the decode cap goes with it. The probe-measured `ceiling_kbps` (a LINK property)
+    /// survives.
     pub(crate) fn on_mode_switch(&mut self) {
         self.host_cap_kbps = None;
         self.short_acks = 0;
         self.cap_probe_windows = 0;
+        self.decode_cap_kbps = None;
+        self.decode_backoff_kbps = 0;
+        self.decode_cap_probe_windows = 0;
         self.encode_means.clear();
     }
 
@@ -427,6 +498,30 @@ impl BitrateController {
                 }
             }
         }
+        // The decode cap re-probes on the same clock and for the same reason: the knee is
+        // content- and thermals-dependent evidence, not a spec limit — a decoder that recovers
+        // must get its headroom back, so the latch clears UPWARD through here rather than ever
+        // being permanent. A still-standing knee re-latches from the next pair of
+        // decode-driven backoffs.
+        if let Some(cap) = self.decode_cap_kbps {
+            if bad {
+                self.decode_cap_probe_windows = 0;
+            } else if self.current_kbps >= cap.saturating_sub(cap / 16) {
+                self.decode_cap_probe_windows += 1;
+                if self.decode_cap_probe_windows >= CAP_REPROBE_WINDOWS {
+                    self.decode_cap_probe_windows = 0;
+                    let lifted = cap.saturating_add(cap / 8).min(self.ceiling_kbps);
+                    if lifted > cap {
+                        tracing::debug!(
+                            from_kbps = cap,
+                            to_kbps = lifted,
+                            "adaptive bitrate: re-probing above the learned decode cap"
+                        );
+                        self.decode_cap_kbps = Some(lifted);
+                    }
+                }
+            }
+        }
         let cooled = self
             .last_change
             .is_none_or(|t| now.duration_since(t) >= CHANGE_COOLDOWN);
@@ -436,6 +531,31 @@ impl BitrateController {
         if (self.bad_windows >= BAD_WINDOWS_TO_DECREASE || (severe && self.bad_windows >= 1))
             && self.current_kbps > self.floor_kbps
         {
+            // Decode-cap learning (see [`decode_cap_kbps`](Self::decode_cap_kbps)): a backoff
+            // with decode-severe evidence — the deep decode excursion, or the flush that
+            // drained the queue behind a stalled decoder — remembers its pre-backoff rate; the
+            // SECOND consecutive one at a similar rate latches that rate as the decoder's
+            // knee. One event never latches (a spurious flush must stay a one-off), and a
+            // backoff without decode evidence in between breaks the streak — whatever it saw,
+            // it wasn't the same knee.
+            if decode_severe || flushed {
+                let rate = self.current_kbps;
+                let similar = self.decode_backoff_kbps > 0
+                    && rate.abs_diff(self.decode_backoff_kbps)
+                        <= self.decode_backoff_kbps / DECODE_CAP_SIMILAR_DIV;
+                if similar && self.decode_cap_kbps.is_none_or(|c| rate < c) {
+                    tracing::info!(
+                        cap_kbps = rate,
+                        "adaptive bitrate: decode cap learned (decoder knee) — climbs stop \
+                         here until it lifts"
+                    );
+                    self.decode_cap_kbps = Some(rate.max(self.floor_kbps));
+                    self.decode_cap_probe_windows = 0;
+                }
+                self.decode_backoff_kbps = rate;
+            } else {
+                self.decode_backoff_kbps = 0;
+            }
             let next = ((self.current_kbps as u64 * 7 / 10) as u32).max(self.floor_kbps);
             self.bad_windows = 0;
             return self.request(next, now);
@@ -447,11 +567,13 @@ impl BitrateController {
         // utilized window after a long-enough clean run climbs immediately.
         let utilized =
             actual_kbps as u64 * UTILIZATION_DEN >= self.current_kbps as u64 * UTILIZATION_NUM;
-        // The effective ceiling folds in the host-taught cap: the probe measured the LINK, but
-        // the host's short acks measured the ENCODER — whichever binds first is the limit.
+        // The effective ceiling folds in both learned caps: the probe measured the LINK, the
+        // host's short acks measured the ENCODER, and the decode cap measured the CLIENT
+        // DECODER — whichever binds first is the limit.
         let eff_ceiling = self
             .ceiling_kbps
-            .min(self.host_cap_kbps.unwrap_or(u32::MAX));
+            .min(self.host_cap_kbps.unwrap_or(u32::MAX))
+            .min(self.decode_cap_kbps.unwrap_or(u32::MAX));
         let cap = eff_ceiling
             .min(self.proven_kbps.saturating_mul(PROVEN_HEADROOM_NUM) / PROVEN_HEADROOM_DEN);
         if self.current_kbps < eff_ceiling && utilized && cap > self.current_kbps {
@@ -1447,6 +1569,243 @@ mod tests {
         }
     }
 
+    #[test]
+    fn env_max_mbps_caps_every_learned_ceiling() {
+        // PUNKTFUNK_ABR_MAX_MBPS=50 (injected — `new` reads the env exactly once, at
+        // construction): a probe "measuring" 886 Mbps (the divisor bug's field figure) must
+        // not out-rank the user's cap…
+        let mut c = BitrateController::with_ceiling_cap(20_000, Some(50_000));
+        c.set_ceiling(886_312);
+        assert_eq!(c.ceiling_kbps, 50_000);
+        // …while a measurement under the cap stands untouched.
+        let mut c = BitrateController::with_ceiling_cap(20_000, Some(50_000));
+        c.set_ceiling(40_000);
+        assert_eq!(c.ceiling_kbps, 40_000);
+        // And the climb honors it: slow start doubles 20→40, the capped ceiling truncates the
+        // next step to 50, then quiet — never a request past the user's limit.
+        let mut c = BitrateController::with_ceiling_cap(20_000, Some(50_000));
+        c.set_ceiling(886_312);
+        let start = Instant::now();
+        assert_eq!(run_clean(&mut c, start, 0, 1), Some(40_000));
+        c.on_ack(40_000);
+        assert_eq!(run_clean(&mut c, start, 2, 1), Some(50_000));
+        c.on_ack(50_000);
+        assert_eq!(run_clean(&mut c, start, 4, 20), None);
+    }
+
+    #[test]
+    fn decode_cap_latches_after_two_consecutive_decode_severe_backoffs() {
+        // The 1440p120 field sawtooth: a decoder knee (~500 Mbps) well under the (inflated)
+        // link ceiling — nothing ever LEARNED the knee, so every re-climb ended in a flush +
+        // dropped-frame burst. Establish a decode baseline on calm windows, choke twice at the
+        // same rate, and the second decode-severe backoff must latch the knee.
+        let mut c = BitrateController::new(500_000);
+        c.set_ceiling(900_000);
+        let start = Instant::now();
+        // Calm baseline windows (2 Mb/s actual: unutilized, so no climb interferes).
+        for i in 0..4 {
+            assert_eq!(
+                c.on_window(
+                    ticks(start, i),
+                    0,
+                    0,
+                    Some(10_000),
+                    Some(8_000),
+                    None,
+                    2_000,
+                    false,
+                    0
+                ),
+                None
+            );
+        }
+        // First deep decode excursion → immediate ×0.7, but ONE event must not latch.
+        assert_eq!(
+            c.on_window(
+                ticks(start, 4),
+                0,
+                0,
+                Some(10_000),
+                Some(60_000),
+                None,
+                490_000,
+                false,
+                0
+            ),
+            Some(350_000)
+        );
+        assert!(c.decode_cap_kbps.is_none());
+        // Second consecutive decode-severe backoff at the same pre-backoff rate: latch.
+        assert_eq!(
+            c.on_window(
+                ticks(start, 6),
+                0,
+                0,
+                Some(10_000),
+                Some(60_000),
+                None,
+                490_000,
+                false,
+                0
+            ),
+            Some(350_000)
+        );
+        assert_eq!(c.decode_cap_kbps, Some(500_000));
+        // The backoff applies; from here every climb must stop AT the knee — not the 900 Mbps
+        // link ceiling the old sawtooth kept re-poking.
+        c.on_ack(350_000);
+        let mut max_req = 0;
+        for i in 8..70 {
+            if let Some(k) = c.on_window(
+                ticks(start, i),
+                0,
+                0,
+                Some(10_000),
+                Some(8_000),
+                None,
+                1_000_000,
+                false,
+                0,
+            ) {
+                assert!(k <= 500_000, "climb past the decode cap: {k}");
+                max_req = max_req.max(k);
+                c.on_ack(k);
+            }
+        }
+        assert_eq!(max_req, 500_000);
+        assert_eq!(c.current_kbps, 500_000);
+        assert_eq!(c.decode_cap_kbps, Some(500_000));
+    }
+
+    #[test]
+    fn a_single_flush_or_dissimilar_backoffs_never_latch_a_decode_cap() {
+        // The latch's false-positive guards. A lone jump-to-live flush (a Wi-Fi clump can
+        // flush once at ANY rate) backs off but teaches nothing…
+        let mut c = BitrateController::new(500_000);
+        c.set_ceiling(900_000);
+        let start = Instant::now();
+        assert_eq!(
+            c.on_window(ticks(start, 0), 0, 0, None, None, None, 490_000, true, 0),
+            Some(350_000)
+        );
+        assert!(c.decode_cap_kbps.is_none());
+        c.on_ack(350_000);
+        // …a LOSS-driven backoff in between breaks the streak…
+        assert_eq!(
+            c.on_window(ticks(start, 2), 1, 0, None, None, None, 340_000, false, 0),
+            Some(245_000)
+        );
+        assert!(c.decode_cap_kbps.is_none());
+        c.on_ack(245_000);
+        // …so the next flush counts as a FIRST decode event again — still no latch…
+        assert_eq!(
+            c.on_window(ticks(start, 4), 0, 0, None, None, None, 240_000, true, 0),
+            Some(171_500)
+        );
+        assert!(c.decode_cap_kbps.is_none());
+        c.on_ack(171_500);
+        // …and two consecutive decode events at DISSIMILAR rates (245 vs 171.5 Mbps — no
+        // common knee) must not latch either.
+        assert_eq!(
+            c.on_window(ticks(start, 6), 0, 0, None, None, None, 170_000, true, 0),
+            Some(120_050)
+        );
+        assert!(c.decode_cap_kbps.is_none());
+    }
+
+    #[test]
+    fn decode_cap_reprobes_after_a_sustained_clean_run() {
+        // The knee is content/thermals evidence, not a spec limit: after ~60 s parked clean at
+        // the latched cap, it lifts one step (+12.5 %, ceiling-bounded) — the re-probe path is
+        // how the latch clears (never permanent), and a still-standing knee just re-latches
+        // from the next pair of decode-driven backoffs.
+        let mut c = BitrateController::new(500_000);
+        c.set_ceiling(900_000);
+        let start = Instant::now();
+        for i in 0..4 {
+            let _ = c.on_window(
+                ticks(start, i),
+                0,
+                0,
+                Some(10_000),
+                Some(8_000),
+                None,
+                2_000,
+                false,
+                0,
+            );
+        }
+        for i in [4, 6] {
+            let _ = c.on_window(
+                ticks(start, i),
+                0,
+                0,
+                Some(10_000),
+                Some(60_000),
+                None,
+                490_000,
+                false,
+                0,
+            );
+        }
+        assert_eq!(c.decode_cap_kbps, Some(500_000));
+        // The host's ack parks the session at the knee (its clamp is authoritative).
+        c.on_ack(500_000);
+        for i in 0..CAP_REPROBE_WINDOWS {
+            let _ = c.on_window(
+                ticks(start, 8 + i),
+                0,
+                0,
+                Some(10_000),
+                Some(8_000),
+                None,
+                490_000,
+                false,
+                0,
+            );
+        }
+        assert_eq!(c.decode_cap_kbps, Some(500_000 + 500_000 / 8));
+    }
+
+    #[test]
+    fn mode_switch_clears_the_decode_cap() {
+        // A 1440p120 knee means nothing at the new mode's pixel rate — the decode cap must
+        // not survive the switch (the probe-measured link ceiling does).
+        let mut c = BitrateController::new(500_000);
+        c.set_ceiling(900_000);
+        let start = Instant::now();
+        for i in 0..4 {
+            let _ = c.on_window(
+                ticks(start, i),
+                0,
+                0,
+                Some(10_000),
+                Some(8_000),
+                None,
+                2_000,
+                false,
+                0,
+            );
+        }
+        for i in [4, 6] {
+            let _ = c.on_window(
+                ticks(start, i),
+                0,
+                0,
+                Some(10_000),
+                Some(60_000),
+                None,
+                490_000,
+                false,
+                0,
+            );
+        }
+        assert_eq!(c.decode_cap_kbps, Some(500_000));
+        c.on_mode_switch();
+        assert!(c.decode_cap_kbps.is_none());
+        assert_eq!(c.ceiling_kbps, 900_000);
+    }
+
     #[test]
     fn ack_silence_disables_the_controller() {
         let mut c = BitrateController::new(20_000);

crates/punktfunk-core/src/client/mod.rs

@@ -883,7 +883,7 @@ impl NativeClient {
     /// `target_kbps` of goodput for `duration_ms`, *briefly pausing video*. Non-blocking — the
     /// measurement accumulates in the background; poll [`NativeClient::probe_result`] until its
     /// `done` flag is set. Starting a probe resets any prior measurement. The host clamps both
-    /// fields (≤ 3 Gbps, ≤ 5 s).
+    /// fields (≤ 10 Gbps, ≤ 5 s).
     pub fn request_probe(&self, target_kbps: u32, duration_ms: u32) -> Result<()> {
         // Reset the accumulator so a fresh run doesn't blend into the previous one.
         *self.probe.lock().unwrap() = ProbeState {
@@ -922,8 +922,12 @@ impl NativeClient {
                 p.rx_bytes_now.saturating_sub(base_b),
             )
         };
-        // The host's burst duration is the throughput denominator. bytes × 8 / ms = kilobits/second.
-        let window_ms = p.host_duration_ms;
+        // The throughput denominator: the client-measured receive interval once the report
+        // froze one, the host's send-window duration as the fallback (see
+        // `ProbeState::measured_interval_ms` for why the host window alone overstates the
+        // link). Both are 0 until the report lands, so a partial read reports 0 throughput —
+        // unchanged. bytes × 8 / ms = kilobits/second.
+        let window_ms = p.throughput_window_ms();
         let throughput_kbps = if window_ms > 0 {
             (delivered_bytes.saturating_mul(8) / window_ms as u64) as u32
         } else {

crates/punktfunk-core/src/client/probe.rs

@@ -1,34 +1,50 @@
 //! Speed-test probe state (`ProbeState`, pump-mirrored) and the public `ProbeOutcome`.
 
 /// Accumulated state of an in-flight / finished speed test. The data-plane pump mirrors the
-/// session's packet-level receive counters here; the control task finalizes the delivered figure
+/// session's probe-scoped receive counters here; the control task finalizes the delivered figure
 /// and folds in the host's [`ProbeResult`] when it lands. Read by [`NativeClient::probe_result`].
 ///
 /// Counting at the *packet* level (every delivered wire packet) — not whole reassembled probe AUs —
 /// is what makes the measurement degrade gracefully: once loss exceeds the FEC budget no AU
 /// completes, so the old AU-based count cliffed to zero even though most bytes still arrived.
+/// Counting *probe* packets only (the reassembler stamps dedicated counters at its FLAG_PROBE
+/// routing) keeps video out of the numerator: the burst pauses video, but frames already in
+/// flight land during its head, and resumed video lands between the last probe packet and the
+/// host's report — both used to inflate the all-datagram byte delta this mirrored before.
 #[derive(Default)]
 pub(crate) struct ProbeState {
     /// A probe is in progress: set by `request_probe`, cleared when the host's [`ProbeResult`]
     /// lands (a re-probe just overwrites the whole state — the latest one wins).
     pub(crate) active: bool,
-    /// `session.stats()` receive counters at the burst's start (snapshotted by the pump on its first
-    /// tick while active) and latest, mirrored every pump iteration.
+    /// Probe-scoped receive counters (`Stats::probe_*`) at the burst's start (snapshotted by the
+    /// pump on its first tick while active) and latest, mirrored every pump iteration.
     pub(crate) base_packets: Option<u64>,
     pub(crate) base_bytes: Option<u64>,
     pub(crate) rx_packets_now: u64,
     pub(crate) rx_bytes_now: u64,
+    /// First / last probe-packet arrival stamps (monotonic ns, 0 = none yet), mirrored from the
+    /// probe-scoped session counters. Their difference is the interval the delivered bytes
+    /// actually arrived in — the honest throughput denominator (see
+    /// [`measured_interval_ms`](Self::measured_interval_ms)).
+    pub(crate) first_arrival_ns: u64,
+    pub(crate) last_arrival_ns: u64,
     /// Delivered wire packets / plaintext bytes (header + shard), frozen when the host's report lands
     /// (so resumed video after the burst can't inflate them).
     pub(crate) delivered_packets: u64,
     pub(crate) delivered_bytes: u64,
+    /// The client-measured receive interval (ms), frozen alongside the delivered figures; 0 = no
+    /// usable interval (the burst delivered fewer than two probe packets) — consumers fall back
+    /// to [`host_duration_ms`](Self::host_duration_ms) via
+    /// [`throughput_window_ms`](Self::throughput_window_ms).
+    pub(crate) client_interval_ms: u32,
     /// The host's end-of-burst report.
     pub(crate) host_goodput_bytes: u64,
     pub(crate) host_au: u32,
     /// Wire packets the host actually put on the link, and the ones its send buffer dropped.
     pub(crate) host_wire_packets: u32,
     pub(crate) host_send_dropped: u32,
-    /// The host's measured burst duration (the throughput denominator).
+    /// The host's measured burst duration (the throughput denominator's FALLBACK — see
+    /// [`throughput_window_ms`](Self::throughput_window_ms)).
     pub(crate) host_duration_ms: u32,
     /// The host's `ProbeResult` arrived → the measurement is final.
     pub(crate) done: bool,
@@ -39,6 +55,40 @@ pub(crate) struct ProbeState {
     pub(crate) duration_ms: u32,
 }
 
+impl ProbeState {
+    /// The client-measured receive interval of a finished burst, in ms: first → last
+    /// probe-packet arrival, floored at 1 (a sub-ms burst divided by 0 ms would read as
+    /// infinite throughput). `None` — the caller falls back to the host's duration — when
+    /// fewer than two probe packets arrived or the stamps are degenerate (unset / identical /
+    /// reversed): a single arrival spans no interval.
+    ///
+    /// Why not the host's `duration_ms`: it measures the SEND window, which closes while the
+    /// bottleneck (switch/kernel) queue is still draining toward the client — the tail of the
+    /// bytes lands *after* it. Dividing client-side bytes by the host-side window therefore
+    /// overstates the link: a 1 GbE link under a 2 Gbps burst target "measured" 1266 Mbps and
+    /// handed the ABR an 886 Mbps ceiling it could never deliver — and
+    /// [`set_ceiling`](crate::abr::BitrateController::set_ceiling) never lowers, so the lie
+    /// was permanent for the session.
+    pub(crate) fn measured_interval_ms(first_ns: u64, last_ns: u64, packets: u64) -> Option<u32> {
+        if packets < 2 || first_ns == 0 || last_ns <= first_ns {
+            return None;
+        }
+        let ms = ((last_ns - first_ns) / 1_000_000).max(1);
+        Some(u32::try_from(ms).unwrap_or(u32::MAX))
+    }
+
+    /// The throughput denominator, in ms: the client-measured receive interval when the burst
+    /// produced one, else the host's send-window duration (an old measurement is better than
+    /// none — and strictly conservative territory only when packets were too few to matter).
+    pub(crate) fn throughput_window_ms(&self) -> u32 {
+        if self.client_interval_ms > 0 {
+            self.client_interval_ms
+        } else {
+            self.host_duration_ms
+        }
+    }
+}
+
 /// A finished/partial speed-test measurement, returned by [`NativeClient::probe_result`].
 #[derive(Clone, Copy, Debug, Default)]
 pub struct ProbeOutcome {
@@ -50,7 +100,11 @@ pub struct ProbeOutcome {
     /// Application goodput bytes / access units the host offered.
     pub host_bytes: u64,
     pub host_packets: u32,
-    /// The burst duration the host measured, in milliseconds (the throughput denominator).
+    /// The throughput denominator, in milliseconds: the client-measured receive interval
+    /// (first → last probe-packet arrival) once `done`; the host's measured send-window
+    /// duration when the burst delivered fewer than two probe packets (no interval to measure
+    /// from). The host duration alone overstates throughput — its window closes while the
+    /// bottleneck queue is still draining toward the client.
     pub elapsed_ms: u32,
     /// Delivered wire throughput = `recv_bytes * 8 / elapsed_ms` (kilobits/second). The figure to
     /// drive a [`Hello::bitrate_kbps`] choice from (allow headroom for the FEC overhead + loss).
@@ -66,3 +120,63 @@ pub struct ProbeOutcome {
     pub wire_packets_sent: u32,
     pub send_dropped: u32,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn interval_needs_two_packets_and_a_nonzero_span() {
+        // <2 packets: no interval exists — the caller must fall back to the host duration.
+        assert_eq!(ProbeState::measured_interval_ms(0, 0, 0), None);
+        assert_eq!(
+            ProbeState::measured_interval_ms(5_000_000, 5_000_000, 1),
+            None
+        );
+        // Two packets in the same ns / a reversed pair / an unset first stamp: same fallback.
+        assert_eq!(
+            ProbeState::measured_interval_ms(5_000_000, 5_000_000, 2),
+            None
+        );
+        assert_eq!(
+            ProbeState::measured_interval_ms(9_000_000, 5_000_000, 2),
+            None
+        );
+        assert_eq!(ProbeState::measured_interval_ms(0, 5_000_000, 2), None);
+    }
+
+    #[test]
+    fn interval_is_floored_at_one_ms() {
+        // Two packets 0.4 ms apart truncate to 0 ms — the floor keeps the division honest
+        // instead of infinite.
+        assert_eq!(ProbeState::measured_interval_ms(1_000, 401_000, 2), Some(1));
+    }
+
+    #[test]
+    fn interval_measures_first_to_last_arrival() {
+        assert_eq!(
+            ProbeState::measured_interval_ms(1_000_000, 801_000_000, 1_000),
+            Some(800)
+        );
+    }
+
+    #[test]
+    fn throughput_window_falls_back_to_the_host_duration() {
+        // No client interval frozen (a <2-packet burst) → the host's send window is the
+        // denominator, exactly the old behavior.
+        let p = ProbeState {
+            host_duration_ms: 800,
+            ..Default::default()
+        };
+        assert_eq!(p.throughput_window_ms(), 800);
+        // With an interval, the client measurement wins — the 1 GbE field case: the same
+        // bytes over 1010 ms instead of the host's 800 ms is the difference between an
+        // honest ~940 Mbps and an impossible 1266 Mbps.
+        let p = ProbeState {
+            client_interval_ms: 1_010,
+            host_duration_ms: 800,
+            ..Default::default()
+        };
+        assert_eq!(p.throughput_window_ms(), 1_010);
+    }
+}

crates/punktfunk-core/src/client/pump/control_task.rs

@@ -132,12 +132,24 @@ impl ControlTask {
                         }
                     } else if let Ok(result) = ProbeResult::decode(&msg) {
                         let mut p = probe.lock().unwrap();
-                        // Freeze the delivered figures now (the burst is done), before resumed
-                        // video can inflate the packet counters.
+                        // Freeze the delivered figures now (the burst is done). The mirrored
+                        // counters are probe-scoped (stamped at the reassembler's FLAG_PROBE
+                        // routing), so video around the burst inflates nothing; the client's
+                        // first→last arrival interval is frozen with them — the denominator
+                        // that measures when the bytes actually ARRIVED, not when the host
+                        // stopped sending (its window closes while the bottleneck queue is
+                        // still draining this way, which is how a 1 GbE link once "measured"
+                        // 1266 Mbps).
                         let base_p = p.base_packets.unwrap_or(p.rx_packets_now);
                         let base_b = p.base_bytes.unwrap_or(p.rx_bytes_now);
                         p.delivered_packets = p.rx_packets_now.saturating_sub(base_p);
                         p.delivered_bytes = p.rx_bytes_now.saturating_sub(base_b);
+                        p.client_interval_ms = ProbeState::measured_interval_ms(
+                            p.first_arrival_ns,
+                            p.last_arrival_ns,
+                            p.delivered_packets,
+                        )
+                        .unwrap_or(0);
                         p.host_goodput_bytes = result.bytes_sent;
                         p.host_au = result.packets_sent;
                         p.host_wire_packets = result.wire_packets_sent;
@@ -151,6 +163,7 @@ impl ControlTask {
                             send_dropped = result.send_dropped,
                             duration_ms = result.duration_ms,
                             delivered_packets = p.delivered_packets,
+                            client_interval_ms = p.client_interval_ms,
                             "speed-test probe result"
                         );
                     } else if let Ok(ack) = BitrateChanged::decode(&msg) {

crates/punktfunk-core/src/client/pump/data.rs

@@ -200,10 +200,23 @@ impl DataPump {
             let probe_active = {
                 let mut p = pump_probe.lock().unwrap();
                 if p.active && !p.done {
-                    p.rx_packets_now = st.packets_received;
-                    p.rx_bytes_now = st.bytes_received;
-                    p.base_packets.get_or_insert(st.packets_received);
-                    p.base_bytes.get_or_insert(st.bytes_received);
+                    // Arm edge (first mirror tick): zero the arrival stamps before the burst can
+                    // claim them — the ProbeRequest is still queued locally (the burst starts a
+                    // round trip later), so the reset cannot race a probe packet. `st` predates
+                    // the reset, so the stamps mirror 0 on this tick and live values after.
+                    let arming = p.base_bytes.is_none();
+                    if arming {
+                        session.reset_probe_arrivals();
+                    }
+                    p.rx_packets_now = st.probe_packets_received;
+                    p.rx_bytes_now = st.probe_bytes_received;
+                    (p.first_arrival_ns, p.last_arrival_ns) = if arming {
+                        (0, 0)
+                    } else {
+                        (st.probe_first_arrival_ns, st.probe_last_arrival_ns)
+                    };
+                    p.base_packets.get_or_insert(st.probe_packets_received);
+                    p.base_bytes.get_or_insert(st.probe_bytes_received);
                 }
                 p.active && !p.done
             };
@@ -280,16 +293,23 @@ impl DataPump {
                 if p.done {
                     capacity_probe_deadline = None;
                     // An all-zero reply is a decline (old host / probe-less build) — keep the
-                    // negotiated ceiling. Otherwise: delivered wire kbps × 0.7.
+                    // negotiated ceiling. Otherwise: delivered wire kbps × 0.7, over the
+                    // CLIENT-measured receive interval (the host's send window closes while the
+                    // bottleneck queue is still draining toward us, so dividing by ITS duration
+                    // overstates the link — a 1 GbE link "measured" 1266 Mbps, and the inflated
+                    // ceiling is permanent because set_ceiling never lowers); the host duration
+                    // is the fallback when the burst delivered too few packets for an interval.
                     if p.host_duration_ms > 0 && p.delivered_bytes > 0 {
-                        let delivered_kbps = (p.delivered_bytes.saturating_mul(8)
-                            / p.host_duration_ms.max(1) as u64)
-                            as u32;
+                        let window_ms = p.throughput_window_ms();
+                        let delivered_kbps =
+                            (p.delivered_bytes.saturating_mul(8) / window_ms.max(1) as u64) as u32;
                         let ceiling = delivered_kbps.saturating_mul(7) / 10;
                         abr.set_ceiling(ceiling);
                         tracing::info!(
                             delivered_kbps,
                             ceiling_kbps = ceiling,
+                            client_interval_ms = p.client_interval_ms,
+                            host_duration_ms = p.host_duration_ms,
                             "adaptive bitrate: link-capacity probe done — climb ceiling set"
                         );
                     } else {

crates/punktfunk-core/src/packet/reassemble.rs

@@ -409,6 +409,27 @@ impl Reassembler {
         // can neither advance the video anchor nor be dropped as stale against it (and its aged-out
         // frames never count as `frames_dropped`, which would fire video loss recovery).
         let is_probe = hdr.user_flags & (FLAG_PROBE as u32) != 0;
+        if is_probe {
+            // Probe-scoped receive accounting (the speed-test numerator + denominator, see
+            // `Stats::probe_first_arrival_ns`), stamped at the routing decision so video in
+            // flight around the burst contaminates neither the byte count nor the arrival
+            // stamps. Byte unit mirrors `bytes_received` (whole plaintext packet). The first
+            // probe packet since the pump armed the probe claims the first-arrival slot (the
+            // pump zeroes it before the burst can reach the host); every probe packet
+            // refreshes the last-arrival stamp.
+            let now_ns = crate::stats::now_monotonic_ns();
+            StatsCounters::add(&stats.probe_packets_received, 1);
+            StatsCounters::add(&stats.probe_bytes_received, pkt.len() as u64);
+            let _ = stats.probe_first_arrival_ns.compare_exchange(
+                0,
+                now_ns,
+                std::sync::atomic::Ordering::Relaxed,
+                std::sync::atomic::Ordering::Relaxed,
+            );
+            stats
+                .probe_last_arrival_ns
+                .store(now_ns, std::sync::atomic::Ordering::Relaxed);
+        }
         let win = if is_probe { probe } else { video };
         win.advance_window(
             hdr.frame_index,

crates/punktfunk-core/src/session.rs

@@ -218,6 +218,18 @@ impl Session {
         self.stats.snapshot()
     }
 
+    /// Re-arm the probe-scoped arrival stamps (see [`Stats::probe_first_arrival_ns`]): zero
+    /// them so the NEXT burst's first packet claims the first-arrival slot. Called by the
+    /// client pump when it arms a probe, strictly before the burst can have reached the host
+    /// (the `ProbeRequest` is still queued locally) — so the reset cannot race a probe packet.
+    /// The cumulative probe byte/packet counters are left alone: per-burst deltas come from
+    /// base snapshots, the same pattern the total counters use.
+    pub fn reset_probe_arrivals(&self) {
+        let l = std::sync::atomic::Ordering::Relaxed;
+        self.stats.probe_first_arrival_ns.store(0, l);
+        self.stats.probe_last_arrival_ns.store(0, l);
+    }
+
     /// Wrap a packet for the wire: when encrypting, prepend the 8-byte big-endian
     /// sequence (the receiver derives the GCM nonce from it) then the ciphertext.
     /// Seal one plaintext packet into the reused `wire` buffer in place (no allocation): the wire is

crates/punktfunk-core/src/stats.rs

@@ -1,6 +1,19 @@
 //! Live counters for the frame-pacing / quality logic and the web UI.
 
 use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::OnceLock;
+use std::time::Instant;
+
+/// Monotonic now, in ns since an arbitrary process-wide epoch — the basis for the probe
+/// arrival stamps below. Monotonic on purpose: the stamps are only ever DIFFERENCED on this
+/// machine (the burst's receive interval), and a wall-clock step mid-burst — the exact event
+/// the clock re-sync machinery exists for — must not corrupt the one measurement the ABR
+/// ceiling is built from, so the CLOCK_REALTIME basis `pts_ns` uses is wrong here. Floored
+/// at 1 so a stamp can never collide with the 0 = "unset" sentinel.
+pub(crate) fn now_monotonic_ns() -> u64 {
+    static EPOCH: OnceLock<Instant> = OnceLock::new();
+    (EPOCH.get_or_init(Instant::now).elapsed().as_nanos() as u64).max(1)
+}
 
 /// Immutable snapshot, copied across the C ABI as `PunktfunkStats`.
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
@@ -26,11 +39,29 @@ pub struct Stats {
     pub fec_late_shards: u64,
     pub bytes_sent: u64,
     pub bytes_received: u64,
+    /// Probe-scoped receive counters: wire packets / plaintext bytes carrying
+    /// [`FLAG_PROBE`](crate::packet::FLAG_PROBE) (speed-test filler), counted at the
+    /// reassembler's probe routing decision. `bytes_received` counts EVERY accepted datagram,
+    /// so a speed-test numerator built from it inherits whatever video was in flight around
+    /// the burst — these keep video out of the probe math. Deliberately NOT mirrored into the
+    /// C-ABI `PunktfunkStats` (probe measurements surface via `ProbeOutcome`).
+    pub probe_packets_received: u64,
+    pub probe_bytes_received: u64,
+    /// First / last probe-packet arrival (monotonic ns, see [`now_monotonic_ns`]; 0 = none
+    /// since the last probe arm). Their difference is the burst's client-side receive
+    /// interval — the honest speed-test denominator: the host's send window closes while the
+    /// switch/kernel queue toward the client is still draining, so dividing client bytes by
+    /// the HOST duration overstates the link (a 1 GbE link "measured" 1266 Mbps). The client
+    /// pump zeroes both when it arms a probe (`Session::reset_probe_arrivals`).
+    pub probe_first_arrival_ns: u64,
+    pub probe_last_arrival_ns: u64,
 }
 
 /// Atomic accumulators owned by a [`Session`](crate::session::Session). Snapshot to
 /// [`Stats`] for readers. `Relaxed` ordering is fine: these are monotonic counters
-/// read for display, never used to synchronize other memory.
+/// read for display, never used to synchronize other memory. (The two probe arrival
+/// stamps are the exception — slots, not counters — but they carry no synchronization
+/// duty either: they are read hundreds of ms after the last write.)
 #[derive(Default)]
 pub struct StatsCounters {
     pub frames_submitted: AtomicU64,
@@ -44,6 +75,10 @@ pub struct StatsCounters {
     pub fec_late_shards: AtomicU64,
     pub bytes_sent: AtomicU64,
     pub bytes_received: AtomicU64,
+    pub probe_packets_received: AtomicU64,
+    pub probe_bytes_received: AtomicU64,
+    pub probe_first_arrival_ns: AtomicU64,
+    pub probe_last_arrival_ns: AtomicU64,
 }
 
 impl StatsCounters {
@@ -66,6 +101,10 @@ impl StatsCounters {
             fec_late_shards: self.fec_late_shards.load(l),
             bytes_sent: self.bytes_sent.load(l),
             bytes_received: self.bytes_received.load(l),
+            probe_packets_received: self.probe_packets_received.load(l),
+            probe_bytes_received: self.probe_bytes_received.load(l),
+            probe_first_arrival_ns: self.probe_first_arrival_ns.load(l),
+            probe_last_arrival_ns: self.probe_last_arrival_ns.load(l),
         }
     }
 }

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

@@ -39,7 +39,7 @@
 // Every `unsafe` block in this file carries a `// SAFETY:` proof; enforce it.
 #![deny(clippy::undocumented_unsafe_blocks)]
 
-use super::wiring_plan::{plan, Endpoint, Wiring};
+use super::wiring_plan::{self, plan, Endpoint, Wiring};
 use anyhow::{anyhow, bail, Result};
 use std::ffi::c_void;
 use std::sync::Mutex;
@@ -75,6 +75,33 @@ pub(crate) fn host_audio_requested() -> bool {
     std::env::var_os("PUNKTFUNK_HOST_AUDIO").is_some()
 }
 
+/// One wiring pass plus the inputs the desktop-audio capture loop's failure handling needs:
+/// the endpoint-set fingerprint ([`wiring_plan::fingerprint`] — the wait key while a plan is
+/// unsatisfiable, snapshotted from the SAME enumeration the plan consumed so a device arriving
+/// mid-pass can't leave the waiter keyed to a set the plan never saw) and the render inventory
+/// (the one-shot "why is there no loopback" diagnosis).
+pub(crate) struct WiredPlan {
+    pub wiring: Wiring,
+    pub fingerprint: u64,
+    pub renders: Vec<Endpoint>,
+}
+
+/// Fingerprint of the CURRENT endpoint set (both directions) WITHOUT a wiring pass: enumeration
+/// and a hash — no plan, no default-device writes, no logs. This is the cheap poll the capture
+/// loop runs while waiting out a failure; the full [`wire_now`] only runs again once this moves.
+/// Must run on a COM-initialized thread, like [`wire_now`].
+pub(crate) fn endpoint_fingerprint() -> u64 {
+    wiring_plan::fingerprint(
+        &list_endpoints(Direction::Render),
+        &list_endpoints(Direction::Capture),
+    )
+}
+
+/// [`wire_now_full`] for callers that only need the assignment (the mic paths).
+pub(crate) fn wire_now(set_playback: bool) -> Wiring {
+    wire_now_full(set_playback).wiring
+}
+
 /// Enumerate endpoints, compute the assignment, apply the default-device changes (unless
 /// `PUNKTFUNK_KEEP_DEFAULT`), and return the plan for the caller to act on (mic target / loopback
 /// echo guard). `set_playback` — true only from the desktop-audio capture open — additionally
@@ -83,14 +110,20 @@ pub(crate) fn host_audio_requested() -> bool {
 /// Must run on a COM-initialized thread (the WASAPI worker threads all `initialize_mta` first).
 /// Logged only when the assignment changes, so per-open recomputation stays quiet in the steady
 /// state.
-pub(crate) fn wire_now(set_playback: bool) -> Wiring {
+pub(crate) fn wire_now_full(set_playback: bool) -> WiredPlan {
     recover_orphaned_default();
     let renders = list_endpoints(Direction::Render);
     let captures = list_endpoints(Direction::Capture);
+    let fingerprint = wiring_plan::fingerprint(&renders, &captures);
     let want = std::env::var("PUNKTFUNK_MIC_DEVICE")
         .ok()
         .map(|s| s.to_lowercase());
     let wiring = plan(&renders, &captures, want.as_deref(), host_audio_requested());
+    let done = |wiring: Wiring| WiredPlan {
+        wiring,
+        fingerprint,
+        renders: renders.clone(),
+    };
 
     // Log assignment changes exactly once (first plan included).
     static LAST: Mutex<Option<Wiring>> = Mutex::new(None);
@@ -105,14 +138,17 @@ pub(crate) fn wire_now(set_playback: bool) -> Wiring {
             mic_render = wiring.mic_render.as_ref().map(|(n, _)| n.as_str()),
             mic_capture = wiring.mic_capture.as_ref().map(|(n, _)| n.as_str()),
             loopback_render = wiring.loopback_render.as_ref().map(|(n, _)| n.as_str()),
+            loopback_last_resort = wiring.loopback_last_resort,
             renders = ?renders.iter().map(|(n, _)| n.as_str()).collect::<Vec<_>>(),
             "audio wiring plan"
         );
-        if wiring.mic_render.is_some() && wiring.loopback_render.is_none() {
+        if wiring.mic_render.is_some() && wiring.loopback_unsatisfiable() {
+            // Inventory + per-endpoint reasons + ONLY the remedies not already taken — the old
+            // static advice here suggested installing the Steam pair to a field box that had it
+            // installed (its Microphone half was exactly what the mic had reserved).
             tracing::warn!(
-                "the virtual mic reserved the only usable render endpoint — desktop audio will be \
-                 unavailable until another output device exists (attach one, or let the host \
-                 install the Steam Streaming pair)"
+                "desktop audio unavailable: {}",
+                wiring_plan::describe_no_loopback(&renders, &wiring)
             );
         }
     }
@@ -123,7 +159,7 @@ pub(crate) fn wire_now(set_playback: bool) -> Wiring {
                 "PUNKTFUNK_KEEP_DEFAULT set — leaving the audio default devices untouched"
             );
         }
-        return wiring;
+        return done(wiring);
     }
     // Default-playback hygiene, on EVERY wire (mic pump at boot included): if the default render
     // endpoint IS the mic target — VB-CABLE installs have been seen grabbing the default — every
@@ -160,18 +196,26 @@ pub(crate) fn wire_now(set_playback: bool) -> Wiring {
         }
     }
     if let Some((name, id)) = &wiring.mic_capture {
-        match set_default_endpoint(id) {
-            Ok(()) => {
-                if changed {
-                    tracing::info!(device = %name,
-                        "audio wiring: default recording = virtual mic (apps record the client's mic)");
+        // `set_default_endpoint` is NOT a no-op on an unchanged default: it unconditionally
+        // fires SetDefaultEndpoint for all three roles (an audio-policy write plus a
+        // device-graph notification, each). Re-asserting on every wiring pass therefore both
+        // churned the policy store AND silently stomped an operator's own recording-device
+        // choice within one reopen cycle — write only when the plan changed or the default
+        // actually drifted off the target.
+        if changed || default_capture_id().as_deref() != Some(id.as_str()) {
+            match set_default_endpoint(id) {
+                Ok(()) => {
+                    if changed {
+                        tracing::info!(device = %name,
+                            "audio wiring: default recording = virtual mic (apps record the client's mic)");
+                    }
                 }
+                Err(e) => tracing::warn!(device = %name, error = %format!("{e:#}"),
+                    "audio wiring: failed to set the default recording device"),
             }
-            Err(e) => tracing::warn!(device = %name, error = %format!("{e:#}"),
-                "audio wiring: failed to set the default recording device"),
         }
     }
-    wiring
+    done(wiring)
 }
 
 /// The operator's default playback endpoint while we have it parked on the loopback sink:
@@ -194,6 +238,18 @@ fn default_render_id() -> Option<String> {
         .ok()
 }
 
+/// The current default CAPTURE endpoint id, if any — the recording-side analogue of
+/// [`default_render_id`], read before asserting the recording default so an already-correct
+/// default costs zero IPolicyConfig writes.
+fn default_capture_id() -> Option<String> {
+    wasapi::DeviceEnumerator::new()
+        .ok()?
+        .get_default_device(&Direction::Capture)
+        .ok()?
+        .get_id()
+        .ok()
+}
+
 /// Once per process: if a crash marker from a previous run exists, the host died while the
 /// playback default was parked — put the operator's device back, but only if the default still
 /// IS the endpoint we set (a manual change since the crash wins). Runs on the first wiring pass

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

@@ -18,9 +18,14 @@
 //! device changing under us — the operator picked a different output mid-stream — and reacts:
 //! a loopback-capturable choice is FOLLOWED (their explicit choice wins; audio then also plays
 //! on the host), a known-dud choice (cable/Steam Speakers/the mic target) snaps back to the
-//! plan. Device errors (endpoint invalidated, engine restart) reopen with backoff instead of
-//! killing audio for the rest of the session. On thread exit (capturer dropped at stream end)
-//! the parked default playback device is restored.
+//! plan. Device errors (endpoint invalidated, engine restart) reopen with a capped exponential
+//! backoff that an endpoint-set change cuts short. A plan with NO loopback endpoint at all is
+//! never retried: `wiring_plan::plan` is pure in the endpoint set, so that verdict holds until
+//! the set changes — the thread says why once, then parks on a cheap fingerprint poll and
+//! re-plans the instant the set moves (the 2026-08 field case hammered a full wiring pass —
+//! IPolicyConfig writes included — every 2 s for 8+ minutes without ever being able to
+//! succeed). On thread exit (capturer dropped at stream end) the parked default playback
+//! device is restored.
 
 use super::{audio_control, wiring_plan, AudioCapturer, SAMPLE_RATE};
 use anyhow::{anyhow, Context, Result};
@@ -131,8 +136,20 @@ enum Next {
     Reopen(TargetMode),
 }
 
-/// Backoff between self-heal reopen attempts after a capture failure.
-const REOPEN_BACKOFF: Duration = Duration::from_secs(2);
+/// Reopen backoff after a TRANSIENT capture failure: starts here and doubles per consecutive
+/// failure up to [`REOPEN_BACKOFF_CAP`], resetting on success or on an endpoint-set change
+/// (mirrors the mic pump's `PUMP_TUNING` shape). The predecessor was a FLAT 2 s retry whose
+/// every attempt re-ran the full wiring pass, IPolicyConfig writes included — tolerable for a
+/// genuinely transient error, an 8-minute hammer in the 2026-08 field case where the failure
+/// was structural.
+const REOPEN_BACKOFF_START: Duration = Duration::from_secs(2);
+const REOPEN_BACKOFF_CAP: Duration = Duration::from_secs(60);
+/// Endpoint-set poll cadence while waiting out a failure (both the transient backoff sleep and
+/// the unsatisfiable-plan wait): one enumerate-and-hash per tick, nothing else. A fingerprint
+/// change ends the wait immediately — a (re)arrived endpoint (the display coming back, plugged
+/// headphones) is exactly the recovery moment — so recovery stays as fast as the old 2 s hammer
+/// without its side effects.
+const ENDPOINT_POLL_EVERY: Duration = Duration::from_secs(2);
 /// Watchdog cadence for "did the default render device change under us?" checks.
 const DEFAULT_CHECK_EVERY: Duration = Duration::from_secs(1);
 /// Total attempts for the FIRST open before its failure surfaces through the `ready` handshake.
@@ -168,14 +185,30 @@ fn capture_thread(
     let mut mode = TargetMode::Assert;
     let mut failures: u64 = 0;
     let mut first_attempts: u32 = 0;
+    let mut backoff = REOPEN_BACKOFF_START;
+    // Endpoint-set fingerprint under which an unsatisfiable plan was already error-logged: an
+    // unchanged set means an unchanged verdict (`wiring_plan::plan` is pure), so the diagnosis
+    // is said once per topology — the field log drowned in 256+ copies of the same line.
+    let mut unsat_logged: Option<u64> = None;
     while !stop.load(Ordering::Relaxed) {
         match capture_once(&tx, &stop, &mut ready, channels, mode) {
             Ok(Next::Stopped) => break,
             Ok(Next::Reopen(m)) => {
                 mode = m;
                 failures = 0;
+                backoff = REOPEN_BACKOFF_START;
+                unsat_logged = None;
             }
             Err(e) if ready.is_some() => {
+                // An unsatisfiable PLAN cannot improve within the handshake window — the
+                // once-per-process Steam-pair install already ran inside `capture_once` — so
+                // fail the open now with the full diagnosis instead of spending the transient
+                // retry budget on a structural verdict. The native plane owns first-open
+                // retries and backs off on its own.
+                if e.downcast_ref::<PlanUnsatisfiable>().is_some() {
+                    let _ = ready.take().unwrap().send(Err(anyhow!("{e:#}")));
+                    break;
+                }
                 first_attempts += 1;
                 if first_attempts >= FIRST_OPEN_ATTEMPTS || stop.load(Ordering::Relaxed) {
                     let _ = ready.take().unwrap().send(Err(anyhow!("{e:#}")));
@@ -190,16 +223,43 @@ fn capture_thread(
                 }
             }
             Err(e) => {
-                failures += 1;
-                if failures.is_power_of_two() {
-                    tracing::warn!(error = %format!("{e:#}"), count = failures,
-                        "audio loopback capture failed — reopening");
-                }
                 mode = TargetMode::Assert;
-                // Backoff in stop-responsive slices.
-                let until = Instant::now() + REOPEN_BACKOFF;
-                while Instant::now() < until && !stop.load(Ordering::Relaxed) {
-                    thread::sleep(Duration::from_millis(100));
+                if let Some(unsat) = e.downcast_ref::<PlanUnsatisfiable>() {
+                    // Structural: retrying against the same endpoints repeats the same verdict,
+                    // and every retry used to re-run the wiring pass — IPolicyConfig writes
+                    // included, stomping any operator default-recording change within 2 s. Say
+                    // why once per topology, then park on the cheap fingerprint poll; the set
+                    // changing IS the recovery moment and re-plans immediately.
+                    failures = 0;
+                    backoff = REOPEN_BACKOFF_START;
+                    if unsat_logged != Some(unsat.fingerprint) {
+                        unsat_logged = Some(unsat.fingerprint);
+                        tracing::error!(
+                            "desktop audio unavailable, and retrying cannot help until the \
+                             audio endpoint set changes — waiting for that change. {unsat}"
+                        );
+                    }
+                    if wait_endpoint_change(&stop, unsat.fingerprint, None) == EndpointWait::Stopped
+                    {
+                        break;
+                    }
+                } else {
+                    unsat_logged = None;
+                    failures += 1;
+                    if failures.is_power_of_two() {
+                        tracing::warn!(error = %format!("{e:#}"), count = failures,
+                            backoff_secs = backoff.as_secs(),
+                            "audio loopback capture failed — reopening after backoff");
+                    }
+                    // Capped exponential backoff, cut short (and reset) the moment the
+                    // endpoint set changes — a re-arrived device is the likeliest cure for
+                    // whatever killed the capture, and it must not wait out a 60 s sleep.
+                    let fp = audio_control::endpoint_fingerprint();
+                    match wait_endpoint_change(&stop, fp, Some(Instant::now() + backoff)) {
+                        EndpointWait::Stopped => break,
+                        EndpointWait::Changed => backoff = REOPEN_BACKOFF_START,
+                        EndpointWait::Elapsed => backoff = (backoff * 2).min(REOPEN_BACKOFF_CAP),
+                    }
                 }
             }
         }
@@ -210,6 +270,75 @@ fn capture_thread(
     Ok(())
 }
 
+/// A wiring plan with NO loopback endpoint, as a typed error: [`wiring_plan::plan`] is pure in
+/// the enumerated endpoint set, so unlike every other capture error this one is PERMANENT until
+/// the topology changes — retrying it is guaranteed futile (the 2026-08 field case retried it
+/// flat-out for 8+ minutes, one full wiring pass per retry). Carries the set's fingerprint
+/// (what the reopen loop waits on) and the full diagnosis: inventory, per-endpoint rejection
+/// reasons, and only the remedies not already taken.
+#[derive(Debug)]
+struct PlanUnsatisfiable {
+    fingerprint: u64,
+    detail: String,
+}
+
+impl PlanUnsatisfiable {
+    fn from_plan(plan: &audio_control::WiredPlan) -> PlanUnsatisfiable {
+        debug_assert!(plan.wiring.loopback_unsatisfiable());
+        PlanUnsatisfiable {
+            fingerprint: plan.fingerprint,
+            detail: wiring_plan::describe_no_loopback(&plan.renders, &plan.wiring),
+        }
+    }
+}
+
+impl std::fmt::Display for PlanUnsatisfiable {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.detail)
+    }
+}
+
+impl std::error::Error for PlanUnsatisfiable {}
+
+/// How a [`wait_endpoint_change`] ended.
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum EndpointWait {
+    /// `stop` was set — the capturer is being dropped.
+    Stopped,
+    /// The endpoint-set fingerprint moved — re-plan NOW (this is the recovery moment).
+    Changed,
+    /// The deadline passed without a change (backoff waits only; `deadline: None` never ends
+    /// this way).
+    Elapsed,
+}
+
+/// Stop-responsive wait that polls the endpoint-set fingerprint every [`ENDPOINT_POLL_EVERY`] —
+/// an enumerate-and-hash, no wiring pass, no IPolicyConfig writes, no logs — until the set
+/// changes, `deadline` passes, or `stop` is set. `deadline: None` waits indefinitely: used while
+/// the plan is unsatisfiable, where ONLY a topology change can alter the verdict.
+fn wait_endpoint_change(
+    stop: &AtomicBool,
+    fingerprint: u64,
+    deadline: Option<Instant>,
+) -> EndpointWait {
+    let mut next_poll = Instant::now() + ENDPOINT_POLL_EVERY;
+    loop {
+        if stop.load(Ordering::Relaxed) {
+            return EndpointWait::Stopped;
+        }
+        if deadline.is_some_and(|d| Instant::now() >= d) {
+            return EndpointWait::Elapsed;
+        }
+        thread::sleep(Duration::from_millis(100));
+        if Instant::now() >= next_poll {
+            next_poll = Instant::now() + ENDPOINT_POLL_EVERY;
+            if audio_control::endpoint_fingerprint() != fingerprint {
+                return EndpointWait::Changed;
+            }
+        }
+    }
+}
+
 /// The current default render endpoint, with its id (`None` on any enumeration failure —
 /// transient failures must not kill the capture).
 fn default_render(en: &DeviceEnumerator) -> Option<(Device, String)> {
@@ -220,7 +349,7 @@ fn default_render(en: &DeviceEnumerator) -> Option<(Device, String)> {
 
 /// One endpoint open + capture loop. Returns how to continue ([`Next`]) or an error (first open:
 /// retried [`FIRST_OPEN_ATTEMPTS`] times, then fatal via the `ready` handshake; later: reopen
-/// with backoff).
+/// with capped backoff — or, for a typed [`PlanUnsatisfiable`], an endpoint-set wait).
 fn capture_once(
     tx: &SyncSender<Vec<f32>>,
     stop: &AtomicBool,
@@ -233,26 +362,23 @@ fn capture_once(
     let keep_default = std::env::var_os("PUNKTFUNK_KEEP_DEFAULT").is_some();
     // Assert-mode without KEEP_DEFAULT is the only shape that parks the playback default.
     let assert_plan = mode == TargetMode::Assert && !keep_default;
-    let mut wiring = audio_control::wire_now(assert_plan);
+    let mut plan = audio_control::wire_now_full(assert_plan);
 
     // Client-only audio needs a silent-on-host sink with a working loopback (the Steam Streaming
     // Microphone's render side). If the plan had to settle for real hardware (or nothing), try —
     // once per process — to install the Steam pair (present when Steam is), then re-plan.
     if assert_plan && !audio_control::host_audio_requested() {
-        let have_silent = wiring
-            .loopback_render
-            .as_ref()
-            .is_some_and(|(n, _)| wiring_plan::silent_sink(&n.to_lowercase()));
-        static INSTALL_TRIED: AtomicBool = AtomicBool::new(false);
-        if !have_silent && !INSTALL_TRIED.swap(true, Ordering::SeqCst) {
-            if super::wasapi_mic::install_steam_audio_pair() {
-                wiring = audio_control::wire_now(true);
-            }
-            if !wiring
-                .loopback_render
+        let have_silent = |w: &wiring_plan::Wiring| {
+            w.loopback_render
                 .as_ref()
                 .is_some_and(|(n, _)| wiring_plan::silent_sink(&n.to_lowercase()))
-            {
+        };
+        static INSTALL_TRIED: AtomicBool = AtomicBool::new(false);
+        if !have_silent(&plan.wiring) && !INSTALL_TRIED.swap(true, Ordering::SeqCst) {
+            if super::wasapi_mic::install_steam_audio_pair() {
+                plan = audio_control::wire_now_full(true);
+            }
+            if !have_silent(&plan.wiring) {
                 tracing::info!(
                     "no silent virtual sink for client-only audio — desktop audio will also play \
                      on the host (install Steam, whose Remote Play streaming drivers provide one)"
@@ -260,6 +386,12 @@ fn capture_once(
             }
         }
     }
+    let wiring = &plan.wiring;
+    // Only the Assert path can knowingly sit on the plan's LAST-RESORT endpoint: Follow captures
+    // the operator's chosen default, and `judge_default` never routes Follow onto the Steam
+    // Speakers (they are `excluded_from_loopback` — a Dud that snaps back to the plan).
+    let last_resort = assert_plan && wiring.loopback_last_resort;
+    let plan_fp = plan.fingerprint;
 
     let en = DeviceEnumerator::new().context("DeviceEnumerator")?;
     // Resolve the endpoint to capture. ECHO GUARD (Follow/KEEP_DEFAULT shapes): the wiring plan
@@ -268,11 +400,11 @@ fn capture_once(
     // fall back to the plan's loopback endpoint, or refuse — no desktop audio beats an echo loop.
     let (device, dev_name, dev_id) = if assert_plan {
         let Some(ep) = wiring.loopback_render.clone() else {
-            anyhow::bail!(
-                "no loopback-capturable render endpoint (every usable endpoint is reserved for \
-                 the virtual mic or has a silent loopback) — attach an output device or install \
-                 the Steam Streaming pair to get desktop audio"
-            );
+            // Detected BEFORE any open attempt, and typed: the plan is a pure function of the
+            // endpoint set, so this cannot resolve until the set changes — the reopen loop
+            // waits on the fingerprint instead of retrying (the old untyped bail was retried
+            // flat-out every 2 s, forever, in the 2026-08 field case).
+            return Err(PlanUnsatisfiable::from_plan(&plan).into());
         };
         let d = audio_control::open_endpoint(&ep)?;
         (d, ep.0, ep.1)
@@ -285,10 +417,15 @@ fn capture_once(
             .is_some_and(|(_, mic_id)| *mic_id == id);
         if default_is_mic {
             let Some(lb) = wiring.loopback_render.clone() else {
+                // Same inventory shape as the Assert bail, but NOT typed as unsatisfiable:
+                // Follow's inputs include the DEFAULT device, which the operator can change
+                // without a topology change (especially under PUNKTFUNK_KEEP_DEFAULT) — the
+                // capped backoff must keep retrying rather than a fingerprint wait sleeping
+                // through a default-only change.
                 anyhow::bail!(
-                    "the only render endpoint is reserved for the virtual mic (capturing it would \
-                     echo the client's voice back) — attach another output device or install the \
-                     Steam Streaming pair to get desktop audio"
+                    "the default render endpoint is reserved for the virtual mic (capturing it \
+                     would echo the client's voice back) — {}",
+                    wiring_plan::describe_no_loopback(&plan.renders, wiring)
                 );
             };
             tracing::warn!(mic = %wiring.mic_render.as_ref().unwrap().0, loopback = %lb.0,
@@ -338,6 +475,7 @@ fn capture_once(
     }
     tracing::info!(device = %dev_name,
         follow = matches!(mode, TargetMode::Follow) || keep_default,
+        last_resort,
         "audio loopback capturing");
 
     // Watchdog seed: the default as it stands right after our open. In Assert mode the plan just
@@ -349,7 +487,7 @@ fn capture_once(
     if assert_plan {
         if let Some(d) = seen_default.as_deref() {
             if d != dev_id {
-                match judge_default(&en, &wiring, d) {
+                match judge_default(&en, wiring, d) {
                     DefaultKind::Capturable(name) => {
                         tracing::info!(default = %name, planned = %dev_name,
                             "could not park the default playback on the planned endpoint — \
@@ -367,10 +505,12 @@ fn capture_once(
 
     let mut bytes: VecDeque<u8> = VecDeque::new();
     let mut last_check = Instant::now();
+    let mut last_fp_check = Instant::now();
     // Triage breadcrumb: a broken loopback (endpoint renders but its loopback tap delivers
     // nothing — the Steam Streaming Speakers failure shape) is indistinguishable from a simply
-    // quiet desktop, so after 30 s with zero packets say so ONCE. Info, not warn: an idle host
-    // is legitimately silent.
+    // quiet desktop, so after 30 s with zero packets say so ONCE. Info, not warn — an idle host
+    // is legitimately silent — EXCEPT on a last-resort endpoint, where the plan already knew
+    // the loopback is silent and zero packets all but confirms the quality risk materialized.
     let opened_at = Instant::now();
     let mut saw_packets = false;
     let mut silence_noted = false;
@@ -396,10 +536,18 @@ fn capture_once(
         }
         if !saw_packets && !silence_noted && opened_at.elapsed() >= Duration::from_secs(30) {
             silence_noted = true;
-            tracing::info!(device = %dev_name,
-                "no audio captured in the first 30 s — fine if the host is quiet; if it should \
-                 be playing audio, this endpoint's loopback may be broken (set \
-                 PUNKTFUNK_HOST_AUDIO=1 to prefer real hardware)");
+            if last_resort {
+                tracing::warn!(device = %dev_name,
+                    "no audio captured in the first 30 s from the LAST-RESORT loopback — the \
+                     Steam Streaming Speakers' loopback is known-silent, so desktop audio is \
+                     most likely not reaching the client; attach any output device to give the \
+                     plan a working endpoint (it re-plans on the change)");
+            } else {
+                tracing::info!(device = %dev_name,
+                    "no audio captured in the first 30 s — fine if the host is quiet; if it \
+                     should be playing audio, this endpoint's loopback may be broken (set \
+                     PUNKTFUNK_HOST_AUDIO=1 to prefer real hardware)");
+            }
         }
         let whole = (bytes.len() / block_align) * block_align;
         if whole > 0 {
@@ -428,7 +576,7 @@ fn capture_once(
                             );
                             return Ok(Next::Reopen(TargetMode::Follow));
                         }
-                        return Ok(match judge_default(&en, &wiring, &nid) {
+                        return Ok(match judge_default(&en, wiring, &nid) {
                             DefaultKind::Capturable(name) => {
                                 tracing::info!(device = %name,
                                     "operator changed the output device mid-stream — following \
@@ -447,6 +595,24 @@ fn capture_once(
                 }
             }
         }
+
+        // A LAST-RESORT capture is a stopgap, not a steady state: the plan chose the
+        // known-silent Steam Speakers only because nothing better existed, so any endpoint-set
+        // change — the display's audio endpoint re-arriving, headphones plugged in — may unlock
+        // a real plan. Re-plan on the change; without this the session would ride the silent
+        // loopback forever AFTER the real endpoint returned (the original field defect in a
+        // quieter costume). Preferred endpoints don't get this watch: mid-stream re-routing
+        // there is the default-device watchdog's job, on the operator's terms.
+        if last_resort && last_fp_check.elapsed() >= ENDPOINT_POLL_EVERY {
+            last_fp_check = Instant::now();
+            if audio_control::endpoint_fingerprint() != plan_fp {
+                audio_client.stop_stream().ok();
+                tracing::info!(
+                    "endpoint set changed while capturing the last-resort loopback — re-planning"
+                );
+                return Ok(Next::Reopen(TargetMode::Assert));
+            }
+        }
     }
 }
 

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

@@ -26,6 +26,19 @@
 //! out of the host's speakers. Real hardware is the fallback (audio then plays on both ends).
 //! With `host_audio` (the `PUNKTFUNK_HOST_AUDIO` opt-in) the order flips back: real hardware
 //! first, so the operator hears the stream locally.
+//!
+//! **Last resort, and the honest failure.** When neither a silent sink nor real hardware
+//! survives the mic reservation, the Steam Streaming *Speakers* are taken as a flagged LAST
+//! resort ([`Wiring::loopback_last_resort`]): their loopback is known-silent (validated live) —
+//! a QUALITY risk the capture side warns about and treats as a stopgap — but holding a parked
+//! endpoint beats holding none (2026-08 field case: the display isolate invalidated the only
+//! real render endpoint mid-session, the mic held the Streaming Microphone, and a plan with no
+//! loopback left the session unrecoverable). Cables, VoiceMeeter strips and generically-
+//! "virtual" endpoints are never a last resort — capturing them re-captures what the mic writes,
+//! an echo/feedback CORRECTNESS risk, unlike silence — so with only those left the plan is
+//! honestly unsatisfiable ([`Wiring::loopback_unsatisfiable`]): a pure verdict on the endpoint
+//! set that cannot change until the set does. Callers must wait for an endpoint-set change
+//! ([`fingerprint`]), not retry.
 
 /// A `(friendly_name, endpoint_id)` pair as enumerated from WASAPI.
 pub(crate) type Endpoint = (String, String);
@@ -42,6 +55,22 @@ pub(crate) struct Wiring {
     pub mic_capture: Option<Endpoint>,
     /// Render endpoint for the desktop-audio loopback; made the default playback device.
     pub loopback_render: Option<Endpoint>,
+    /// `loopback_render` is the flagged LAST RESORT (the Steam Streaming Speakers, whose
+    /// loopback is known-silent — validated live), taken only because nothing better survived
+    /// the mic reservation. The capture side treats it as a stopgap: it warns when the silence
+    /// materializes and re-plans on any endpoint-set change instead of riding it out.
+    pub loopback_last_resort: bool,
+}
+
+impl Wiring {
+    /// This plan has NO loopback endpoint — not even the last resort. Because [`plan`] is pure,
+    /// this is a STRUCTURAL verdict on the endpoint set, not a transient device error:
+    /// reattempting a capture open without an endpoint-set change must fail identically (the
+    /// 2026-08 field case spent 8+ minutes of flat 2 s retries proving exactly that). Callers
+    /// wait for the set's [`fingerprint`] to move instead of retrying.
+    pub(crate) fn loopback_unsatisfiable(&self) -> bool {
+        self.loopback_render.is_none()
+    }
 }
 
 /// Render-endpoint friendly-name substrings (lowercased) usable as the virtual-mic write target,
@@ -134,7 +163,8 @@ pub(crate) fn plan(
 
     // 3. Loopback from the REMAINING renders. Client-only (default): the silent sink (Steam
     //    Streaming Microphone — its loopback works, unlike the Speakers') > real hardware
-    //    (audible fallback) > any non-excluded leftover. `host_audio`: real hardware first.
+    //    (audible fallback). `host_audio`: real hardware first. Either order can fall through
+    //    to the flagged last resort below.
     let not_mic = |id: &str| mic_render.as_ref().is_none_or(|(_, mid)| mid != id);
     let real_hw = || {
         renders.iter().find(|(n, id)| {
@@ -147,29 +177,131 @@ pub(crate) fn plan(
             .iter()
             .find(|(n, id)| not_mic(id) && silent_sink(&n.to_lowercase()))
     };
-    // `virtualish` here too: a virtual endpoint that slipped past `excluded_from_loopback`'s
-    // name list (a future cable/mixer sibling) is an internal-feedback loop waiting to happen —
-    // no loopback is the honest answer, exactly like the cable-only case.
-    let leftover = || {
-        renders.iter().find(|(n, id)| {
-            let ln = n.to_lowercase();
-            not_mic(id) && !excluded_from_loopback(&ln) && !virtualish(&ln)
-        })
+    // LAST RESORT — the Steam Streaming Speakers, and ONLY them. Their loopback is known-silent
+    // (validated live): a QUALITY risk, flagged so the capture side can warn when the silence
+    // materializes and re-plan when the endpoint set changes — but a parked endpoint beats none
+    // (2026-08: the display isolate invalidated the only real render endpoint mid-session and a
+    // loopback-less plan left the session unrecoverable). Never a cable, a VoiceMeeter strip, or
+    // a generically-"virtual" endpoint: those re-capture what the mic writes — echo/feedback
+    // CORRECTNESS risks — so "no loopback" stays the honest answer there. NOTE
+    // `excluded_from_loopback` itself stays untouched: it also powers the capture watchdog's
+    // judgement of a NEW operator-chosen default, where admitting the Speakers would change
+    // mid-stream snap-back semantics.
+    let last_resort = || {
+        renders
+            .iter()
+            .find(|(n, id)| not_mic(id) && n.to_lowercase().contains("steam streaming speakers"))
     };
-    let loopback_render = if host_audio {
-        real_hw().or_else(silent).or_else(leftover)
+    let preferred = if host_audio {
+        real_hw().or_else(silent)
     } else {
-        silent().or_else(real_hw).or_else(leftover)
-    }
-    .cloned();
+        silent().or_else(real_hw)
+    };
+    let (loopback_render, loopback_last_resort) = match preferred {
+        Some(ep) => (Some(ep.clone()), false),
+        None => match last_resort() {
+            Some(ep) => (Some(ep.clone()), true),
+            None => (None, false),
+        },
+    };
 
     Wiring {
         mic_render,
         mic_capture,
         loopback_render,
+        loopback_last_resort,
     }
 }
 
+/// Order-independent fingerprint of an enumerated endpoint set. [`plan`] is a pure function of
+/// these inputs (the env knobs are process-stable), so an unchanged fingerprint PROVES an
+/// unchanged verdict: re-planning an unsatisfiable set before the fingerprint moves only repeats
+/// the same answer, with IPolicyConfig default-device writes as the side effect. The capture
+/// loop polls this instead of re-planning, and treats a change as the recovery moment.
+pub(crate) fn fingerprint(renders: &[Endpoint], captures: &[Endpoint]) -> u64 {
+    use std::collections::hash_map::DefaultHasher;
+    use std::hash::{Hash, Hasher};
+    let mut h = DefaultHasher::new();
+    // Each direction hashes as a length-prefixed sorted slice, so renders and captures cannot
+    // alias each other and endpoint order (enumeration order churns) never matters.
+    for eps in [renders, captures] {
+        let mut sorted: Vec<&Endpoint> = eps.iter().collect();
+        sorted.sort();
+        sorted.hash(&mut h);
+    }
+    h.finish()
+}
+
+/// The one-shot diagnosis for a plan with no loopback endpoint: every enumerated render with WHY
+/// it was rejected, then ONLY the remedies not already taken. The static advice this replaces
+/// ("attach one, or let the host install the Steam Streaming pair") was already satisfied in the
+/// 2026-08 field case — the pair WAS installed, its Microphone half reserved by the mic — so the
+/// message pointed at a fix the box already had. Pure, like [`plan`]: callers pass the same
+/// enumeration the plan consumed.
+pub(crate) fn describe_no_loopback(renders: &[Endpoint], wiring: &Wiring) -> String {
+    debug_assert!(wiring.loopback_unsatisfiable());
+    let mic_id = wiring.mic_render.as_ref().map(|(_, id)| id.as_str());
+    let rejected: Vec<String> = renders
+        .iter()
+        .map(|(name, id)| {
+            let ln = name.to_lowercase();
+            let why = if Some(id.as_str()) == mic_id {
+                "reserved for the virtual mic (its loopback would echo the client's voice back)"
+            } else if ln.contains("cable") {
+                "virtual cable (its loopback re-captures what is written into it)"
+            } else if ln.contains("voicemeeter") {
+                "VoiceMeeter strip (shares the mixer the mic writes into — a feedback loop)"
+            } else if ln.contains("steam streaming speakers") {
+                // Reachable only when the Speakers ARE the mic target (operator override) —
+                // the last-resort tier takes them otherwise.
+                "known-silent loopback (validated live)"
+            } else if ln.contains("virtual") {
+                "unrecognized virtual endpoint (assumed feedback/silence risk)"
+            } else {
+                // `plan` accepts any non-virtual render — reaching this arm means a tier
+                // changed without updating this diagnosis.
+                "rejected by the wiring plan"
+            };
+            format!("{name:?}: {why}")
+        })
+        .collect();
+    let inventory = if rejected.is_empty() {
+        "no render endpoints exist at all".to_string()
+    } else {
+        rejected.join("; ")
+    };
+    let has = |needle: &str| {
+        renders
+            .iter()
+            .any(|(n, _)| n.to_lowercase().contains(needle))
+    };
+    let mut remedies = vec!["attach any output device (headphones, or a monitor/TV with audio)"];
+    // Only useful when the mic would actually vacate a loopback-capable endpoint: with the mic
+    // on the Steam Streaming Microphone, a cable frees that silent sink for the loopback. A mic
+    // on a VoiceMeeter strip frees nothing capturable, so the advice is withheld there.
+    if !has("cable")
+        && wiring
+            .mic_render
+            .as_ref()
+            .is_some_and(|(n, _)| silent_sink(&n.to_lowercase()))
+    {
+        remedies.push(
+            "install VB-Audio Virtual Cable — the mic then takes the cable and frees the Steam \
+             Streaming Microphone's render side for the loopback",
+        );
+    }
+    if !has("steam streaming microphone") {
+        remedies.push(
+            "install Steam — its Remote Play streaming drivers add a loopback-capable virtual \
+             sink",
+        );
+    }
+    format!(
+        "no loopback-capturable render endpoint: {inventory}. Remedies: {}",
+        remedies.join("; or ")
+    )
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -296,6 +428,10 @@ mod tests {
             w.loopback_render.unwrap().0,
             "Speakers (Steam Streaming Microphone)"
         );
+        assert!(
+            !w.loopback_last_resort,
+            "the silent sink is a PREFERRED pick"
+        );
         assert_eq!(
             w.mic_capture.unwrap().0,
             "CABLE Output (VB-Audio Virtual Cable)"
@@ -330,16 +466,88 @@ mod tests {
         assert!(w.loopback_render.is_none());
     }
 
-    /// Steam Streaming Speakers never become the loopback (silent loopback, validated live) —
-    /// even when they're the only non-mic endpoint.
+    /// Steam Streaming Speakers are never a PREFERRED loopback (their loopback is silent —
+    /// validated live) — but when they are the only non-mic endpoint they ARE taken, flagged as
+    /// the last resort: a silent loopback the capture side can warn about beats a plan with no
+    /// endpoint at all (which is unrecoverable until the topology changes).
     #[test]
-    fn steam_speakers_never_loopback() {
+    fn steam_speakers_only_as_last_resort() {
         let renders = [
             ep("CABLE Input (VB-Audio Virtual Cable)"),
             ep("Speakers (Steam Streaming Speakers)"),
         ];
-        let w = plan(&renders, &[], None, false);
-        assert!(w.loopback_render.is_none());
+        for host_audio in [false, true] {
+            let w = plan(&renders, &[], None, host_audio);
+            assert_eq!(
+                w.loopback_render.as_ref().unwrap().0,
+                "Speakers (Steam Streaming Speakers)",
+                "host_audio={host_audio}"
+            );
+            assert!(w.loopback_last_resort, "host_audio={host_audio}");
+        }
+    }
+
+    /// THE 2026-08 field case: no cable, only the Steam pair left after the display isolate
+    /// invalidated the monitor's DP audio endpoint. The mic reserves the Streaming Microphone
+    /// (the only mic candidate), and the plan must then take the Speakers as the last resort —
+    /// the old plan yielded no loopback here and the session never recovered.
+    #[test]
+    fn field_case_steam_pair_only_takes_speakers_as_last_resort() {
+        let renders = [
+            ep("Altavoces (Steam Streaming Speakers)"),
+            ep("Altavoces (Steam Streaming Microphone)"),
+        ];
+        let captures = [ep("Microphone (Steam Streaming Microphone)")];
+        let w = plan(&renders, &captures, None, false);
+        assert_eq!(
+            w.mic_render.unwrap().0,
+            "Altavoces (Steam Streaming Microphone)"
+        );
+        assert_eq!(
+            w.loopback_render.unwrap().0,
+            "Altavoces (Steam Streaming Speakers)"
+        );
+        assert!(w.loopback_last_resort);
+    }
+
+    /// The last resort never shadows a real pick: with real hardware present the Speakers stay
+    /// unchosen and the flag stays down, in both preference modes.
+    #[test]
+    fn last_resort_never_beats_real_hardware() {
+        let renders = [
+            ep("Speakers (Steam Streaming Microphone)"),
+            ep("Speakers (Steam Streaming Speakers)"),
+            ep("Speakers (Realtek HD Audio)"),
+        ];
+        let captures = [ep("Microphone (Steam Streaming Microphone)")];
+        for host_audio in [false, true] {
+            let w = plan(&renders, &captures, None, host_audio);
+            assert_eq!(
+                w.loopback_render.as_ref().unwrap().0,
+                "Speakers (Realtek HD Audio)",
+                "host_audio={host_audio}"
+            );
+            assert!(!w.loopback_last_resort, "host_audio={host_audio}");
+        }
+    }
+
+    /// Cables and VoiceMeeter strips are CORRECTNESS risks (they re-capture what the mic
+    /// writes — echo/feedback), not quality risks: never the loopback, not even as a last
+    /// resort. The plan stays honestly unsatisfiable.
+    #[test]
+    fn cable_and_voicemeeter_never_last_resort() {
+        let renders = [
+            ep("CABLE Input (VB-Audio Virtual Cable)"),
+            ep("CABLE In 16ch (VB-Audio Virtual Cable)"),
+            ep("Voicemeeter Aux Input (VB-Audio Voicemeeter AUX VAIO)"),
+        ];
+        let captures = [ep("CABLE Output (VB-Audio Virtual Cable)")];
+        for host_audio in [false, true] {
+            let w = plan(&renders, &captures, None, host_audio);
+            assert!(w.loopback_render.is_none(), "host_audio={host_audio}");
+            assert!(!w.loopback_last_resort, "host_audio={host_audio}");
+            assert!(w.loopback_unsatisfiable(), "host_audio={host_audio}");
+        }
     }
 
     /// Operator override beats the candidate order.
@@ -413,9 +621,9 @@ mod tests {
         }
     }
 
-    /// A generically-"virtual" leftover (unknown vendor cable) is refused too: `leftover()`
-    /// applies `virtualish`, so a virtual endpoint that slips past the name list can't become
-    /// the loopback.
+    /// A generically-"virtual" leftover (unknown vendor cable) is refused too: the last resort
+    /// accepts ONLY the Steam Streaming Speakers, so a virtual endpoint that slips past
+    /// `excluded_from_loopback`'s name list still can't become the loopback.
     #[test]
     fn unknown_virtual_never_loopback() {
         let renders = [
@@ -425,4 +633,44 @@ mod tests {
         let w = plan(&renders, &[], None, false);
         assert!(w.loopback_render.is_none());
     }
+
+    /// The fingerprint keys the capture loop's "wait for an endpoint change" state: it must
+    /// ignore enumeration order (Windows churns it), react to any topology change, and never
+    /// alias the render and capture directions.
+    #[test]
+    fn fingerprint_order_independent_topology_sensitive() {
+        let a = [ep("Speakers (Realtek HD Audio)"), ep("CABLE Input")];
+        let a_rev = [ep("CABLE Input"), ep("Speakers (Realtek HD Audio)")];
+        let caps = [ep("CABLE Output")];
+        assert_eq!(fingerprint(&a, &caps), fingerprint(&a_rev, &caps));
+        assert_ne!(fingerprint(&a, &caps), fingerprint(&a[..1], &caps));
+        assert_ne!(fingerprint(&a, &caps), fingerprint(&caps, &a));
+    }
+
+    /// The unsatisfiable-plan diagnosis must name what the mic reserved and advise ONLY the
+    /// remedies not already taken: in the field case the Steam pair was installed (so "install
+    /// Steam" would point at a fix the box already had) and the cable was missing (so VB-CABLE
+    /// is the advice that actually frees the silent sink).
+    #[test]
+    fn describe_no_loopback_skips_satisfied_remedies() {
+        // Field shape minus the Speakers (mic holds the Streaming Microphone, nothing else).
+        let renders = [ep("Altavoces (Steam Streaming Microphone)")];
+        let captures = [ep("Microphone (Steam Streaming Microphone)")];
+        let w = plan(&renders, &captures, None, false);
+        assert!(w.loopback_unsatisfiable());
+        let msg = describe_no_loopback(&renders, &w);
+        assert!(msg.contains("reserved for the virtual mic"), "{msg}");
+        assert!(msg.contains("VB-Audio Virtual Cable"), "{msg}");
+        assert!(!msg.contains("install Steam"), "{msg}");
+
+        // Cable-only headless box: VB-CABLE is already installed (and freeing it wouldn't help
+        // anyway), while the Steam pair is the remedy that adds a capturable sink.
+        let renders = [ep("CABLE Input (VB-Audio Virtual Cable)")];
+        let captures = [ep("CABLE Output (VB-Audio Virtual Cable)")];
+        let w = plan(&renders, &captures, None, false);
+        assert!(w.loopback_unsatisfiable());
+        let msg = describe_no_loopback(&renders, &w);
+        assert!(msg.contains("install Steam"), "{msg}");
+        assert!(!msg.contains("install VB-Audio Virtual Cable"), "{msg}");
+    }
 }

crates/punktfunk-host/src/native/handshake.rs

@@ -338,7 +338,10 @@ pub(super) async fn negotiate(
     // PyroWave does its own RGB→YCbCr CSC and its capture mode always delivers a full-chroma
     // (RGB/BGRA) source on both OSes — the capturer gate is inherently satisfied; the real
     // gate is `can_encode_444` (the full-res-chroma CSC variant existing on this OS).
-    let capture_supports_444 = codec == crate::encode::Codec::PyroWave
+    // Named for the whole capture→encoder INGEST chain, not the capturer: on Windows the
+    // deciding fact is the encoder backend (direct NVENC only), and a field report burned
+    // real time hunting a capture problem because the old `capture_supports_444` key said so.
+    let ingest_chain_supports_444 = codec == crate::encode::Codec::PyroWave
         || crate::capture::capturer_supports_444(crate::encode::resolved_backend_ingests_rgb_444());
     // 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
@@ -350,7 +353,7 @@ pub(super) async fn negotiate(
         crate::encode::Codec::H265 | crate::encode::Codec::PyroWave
     ) && host_wants_444
         && client_supports_444
-        && capture_supports_444
+        && ingest_chain_supports_444
     {
         tokio::task::spawn_blocking(move || crate::encode::can_encode_444(codec))
             .await
@@ -358,6 +361,23 @@ pub(super) async fn negotiate(
     } else {
         false
     };
+    // The client's 4:4:4 setting IS the VIDEO_CAP_444 bit — when the user flipped it on and
+    // the session still resolves 4:2:0, name the losing gate. (The PyroWave mode-size gate
+    // below warns for itself.)
+    if host_wants_444 && client_supports_444 && !gpu_supports_444 {
+        let reason = if !matches!(
+            codec,
+            crate::encode::Codec::H265 | crate::encode::Codec::PyroWave
+        ) {
+            "the negotiated codec only carries 4:2:0 — 4:4:4 needs HEVC or PyroWave"
+        } else if !ingest_chain_supports_444 {
+            "this host's encoder backend can't ingest full chroma — 4:4:4 needs direct \
+             NVENC (NVIDIA) or the PyroWave codec"
+        } else {
+            "the GPU declined the 4:4:4 encode profile probe"
+        };
+        tracing::info!(reason, "4:4:4 requested but the session negotiates 4:2:0");
+    }
     let chroma = if gpu_supports_444 {
         crate::encode::ChromaFormat::Yuv444
     } else {
@@ -383,7 +403,7 @@ pub(super) async fn negotiate(
         chroma = ?chroma,
         host_wants_444,
         client_supports_444,
-        capture_supports_444,
+        ingest_chain_supports_444,
         "encode chroma"
     );
 

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

@@ -71,7 +71,7 @@ pub(super) fn synthetic_stream(
     Ok(())
 }
 
-/// Bounds a speed-test [`ProbeRequest`] before bursting: a 3 Gbps / 5 s ceiling keeps a probe from
+/// Bounds a speed-test [`ProbeRequest`] before bursting: a 10 Gbps / 5 s ceiling keeps a probe from
 /// monopolizing the link or stalling the stream for too long. The ceiling is set ABOVE the session
 /// bitrate cap ([`MAX_BITRATE_KBPS`], 2 Gbps) on purpose — a probe should be able to demonstrate
 /// headroom past the rate a session will actually be configured to use, so the client can pick a

docs-site/content/docs/configuration.md

@@ -241,6 +241,10 @@ A few knobs are read by the native **clients**, not the host:
 | `PUNKTFUNK_PREFER_PYROWAVE` | `1` | Ask for the [PyroWave](/docs/pyrowave) wavelet codec on a wired link, where the client's own setting isn't reachable (the gamepad console, a headless launch). |
 | `PUNKTFUNK_OSD_SCALE` | multiplier, e.g. `1.5` *(default `1`)* | Size of the in-stream overlay — the stats OSD, the capture hint and the start banner. They already follow your display's scaling setting (200 % display → twice the pixels), so set this only to nudge that: bigger for a TV across the room, smaller if your compositor reports an aggressive scale. Clamped to 0.5×–4×, and a line that would run off the screen is shrunk to fit. |
 | `PUNKTFUNK_NO_AEC` | `1` | Turn the microphone's echo cancellation off for this run, whatever **Echo cancellation** says in [client settings](/docs/client-settings#audio). One-way: it can only switch the processing off, never back on, and the setting is the normal way to control it. Linux and Windows clients. |
+| `PUNKTFUNK_PRESENT_MODE` | `mailbox` *(default)* · `fifo` · `immediate` · `fifo_relaxed` | How decoded frames meet the display (the Vulkan present mode). The default prefers MAILBOX — tear-free without queueing behind the vertical refresh — and falls back to FIFO (classic vsync) where the driver doesn't offer it. **AMD's Windows driver offers no MAILBOX**, so those clients run FIFO, which adds a standing frame-pacing wait (up to one refresh interval). `immediate` removes that wait but can tear; `fifo_relaxed` only tears when a frame is late. If your latency floor matters more than tearing, try `immediate` and judge by eye. |
+| `PUNKTFUNK_ABR_PROBE_KBPS` | kbps, e.g. `900000` | The startup link-capacity probe's burst target (default 2 Gbps — deliberately above any plausible link so the burst measures the link, not itself). Lower it on links the burst shouldn't slam, or when the measured ceiling comes out wrong for your setup. |
+| `PUNKTFUNK_ABR_PROBE` | `0` | Skip the startup link-capacity probe entirely. The adaptive-bitrate climb ceiling then stays at the negotiated starting rate — a blunt instrument; prefer `PUNKTFUNK_ABR_MAX_MBPS`. |
+| `PUNKTFUNK_ABR_MAX_MBPS` | Mbps, e.g. `300` | Hard cap on the adaptive bitrate's climb ceiling, whatever the startup probe measured. The escape hatch when adaptive sessions keep climbing past what your client's **decoder** can sustain (periodic hitch + "receive backlog stopped draining" in the client log). An explicit bitrate setting still bypasses ABR entirely. |
 
 ## Bitrate
 

docs/releases/README.md

@@ -31,6 +31,35 @@ even across a tag re-point.
 Canary / `-rc` builds have **no** file here on purpose: they get no curated body and are not
 announced.
 
+## Google Play "What's new": `whatsnew/vX.Y.Z.txt`
+
+Play shows its own release notes on the Play Store listing and in the Play Store app, and caps
+them at **500 characters per language** — the `vX.Y.Z.md` body is two orders of magnitude too
+long, so it gets its own short file: `docs/releases/whatsnew/vX.Y.Z.txt`.
+
+Write it for a **phone/TV user**, not a host operator: only what changed in the Android app is
+worth their 500 characters. Plain text (Play renders no markdown), one `•` bullet per line, same
+voice rules as below. Copy `whatsnew/TEMPLATE.txt`.
+
+**A `vX.Y.Z` tag without this file fails the android job before it builds.** This is a hard gate,
+not a warning, because the failure it prevents is silent: when the file is missing Play does not
+show an empty "What's new" — it **carries the previous release's text onto the new version**, so
+the store listing describes a build nobody is getting, and nothing surfaces that but reading the
+listing. It is the same shape as the v0.22.3 notes announcing a feature that release never
+contained. The gate also rejects a file byte-identical to another release's, which is that bug
+reached by copy-paste instead of by omission.
+
+The gate runs first in the job, so a miss costs a second and leaves nothing half-published —
+no build, no assets on the Gitea release, nothing on Play. Two more checks sit downstream:
+`play-upload.py` refuses text over the 500-char cap (printing the real count) before it uploads,
+because the API only rejects oversized notes at commit, by which point the AAB is already on Play.
+
+Canary is exempt: it has no curated notes, and Play reusing text for internal testers costs
+nothing.
+
+Same freeze rule as the notes: once the tag exists, this file is the record of what that
+versionCode shipped.
+
 ## Voice & format
 
 **Write for the people who USE Punktfunk to stream their games and desktops — not for the people who

docs/releases/whatsnew/TEMPLATE.txt

@@ -0,0 +1,27 @@
+• <The headline change, in what the user gets — not what was built.>
+• <Second thing. Name devices they recognize: a phone, an Android TV, a DualSense.>
+• <Third. Stop at what fits; 500 characters is the hard cap, and it is small.>
+
+HOW TO USE THIS FILE
+  Copy to vX.Y.Z.txt, replace every line, delete this block. It is skipped by the CI gate by
+  name, so leaving it in place never blocks a release — but a copy that still says "<The
+  headline change>" will ship to the Play Store exactly as written. Nothing checks your prose.
+
+WHAT BELONGS HERE
+  Only what changed in the ANDROID APP. Host-side work — Windows installers, gamescope, the web
+  console — means nothing to someone reading a phone app's store listing, and it is spending
+  characters you do not have. The full release notes in ../vX.Y.Z.md are where that lives.
+
+RULES THE CI GATE ENFORCES (.gitea/workflows/android.yml)
+  * The file must exist for a vX.Y.Z tag, or the release fails before it builds. Play does not
+    show "no notes" when the file is missing — it carries the PREVIOUS release's text onto the
+    new version, and nobody notices until they read the store listing.
+  * It must not be byte-identical to another release's file.
+  * play-upload.py refuses anything over 500 characters and prints the real count.
+
+RULES NOTHING ENFORCES
+  * Plain text. No markdown — Play renders none of it, so `**bold**` ships as asterisks.
+  * One `•` bullet per line.
+  * Same voice as ../README.md: lead with what the user can now do, no internal vocabulary.
+  * Frozen once the tag exists. Editing it later does not change what already shipped; it only
+    misleads the next person who reads it as the record of that versionCode.

docs/releases/whatsnew/v0.23.0.txt

@@ -0,0 +1,4 @@
+• Much lower latency: a new frame scheduler cut glass-to-glass delay by about a third on the phones we measured, and the host can now line its capture up with your screen.
+• Microphone: mute it mid-stream, and echo cancellation is on by default.
+• DualSense controllers work over USB.
+• AV1 is picked automatically when your phone and host both support it.

include/punktfunk_core.h

@@ -1767,7 +1767,11 @@ typedef struct {
     // Application goodput bytes / access units the host offered.
     uint64_t host_bytes;
     uint32_t host_packets;
-    // The host's measured burst duration, milliseconds (the throughput denominator).
+    // The throughput denominator, milliseconds: the client-measured burst receive interval
+    // (first → last probe-packet arrival) once `done`; the host's measured send-window
+    // duration when fewer than two probe packets arrived (no interval to measure from). The
+    // host duration alone overstates throughput — its window closes while the bottleneck
+    // queue is still draining toward the client.
     uint32_t elapsed_ms;
     // Delivered wire throughput = `recv_bytes * 8 / elapsed_ms` (kilobits/second).
     uint32_t throughput_kbps;
@@ -2846,7 +2850,7 @@ PunktfunkStatus punktfunk_connection_wants_decode_latency(const PunktfunkConnect
 
 #if defined(PUNKTFUNK_FEATURE_QUIC)
 // Start a bandwidth speed test: ask the host to burst filler over the data plane at
-// `target_kbps` of goodput for `duration_ms` (each clamped host-side to ≤ 3 Gbps / ≤ 5 s),
+// `target_kbps` of goodput for `duration_ms` (each clamped host-side to ≤ 10 Gbps / ≤ 5 s),
 // *briefly pausing video*. Non-blocking — poll [`punktfunk_connection_probe_result`] until its
 // `done` field is 1. Starting a probe resets any prior measurement.
 //

packaging/windows/drivers/pf-gamepad/src/lib.rs

@@ -109,10 +109,13 @@ static DS_FEATURE_PAIRING: [u8; 20] = [ // 0x09 pairing info (MAC at 1..7)
     0x00, 0x00, 0x00, 0x00,
 ];
 #[rustfmt::skip]
-static DS_FEATURE_FIRMWARE: [u8; 64] = [ // 0x20 firmware info
+static DS_FEATURE_FIRMWARE: [u8; 64] = [ // 0x20 firmware info; bytes 44..46 = update version,
+    // kept ABOVE Sony's real releases (0x0630 as of 2026-08) — an older value makes PlayStation
+    // Accessories and libScePad titles demand a firmware update the virtual pad cannot take.
+    // Mirrors inject/proto/dualsense_proto.rs DS_FEATURE_FIRMWARE; keep the two in sync.
     0x20, 0x4A, 0x75, 0x6E, 0x20, 0x31, 0x39, 0x20, 0x32, 0x30, 0x32, 0x33, 0x31, 0x34, 0x3A, 0x34,
     0x37, 0x3A, 0x33, 0x34, 0x03, 0x00, 0x44, 0x00, 0x08, 0x02, 0x00, 0x01, 0x36, 0x00, 0x00, 0x01,
-    0xC1, 0xC8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x54, 0x01, 0x00, 0x00,
+    0xC1, 0xC8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x99, 0x09, 0x00, 0x00,
     0x14, 0x00, 0x00, 0x00, 0x0B, 0x00, 0x01, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 ];
 

packaging/winget/server/README.md

@@ -108,16 +108,34 @@ trusted certificate, which is what the edge vhost provides in production.
 
 1. **DNS** — `winget.punktfunk.unom.io` → the unom-1 hcloud box, in the `unom.io` Cloudflare zone
    (DNS-only, same as `docs`). ✅ *done*
-2. **Caddy vhost** on unom-1, next to the existing `docs.punktfunk.unom.io` block:
+2. **Caddy vhost** — in **`unom/infra`, `caddy/Caddyfile`**, next to the existing
+   `docs.punktfunk.unom.io` block. ✅ *done*
 
    ```caddyfile
    winget.punktfunk.unom.io {
-       reverse_proxy 127.0.0.1:3240
+       import security_headers
+       reverse_proxy localhost:3240
    }
    ```
 
-   Until this exists the hostname resolves but the TLS handshake fails — Caddy has no certificate
-   for a name it does not serve. That is the expected state, not a broken deploy.
+   ⚠ **Not by hand on the box.** `~/caddy/Caddyfile` on unom-1 looks like the config but is a copy
+   that `deploy-all.sh` rsyncs over from `unom/infra`, and there is no `.git` there to warn you. A
+   vhost added only on the box survives until the next deploy and no longer: this one was
+   hand-added on 2026-07-26, and the 2026-07-31 hardening commit rewrote the file from the repo's
+   own copy and deleted it — its message says "all 7 vhosts" when there were 8 live.
+
+   Until the vhost exists the hostname resolves but the TLS handshake fails — Caddy has no
+   certificate for a name it does not serve. That is the expected state on first setup, not a
+   broken deploy, but it is also exactly how the clobber presents later: an `internal_error`
+   (alert 80) with no peer certificate, which winget reports as
+   `WINHTTP_CALLBACK_STATUS_FLAG_SECURITY_CHANNEL_ERROR` / `0x8a15003b` and which looks like a
+   client bug. Diagnose by SNI, not by port 80 — Caddy 308s *every* Host to https, including names
+   it has never heard of, so a redirect there proves nothing:
+
+   ```bash
+   openssl s_client -connect winget.punktfunk.unom.io:443 \
+     -servername winget.punktfunk.unom.io </dev/null 2>&1 | grep -E '^subject=|alert'
+   ```
 3. Run `deploy-services.yml` to place the compose file and start the container. It serves 503 until
    a catalogue exists — expected, and visible on `/healthz`.
 4. Publish a stable tag, or build and ship the catalogue by hand: