docs(windows-client): correct the WinUI 3 record — reactor IS used (PR #4499)

The winit-commit docs claimed "Reactor rejected, no SwapChainPanel hatch" — that was wrong.
windows-rs PR #4499 added the SwapChainPanel widget; the client now uses WinUI 3 via
windows-reactor. Update CLAUDE.md M4, the bootstrap-doc status banner (reactor integration:
pinned git dep, CARGO_WORKSPACE_DIR, App-SDK build.rs, LL-hook stream input), and the
docs-site clients page (WinUI 3, launch-and-pick-a-host).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -113,20 +113,25 @@ Low-latency desktop/game streaming stack, Linux-first, with a shared Rust protoc
    presenter (wp_presentation feedback, tearing-control, Vulkan Video on NVIDIA) —
    **wgpu/winit rejected** (no dmabuf import / presentation feedback / shortcuts-inhibit).
    **Windows stage 1 done 2026-06-15** (`crates/punktfunk-client-windows`, binary
-   `punktfunk-client`): pure-Rust **winit + Direct3D11 flip-model swapchain** present (WARP
+   `punktfunk-client`): pure-Rust **WinUI 3** UI via **windows-reactor** (a declarative React-like
-   fallback for the GPU-less dev box; runtime-compiled fullscreen-triangle shaders, Contain-fit
+   framework backed by WinUI; PR #4499 added the `SwapChainPanel` widget + `set_swap_chain`). The
-   letterbox), **FFmpeg software HEVC decode** (D3D11VA hw decode is the follow-up), **WASAPI**
+   video is a **`SwapChainPanel`** bound to a **D3D11 composition swapchain** (WARP fallback for
-   shared-mode render + mic capture, keyboard (physical-`KeyCode`→VK) + absolute mouse + wheel
+   the GPU-less dev box; runtime-compiled fullscreen-triangle shaders, Contain-fit letterbox),
-   capture (Moonlight-style click-to-capture, Ctrl+Alt+Shift+Q release), **SDL3** gamepads
+   driven by reactor's per-frame `on_rendering`. **FFmpeg software HEVC decode** (D3D11VA hw decode
-   (rumble/lightbar/DualSense, built from source), `mdns-sd` discovery, shared client identity
+   is the follow-up), **WASAPI** render + mic capture, **SDL3** gamepads (rumble/lightbar/DualSense),
-   + TOFU + SPAKE2 PIN pairing (`--connect`/`--discover`/`--pair`/`--headless`). Builds + clippy
+   `mdns-sd` discovery, and the full trust surface — all **in-app**: host list (live mDNS + saved +
-   + fmt + tests green on `x86_64-pc-windows-msvc` (built on the dev VM). **UI = winit + raw
+   manual), settings (resolution/refresh/mic), SPAKE2 PIN pairing screen, TOFU, pinned-fp-mismatch
-   D3D11, NOT WinUI3/Reactor** — a research pass confirmed windows-rs Reactor ships no
+   re-pair. **Stream input** is Win32 low-level hooks (`WH_KEYBOARD_LL`/`WH_MOUSE_LL`) — reactor
-   `SwapChainPanel`/`SetSwapChain` escape hatch, so it can't host the presenter (the bootstrap
+   exposes no raw key/pointer events; native Windows VK + absolute mouse (client-rect Contain-fit) +
-   doc's sanctioned fallback). Gotcha: `CARGO_HOME` must be an ASCII path — the `ü` in the dev
+   wheel, Ctrl+Alt+Shift+Q capture toggle. `--headless`/`--discover` keep CLI paths. Builds + clippy
-   box's username breaks SDL3's MSVC precompiled-header build. Next: live host validation
+   + fmt green on `x86_64-pc-windows-msvc` (on the dev VM). **windows-reactor is unpublished** (git
-   (no GPU on the dev box → glass-to-glass defers to the RTX box), D3D11VA hw decode + 10-bit/HDR
+   dep pinned to commit `b4129fcc`; `windows` pinned to the SAME commit so `IDXGISwapChain1` unifies
-   present, a native host-list/settings GUI, and RAWINPUT relative-mouse pointer-lock.
+   with `set_swap_chain`); its `build.rs` downloads the Win App SDK NuGets + needs `CARGO_WORKSPACE_DIR`
+   set (in the VM build env; `/temp`+`/winmd` gitignored). Gotcha: `CARGO_HOME` must be an ASCII path
+   — the `ü` in the dev box's username breaks SDL3's MSVC precompiled-header build. Next: **on-glass
+   validation** (the dev VM is headless/Session-0 → the WinUI window needs a display: RDP or the RTX
+   box), D3D11VA hw decode + 10-bit/HDR present, RAWINPUT relative-mouse pointer-lock, and a per-host
+   speed test in the UI.
 2. **Sub-frame pipelining**: overlap encode and transmit within a frame. Requires a direct
    NVENC SDK wrapper (libavcodec only emits whole AUs) — the next big latency lever (~2–4 ms
    at high res).

docs-site/content/docs/clients.md

@@ -57,16 +57,17 @@ punktfunk-client --connect <host>:9777   # skip the picker, start a session imme
 ## Windows desktop client (in development)
 
 `punktfunk-client` for Windows (`crates/punktfunk-client-windows`) is the native graphical client
-for Windows — pure Rust, the same `punktfunk/1` core as the Apple and Linux apps, with a winit +
+for Windows — pure Rust, the same `punktfunk/1` core as the Apple and Linux apps, with a **WinUI 3**
-Direct3D11 present surface, WASAPI audio, FFmpeg decode, SDL3 controllers, network discovery, and
+UI (host list, settings, PIN pairing) and the video on a `SwapChainPanel`, plus WASAPI audio, FFmpeg
-PIN pairing. It builds on `x86_64-pc-windows-msvc` and runs the connect/decode/present/input path;
+decode, SDL3 controllers, network discovery, and PIN pairing. Launch it and pick a host from the
-hardware (D3D11VA) decode, 10-bit/HDR present, and a native host-list/settings window are in
+list, just like the Apple and Linux apps. It builds on `x86_64-pc-windows-msvc`; hardware (D3D11VA)
-progress, so it is not yet packaged. For now it is driven from the command line:
+decode, 10-bit/HDR present, and packaging are in progress, so it is not yet shipped. A headless CLI
+path exists for scripting/measurement:
 
 ```sh
+punktfunk-client                                   # open the WinUI 3 window (host list / settings)
 punktfunk-client --discover                        # list hosts on the network
-punktfunk-client --connect <host>:9777            # stream (trust-on-first-use)
+punktfunk-client --headless --connect <host>:9777  # no window: connect, count frames, print stats
-punktfunk-client --connect <host>:9777 --pair 1234 # pair with the PIN the host shows
 ```
 
 Until it ships, **Moonlight** remains the recommended way to stream to Windows (see below).

docs/windows-client-bootstrap.md

@@ -5,28 +5,42 @@ and live-validated on a real RTX 4090; the client is the remaining piece. This d
 starting point: the locked decisions, the reference code to port, the stack swaps, the dev loop, and
 the gotchas. Read it top to bottom, then start at **Phase 1** (de-risk Reactor first).
 
-## Status — stage 1 landed (2026-06-15)
+## Status — WinUI 3 client landed (2026-06-15)
 
 The client is implemented in `crates/punktfunk-client-windows` (binary `punktfunk-client`) and is
-**build + clippy + fmt + test green on `x86_64-pc-windows-msvc`** (built on the dev VM). Done: winit
+**build + clippy + fmt green on `x86_64-pc-windows-msvc`** (built on the dev VM). It is the **WinUI 3**
-window + **Direct3D11 flip-model swapchain** present (WARP on the GPU-less box; runtime-compiled
+client this doc planned: native chrome (host list, settings, in-app SPAKE2 PIN pairing) + the video on
-fullscreen-triangle shaders, Contain-fit letterbox), **FFmpeg software HEVC decode**, **WASAPI** render
+a **`SwapChainPanel`**, all in pure Rust.
-+ mic capture, keyboard/mouse/wheel capture (physical-`KeyCode`→VK, click-to-capture), **SDL3**
-gamepads, `mdns-sd` discovery, and the full trust surface (identity + TOFU + SPAKE2 PIN over
-`--connect`/`--discover`/`--pair`/`--headless`).
 
-- **Reactor was evaluated and rejected** (a research pass + the points below): windows-rs Reactor
+- **Reactor is viable after all — it is what we use.** The locked decision held. windows-rs
-  ships **no `SwapChainPanel` and no `ISwapChainPanelNative::SetSwapChain` escape hatch**, so it
+  [PR #4499](https://github.com/microsoft/windows-rs/pull/4499) (merged 2026-06-01) added a
-  cannot host a DXGI presenter. The client uses the doc's sanctioned fallback — **winit + a raw
+  `SwapChainPanel` widget to **`windows-reactor`** with `set_swap_chain` over
-  D3D11 swapchain on the HWND** — which builds and runs against WARP on the GPU-less VM. A native
+  `CreateSwapChainForComposition` — so a DXGI presenter *can* be hosted. (An earlier read that Reactor
-  WinUI look would need the `SwapChainPanel` hatch to land upstream first.
+  had no swapchain hatch was wrong/stale.) The UI is a declarative React-like tree
-- **Build gotcha (in addition to the ASCII *output* path below):** `CARGO_HOME` itself must be on an
+  (`App::new().render(app)`, `use_state`/`use_resource`/`use_effect` hooks, `list_view`/`text_box`/
-  **ASCII path** (e.g. `C:\Users\Public\.cargo`). SDL3's `build-from-source` compiles a precompiled
+  `combo_box`/`content_dialog`/`button`/`ToggleSwitch`); the video page is `swap_chain_panel()
-  header whose `#include` embeds the registry source path; the `ü` in the dev box's username makes
+  .on_ready(|p| p.set_swap_chain(&sc))` driven by `on_rendering`. **`present.rs`** owns the D3D11
-  MSVC's PCH/structured-output fail (`MSB8084` / `C4828`). Set `CARGO_HOME=C:\Users\Public\.cargo`.
+  composition swapchain (WARP fallback, runtime shaders, Contain-fit) — the same renderer, bound to
-- **Still pending:** live host validation (the dev box has no GPU → glass-to-glass numbers defer to
+  the panel instead of an HWND.
-  the RTX box), **D3D11VA hardware decode** + **10-bit/HDR present**, a native host-list/settings
+- **windows-reactor is unpublished** (`version 0.0.0`) and fast-moving — depend on it as a **git dep
-  GUI (CLI flags for now), and RAWINPUT relative-mouse pointer-lock. Phases 4–7 below are the map.
+  pinned to a commit** (`b4129fcc`), and pin the `windows` crate to the **same commit** so the
+  `IDXGISwapChain1` you pass to `set_swap_chain` satisfies reactor's `windows_core::Interface`. Its
+  `build.rs` downloads the Windows App SDK NuGets (Foundation/Interactive/Runtime) and stages the
+  bootstrap DLL + `resources.pri` next to the exe; it **`.unwrap()`s `CARGO_WORKSPACE_DIR`**, so set
+  it in the build env (`CARGO_WORKSPACE_DIR=C:\Users\Public\punktfunk`). It writes `/temp` + `/winmd`
+  to the workspace root (gitignored). The App SDK runtime must be installed to *run*.
+- **Stream input is Win32 low-level hooks**, not XAML: reactor exposes only keyboard *accelerators* +
+  pointer *button-state* (no raw key-down/up, no pointer position, no wheel), insufficient for a game
+  stream. `input.rs` installs `WH_KEYBOARD_LL`/`WH_MOUSE_LL` on the stream page (uninstalled on exit),
+  maps the pointer through the window client rect, sends native VK + abs mouse + wheel, with a
+  Ctrl+Alt+Shift+Q capture toggle. (A future alternative: generate `Microsoft.UI.Xaml.UIElement`
+  bindings from the staged winmd and subscribe to `KeyDown`/`PointerMoved` — scoped to the panel.)
+- **Build gotcha:** `CARGO_HOME` must be on an **ASCII path** (`C:\Users\Public\.cargo`). SDL3's
+  `build-from-source` PCH embeds the registry source path; the `ü` in the dev box's username makes
+  MSVC fail (`MSB8084` / `C4828`).
+- **Still pending:** **on-glass validation** — the dev VM is headless / SSH Session 0, so the WinUI
+  window can't show there; validate over RDP or on the RTX box. Then **D3D11VA hardware decode** +
+  **10-bit/HDR present**, RAWINPUT relative-mouse pointer-lock, and a per-host speed test in the UI.
 
 ## What we're building