WebXR Chromium: verified in the headset, including 360 video

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/how-the-frame-works.md

@@ -44,7 +44,7 @@ Lepton (Android 11, podman container "lepton-dev") ← its own panel, app 305600
 | Lepton Development deletes every ADB-installed app when it exits (`clear_baked_app_data "non steamlaunch container"` in `…/common/Lepton/lepton`) unless `LEPTON_NO_CLEANUP` is set. | [apks.md](apks.md) |
 | Any APK can run as its own Lepton instance: run `…/common/Lepton/lepton waitforexitandrun -- app.apk` with `SteamAppId` set and `STEAM_COMPAT_DATA_PATH` under `~/.local/share/Steam`. Data persists and each gets its own container and panel. `frame/android/lepton-app.sh`, `ui/frame_android.py`. | [apks.md](apks.md) |
 | The Steam client runs with `-cef-enable-debugging`, so its UI answers Chrome DevTools on loopback `127.0.0.1:8080`. The `SharedJSContext` page has `appStore` (owned apps), `downloadsStore` and `SteamClient.*`. `steam steam://install/<appid>` over SSH installs an owned game; when the options dialog shows (state 7), `SteamClient.Installs.ContinueInstall()` accepts it. **Verified 2026-09-25** with Balatro and Broforce. The Frame rating is `steam_hw_compat_category_packed >> 8 & 3`. | [steam-games.md](steam-games.md), `ui/frame_steam.py` |
-| Chromium Flatpak 154 has **no immersive WebXR**: `navigator.xr` exists, but `isSessionSupported("immersive-vr")` returns `false`. Web VR180 players (DL8/DeoVR embeds) still play video inline as a flat, pannable view, and their VR button opens a tab on immersiveweb.dev. Forcing it doesn't help. `--enable-features=OpenXR,WebXR --force-webxr-runtime=openxr`, with `/opt/steamvr` and `XR_RUNTIME_JSON` exposed to the Flatpak, still returns `false`. The aarch64 Linux binary has no OpenXR code at all (no `XR_RUNTIME_JSON`, `xrGetInstanceProcAddr` or loader strings), even though `chrome://flags` lists `#webxr-runtime` → OpenXR. **Why (verified against source 2026-09-25):** M154 is the first release that compiles OpenXR on Linux (`enable_openxr` includes `is_linux`, `checkout_openxr` is true in Flathub's tarball, and Flathub's GN args don't turn it off). But `content/services/isolated_xr_device/xr_runtime_provider.cc` only creates an OpenXR device under `ENABLE_OPENXR && IS_WIN`, on 154, 155 and `main`. Nothing on Linux calls the OpenXR code, so the linker drops it. The missing pieces are two unmerged Gerrit CLs (bug 506004811): [8132979](https://chromium-review.googlesource.com/c/chromium/src/+/8132979) wires the provider on Linux (with `kOpenXR` still off by default, so it needs `--enable-features=OpenXR`), and [8441736](https://chromium-review.googlesource.com/c/chromium/src/+/8441736) runs the XR service in a sandbox that allows SteamVR's sockets. The Frame does have an aarch64 runtime: `~/.config/openxr/1/active_runtime.json` → SteamVR `bin/linuxarm64/vrclient.so`. To watch in 3D, use a native player, or a Chromium built with those two CLs ([webxr-chromium.md](webxr-chromium.md)). That build (156.0.8071.0, arm64) reports `immersive-vr` as supported and starts a session that SteamVR takes as its scene app (verified 2026-09-26, seccomp sandbox off). What it looks like in the headset is still untested. Started with `--remote-debugging-port=9222`, Chromium answers DevTools on loopback. **Verified 2026-09-25**, BUILD_ID 20260922.6101926. | Web video, [panels.md](panels.md) |
+| Chromium Flatpak 154 has **no immersive WebXR**: `navigator.xr` exists, but `isSessionSupported("immersive-vr")` returns `false`. Web VR180 players (DL8/DeoVR embeds) still play video inline as a flat, pannable view, and their VR button opens a tab on immersiveweb.dev. Forcing it doesn't help. `--enable-features=OpenXR,WebXR --force-webxr-runtime=openxr`, with `/opt/steamvr` and `XR_RUNTIME_JSON` exposed to the Flatpak, still returns `false`. The aarch64 Linux binary has no OpenXR code at all (no `XR_RUNTIME_JSON`, `xrGetInstanceProcAddr` or loader strings), even though `chrome://flags` lists `#webxr-runtime` → OpenXR. **Why (verified against source 2026-09-25):** M154 is the first release that compiles OpenXR on Linux (`enable_openxr` includes `is_linux`, `checkout_openxr` is true in Flathub's tarball, and Flathub's GN args don't turn it off). But `content/services/isolated_xr_device/xr_runtime_provider.cc` only creates an OpenXR device under `ENABLE_OPENXR && IS_WIN`, on 154, 155 and `main`. Nothing on Linux calls the OpenXR code, so the linker drops it. The missing pieces are two unmerged Gerrit CLs (bug 506004811): [8132979](https://chromium-review.googlesource.com/c/chromium/src/+/8132979) wires the provider on Linux (with `kOpenXR` still off by default, so it needs `--enable-features=OpenXR`), and [8441736](https://chromium-review.googlesource.com/c/chromium/src/+/8441736) runs the XR service in a sandbox that allows SteamVR's sockets. The Frame does have an aarch64 runtime: `~/.config/openxr/1/active_runtime.json` → SteamVR `bin/linuxarm64/vrclient.so`. To watch in 3D, use a native player, or a Chromium built with those two CLs ([webxr-chromium.md](webxr-chromium.md)). That build (156.0.8071.0, arm64) reports `immersive-vr` as supported and starts a session that SteamVR takes as its scene app. With the headset on, the WebXR samples scene and three.js's stereo 360 video demo showed in 3D (verified 2026-09-26, seccomp sandbox off). Started with `--remote-debugging-port=9222`, Chromium answers DevTools on loopback. **Verified 2026-09-25**, BUILD_ID 20260922.6101926. | Web video, [panels.md](panels.md) |
 | **DeoVR (Steam app 837380, Windows/Unity) runs immersively** under Proton ARM64 + FEX: Unity's OpenVR XR plugin finds `OpenVR Headset(Steam Frame)` and the `frame_controller`, the GPU shows as Turnip Adreno 750, and AVPro Video decodes through `MF-MediaEngine-Hardware`. It played 7680×3840 and 8192×4096 H.265 VR180 SBS streams in dome/fisheye mode (`FirstFrameReady`). Unity's own `VideoPlayer` (used for grid thumbnails) fails with `0xc00d36bb`, so thumbnail previews stay blank. The first launch takes about 45 s (`ComputeShaders: InitAsync`). Log: `compatdata/837380/pfx/drive_c/users/steamuser/AppData/LocalLow/Deo VR/Deo VR/Player.log`. **Verified 2026-09-25**, BUILD_ID 20260922.6101926. | [vr-video.md](vr-video.md) |
 | **Wolvic (VR browser APK) runs in Lepton against SteamVR's OpenXR**, with limits. The stock Lynx build aborts (`Runtime doesn't support selected swapChain color format`: it wants `GL_RGBA8`), and the stock Quest build fails with `XR_ERROR_API_VERSION_UNSUPPORTED`. Patching `DeviceDelegateOpenXR::GetSwapChainCreateInfo` in the Lynx build's `libnative-lib.so` to `GL_SRGB8_ALPHA8` (0x8C43) and re-signing fixes start-up. The Gecko engine then segfaults in `libxul`. The Chromium-engine build (Lynx v1.3-chromium) browses fine as an immersive app. Its page reports `isSessionSupported("immersive-vr") == true`, and `requestSession` succeeds, running about 36 rAF/s, but the headset shows **black** for WebXR content, or Wolvic's loading spinner that never clears, until the session is ended. Video decodes on the software `OMX.google.h264.decoder`. Tapping the URL bar's selection menu crashes it (no clipboard service). Open URLs with `am start -a VIEW -n com.igalia.wolvic/.VRBrowserActivity -d <url>` over the instance's ADB. DevTools is at `localabstract:content_shell_devtools_remote`. **Verified 2026-09-25**, BUILD_ID 20260922.6101926. | Web VR video, [apks.md](apks.md) |
 | Tailscale runs without root as a userspace `tailscaled` user service (static arm64 build in `~/.local/share/tailscale`, lingering on). In userspace mode, inbound tailnet connections reach the Frame's **loopback**, so every port, including DevTools on 8080, is reachable from the tailnet. **Verified 2026-09-25.** | [tailscale.md](tailscale.md), `scripts/tailscale-on-frame.sh` |