Piik/docs/research/native-client-lifecycle.md

Native App Lifecycle

• Reviewed: 2026-09-17
• Scope: Windows capture idle/border semantics, native loopback input isolation, and Browser visibility of an unexpected App disconnect.
• Status: quiet-source, preview-queue and App-crash checks pass. The owner confirmed Windows 10 monitor sharing resolved; game-specific window replacement is not established by the quiet-source checks.

Current Evidence

An idle WGC source is not a capture-end signal. Source/target closure, control session loss and individual edge failures have separate owners. A Viewer may need a keyframe from the retained image while a source remains unchanged.

Source previews use the same serial control connection as share startup. A virtual-time reproduction with three three-second previews made the real NativeClient.startShare() time out at eight seconds, before its handler ran at nine seconds. The picker now sends one preview at a time, cancels unsent work when its source view is retired, and waits for the remaining preview before starting native media. Refresh and App replacement fence old results.

Browser Local-Network Consent

Chromium local-network access can hold a public site's loopback fetch until the user answers a browser prompt. Its split-permission implementation exposes loopback-network, with the older local-network-access name retained for browsers using a combined permission. An unsupported permission query is unknown, not denial. A loopback page can report prompt even though its loopback-to-loopback request needs no consent.

Fresh-profile Windows/Chrome 152 checks confirmed a real prompt, successful discovery after granting access, and source-list recovery by refreshing after the discovery deadline. Optional Viewer discovery consults the permission before waiting; later grants can be used by later connections without replacing healthy Browser media. These checks do not identify the original missing-window reporter's cause or establish other browsers' permission behavior.

Scope Decisions

• Keep one strict loopback wire and one-share/one-session fence.
• Recovery does not choose a different capture target, codec or media route.
• Do not add a tunnel watchdog, local-process authentication scheme, custom quality score, or compatibility alias in this phase.

The loopback identifier boundary is now aligned at 8-256 bytes, and the link gate is included in TypeScript checking. Evidence wording distinguishes scripted package gates from physical-device gates. The possible cloudflared orphan and the intentionally per-user local trust boundary remain separate decisions; no runtime change for either is claimed here.

Implemented Boundary

• Windows capture treats a quiet frame pool as idle. It retains one latest converted frame and emits it only when an explicit recovery keyframe request arrives; source-close and target-process signals remain the end conditions.
• Native Pion candidate input is syntax-checked with the existing ICE parser, bounded before queuing, and discarded when malformed, stale, or over capacity. Repeated answers for an edge are idempotent. Profile updates remain fenced to that same share session in the current loopback v9 wire.
• An unexpected Browser control-socket close now notifies the active Host owner; intentional user cleanup remains silent and uses the existing share fence.

Physical Evidence

• On 2026-09-04, a blank Windows Notepad window was selected as a native source. The capture process stayed alive beyond seven seconds without a new source change, grew from 7,664 to 16,095 output bytes after a K request, and then exited cleanly. This validates the quiet-source and retained-frame path on the current Windows host; it does not claim a cross-version Windows matrix.
• The same day, the local Native Host gate started a real Host/Viewer share, terminated the App process, and observed the Host return to its start-share control within the bounded gate. Browser, capture, server, ports, and profile cleanup all passed.
• On 2026-09-05, a Windows 11 build 26200 display-source check produced 91 hardware-H.264 frames at the 720p30 profile and exited normally. A separate source-window check stayed alive through 7.02 seconds without frames while minimized, then produced 17 frames within 540 ms of restoration. All owned processes, ports and profiles were cleaned up. Neither check establishes the reported Windows 10 monitor-start failure or game HWND recreation as fixed.
• On 2026-09-08, the current multi-output Windows VP8 Host gate captured only its own animated Chrome window. Live presets, paused changes, minimize/change resolution/restore/another change, and source replacement preserved the Viewer's media object. Closing the actual source ended the share; restarting delivered 30 new Viewer frames. Server-accepted Native quality evidence and process/port/profile cleanup passed. The gate's stale Node JSON-log assertion was corrected to the current Go text format, without changing evidence eligibility. This is not H264 overload, Win10, or game-window replacement evidence. The same owned-window sequence subsequently passed H264. Further physical runs use the serialized plan in TODO.

The multi-output Windows worker initially reapplied the source's frame-rate limit from each worker's first input timestamp. With jitter and a later worker start, this second limiter could reject frames already admitted by capture. Captured inputs now carry their existing cadence bound; a worker limits only when it needs a lower rate. Received encoded input has no such bound and keeps its output limiter. No capture ceiling, media clock or quality setting changed. In the same owned-window H264 720p15 SFU gate, the reported Native output went from 12 fps before this correction to 15 fps after it. Both runs decoded 300 720p frames, applied a live 480p change and cleaned up. This is a local cadence comparison, not a claim about hardware overload or all games.

Open Capture Reports

The Windows 10 report concerns selecting one entire monitor; application/window capture, including fullscreen games, works. CreateForMonitor supports Windows 10 1903 and later; the current single-HMONITOR call, identity checks and CreateFreeThreaded setup match the documented API. No missing general permission request has been established. Community reports of disabled capture services or invalid display contexts are leads, not a diagnosis of this user's machine. Projected WinRT exceptions now reach the existing capture-error boundary instead of escaping std::exception; that correction alone does not prove startup fixed. On 2026-09-09, the owner confirmed whole-display sharing works and closed this report. That field confirmation does not establish which earlier correction or environment change resolved it; no further workaround is justified by this report.

The original converter always fitted the captured pixel aspect into the output: 1280x960 into 1920x1080 yielded 1440x1080 content and 240-pixel side bars, even when Windows explicitly stretched that desktop source onto a 1920x1080 target. The Windows adapter now reads the active QueryDisplayConfig path and applies its target aspect only for explicit STRETCHED, a unique display path, exact source/frame dimensions, and display or physical full-client-area capture. Rotation changes the target aspect, not the orientation of already-oriented WGC pixels. Output profile dimensions and the one-encode media path are unchanged.

Display metadata refreshes on source geometry changes and existing periodic keyframes, without another timer or display-setting writes. Unknown/custom scaling, ambiguous cloned outputs and normal windows keep captured aspect. This does not prove fidelity to monitor-side scaling or vendor-private game panel-fit/MPO transforms: those may not appear in desktop display-path metadata. The CPU geometry check covers stretch, ordinary aspect, rotation and already- scaled input; the reported game's physical comparison remains acceptance work.

Windows explicitly permits a capture item to close when its application silently replaces the underlying window. Reattaching to another window is not equivalent to resuming the same selected target; this remains separate from the verified quiet/minimized-source behavior.

The 2026-09-08 owner clarification names CS2, fullscreen 4:3 stretched: leave the game, change advanced share settings, then return; the share ends on return. The ordinary-window gate does not reproduce exclusive-fullscreen/display-mode changes. Capture replacement overlap, target identity and device state remain separate hypotheses until that exact transition is observed.

Later that day, the Windows 11 candidate ran the actual installed CS2 in fullscreen 1920x1440. The desktop changed from 2560x1440 while the game was minimized to 1920x1440 after return. Two real HostPage pending updates returned to the game after 1,703 ms and 1,545 ms: H264 1080p30 to 720p30 and back. The Viewer received both actual sizes, retained its media object, and the game kept its HWND/process generation. The current candidate did not reproduce the reported interruption in this menu-level sequence. Game settings were restored byte-for-byte and all owned processes, ports and Browser profiles closed. An additional prolonged-background case failed to keep CS2 minimized before the settings action, so it is not a passed or failed capture check. Vendor-side stretch fidelity, in-match execution and the affected machine remain unverified.

The end-to-end review did confirm a separate presentation defect: share termination during a pending update cleared its token but retained the advanced draft. A restart used the last applied settings while controls could show the failed draft. Cleanup now restores the applied settings through the existing commit helper; no new state or recovery mechanism was added. This alone is not claimed as the cause of CS2 capture termination.

The later owner-supplied cbdd751 CS2 diagnostic bundle records three 720p30 update requests, all rejected while the existing 1080p30 share remains live. It contains no successful 720p commit or explicit rollback-to-1080 request. The Browser's failed-request rollback explains its controls returning to the committed profile, but the original generic error does not identify which preparation step failed or explain the reported brief Viewer-size change. Current diagnostics add fixed preparation rejection stages without changing capture recovery policy. Do not label the affected-device report resolved.

The matched 0675265 local reproduction then held CS2 minimized continuously for 8.6 seconds during a 720p request. Preparation failed with wait-timeout after 5,015 ms and controls reverted; the Viewer retained 1080p and its media object. The identical request succeeded in 438 ms after restoring the game. The affected machine's subsequent bundle independently records eleven update timeouts, three successes and one cancellation caused by share termination. This establishes a quiet-source/readiness error in the live-update path, not an old setting request overwriting a successfully installed replacement.

On 2026-09-09, matched cbb3d77 passed the corrected path through actual Windows Graphics Capture and Browser playback. An owned source stopped repainting and remained minimized for 8,378 ms: the 720p request stayed pending while the Viewer retained 1080p. Restoring the source delivered 720p in 1,868 ms; the next 1080p request delivered in 480 ms, retaining the media object. Both updates succeeded; all processes, ports and Browser profiles closed. This closes the reproduced quiet-source timeout defect. CS2 foreground automation did not complete that same post-fix sequence, so this does not establish game-specific display-mode or HWND replacement behavior.

That same bundle also contains two independent adaptive-output capture failures at H264 1440p60, one without a settings update in progress. A controlled 1440p60/12 Mbps high-entropy input produced a valid 1,609,216-byte keyframe and reproduced the one-MiB capture-envelope rejection. The MFT and RTP access-unit owners already permit four MiB. Aligning capture readers/writers removes that false fatal rejection, but does not by itself establish delivery: the separate 500-packet forwarding/pacing bound also loses that large recovery frame. Both boundaries must be verified before describing the large-frame report as fixed.

The aligned 4,096-packet source/pacing/reassembly window subsequently delivered two copies of that actual keyframe byte-for-byte with zero paced drops or assembly loss. The 500-packet comparison dropped 1,182 packets and reconstructed none. Active fixture heap usage increased by roughly ten to thirteen MiB; LiveKit's packet cache still grows lazily and all queues remain bounded. Go capture and transport now share the encoded-frame bounds owner. This fixes a reproduced legal-input failure, not proof that every compound adaptive-output error in the field had the same cause; distinct failure stages preserve that remaining distinction.

The cbdd751 Vivaldi bundle shows two successful Native H264 1080p30 capture starts followed by a local outbound PeerConnection remaining connecting for about 7.985 seconds. The Browser bridge's eight-second startup timeout then stops the Native share cleanly. This is a local media-bridge failure boundary, not evidence that Windows capture or the control WebSocket failed. That bundle does not distinguish ICE from DTLS or a Browser policy. Current diagnostics record those states and candidate-type counts separately; the UI reports a connection error. The subsequent 0675265 bundle shows four successful capture starts, each with two Native UDP host candidates, no usable remote candidates, ICE stuck checking and no DTLS connection before the same deadline.

The owner then confirmed the affected Vivaldi report was resolved: a VPN extension forcibly disabled Broadcast IP for Best WebRTC Performance; correcting the setting/extension restored Native sharing. The confirmed cause is that extension's WebRTC policy, not unsupported Windows capture. VPN extensions may reapply the override; the Chromium WebRTC FAQ owns the user steps. This does not authorize a Browser-specific transport fallback.

An isolated Chrome 152.0.7977.82 data-channel A/B verifies the policy mechanism: default handling gathers one UDP host candidate per peer and connects ICE/DTLS in 33 ms; disable_non_proxied_udp gathers no candidates and remains unconnected at 8,009 ms. The check uses fresh profiles and the effective --webrtc-ip-handling-policy switch, without capture, encoding or user-profile changes. This establishes Chromium's policy mechanism; the affected Vivaldi case was resolved by the owner's setting correction above. Extra STUN or a longer timeout cannot restore candidates disabled by that policy.

Primary references: CreateForMonitor, CreateFreeThreaded, capture item closure, and WinRT exceptions. Aspect references: active display paths, scaling modes, active signal size, and independent panel fitting/MPO.

Windows Capture Borders

The accepted scope keeps WGC for Windows capture and previews. Piik does not add DXGI or inject into system processes to hide the border. The reader-facing troubleshooting guide owns the optional external-mod procedure; the evidence below records its limits and the alternative's integration cost.

Consumer Windows 10 does not expose the WGC border-control API: Microsoft's IsBorderRequired starts at build 20348, beyond consumer Windows 10 build 19045. The current capture helper therefore retains the system border there. Browser capture indicators remain Browser-owned.

On Windows 11 build 26200, a 2026-09-21 controlled native-window check confirmed borderless permission was allowed and the default capture had no border. A second session explicitly requiring a border made it visible; gracefully ending that session cleared it while borderless capture continued. Force-killing the bordered capture instead left the outline behind in this fixture, even after the remaining capture ended.

The stream owner previously connected parent cancellation directly to exec.CommandContext, killing the child before its existing bounded stop sequence could release the platform session. Parent cancellation now enters that same Stream.Close sequence; an unresponsive process still has the existing one-second kill deadline. Subprocess regression checks cover explicit stop, parent cancellation, concurrent stop and an unresponsive child. A real WGC capture cancelled through this Go owner exited normally and cleared the border. This establishes a retirement defect and its local repair, not the cause of every reported Windows 11 border: denied consent and other active captures remain distinct Windows-owned limits.

An unofficial WGC-preserving option exists: Windhawk's DWM Custom Projection Border documents disabling the border on Windows 10 21H2. Source inspection confirms injection into dwm.exe and hooks of private uDWM.dll CProjectionBorderVisual drawing methods. Its disable flag has no per-app filter. This is a desktop-compositor modification, not a missing Piik session option; compatibility with private Windows methods is outside WGC's contract. It has not been locally verified on Windows 10 and is not a bundled dependency or automatic workaround. The official border privacy policy applies to Windows 11 onward, so registry/policy recipes do not establish a supported Windows 10 solution.

The official Desktop Duplication API is a borderless alternative for a selected display. It is not window-isolated capture: cropping the desktop can expose overlapping windows. Do not silently substitute it for a selected window. OBS's display capture implementation also retains distinct DXGI/WGC paths and selects WGC for some multi-adapter laptops; a mature implementation does not establish universal DXGI availability. OBS is a design reference, not source to copy into Piik's MIT implementation.

The pinned WebRTC SDK already contains ScreenCapturerWinDirectx and DesktopAndCursorComposer. A bounded standalone probe on Windows 11 build 26200 on 2026-09-16 linked that existing SDK and returned six 2560x1440 frames with cursor composition, then exited. These frames expose CPU data and no GPU texture. Piik's current capture/encoder boundary consumes D3D11 textures, so this reuse would add a readback/upload path; the probe establishes neither encoding throughput nor Windows 10 support. SDK build defines must match: RTC_ENABLE_WIN_WGC changes DesktopCaptureOptions layout even when selecting DXGI; omitting it caused heap corruption in the isolated probe. No product capture path was changed by this experiment.

If DXGI is reconsidered, compare this reuse against the current GPU path under game motion and quiet scenes on Windows 10. Cover selected-output/GPU identity, cursor and rotation, source previews, display/fullscreen changes, and bounded cancellation. DXGI requires the output's own adapter; access loss requires recreating the duplication object. Preview capture must follow the same backend decision or it can still produce a WGC border. Retain window scope and the existing encoder/output/stop owners.

Acceptance

• Static Windows source remains a live share for a bounded physical run, and a new Viewer can obtain a keyframe without a source change.
• A malformed/stale ICE candidate or repeated per-edge answer does not close the control session or terminate sibling edges; a real edge lifecycle failure remains observable.
• Killing the App causes the active Host owner to leave the native share path promptly, while ordinary user-initiated cleanup does not recurse.
• npm run check and the relevant App checks pass; no credentials or raw media identifiers enter logs or documentation.

Cross-version capture and browser matrices remain separate acceptance work. They are not claimed by the current Windows gate.