# HANDOFF — Session State

## Branch / Commit State

**`main`** — Unit A (render starvation, slice 2) committed locally this session; push on the user's word
(his pattern: says "push" explicitly). Slice 1 (deadline pacing + row-blit, take-3 fix) is already on
`origin/main` as `716a77f`.

## What just happened (2026-09-04, Unit A slice 2)

Take 4 verdict: pacing HELD (no stall cliff, sync intact — user confirmed game+webcam in-sync) but render
stayed **58.9ms** (budget 16.7) → file still ~3.4x time-lapse. Root: the 2M-iteration managed row walk +
8.3MB fresh buffer every tick. Shipped:

1. **`VideoFrame.IsOpaque`** producer-contract flag — set ONLY by `ScreenCaptureFrameSource` +
   `MediaCaptureFrameSource` (DWM/MF fill alpha 255). Full-canvas aligned blit of an opaque frame =
   ONE `Buffer.BlockCopy`; black pre-fill skipped when the backdrop covers.
2. **Integer fixed-point bilinear** in `BlitContent` general path (webcam: round/mirror/scaled) — no
   divisions, no `Math.Round`; ±1 of the float reference (tests allow ±2).
3. **Pump scratch pool** — `AcquireScratch`/`ReleaseScratch` (max 4, length-keyed, owned-by-reference so
   bake-cache/social-bar/static-art arrays can never be captured). Release strictly AFTER
   `SubmitFrameAsync` returns (stdin write copies). `FakeEncoder` now snapshots frames like the real
   encoder (holds would race legitimate recycling).
4. **Dead code kill:** the per-tick `fromScene` render in the transition branch fed NOTHING
   (`BlendFrame` uses `TransitionService.FromFrame` captured at `Start`) — removed with the
   `fromSceneProvider` seam + `MainViewModel.cs` call site. Transition cost halves as a side effect.

Bugs caught by the pixel probes before shipping (see MyMistakes take-4 follow-ups): first `Bilinear`
double-shifted (both stages scaled → solid-255 sampled to ~1 → general path drew nothing); sentinel
0xAB collided with a legitimate `x+y` value; pacing-fake synchronous completion hangs vstest (known,
re-trod).

**Verification:** clean build 0 warnings (both projects); per-class vstest 59/59 (FramePump 11 incl. the
new pooling test, SceneCompositor incl. NEW `Composite_OpaqueFullCover...`, SceneGraph, SocialBar, StretchMath,
Camera/ScreenCapture/MediaVideoSource producers, WebcamOutputKey, SessionTeardown) + SourceNaming
RealApp boot-smoke. Scope-check passed.

## OPEN — next, in order

1. **Take 5 happened (2026-09-04 10:49):** `138/300 frames per 5s, avg render 25.5ms` — blits
   fixed but the resolver's `RenderChatBox` full-rasterized the chat box EVERY tick whenever the
   message buffer was non-empty (the buffer survives sessions — a signed-out record-only take paid
   chat render cost!). **Slice 3 shipped same day:** `ChatOverlayLayer` content-versioned cache —
   raster on message/config change, blit the cached frame every tick (OBS text-source pattern).
   Tests: `ChatOverlayLayerCacheTests` (the ONE, RealApp) + full regression green (62 across
   touched classes), clean build 0 warnings.
2. **Takes 7/8 + slice 5 (2026-09-04):** the stamp (f190587b) settled attribution — chat cache REAL
   (`resolve ≈ 0`) but render stayed 26-27ms: the compositor re-rasterized every non-opaque layer
   per tick (his Live scene: chat+web+image+cam ≈ 680k samples @ ~38ns). Slice 5: `BlitCachedLayer`
   — one raster per (source-array, rect, round/mirror), paste at integer pos with opacity; static
   layers now cost row-blends, only content changes resample; drag/opacity changes are paste params,
   not cache keys. Tests: `PasteCache_...` + 85/85 across compositor/pump/chat/capture/session
   classes; clean build 0 warnings. (Cam bypasses the cache via IsOpaque; revisit if take 9 is
   borderline. Follow-ups unchanged: vertical-tier alloc, debounced chat re-render on bursts.)
3. **Take 9/10 + slices 6-7 (2026-09-04):** slice 6 broke the 15.6ms Task.Delay sleep quantum (timeBeginPeriod + bulk-sleep + 2ms spin tail + wait stat); take 10's `wait 10ms after render 22ms` then exposed the FINAL structural bug: the pump loop's await-continuations inherited the UI SynchronizationContext — the "WPF-free" producer had been rendering ON THE DISPATCHER, queued behind the live preview, the whole time (explains every 'zero change' complaint). Slice 7: Task.Run the loop (OBS pattern) + StaticPixelCache lock + chat raster-miss marshalled to dispatcher + SustainedLowLatency GC + `worst render` stat + webcam through paste cache. Test `Pump_Produces_OffTheStartingContext`. 70/70 green, clean build. paste cache moved render 26.5→22.4ms yet
   period stayed ~37ms — the gap is Task.Delay's ~15.6ms Windows sleep quantum padding every sub-tick
   wait. **This is why takes 7→9 read as "zero change" despite real wins: the sleep floor dominated.**
   Fixed (media-app canon, cited in code + MyMistakes #3): timeBeginPeriod(1) for the pump's life
   (paired End in finally), sleep the bulk, SPIN the last 2ms across the deadline; stats gained
   `avg wait` so render+submit+wait ≈ period (accounting closed — nothing can hide). Webcam now
   routes through the paste cache too (bypass re-sampled 156k px even between identical device
   frames). 52/52 per-class green, clean build 0 warnings, committed this slice.
4. **Take 11 ran + slice 8 (2026-09-04, committed with the audio unit below):** off-UI loop
   WORKED — typical frames land exactly on the deadline (work ~10 + wait ~6.8 = 16.7; 212/300).
   Remaining gap = periodic 35-65ms spikes growing across the take = gen2 GC pauses; the capture
   path minted a fresh ~8.3MB byte[] per DWM frame (~500MB/s LOH). Slice 8: 4-deep buffer ring
   in ScreenCaptureFrameSource (size-matched slots, reused row scratch) + `VideoFrame.Epoch`
   joins the paste-cache key so recycled arrays can never false-hit + `gen2 +N` per stats window
   (suspect-or-acquit — never guess at the tail again). Test `PasteCache_RecycledArrayWithNewEpoch_
   ReRasterizes_NotStaleHits` fails on the old key by construction. 37/37 compositor/pump green.
4b. **AUDIO (creator ask 2026-09-04):** post-mix volume up ~40% — constant master gain applied
   in AudioMixer.FillAndMix BEFORE the −1 dBFS limiter (limiter still owns the ceiling: the
   gain can't add clipping, it just makes the limiter bind sooner on hot material). If the
   creator reports pumping on loud game audio → the constant is the tuning knob (or per-input
   defaults need raising instead — discuss with data).
5. **Take 12 (user, ~30s record + talk):** stats: `gen2 +N` should be ~0-1/window, `worst render`
   → ~16-20ms, n/300 → 300; playback honest speed; file audio ~40% hotter than before. If gen2
   still >2/window: next suspect is the 10Hz WebView2 capture (full-canvas PNG decode + fresh
   arrays on the UI thread) — throttle or move it, cited pattern first.
6. **Unit B — the top bar + session logic (user spec 2026-09-04 re-sent twice + decisions settled in Q&A):**
   - Two-line top bar. Line 1: center = REC + **LIVE** pills (text renamed from ON-AIR; pills become
     mutually-exclusive RADIOS — record-OR-stream ruling), right = avatar + **Login/Logout** button
     (no account status light). Line 2: centered primary **Start** (grayed while NO pill armed —
     INVERTS the 2026-09-01 "unarmed Start records" rule; fix the map when landing) that becomes the
     Stop/End button while active.
   - Avatar right-click → **Change Account** (creator: "standard google thing ... on a portrait
     right-click"). Login = `SignInCommand` direct (context menu on Start dies; "Choose Record Folder"
     lives in gear → App Settings only).
   - LIVE pill stays login-gated (`CanToggleOnAir` exists ✓ 3a.viii).
   - REC+Start → `Microsoft.Win32.SaveFileDialog` (InitialDirectory = settings folder, default name
     `ty-…-0000.mp4`, NATIVE overwrite prompt covers exists/validate, Enter confirms). Cancel →
     abort + disarm pill (lit pill with no session is a lie). Up-front naming RETIRES the stop-time
     rename modal (assumption stated; user's dialog answer was about Go-Live confirmation).
   - LIVE+Start → **Go-Live dialog stays** as preflight: prefilled from Text-drawer `Broadcast.*`,
     unfilled fields visibly prompted, explicit confirm → `PrepareAndStartLiveAsync` (user: "going
     live is scary — confirmation allows back-out + testing up to go-live").
   - Bottom-bar metrics init/maintain: `ResetHealth` + `HealthUpdated` exist — verify on take 6.
   - F6 "start/end" hotkey routes through `HandleHotkey` — check it honors the new grayed-Start gate.
   - Login button text: "Login" (disconnected, LIVE pill greyed) → "Logout" (connected, avatar
     appears left of it). The account status LIGHT is deleted per spec 2a.
   - Primary button: grayed "Start" when NO pill armed (inverts 2026-09-01 rule — fix the map in
     the landing commit); enabled when either armed; REC path = file dialog flow; LIVE path =
     go-live after dialog confirm; becomes the Stop/End face while active (user's "Stop button
     never active" complaint gets a hermetic test pinning visibility+CanExecute).
   - ONE integration test (hermetic): pills↔button state machine + record-path seam (an
     `internal static Func<SaveFileDialog-ish prompt>` override seam mirroring `RegistrarOverride`
     — never pop real dialogs in tests).
3. **Follow-ups recorded (don't fix opportunistically):** vertical-tier `BilinearScale` per-frame
   alloc; cosmetic `FramePump: encoder stop failed: No process is associated` double-stop race;
   1440p capture downscale alloc.

## Landmines

- testhost shares startup.log with the app — filter by time when triaging.
- Stale testhost/exe locks the DLL (MSB3027): `taskkill /F /IM testhost.exe` / `ytLive.exe` first.
- Do NOT run full-suite vstest (WASAPI hang, pre-existing); flow = clean build + per-class + scope-check.
- Pacing-seam fakes MUST await/yield (sync-completed task → pump runs inline on StartAsync → hang).
- `FakeEncoder` snapshots submitted frames — keep any new fake encoder honest about buffer recycling.
- Multi-stage fixed-point: shift only at the end (MyMistakes 2026-09-04).
- Real-`MainWindow` tests: `LayoutPathOverride` + temp DB mandatory; `VolumePushOverride` for volume.
- ffmpeg: month-end pinned build; `Startup.log` "Recording saved:" lines show the real final path.

## @ User note

Recording fix FIRST (his order), UX queue right behind — spec + settled decisions above, don't re-ask.
Keep responses SHORT; one integration test per change; commit every unit; push on his word only.