HANDOFF — 2026-10-09 (TASK 51 slice 1 shipped: background-effects engine)

Branch

main (no feature branch). Pushed through f8dd107; the TASK 51 slice-1 commit sits on top, not pushed (push at the user's call).

The in-flight "pinned chat" work unit: Models/YouTube.cs, ViewModels/MainViewModel.Chat.cs, Controls/LeftPanel.xaml, untracked Helpers/RelayCommandGeneric.cs.
The creator's untracked logo art in Assets/ (llamacasty text.*, llamacasty-text-nobg*.png, thin logo wordmark.png).

Model: Google's official MediaPipe Selfie Segmenter (landscape, 144×256, Apache-2.0), converted to ONNX by our own tools/selfie-seg/convert_tflite_to_onnx.py and verified against MediaPipe's own runtime (verify_against_mediapipe.py, max |diff| 5e-5). Embedded in the exe (Assets/Models/selfie_segmenter_landscape.onnx, 430 KB, in git).
Code: Services/BackgroundEffects/ — IPersonSegmenter seam, OnnxPersonSegmenter (onnxruntime 1.31.0 CPU, never throws), BackgroundEffectProcessor (None passthrough, Remove = alpha mask, Blur = passthrough until slice 2). Models/BackgroundEffect.cs enum.
Not wired: nothing calls it yet — no config, UI, or camera hookup. Zero risk to the live path.
Docs: ai.md (stale "background removal PERMANENTLY OUT" bullet replaced by the reversal + a "Webcam background effects" section + a model-provenance licensing guard), THIRD-PARTY-NOTICES items 11 (ONNX Runtime, MIT) + 12 (MediaPipe model, Apache-2.0 with §4b change note), TASK 51 file + TASKS.md row, Services/Models indexes, MyMistakes conversion recipe.

Full suite 408 passed / 0 failed, 0 build warnings. New: BackgroundEffectEngineTests (Remove integration test with a fake segmenter; bundled-model contract test vs a MediaPipe reference mask, fixtures in ytLive.Tests/Fixtures/).

64-bit only (2026-10-09): PlatformTarget=x64 in both csproj files (verified: ytLive.dll PE machine 0x8664, 408/408 green). TASK 48 item 2 carries the x64-only MSIX + -r win-x64 publish.
onnxruntime.dll is ~17 MB; an RID-less build copies every RID's native folder — TASK 48's MSIX publish must pin win-x64.
THIRD-PARTY-NOTICES.txt header + ai.md Licensing/packaging sections still say "paid, closed-source" / Store IAP / branding-flash paid delta (pre free-forever + planned public GPL-3.0 release) — the creator is choosing the license; rewrite those with it.
Carried: "Use default background" toggle still not working (from 2026-10-07).

TASK 51 slice 2: Blur in BackgroundEffectProcessor (separable box/gaussian, strength), one integration test. Then slice 3 config + persistence, slice 4 camera-path hookup + perf check on the creator's box, slice 5 properties-panel UI.