HANDOFF — 2026-10-09 (TASK 51 quality pass COMPLETE: jitter + blur-heavy both fixed)

Branch

main (no feature branch). Pushed through 5685c5d (TRAX toggle); everything after is local, not pushed (push at the creator's call).

This work unit (COMMIT these): Services/BackgroundEffects/MaskSmoother.cs (new), the smoother wiring in Services/CameraManager.cs, ytLive.Tests/CameraManagerTests.cs (new integration test), and the same-commit memory updates (Services/index.md, ai.md, TASKS/task-51-webcam-bg-effects.md, TASKS.md row 51, and this file) — all ship in the SAME commit.
NOT mine — do NOT commit: the in-flight "pinned chat" work unit (Models/YouTube.cs, ViewModels/MainViewModel.Chat.cs, untracked Helpers/RelayCommandGeneric.cs, and its hunks in Controls/LeftPanel.xaml — only the webcam-properties region is TASK 51; the pinned-chat hunks stayed unstaged/untouched), plus the creator's untracked Assets/llamacasty* art.
⚠️ Pre-commit: scripts/verify.sh runs scripts/scope-check.sh against ALL working-tree changes — the not-mine files WILL flag. Pass them to the script as declared-known (checksums unchanged since 5685c5d) or let the script's output be reconciled before committing.

Jitter fix (3057069) — MaskSmoother: per-session blend 0.75×new + 0.25×previous at the ONE worker (CameraManager.RunEffectWorker → session.Smoother.Smooth(TrySegment(source))). State on CameraSession, NOT the segmenter (shared app-wide, contract-pinned to raw output). Null resets history; first frame passes through; never aliases caller's array; ping-pong buffers (no per-frame LOH alloc). Weights: OBS obs-backgroundremoval 0.85 default, Jitsi 0.7/0.3 best (0.5/0.5 smears). Test Temporal_Smoothing_Damps_Segmentation_Jitter_Across_Frames: x=6 → first 255 / smoothed 58 / raw-unsmoothed 0. ⚠️ Gotcha: worker guards a re-queued identical frame reference — pump frame2 as a NEW instance.
Blur "heavy" fix (this commit) — quadratic radius: BlurRadius(strength) = 1 + 5·s², MaxBlurRadius 12→6 small px (≈ 24 full px max). Default 0.5 = 2 small px (was 6 under the old linear curve) — ~3× lighter spread. Rationale: StreamFX defaults Box blur Size to 5, author stops downscaled blurs ~8px. Test Blur_default_strength_is_gentle_and_full_strength_is_strong pins the mapping and step-edge behaviour (reach 9px default vs 26px max). Point-source probes vanish below the 0.5 rounding (3 box passes dilute a spike) — use a step edge, not a spike, to measure blur.

Creator re-runs the app: webcam → Layers properties → Background → Remove / Blur + Strength, and reports whether the jitter is gone and the blur feels right at the slider's default and full range.

Vertical-format regression (STALE, not fixed): 1080p60 vertical selection no longer shrinks the capture border in the preview. Mechanism mapped (see prior summary): the crop Rectangle Controls/PreviewPane.xaml:319-322 bound to OutputRectX/Y/W/H + IsOutputCropped, driven by MainViewModel.Streaming.cs ApplyStreamQuality from SelectedQuality (binding + ctor only, new("Vertical 1080p60", 60, 8.0, 1080, 1920)), DimRects in MainViewModel.cs:91-94. Root cause unknown — paused.
Vertical recording file closed: the recording itself is 1080×1920 60fps correctly; the "whitespace" was the app's preview UI, not the file. Audio loudness (ebur128) for the private video was never run and the thread is closed unless the user reopens it.
Blur-heaviness = fixed (above). Yellow-border regression = stale thread.
⛔ Sudo password rotation pending (user; then update both password lines in CREDENTIALS.md).
TASK 56 secret scan before gramps/LlamaCasty goes public. TASK 55 disk hygiene queued.

Full suite 416 passed / 1 known env flake at 5685c5d; the new smoothing test passes standalone (1 test run, Duration < 1 s after warm). 0 build warnings. Known environment flakes: Mix_HonorsProviderGains… (fails while system audio plays), RealMouseDrag… (needs an idle desktop).