docs(issues): capture the #290 recurrence playbook — window unconfirmed, reporter-stranding mechanism first

docs/outstanding-issues-inbox/bbf8ba3d-cdfb-49ef-80f2-09964ac8483d.json

@@ -0,0 +1,13 @@
+{
+ "version": 1,
+ "id": "bbf8ba3d-cdfb-49ef-80f2-09964ac8483d",
+ "createdOn": "2026-08-13",
+ "action": "add",
+ "payload": {
+ "pri": "P3",
+ "type": "rec",
+ "summary": "If the ui-smoke scroll-hide flake (archived #290) recurs, start from the reporter-stranding mechanism — and treat the old regression window as unconfirmed",
+ "detail": "Independent verification on 2026-08-13 (second session, fresh cloud container, pinned Chromium 1234 installed per #312) measured the archived #290 flake at BOTH ends of its recorded window and corrects the archive's causal story: the bad SHA 9ab3b73ad itself passed 16 recorded executions — reproducer isolated --repeat-each=5 (5 passed, ~1.0s each), one full tests/ui-smoke.spec.ts --project=chromium run (98 tests passed, 2.5m, 0 flaky), and reproducer x10 under deliberate CPU contention (6 busy-loop processes on 4 cores, run times 1.2-1.5s: 10 passed). Current main a76f280 also 5/5. So the recovery was NOT drift — the exact commit that measured 2/5-3/5 failures passes cleanly here — and the e8adde1b9..9ab3b73a window is unconfirmed; the failure was specific to the original machine's environment/load profile. Recorded as a comment on PR #1884 (issuecomment-5272932999). On recurrence, do not re-bisect first: test the stranding mechanism. computeScrollHideUpdate (src/components/clinical-dashboard/use-hide-on-scroll.ts) re-evaluates only on scroll/resize events, and its viewportHeightChanged / maxOffset-range-change guards deliberately zero accumulated down-travel (contract-asserted in tests/use-hide-on-scroll.test.ts) — so geometry churn consuming the final steps of a gesture strands the not-hidden state permanently until the next event, matching the recorded ~11.5s toHaveAttribute timeout signature (the assertion DOES auto-retry for 10s; the attribute genuinely never flips). Fastest confirmation: a diagnostic page.on('console') trace logging which guard fires per evaluation. The window itself was one PR (#1744 mode-routing, true merge a503c22) whose net diff touched no scroll-hide code — content-bisect axes, if ever needed: tests/ vs src/ split, use-home-mode-seed/use-last-app-mode neutralized, prefetchModeDestination reverted, positional heading click restored to a settle wait. Stop: any guard change is a behaviour change to protected phone chrome — needs a failing trace first, never speculatively; do not weaken the assertion or tap targets.",
+ "source": "session 2026-08-13; PR #1884 comment; archived #290; #312"
+ }
+}