fix(mobile): taps on Home right after a fling open the thread on Android

[AKolenda]

Stacked on #14004. The first three commits are #14004; this PR is the last two.

What Changed

Two changes to the Home list in HomeScreen.tsx, both for taps that land right after a fling on Android:

• overScrollMode="never".
• On Android, the list's scroll view no longer holds taps for its JS momentum check. refScrollView replaces the scroll view's _isAnimating with one that returns false.

Why

A tap right after a fling did nothing on Android in two ways:

1. Stretch overscroll. Android's stretch effect claims any touch that lands while it springs back (ScrollView.onInterceptTouchEvent). So a tap just after a fling reaches either end of the list only stops the stretch.
2. JS momentum check. React Native's JS scroll view becomes the responder for any touch while _isAnimating() is true: until onMomentumScrollEnd arrives, and for 16 ms after.
   • Android sends that event after three stable frames. In my logs it reached JS 60–150 ms after the list visibly stopped, and later while JS rendered the rows a fling revealed.
   • Logged taps on a list that had stopped moving showed the event arriving 0–1 ms before the tap, and the scroll view took the touch.

The native scroll view already intercepts a touch that lands during a fling; the logs show touchCancel then onScrollBeginDrag. So Android doesn't need the JS check: a tap on a moving list still just stops it, and only a tap on a list that has stopped now reaches the row.

_isAnimating is private to ScrollView.js. The override checks that it exists, so if React Native renames it, this becomes a no-op rather than an error. Patching react-native itself would change the lockfile entry of every package that peers on it.

Pixel 9, real account, release builds installed in place.

	before	this PR
taps 0.15 s after a fling hits the end of the list (builds of main, same mobile code as today's main, differing only by overScrollMode)	0/7	7/7
taps 1.0 s after a mid-list fling (my test build with #14004, differing only by the momentum check)	6/11	10/11
taps 0.9 s after a mid-list fling (same builds; the list is usually still moving)	0/11	2/11

Taps 0.3 s or more after reaching an end already worked on main. The trade-off is that Home no longer shows the stretch effect at its ends. The JS bundle grows by 23 bytes for the overscroll change and 136 bytes for the momentum check.

UI Changes

A fling, then a tap on a row about 1 s later. On the left is my test build before #14004 and this PR, where the tap is ignored. On the right, with both, the thread opens. The GIF is at half speed (MP4).

Android performance series

These are separate PRs, each reviewable on its own:

• perf(mobile): lighter Home rows away from the viewport #13702 Lighter Home rows away from the viewport (merged)
• perf(mobile): render Home rows further ahead while scrolling #13705 Render Home rows further ahead while scrolling (merged)
• fix(mobile): running threads open at the latest message #13530 Running threads open at the latest message (merged)
• fix(mobile): skip unhandled animation events on Android #13325 Skip unhandled animation events on Android (ANRs while scrolling the thread list)
• perf(mobile): chats left mid-turn reopen from the phone's cache #13900 Chats left mid-turn reopen from the phone's cache
• fix(mobile): Home rows keep their content when they wake or are reused #14004 Home rows keep their content when they wake or are reused
• fix(mobile): taps on Home right after a fling open the thread on Android #14005 Taps on Home right after a fling open the thread (stacked on fix(mobile): Home rows keep their content when they wake or are reused #14004; this PR)
• perf(mobile): Android back leaves a thread without waiting for JS #14054 Android back leaves a thread without waiting for JS

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Summary by CodeRabbit

• Bug Fixes
  • Fixed Android home-screen rows not responding to taps after a scroll fling or stretch overscroll.
  • Improved swipe-row behavior when content changes: rows reset stale swipe state, and dormant rows remain closed with swipe actions unavailable.

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• apps/mobile/src/features/home/thread-swipe-actions.tsx

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📝 Walkthrough

Walkthrough

The home list now adjusts Android scroll handling to allow taps after a fling and prevent stretch overscroll. Swipeable rows remain mounted while dormant, with actions and gestures disabled. Changes to resetKey reset the existing row in place.

Changes

Android list tap handling

Layer / File(s)	Summary
Scroll tap handling apps/mobile/src/features/home/HomeScreen.tsx	Adds an Android-only helper that overrides the scroll responder’s _isAnimating check when available. The list uses the helper and sets overScrollMode to "never".

Swipe row dormant state

Layer / File(s)	Summary
Dormant row lifecycle apps/mobile/src/features/home/swipe-row-activation.ts, apps/mobile/src/features/home/thread-swipe-actions.tsx	Updates dormant-row comments and props. Rows remain mounted without actions or swipe gestures while dormant. A resetKey change cancels animations, completes any pending dismissal, clears full-swipe arming, and closes the row. Dismissal restores apply only to the current content generation. Open and close callbacks track row state.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to 8cea1

The reported partial-swipe issue does not block merging; no actionable merge-blocking risk remains after normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 8cea1

The reviewed changes do not show an expanded permission boundary or a new path to perform thread actions. A timing-dependent row-reuse issue could leave a recycled row visually dismissed; its impact appears confined to the mobile list.

Retained concerns

• Low · reliability · inferred: A dismissal worklet queued for previous row content may run after in-place reuse and alter the new row's visible state. Reset and the generation-guarded restore do not guard that worklet; the outcome depends on unverified scheduling order.

Security review details

Security Blast Radius

• inferred — The identified stale-worklet path affects on-device row presentation and dismissal cleanup. The reviewed caller and row code do not show it changing which thread action callback is selected.

Trust Boundaries and Controls

• observed — The list supplies action callbacks and identity; the row disables gestures while dormant or dismissing and suppresses dormant actions. The changed row function is not itself exported.

Resilience and Maintainability Implications

• observed — Reset and unmount resolve a pending dismissal wait and cancel active animations, while a generation check prevents an old restore from resetting newer content.

Hardening Proposals

• proposed — Make the queued dismissal worklet validate a content-generation or cancellation token before changing shared row state, including when it starts after reset.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 60.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing Android Home row taps immediately after a fling.
Description check	✅ Passed	The description includes the required What Changed, Why, UI Changes, and Checklist sections. It explains the implementation, trade-offs, test results, screenshots, and interaction video.

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Inline comments:
Review comments at @apps/mobile/src/features/home/thread-swipe-actions.tsx:
- Line 347: Update restoreRow so recycling an open row also clears the nested
tap gesture state, preventing it from competing with the child Pressable after
ReanimatedSwipeable.reset() closes the row.

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Reviewing files that changed from the base of the PR and between 94f92a7 and 74c6112.

📒 Files selected for processing (3)

• apps/mobile/src/features/home/HomeScreen.tsx
• apps/mobile/src/features/home/swipe-row-activation.ts
• apps/mobile/src/features/home/thread-swipe-actions.tsx

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Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The PR changes Home's Android interaction defaults by disabling stretch overscroll and overriding a private React Native momentum responder check, while also changing recycled swipe-row lifecycle behavior. These are focused changes with a clear bug-fix goal, but the user-visible default change and private API usage warrant human review.

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