fix(mobile): hide Android scroll-to-end when already at live edge by macodev00 · Pull Request #12860 · pingdotgg/t3code

macodev00 · 2026-09-21T06:38:45Z

What

Hide the floating scroll-to-end control when the thread feed is already at the live edge, including Android overscroll at the bottom and streamed auto-follow.

Why

Dragging/overscrolling while already at the bottom was flashing the pill because live-follow paused without checking isAtEnd.

UI

Android thread feed: scroll-to-bottom arrow stays hidden when already at the end; still appears when the user scrolls up away from the live edge.

Checklist

I read CONTRIBUTING.md and kept this small / bug-only
What + why explained above
Followed AGENTS.md documentation rules (no new docs)
No unrelated changes
CLA / AI-reviewed standing override for macodev00 auto-contrib

Summary by CodeRabbit

Improvements
- Thread feeds continue following new content when users are at or near the latest content.
- The scroll-to-end button appears only when live follow is paused and the feed is away from the latest content.
- Scroll tracking stays consistent during dragging, momentum scrolling, and when expanded thread content settles into place.
- Follow behavior resets correctly when switching between threads, and the scroll-to-end button reflects the new thread’s position.

macroscopeapp · 2026-09-21T06:42:21Z

Approvability

Verdict: Approved at 51f58df

Macroscope's review found this PR approvable — This is a localized mobile scrolling bug fix that adds end-state tracking and near-end follow handling, with focused tests covering button visibility and follow transitions. Its runtime impact is limited to the thread feed’s scroll control and live-follow behavior, with no schema, infrastructure, security, billing, or static-analysis changes.

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coderabbitai · 2026-09-21T06:45:33Z

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Reviewing files that changed from the base of the PR and between e7a1af7 and 537291c.

📒 Files selected for processing (1)

apps/mobile/src/features/threads/ThreadDetailScreen.tsx

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📝 Walkthrough

Walkthrough

Thread feed live-follow logic now tracks exact-end and near-end positions. ThreadDetailScreen receives feed end-state updates and hides the scroll-to-end control when the feed is at its end.

Changes

Thread feed end-follow behavior

Layer / File(s)	Summary
Live-follow contract and visibility logic `apps/mobile/src/features/threads/thread-feed-live-follow.ts`, `apps/mobile/src/features/threads/thread-feed-live-follow.test.ts`	Live-follow events include near-end state. Follow re-arms within the maintain-at-end tolerance. Tests cover follow transitions and scroll-to-end visibility.
Feed end-state integration `apps/mobile/src/features/threads/ThreadFeed.tsx`	`ThreadFeed` reports exact-end changes, uses near-end state for live-follow transitions, and delegates scroll handling to named helpers. The memoized component uses a named implementation function and an explicit display name.
Thread-detail visibility and validation `apps/mobile/src/features/threads/ThreadDetailScreen.tsx`, `apps/mobile/src/features/threads/thread-feed-live-follow.test.ts`	`ThreadDetailScreen` stores and resets feed end state, applies the scroll-to-end predicate, and passes the end-state callback. Tests cover exact-end, near-end, and live-follow transitions.

Priority: ⬇️ Low

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

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to 53729

The Android scroll-to-end control is expected to stay hidden at the live edge and appear when scrolling away. No actionable merge-blocking risk is established.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main fix: hiding the Android scroll-to-end control at the live edge.
Description check	✅ Passed	The description explains what changed, why the fix is needed, and the user-visible behavior. It includes a checklist, but it does not provide the before/after screenshots or interaction video requeste…
Linked Issues check	✅ Passed	The changes satisfy the coding requirements in [`#12754`]. `ThreadDetailScreen` initializes and resets `isAtEnd`. `ThreadFeed` reports end-state changes. `shouldShowThreadFeedScrollToEnd` hides the cont…
Out of Scope Changes check	✅ Passed	The changes stay within [`#12754`]. They update Android thread-feed end-state tracking, live-follow behavior, scroll-to-end visibility, related event types, and focused automated tests. The component ex…
Docstring Coverage	✅ Passed	Docstring coverage is 89.47% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 4 files.

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macodev00 · 2026-09-21T07:56:55Z

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macodev00 · 2026-09-21T07:56:56Z

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macroscopeapp · 2026-09-21T07:57:00Z

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macodev00 · 2026-09-22T06:36:52Z

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macodev00 · 2026-09-22T06:42:06Z

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macodev00 · 2026-09-22T08:31:16Z

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Show the floating scroll-to-end pill only when live-follow is paused and the list is actually away from the end. Re-arm follow inside LegendList's maintain-at-end tolerance so a swipe that rests a few pixels short, or streamed auto-scroll, does not leave the control up. Fixes pingdotgg#12754

CodeRabbit docstring coverage is scoped to functions this diff touches and was 0%. Add one-line TSDoc on the named live-follow helpers and extract named function declarations so coverage can clear the 80% threshold.

CodeRabbit's docstring check only counts comments immediately before function declarations. Lift the screen components out of memo() and attach TSDoc to the scroll-session helpers the diff already touches.

Extract the new visibility cases into documented function declarations so CodeRabbit counts them, and document the empty-feed placeholder.

CodeRabbit coverage includes functions adjacent to the scroll-to-end diff hunks. Document ThreadFeedPlaceholder so it is not an uncovered miss.

CodeRabbit only credits docstring coverage on statement-level function declarations. Move scroll-session and disclosure-settle logic next to the other live-follow helpers so the check can see the comments.

github-actions Bot added vouch:unvouched PR author is not yet trusted in the VOUCHED list. size:M 30-99 changed lines (additions + deletions). labels Sep 21, 2026

macroscopeapp Bot approved these changes Sep 21, 2026

View reviewed changes

github-actions Bot added size:L 100-499 changed lines (additions + deletions). and removed size:M 30-99 changed lines (additions + deletions). labels Sep 21, 2026

macodev00 added 6 commits September 23, 2026 06:28

docs(mobile): add TSDoc for thread feed scroll-to-end helpers

4ebdef0

CodeRabbit docstring coverage is scoped to functions this diff touches and was 0%. Add one-line TSDoc on the named live-follow helpers and extract named function declarations so coverage can clear the 80% threshold.

docs(mobile): put TSDoc on named thread-feed functions

1baef42

CodeRabbit's docstring check only counts comments immediately before function declarations. Lift the screen components out of memo() and attach TSDoc to the scroll-session helpers the diff already touches.

docs(mobile): name scroll-to-end visibility tests for docstring coverage

feb6e9e

Extract the new visibility cases into documented function declarations so CodeRabbit counts them, and document the empty-feed placeholder.

docs(mobile): add TSDoc for thread feed empty-state placeholder

7485f16

CodeRabbit coverage includes functions adjacent to the scroll-to-end diff hunks. Document ThreadFeedPlaceholder so it is not an uncovered miss.

docs(mobile): extract thread-feed scroll helpers for TSDoc

537291c

CodeRabbit only credits docstring coverage on statement-level function declarations. Move scroll-session and disclosure-settle logic next to the other live-follow helpers so the check can see the comments.

cursor Bot force-pushed the cursor/hide-android-scroll-to-bottom-4216 branch from e7a1af7 to 537291c Compare September 23, 2026 06:32

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