perf(mobile): keep live chats responsive

[luinbytes]

Summary

• virtualize active DM and group transcripts with an inverted FlatList instead of mounting the full conversation
• memoize message bubbles, stabilize their action handlers, and replace per-message reply scans with one lookup map
• retain the bounded ScrollView only for search around-pages so variable-height message jumps remain exact

QA

• resource-limited Android 36 emulator: 2 vCPU, headless, 720x1280, no audio or boot animation
• synthetic 200-message markdown transcript with progress updates every 50 ms remained interactive and visibly advanced through Working 409
• variable-height search jump landed exactly on Message 25
• mobile tests: 77 passed
• chat-ui tests: 4 passed
• mobile Expo dependency and TypeScript checks passed
• production Android Hermes export passed with one Metro worker
• native Android debug assembly passed with one Gradle worker and a 1536 MB heap

Broader repository check

A bounded full Vitest run reached 1,520 passing and 8 skipped tests. It also exposed pre-existing setup/baseline issues outside this change: 34 suites cannot load the absent generated Prisma client, and one desktop sandbox inode-containment test fails. The mobile-scoped gates above are green.

Summary by CodeRabbit

• Improvements
  • Updated the thread view for smoother, more responsive message scrolling.
  • Added dedicated scrolling for pinned content and jump-to-message navigation.
  • Improved loading and navigation when viewing older messages.
  • Improved message rendering performance for more responsive interactions.
  • Updated answer, bot, and speak actions to work directly with the selected message.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
rakazo-www	Skipped		Aug 30, 2026 7:47am

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 16a3cc42-133e-4926-bae5-5f9120d26452

📥 Commits

Reviewing files that changed from the base of the PR and between 7869b81 and 89355b1.

📒 Files selected for processing (1)

• apps/mobile/app/thread.tsx

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📝 Walkthrough

Walkthrough

The mobile thread screen now uses an inverted FlatList for messages and a separate ScrollView for pinned pages. Callback functions are memoized. MessageBubble is memoized and receives the current message in answer and speak handlers.

Changes

Mobile thread rendering

Layer / File(s)	Summary
Scroll and callback state apps/mobile/app/thread.tsx	Scroll refs now target FlatList<MobileMessage> and pinned-page scrolling. Loading preserves pinned-page targets. Several handlers now use useCallback.
Message list and pinned-page rendering apps/mobile/app/thread.tsx	The main thread renders reversed messages with an inverted FlatList. Pinned pages render through a separate ScrollView. Reply previews use a message map. Message rows include activity bot and jump-scroll handling.
Message bubble action wiring apps/mobile/app/thread.tsx	MessageBubble now uses memo. Answer and speak callbacks receive the associated message.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to 89355

This change virtualizes mobile chat transcripts and preserves existing message actions and thread behavior; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: elie222, cursoragent, bnsd55

Sequence Diagram(s)

sequenceDiagram
  participant ThreadScreen
  participant FlatList
  participant pinnedScroll
  participant MessageBubble
  ThreadScreen->>FlatList: render reversed messages
  FlatList->>MessageBubble: render each message
  ThreadScreen->>pinnedScroll: render selected pinned page

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: improving responsiveness for live mobile chats through virtualization, memoization, and stabilized handlers.
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.

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[greptile-apps]

Greptile Summary

The PR improves mobile chat responsiveness while preserving exact search-result navigation.

• Virtualizes active transcripts with an inverted FlatList.
• Retains a bounded ScrollView for search-around pages and keeps it mounted while earlier history loads.
• Memoizes message bubbles and stabilizes message action callbacks.
• Replaces repeated reply-message scans with a lookup map.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
apps/mobile/app/thread.tsx	Adds transcript virtualization and memoized message rendering while preserving the pinned search page across history-loading outcomes.

_{Reviews (3): Last reviewed commit: "merge(main): resolve thread.tsx conflict..." | Re-trigger Greptile}

[luinbytes]

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Updated for commit 89355b1.