[codex] Upgrade Legend List chat scrolling (#3545)

[aaditagrawal]

What Changed

Why

UI Changes

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

• New Features

  • Chat and thread views now keep replies anchored around newly sent messages, improving scroll positioning after sending.
  • Composer height is now measured more accurately, so message lists and “scroll to bottom” controls stay aligned with the input area.
  • Branch, model, and chat lists now handle keyboard navigation and item types more smoothly.

• Bug Fixes

  • Improved thread and chat scrolling behavior when switching conversations or sending messages.
  • Updated several app dependencies for stability and compatibility.

[coderabbitai]

Warning

Review limit reached

@aaditagrawal, we couldn't start this review because you've reached your PR review rate limit.

More reviews will be available in 42 seconds. Learn how PR review limits work.

Your organization has used up its prepaid credits, and credit purchases are no longer available. Enable the review add-on in the billing tab to keep reviews running — you're only billed for reviews past your plan's rate limits ($0.25/file).

⌛ How to resolve this issue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based credits.

🚦 How do rate limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please see our Fair Usage Limits Policy for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 398a4506-e2a1-4bd4-a331-2b97bc80c40b

📥 Commits

Reviewing files that changed from the base of the PR and between b89ca56 and 8a89796.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (20)

• apps/mobile/package.json
• apps/mobile/src/features/threads/ThreadComposer.tsx
• apps/mobile/src/features/threads/ThreadDetailScreen.tsx
• apps/mobile/src/features/threads/ThreadFeed.tsx
• apps/mobile/src/lib/threadActivity.test.ts
• apps/mobile/src/lib/threadActivity.ts
• apps/mobile/src/lib/threadFeedLayout.test.ts
• apps/mobile/src/lib/threadFeedLayout.ts
• apps/mobile/src/state/use-thread-composer-state.ts
• apps/web/package.json
• apps/web/src/components/BranchToolbarBranchSelector.tsx
• apps/web/src/components/ChatView.tsx
• apps/web/src/components/chat/ChatComposer.tsx
• apps/web/src/components/chat/MessagesTimeline.test.tsx
• apps/web/src/components/chat/MessagesTimeline.tsx
• apps/web/src/components/chat/ModelPickerContent.tsx
• apps/web/src/index.css
• packages/shared/package.json
• packages/shared/src/chatList.test.ts
• packages/shared/src/chatList.ts

📝 Walkthrough

Walkthrough

The PR adds shared chat list anchoring utilities, rewires mobile and web thread flows to return message IDs and anchor timelines around sent messages, updates composer and inset handling, and adjusts branch/model list interactions to the updated LegendList API.

Changes

Chat anchoring and composer flow

Layer / File(s)	Summary
Shared anchor resolver packages/shared/src/chatList.ts, packages/shared/src/chatList.test.ts, packages/shared/package.json	resolveChatListAnchoredEndSpace is added, exported, and covered by tests for matching, override, and null-anchor cases.
Mobile send contract apps/mobile/src/lib/threadActivity.ts, apps/mobile/src/lib/threadActivity.test.ts, apps/mobile/src/state/use-thread-composer-state.ts, apps/mobile/src/features/threads/ThreadComposer.tsx	Thread activity, composer state, and composer props now return message IDs and stop emitting queued-message rows.
Mobile thread anchoring apps/mobile/src/features/threads/ThreadDetailScreen.tsx, apps/mobile/src/features/threads/ThreadFeed.tsx, apps/mobile/package.json	Thread detail and feed wiring now measure composer layout, pass anchor/freeze inputs, and switch to the updated keyboard-aware LegendList dependency.
Web chat anchor flow apps/web/src/components/ChatView.tsx, apps/web/src/components/chat/MessagesTimeline.tsx, apps/web/src/components/chat/MessagesTimeline.test.tsx, apps/web/src/components/chat/ChatComposer.tsx, apps/web/src/index.css, apps/web/package.json	Chat view and timeline now measure the composer overlay, anchor the message list around a sent message, and update the composer surface styles and list dependency.

LegendList picker updates

Layer / File(s)	Summary
Picker list behavior apps/web/src/components/BranchToolbarBranchSelector.tsx, apps/web/src/components/chat/ModelPickerContent.tsx	Branch and model picker lists now classify items and ignore optional scroll-call results.

Sequence Diagram(s)

sequenceDiagram
  participant ChatView
  participant ChatComposer
  participant MessagesTimeline
  participant LegendList
  ChatView->>ChatComposer: render composer overlay
  ChatComposer-->>ChatView: ResizeObserver reports height
  ChatView->>MessagesTimeline: anchorMessageId and contentInsetEndAdjustment
  MessagesTimeline->>LegendList: anchoredEndSpace and adjusted inset

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• aaditagrawal/t3code#9: Introduced the modular chat component structure that these chat anchoring and overlay changes build on.

Suggested labels

size:XXL

Poem

A rabbit hopped through lists at dusk,
with anchor carrots in its tusk.
The composer glowed, the threads aligned,
and scrolls at end were sweetly timed. 🐇
Thump thump — the chats are now refined.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description is just the template placeholders, with no actual What Changed, Why, or UI Changes details filled in.	Fill in What Changed, Why, and UI Changes with concrete details, and update the checklist to reflect the PR's scope.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately summarizes the main change: upgrading Legend List chat scrolling.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch sync/upstream-20260626-chat-scroll-list

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[aaditagrawal]

• fix(grok): Harden ACP resume with replay-idle load readiness (#3156) #129
• [codex] Fix preview automation edge cases (#3561) #128
• Route preview automation through live owner streams (#3548) #127
• Fix Electron dev and packaged renderer startup (#3557) #126
• Restore right panel inset when maximized (#3555) #125
• [codex] Upgrade Legend List chat scrolling (#3545) #124 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@apps/mobile/src/features/threads/ThreadComposer.tsx`:
- Around line 450-452: The handleSend callback in ThreadComposer currently
discards the promise from onSendMessage, which can leave send failures
unhandled. Update handleSend to explicitly handle rejections from onSendMessage,
either by attaching a catch for logging/cleanup or by ensuring the onSendMessage
contract cannot reject. Use the existing handleSend and onSendMessage symbols to
locate the change.

In `@apps/web/src/components/ChatView.tsx`:
- Around line 3731-3740: The new message anchoring is only applied in the main
send flow, so plan follow-up sends still bypass the anchored timeline behavior.
Update the plan follow-up send path in ChatView.tsx, alongside the existing
onSend logic that sets timelineAnchor, so the optimistic message created for
“implement/refine plan” also sets the same anchored target using threadKey and
messageId. Keep the behavior consistent with the main send path so follow-up
sends land in the reserved anchored space instead of using the old bottom-scroll
flow.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 0f7fd6b1-f6af-4619-a9e6-5a380ddfbe90

📥 Commits

Reviewing files that changed from the base of the PR and between d7b8d8e and b89ca56.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (20)

• apps/mobile/package.json
• apps/mobile/src/features/threads/ThreadComposer.tsx
• apps/mobile/src/features/threads/ThreadDetailScreen.tsx
• apps/mobile/src/features/threads/ThreadFeed.tsx
• apps/mobile/src/lib/threadActivity.test.ts
• apps/mobile/src/lib/threadActivity.ts
• apps/mobile/src/lib/threadFeedLayout.test.ts
• apps/mobile/src/lib/threadFeedLayout.ts
• apps/mobile/src/state/use-thread-composer-state.ts
• apps/web/package.json
• apps/web/src/components/BranchToolbarBranchSelector.tsx
• apps/web/src/components/ChatView.tsx
• apps/web/src/components/chat/ChatComposer.tsx
• apps/web/src/components/chat/MessagesTimeline.test.tsx
• apps/web/src/components/chat/MessagesTimeline.tsx
• apps/web/src/components/chat/ModelPickerContent.tsx
• apps/web/src/index.css
• packages/shared/package.json
• packages/shared/src/chatList.test.ts
• packages/shared/src/chatList.ts

💤 Files with no reviewable changes (2)

• apps/mobile/src/lib/threadFeedLayout.ts
• apps/mobile/src/lib/threadFeedLayout.test.ts

[aaditagrawal]

Merge activity

• Jun 26, 3:03 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jun 26, 3:04 PM UTC: @aaditagrawal merged this pull request with Graphite.