[juliusmarminge]

Problem

ChatComposer cleared its scroll-collapsed flag in a passive useEffect whenever the composer stopped being eligible for scroll-collapse (multiline prompt, expanded chrome, mobile viewport, non-server route, or the "collapse on scroll" setting turned off). The value it reacted to is already computed in render, so the effect only mirrored derived state into local state, and each eligibility drop while collapsed committed the component twice: once with the stale flag, then again after paint.

Change

The flag is plain useState inside useComposerFocusState, called by ChatComposer itself, so it is reset during render with a guard (!canScrollCollapseComposer && isComposerScrollCollapsed), the same pattern the file already uses for the model picker. The guard stops once the flag is false, and canScrollCollapseComposer does not read the flag, so it cannot loop. The effect is deleted.

Behavior: none intended. The flag is still cleared rather than masked, so the composer still does not re-collapse by itself when it becomes eligible again. The only difference is timing: the stale collapsed render is discarded before commit instead of being painted for one frame.

What this improves

• Sync removed: one effect that mirrored a render-derived value into state.
• Renders avoided: one extra post-paint commit of ChatComposer (and its layout effects) on each eligibility flip while collapsed.
• No bug-fix claim, so no regression test.

Effects

• apps/web/src/components/chat/ChatComposer.tsx: 17 -> 16 useEffect

Verification

• vp run check:changed: format, lint, knip 1/2, knip 2/2, typecheck (3 packages), test all pass.

Model: Claude Opus 5.5, Claude Code harness.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at 325d841

Macroscope's review found this PR approvable — This is a narrowly scoped refactor in ChatComposer that moves an existing state reset before paint, removing a transient stale collapsed frame and an extra commit. It does not change product defaults or add any static-analysis overrides.

^{You can add or adjust custom eligibility rules. Learn more.}

[coderabbitai]

No actionable comments were generated in the recent review.

Recent review info

Run configuration

• Source mode: Auto
• Repository: pingdotgg/t3code
• Branch: effect/split-a2-composer-scroll-collapse
• File: .coderabbit.config.ts
• Commit: 325d841
• Layers: Repository TS config
• Review profile: CHILL
• Plan: Team
• Run ID: 6c4f2102-d82e-4578-b609-b95c49adc698

Commits

Reviewing files that changed from the base of the PR and between 79f6cd3 and 325d841.

Files selected for processing: 1

• apps/web/src/components/chat/ChatComposer.tsx

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 3 remain after this review.

Walkthrough

ChatComposer now clears its scroll-collapsed state during rendering when scroll-collapse eligibility becomes false. The effect that previously cleared the state after rendering was removed.

Changes: Composer scroll-collapse reset

Layer / File(s)	Summary
Reset collapsed state when eligibility is lost apps/web/src/components/chat/ChatComposer.tsx	When scroll-collapse eligibility becomes false, ChatComposer clears the collapsed state during rendering instead of in an effect.

Priority: Low

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Refactor

Suggested labels: size:M

Suggested reviewers: macroscopeapp

Merge Risk: Minimal · up to 325d8

The change preserves scroll-collapse reset behavior without introducing an identified merge-blocking risk.

Pre-merge checks: 3 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Description check		The description clearly explains the problem, implementation, unchanged behavior, and verification results. It does not include the required Scope and approval section or explain why this focused refa…	Add a Scope and approval section with the linked issue or maintainer approval, or explain why this focused refactor is an obvious bug-free change that qualifies without prior approval. Add before/after UI screenshots, or state why screensho…

Passed checks: 3 passed

Check name	Status	Explanation
Title check		The title is concise, specific, and accurately describes the main change: clearing the composer scroll-collapse state during render instead of after paint.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description clearly explains the problem, implementation, unchanged behavior, and verification results. It does not include the required Scope and approval section or explain why this focused refactor qualifies without prior approval. It also does not provide the required UI screenshots or state why they could not be provided.

Resolution

Add a Scope and approval section with the linked issue or maintainer approval, or explain why this focused refactor is an obvious bug-free change that qualifies without prior approval. Add before/after UI screenshots, or state why screenshots are not meaningful for this timing-only change.

Finishing Touches

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