fix(web): collapsed composer reserves room for wide send actions

[maria-rcks]

When the composer collapses on scroll, its actions float over the one-line prompt row. The row reserved a fixed right inset sized for the round send button, so wider actions like the compact-before-send chip covered the placeholder.

The collapsed row now measures the floating actions with a ResizeObserver and reserves that width plus 1rem, so the placeholder truncates before the actions.

Verification: reproduced on a stale 142k-token Claude thread in a dev server with copied data, scrolled up to collapse the composer, captured main and this branch at 900px and 1280px wide (dark theme). Lint, format, and web typecheck pass. The plain send-button resting state was not captured; its reserved width changes by about 4px from the old fixed inset.

Before, 900px:

After, 900px:

Before, 1280px:

After, 1280px:

Opus 5.5 via Claude Code in T3 Code.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at 1bed22e

Macroscope's review found this PR approvable — This is a focused UI layout fix confined to the existing chat composer. It dynamically reserves space for the already-present send actions while leaving expanded behavior and message operations unchanged.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The resting composer prompt row now sets its right padding from the measured width of the right-side actions. The composer updates this measurement when the actions element resizes.

Changes

Resting composer action spacing

Layer / File(s)	Summary
Measure actions and apply resting padding apps/web/src/components/chat/ChatComposer.tsx	The composer measures the resting actions container and observes it for size changes. The prompt row uses the measured width plus 1rem for right padding. When the composer is not resting or no width is available, it applies no inline padding.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: juliusmarminge

Merge Risk: 🔵 Low · up to 1bed2

In long, scroll-collapsed desktop threads, the placeholder can overlap the send button when hovered. The impact is a bounded visual issue, and a small padding adjustment would preserve separation.

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description clearly explains the problem, implementation, verification steps, screenshots, and agent usage. It does not include the required Scope and approval section or explain why this focused …	Add a Scope and approval section. Link the triaged issue or maintainer approval, or explain why this is an obvious, focused bug fix that qualifies without prior discussion.

✅ Passed checks (3 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 fix: reserving space for wide send actions in the collapsed web composer.

Full details: Description check

Explanation

The description clearly explains the problem, implementation, verification steps, screenshots, and agent usage. It does not include the required Scope and approval section or explain why this focused fix qualifies without prior issue or maintainer approval.

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Dismissing prior approval to re-evaluate ed285d9

Dismissing prior approval to re-evaluate 1bed22e

[coderabbitai]

Actionable comments posted: 1

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Inline comments:
Review comments at @apps/web/src/components/chat/ChatComposer.tsx:
- Around line 5223-5235: Adjust the reserved prompt width calculation that uses
restingActionsWidth in ChatComposer so it includes the resting footer’s
horizontal inset and enough clearance for the scaled send button. Preserve the
existing action-width and 1rem spacing while adding the required extra 4px.

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between ed285d9 and 1bed22e.

📒 Files selected for processing (1)

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

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