🤖 fix: prevent transcript loading indicator layout flash

[ammar-agent]

Summary

Fix the transcript layout flash caused by the “Loading messages” indicator during history catch-up. Keep loading feedback out of the composer’s normal layout flow so its appearance/removal cannot resize the dock or move cached messages.

Background

Regression introduced by #4125, “🤖 feat: show chat history loading above the composer” (commit d8d368d4bfd49f7b761e6b19d2923b0865458f07). That change inserted a transient 24px row into the in-flow composer dock, changing transcript geometry on workspace switches and catch-up completion.

Implementation

• Position the compact, non-interactive loading indicator above the dock without consuming layout space. Keep a permanent transcript gutter so the badge cannot cover compact tail rows; the gutter does not toggle with loading.
• Preserve editable/read-only replay feedback and existing stream/monitor suppression. Yield to “Jump to bottom” while scrolled up so the controls cannot overlap on phones.
• Extend existing desktop and pinned-phone stories with long cached history, scroll navigation, non-overlap checks against the transcript content boundary, and assertions that catch-up preserves dock height, message position, and scroll height.

Validation

• make static-check passed.
• Hydration/reveal and layout-stack unit tests: 8 passed.
• Chromium Storybook Replay and Phone plays passed, including editable/read-only geometry and phone navigation.
• Red/green check: returning the loading indicator to normal flow fails both stories on the 24px dock-height change (176 → 152); restoring the fix passes both.
• Storybook coverage contract passed (38 tests). The separate snapshot-budget tests fail unchanged on the baseline as well (509 estimated snapshots versus a 305 cap); this change adds no stories or viewport variants.

Risks

The indicator is now a small overlay above the composer rather than an extra row. History/subscription state and composer behavior are unchanged. Desktop-agent visual inspection was unavailable in this SSH environment; responsive checks ran in real Chromium via the pinned-phone story.

---

Generated with xum • Model: openai:gpt-6-astra • Thinking: medium • Cost: $9.15

[ammar-agent]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-08T22:07:24.304945Z	096c620	Manual request
🔒 Security Review	✅ Completed 2026-09-08T22:07:22.966314Z	096c620	Manual request

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: a77ee000d1

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[ammar-agent]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: 096c620fb3

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[ammar-agent]

Codex approved commit 096c620 with no major issues, and both security reviews reported no security issues. The legacy Codex Comments gate treats the two clean-security informational comments as unresolved findings; marking those informational comments resolved (collapsed, not deleted) so the gate can reflect the actual review result. The substantive tail-overlap finding was fixed and its thread resolved.