fix(web): keep ref picker steady when opening

[Adamulek123]

What Changed

Single-select comboboxes now use their trigger as the positioning anchor from the first frame. The branch picker trigger also stays at full scale while pressed.

Why

The old empty chips anchor caused a second positioning pass, and the trigger's press scale moved the live popup anchor a few pixels. Together these made the ref picker jump as it opened.

The composer-focus portion of the original PR is no longer needed after main stopped collapsing the desktop composer on focus loss in #10437, so it was dropped during the rebase.

UI Changes

Before

Screen.Recording.2026-09-03.205609.mp4

After

Screen.Recording.2026-09-03.212547.mp4

Validation

• vp test run apps/web/src/components/chat/composerEventScope.test.ts (7 tests passed)
• git diff --check
• Clean merge-tree against current main
• Fresh CI triggered for the rebased head

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after UI evidence
• I included video for the interaction change

Built with GPT-5.6 Sol in the Codex harness.

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Note

Medium Risk
Changes desktop composer expand/collapse focus rules and global single-select combobox popup anchoring, so regressions could show up outside the branch picker if other comboboxes relied on the old implicit anchor.

Overview
Fixes the branch/ref picker jumping sideways when opened from the expanded thread composer. Focus moving into the portaled combobox was treated as leaving the composer, which collapsed the surface and re-anchored the popup mid-open.

Composer focus scope now treats context toolbar controls (via data-chat-composer-focus-scope) and existing composer floating layers as in-composer for blur and desktop focus tracking. resolveDesktopComposerFocus keeps an already expanded composer focused across branch-picker focus transitions but does not expand a resting composer when only the picker receives focus.

Branch picker UI: the selector wrapper is marked as a composer focus scope, and the combobox trigger uses active:scale-100 so press-scale does not shrink the anchor while the popup is aligned to it.

Combobox positioning: ComboboxPopup only falls back to chipsRef as the positioner anchor when multiple is true; single-select popups use the default trigger anchor from the first frame, avoiding a second layout pass that used an empty chips anchor.

^{Reviewed by Cursor Bugbot for commit 4174026. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix ref picker popup shift by disabling trigger scale and restricting chips anchor

• Prevents the BranchToolbarBranchSelector trigger from applying a scale transform while pressed, which stops the popup anchor from shifting.
• Restricts the implicit chips anchor reference to multi-select comboboxes only in ComboboxPopup.
• Behavioral Change: Single-select combobox popups no longer use the chips reference as their implicit positioner anchor unless an explicit anchor is provided.

^{Macroscope summarized a862ba8.}

Summary by CodeRabbit

• Bug Fixes
  • Improved branch selector button behavior while its popup is open.
  • Corrected popup positioning for single-select and multi-select comboboxes.

[macroscopeapp]

Approvability

Verdict: Approved at a862ba8

Macroscope's review found this PR approvable — This is a narrowly scoped UI positioning fix: it prevents the branch trigger from shifting under press and uses the correct anchor behavior for single-select popups while preserving multi-select handling. The shared-component impact is limited to popup geometry, with no schema, security, deployment, or static-analysis changes.

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

Dismissing prior approval to re-evaluate 2ba160b

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Team

Run ID: abeedd7b-1e50-4c2f-838e-40e8bffc4bb6

📥 Commits

Reviewing files that changed from the base of the PR and between 1d1bf50 and a862ba8.

📒 Files selected for processing (2)

• apps/web/src/components/BranchToolbarBranchSelector.tsx
• apps/web/src/components/ui/combobox.tsx

🚧 Files skipped from review as they are similar to previous changes (1)

• apps/web/src/components/ui/combobox.tsx

Included review availability: Your plan provides up to 10 included reviews per hour; 7 remain after this review.

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📝 Walkthrough

Walkthrough

The branch trigger now keeps its scale while pressed. Single-select combobox popups no longer use the chips container as their default anchor.

Changes

Branch popup behavior

Layer / File(s)	Summary
Adjust branch popup positioning apps/web/src/components/BranchToolbarBranchSelector.tsx, apps/web/src/components/ui/combobox.tsx	The branch trigger adds active:scale-100. ComboboxPopup anchors to chipsRef only for multi-select comboboxes.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to a862b

This updates branch-picker popup alignment behavior and removes press scaling from its trigger. No concrete current-head merge-blocking risk remains.

Suggested reviewers: juliusmarminge

🚥 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 5 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 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 primary change: keeping the ref picker stable while it opens.
Description check	✅ Passed	The description includes the required What Changed, Why, UI Changes, and Checklist sections. It explains the fix, provides before/after UI evidence, documents validation, and identifies the interactio…

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Note

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Dismissing prior approval to re-evaluate a862ba8