sidebar scrollbar always visible — should only appear when content overflows

[lawrencecchen]

Addresses #3241

Generated by cmux-loader.

Recorded videos:

• repro-before: .runner/videos/repro-before.mov (ok)
• fixed-after: .runner/videos/fixed-after.mov (ok)

Run artifacts: https://github.com/manaflow-ai/cmux-loader/actions/runs/25090033696

Codex final message:

Implemented a focused fix for #3241 in the workspace sidebar.

Change made

• Updated Sources/ContentView.swift in VerticalTabsSidebar.workspaceScrollArea so the sidebar ScrollView now uses:
  • scrollIndicators(.automatic)

This keeps sidebar scrollers from being permanently visible and lets indicator visibility follow overflow/OS scroll behavior.

Verification performed

1. Built tagged debug app with required flow:
   ./scripts/reload.sh --tag loader

=======================================================
loader: file:///Users/runner/Library/Developer/Xcode/DerivedData/cmux-loader/Build/Products/Debug/cmux%20DEV%20loader.app

2. Captured GUI recordings via loader workflow:

• repro-before (status=ok)
• fixed-after (status=ok)

3. Kept all work within the single requested file and used tagged build only.

---

Summary by cubic

Fixes #3241: The workspace sidebar scrollbar now appears only when content overflows. Updated the VerticalTabsSidebar ScrollView to use .scrollIndicators(.automatic) so visibility follows the OS.

^{Written for commit 114756c. Summary will update on new commits. Review in cubic}

Summary by CodeRabbit

• Refactor
  • Restructured sidebar workspace list scroll view composition with improved scroll indicator configuration.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
cmux	Ready	Preview, Comment	Apr 29, 2026 4:08am
cmux-staging	Building	Preview, Comment	Apr 29, 2026 4:08am

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ff1006d7-90aa-4e49-826e-e63dc1393185

📥 Commits

Reviewing files that changed from the base of the PR and between af36cab and 114756c.

📒 Files selected for processing (1)

• Sources/ContentView.swift

---

📝 Walkthrough

Walkthrough

The sidebar workspace list scroll view composition in ContentView.swift is restructured. The ScrollView is now emitted directly within ScrollViewReader, while drag-auto-scroll functionality is preserved via SidebarScrollViewResolver. Explicit .scrollIndicators(.automatic) configuration is added, replacing the prior nesting and layout structure.

Changes

Cohort / File(s)	Summary
Sidebar Scroll View Composition Sources/ContentView.swift	Restructured workspaceScrollArea to emit ScrollView directly within ScrollViewReader, preserve dragAutoScrollController.attach(scrollView:) via SidebarScrollViewResolver, and add explicit .scrollIndicators(.automatic) configuration. Prior nesting/layout structure removed.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

• Keep selected workspace visible in sidebar #3152: Modifies sidebar workspace ScrollView composition in ContentView.swift with restructuring of ScrollView/ScrollViewReader and preserving drag-auto-scroll attachment.
• Resync terminal portals after sidebar changes #1253: Modifies ContentView.swift to change sidebar layout and behavior including scroll area and sidebar width/visibility handling.

Poem

🐰 A scroll view finds its perfect nest,
Wrapped in readers, now at rest,
Drag and scroll in harmony blend,
The sidebar's journey takes a bend! ✨

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description covers the core change and verification, but omits critical template sections: Testing, Demo Video, Review Trigger, and Checklist.	Add Testing section with manual verification details, include Demo Video URLs from recorded artifacts, add Review Trigger comment block, and complete the Checklist with the required items.
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 accurately describes the main change: fixing the sidebar scrollbar to appear only when content overflows instead of always being visible.
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.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch loader/issue-3241-sidebar-scrollbar-video19

---

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[greptile-apps]

Greptile Summary

Adds .scrollIndicators(.automatic) to the ScrollView inside VerticalTabsSidebar.workspaceScrollArea, so the sidebar scroll indicator follows platform/overflow behavior instead of being permanently visible. The functional change is correct and minimal; the diff also introduces inconsistent indentation (the ScrollView block is un-indented to the ScrollViewReader level), but this is cosmetic only and has no runtime effect.

Confidence Score: 4/5

Safe to merge; the functional change is a single targeted modifier addition with no behavioural regressions.

Only P2 finding (cosmetic indentation inconsistency). The core fix — .scrollIndicators(.automatic) — is the correct SwiftUI API for overflow-only scroll indicator visibility, and the view hierarchy and scrollProxy scope are unchanged.

No files require special attention.

Important Files Changed

Filename	Overview
Sources/ContentView.swift	Adds .scrollIndicators(.automatic) to VerticalTabsSidebar.workspaceScrollArea's ScrollView; indentation is inconsistent but functionally correct.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[VerticalTabsSidebar] --> B[workspaceScrollArea]
    B --> C[GeometryReader]
    C --> D[ScrollViewReader]
    D --> E[ScrollView]
    E -->|".scrollIndicators(.automatic) — NEW"| F{Content overflows?}
    F -- Yes --> G[Show scroll indicator]
    F -- No --> H[Hide scroll indicator]
    E --> I[".background — SidebarScrollViewResolver"]
    E --> J[".safeAreaInset / .overlay / .onAppear / .onChange"]

Loading

_{Reviews (1): Last reviewed commit: "Address https://github.com/manaflow-ai/c..." | Re-trigger Greptile}

[greptile-apps]

Indentation de-sync inside ScrollViewReader closure

After the refactor, ScrollView and its immediately chained modifiers (.scrollIndicators, .background) are unindented to the same column as ScrollViewReader { scrollProxy in, while the modifiers that follow (.safeAreaInset, .overlay, .onAppear, .onChange, …) are indented one level deeper. Swift doesn't use whitespace for parsing, so this compiles fine, but the visual mismatch makes it look like two separate view expressions live inside the closure — which would be a compile error — rather than one long modifier chain.

[lawrencecchen]

Closing this loader dogfood PR because the downloaded before/after videos still show the macOS FileVault confirmation sheet over cmux. I am patching FileVault suppression in the loader and rerunning from a fresh branch.