fix(mobile): adapt workspace navigation and expand controls

[juliusmarminge]

What Changed

Settings and New Task now open in the main content pane on wide iOS viewports, using the existing workspace breakpoints. Compact iOS keeps sheets, and Android keeps its existing screen presentation.

Split-view Settings and New Task flows use Back without an expand button on both platforms. Home's "Select a thread" view always keeps the sidebar visible. Android's workspace toggle uses two diagonal arrows to expand content and a sidebar icon to show the thread list again. Android header buttons no longer have filled selected backgrounds; accessibility still exposes their selected state.

The iOS split-view Terminal header uses Back grouped with its expand control, matching Files and Review.

Why

Workspace flows should behave like normal screens, with a persistent thread list and navigation controls appropriate to each route.

UI Changes

Manually tested on iPad by the maintainer. Verified Android tablet navigation through Settings, Choose Project, and Add Project, plus expanding and restoring a chat. Confirmed the plain header buttons and two-arrow expand icon in the running Android app. Screenshots waived at the maintainer's request.

Checklist

• Small and focused.
• Changes and rationale explained.
• 72 focused layout, navigation, and new-task tests passed.
• Mobile typecheck and targeted formatting/lint checks passed.
• UI verified; screenshot/video evidence waived by the maintainer.

Implemented with GPT-6 in Codex.

Summary by CodeRabbit

• New Features

  • Added adaptive sheet presentations based on device platform and available screen space.
  • Improved split-view navigation with clearer back controls and native iOS toolbar actions.
  • Updated sidebar controls with expanded/collapsed indicators and improved accessibility labels.
  • Kept the primary sidebar visible on the home screen for more consistent workspace navigation.

• Bug Fixes

  • Corrected split-view header behavior so back buttons remain available when sidebars are disabled.
  • Terminal back navigation now returns to chat instead of closing the terminal.
  • Refined mobile header icons and maximize controls for clearer visual feedback.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This changes production mobile navigation and workspace behavior across Settings, New Task, Home, Terminal, and shared split-view headers, including route presentation and sidebar defaults. The cross-screen runtime impact warrants human review.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	+21 B (+0.2%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	+1 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.5 KiB	+20 B (+0.3%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.3 KiB	56.3 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	+6 B (+0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+3 B (+0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.4 KiB	+3 B (+0.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 803f94e · PR result: 50c86a2 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 114.0 KiB
• Claude decoded thread snapshot: 114.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

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• apps/mobile/src/features/terminal/ThreadTerminalRouteScreen.tsx

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📝 Walkthrough

Walkthrough

The mobile app adapts sheet presentation and split-view headers to platform and workspace layout. The home route keeps its sidebar visible, while settings, new-task, and terminal routes use split-view navigation controls.

Changes

Mobile workspace adaptation

Layer / File(s)	Summary
Adaptive navigation presentation apps/mobile/src/Stack.tsx	The root navigator selects card presentation for Android and split-view layouts, and a detented form sheet for compact iOS.
Home workspace layout state apps/mobile/src/features/layout/AdaptiveWorkspaceLayout.tsx	The home route keeps the primary sidebar visible and disables sidebar toggling and its hardware command.
Split-view header behavior apps/mobile/src/components/ScreenHeader.tsx, apps/mobile/src/features/home/HomeRouteScreen.tsx, apps/mobile/src/features/layout/workspace-sidebar-toolbar.tsx, apps/mobile/src/features/settings/..., apps/mobile/src/features/threads/NewTaskRouteScreen.tsx, apps/mobile/src/features/terminal/ThreadTerminalRouteScreen.tsx, apps/mobile/src/components/AndroidScreenHeader.tsx, apps/mobile/src/components/AppSymbol.tsx	Home, settings, new-task, and terminal screens now use platform-specific split-view headers and back actions. The shared workspace sidebar toolbar was removed. Related Android header labels, icons, and button styling were updated.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant RootStack
  participant Layout
  participant SettingsSheet
  participant NewTaskSheet
  RootStack->>Layout: read platform and window layout
  Layout-->>RootStack: return split-view state
  RootStack->>SettingsSheet: apply adaptive presentation
  RootStack->>NewTaskSheet: apply adaptive presentation

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Suggested reviewers: chrisdeeming

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 8.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 12 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.
Description check	✅ Passed	The description includes What Changed, Why, UI Changes, and Checklist sections. It explains the navigation updates, validation results, and the maintainer-approved screenshot waiver.
Title check	✅ Passed	The title clearly summarizes the main changes: mobile workspace navigation updates and expanded controls.

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Actionable comments posted: 1

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Inline comments:
In `@apps/mobile/src/components/AndroidScreenHeader.tsx`:
- Line 28: Update AndroidHeaderIconButton to preserve the selected tonal style
by passing variant="tonal" when props.selected is true and variant="standard"
otherwise, while retaining the existing props spread and tintColorClassName.

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📒 Files selected for processing (3)

• apps/mobile/src/components/AndroidScreenHeader.tsx
• apps/mobile/src/components/AppSymbol.tsx
• apps/mobile/src/features/layout/workspace-sidebar-toolbar.tsx

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