fix(mobile): Android composer picker scrolls past the first four rows

[shivamhwp]

On Android, the composer pickers in an open thread (@ files, $ skills, / commands, #) showed four rows and wouldn't scroll, so anything past the fourth result was unreachable. Taps worked. Swipes went to the chat behind the picker instead.

The picker hung above the composer with absolute bottom-full, outside its parent's bounds. Android only sends drags to views inside their parent's bounds, so the picker's list never got the swipe.

On Android the picker now renders into ComposerPopoverHost, a full-size layer inside the composer's KeyboardStickyView. That layer covers the picker, so Android delivers its swipes, and it moves with the keyboard, so the picker stays right above the composer without any keyboard timing. The anchor re-measures the composer's resting position with measureLayout against the host after each composer render, and when the composer or the host resizes. iOS keeps the old wrapper.

Testing

Xiaomi POCO M3 Pro, Android 13, dev build. Same steps in both videos: type $, swipe up three times inside the skills list, then swipe down three times.

Before: the list stays on babysit-pr, the chat behind it scrolls	After: the list scrolls down to test-t3-app and back, the chat stays put
Full video	Full video

The @ file picker on the fixed code, before and after one swipe. It moves from threads down to files:

Also checked on the fixed code: the picker sits right above the composer with the keyboard up and down and keeps scrolling in both, and it isn't shown over thread settings. Mobile typecheck and lint on the changed files pass. iOS isn't tested since that path is unchanged.

Closes #15658

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This targeted Android UI fix introduces a stateful popover host, cross-view measurement, and a structural wrapper around the production composer and keyboard layer. Because those changes affect runtime layout and touch handling beyond a simple local edit, focused human review is warranted.

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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	5.0 KiB	5.0 KiB	0 B (0.0%)	6.8 KiB	✅
Codex	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.2 KiB	1.2 KiB	0 B (0.0%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	20.9 KiB	20.9 KiB	0 B (0.0%)	29.3 KiB	✅
Codex	Live turn messages	2	2	0 (0.0%)	8	✅
Claude	Total thread wire	5.0 KiB	5.0 KiB	0 B (0.0%)	6.8 KiB	✅
Claude	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Claude	Live turn WebSocket wire	1.2 KiB	1.2 KiB	0 B (0.0%)	2.0 KiB	✅
Claude	Live turn WebSocket decoded	21.2 KiB	21.2 KiB	0 B (0.0%)	29.3 KiB	✅
Claude	Live turn messages	1	1	0 (0.0%)	8	✅

Baseline: a1d9d72 · PR result: bd654f7 · 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: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

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

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📥 Commits

Reviewing files that changed from the base of the PR and between d7c8378 and bd654f7.

📒 Files selected for processing (3)

• apps/mobile/src/features/threads/ComposerPopoverAnchor.android.tsx
• apps/mobile/src/features/threads/ComposerPopoverHost.tsx
• apps/mobile/src/features/threads/ThreadDetailScreen.tsx

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📝 Walkthrough

Walkthrough

The change adds a host for composer popover content and an anchor for positioning it. ThreadDetailScreen provides the host, and ThreadComposer uses the anchor for ComposerCommandPopover. On Android, the anchor measures its position relative to the host and updates the popover position.

Changes

Composer popover hosting and anchoring

Layer / File(s)	Summary
:---	:---
Host context and screen wiring apps/mobile/src/features/threads/ComposerPopoverHost.tsx, apps/mobile/src/features/threads/ThreadDetailScreen.tsx	ComposerPopoverHost provides a host view, content setter, and layout version through context. ThreadDetailScreen wraps its existing floating composer overlay in the host.
Anchor positioning apps/mobile/src/features/threads/ComposerPopoverAnchor.tsx, apps/mobile/src/features/threads/ComposerPopoverAnchor.android.tsx	The shared anchor renders children above the composer. On Android, it measures its position relative to the host, updates host content with the measured position, and clears that content on unmount.
ThreadComposer integration apps/mobile/src/features/threads/ThreadComposer.tsx	ThreadComposer wraps ComposerCommandPopover in ComposerPopoverAnchor instead of an absolute bottom-aligned View.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to bd654

No actionable issue remains before merge under normal checks. Android gesture delivery has not been independently verified at runtime.

Security Architecture Review

Security architecture risk: ⚪ Minimal · up to bd654

The change relocates the Android picker without changing command-selection permissions or thread binding. Each screen owns its picker state, and closing the picker clears the hosted content. No material security risk was identified in this change.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The introduced mutable projection is scoped to a host instance in the thread screen. The current topology has one anchor under each host, so separate screen instances do not share the projection slot.

Trust Boundaries and Controls

• observed — Picker visibility and selection remain controlled by ThreadComposer’s existing menu. Its menu retains owner, environment, and current-thread inputs; ThreadDetailScreen continues passing the same thread/environment props. The host relocation does not add a command handler or permission bypass in this flow.

Resilience and Maintainability Implications

• inferred — Closing or unmounting the anchor clears hosted content. A late measurement callback updates only the originating anchor’s local state and cannot directly republish into the host after unmount. The setter has no owner token, but the inspected single-writer topology does not exercise competing-owner cleanup.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 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	Issue #15658 requires the Android picker in an open thread to scroll beyond the visible rows. ThreadComposer now uses ComposerPopoverAnchor; on Android, the anchor renders the picker in `ComposerP…
Out of Scope Changes check	✅ Passed	The host, anchor, and ThreadDetailScreen wrapper support the Android picker fix in issue #15658. The shared picker includes the @, $, /, and # entries identified in the issue. The iOS fallba…
Title check	✅ Passed	The title clearly identifies the Android composer picker scrolling fix and uses a concise conventional format.
Description check	✅ Passed	The description explains the problem, the change, and focused verification, including before-and-after evidence and test limitations. It links issue #15658 but does not state that the issue was triage…

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