fix(mobile): a message that fails to send now says why in the thread

[shivamhwp]

Problem

On mobile, when the server rejected a message, the app put the text back in the composer and showed nothing. It looked like the Send tap didn't register. The reason was saved, but only the Add Environment screen renders it, so it showed up there later as if pairing had failed. Web shows the same error in a banner on the thread.

This is a regression: the thread screen stopped reading that value in #2978. Full repro, before evidence and cause are in #15801.

Change

Send failures now go to a per-thread error shown above that thread's composer:

• thread-composer-error.ts keeps one error per thread in a single map. The outbox can reject a message after you've left the thread, so it waits there until you come back.
• The outbox restore path, the queued-edit "already started" notice and a failed outbox write now set that thread's error instead of the global pairing error.
• ComposerErrorNotice shows the reason above the composer, using the same card as the existing feedback notice, with a dismiss button.
• Sending again clears it, like web. An error from the outbox records which message it's about. If that message is delivered on a later retry, its error clears, and an error about a different message stays.
• The error is set before the restored text appears in the composer. A resend while the restore is still saving therefore always clears it, and every path where the restore backs out withdraws it.
• Removing an environment clears its threads' errors along with its drafts and outbox.
• VoiceOver announces the error. accessibilityLiveRegion only reaches TalkBack.
• A rejected new task is unchanged. Its failure card already shows the reason and replaces the composer.

The Add Environment screen no longer shows send errors.

Not in this PR: git status refresh errors, review-comment image picks and composer paste errors still write to the old global value. They happen in other sheets or on paths I couldn't trigger in the app (the paste handler onPasteIntoDraft has no caller). They need their own decision about where to show the error, so I left them for a follow-up.

Scope and approval

A focused fix for #15801, with a reproduction and the cause linked there. It restores feedback the thread screen had before #2978 and matches what web already does. Mobile only, no contract or server changes.

Verification

Unit tests. vp test run apps/mobile/src/state/use-thread-outbox-drain.test.ts apps/mobile/src/state/thread-composer-error.test.ts: 29 passed. They check that:

• a rejected follow-up sets that thread's error
• a failed recovery retry ends with the right error
• a rejected new task sets no error
• delivering a message clears only its own error
• removing an environment clears only that environment's errors
• resending the restored text mid-restore leaves no error
• a restore that backs out because of an edit withdraws its error
• a rejected new task's earlier recovery error is dropped once its failure card takes over

Against the old outbox code, 4 of the outbox tests fail. Each newer test fails when the line it covers is removed.

Typecheck and lint. tsc --noEmit for apps/mobile passes. vp lint reports no errors on the changed files.

iOS simulator. Run on the first commit, rerun on 6dac48d (banner after a rejected send, still there after leaving and returning, dismiss), and again on 23a1eea after a clean app restart (banner shows and the text is restored). iPhone 17 Pro, iOS 26.5, dev client from this branch, against a local server with a copy of real threads. One thread uses a provider instance (codex-p) the server doesn't have, so every send to it is rejected.

Check	Result
Send in the rejected thread	Before: text goes back to the composer, no feedback. After: "No orchestration provider adapter is registered for codex-p." appears above the composer within about 2s. The text stays in the composer.
Leave the thread and come back	The error is still there
Add Environment screen	Before: showed the send error. After: clean
Send again	The error clears on the tap and returns when the send fails again
Dismiss	The error goes away
Dark mode	Readable, matches the feedback card
Queued message starts while you edit it	"That message already started. Your edit is back in the composer." shows above the composer
Normal send in a working Claude thread	No banner, the agent replies

Before and after, same thread, same message. Left is main: the text comes back with no error. Right is this branch: the reason shows above the composer.

send-failure-before-after.mp4

Not checked:

• Android. It's the same shared code, and the icon is mapped in AppSymbol.tsx.
• A physical iPhone.
• The VoiceOver announcement, since the simulator has no VoiceOver.
• A failed outbox write, which needs a disk write error.
• Clearing errors on environment removal in the app. The clear function is unit tested, and the hook into removal is one line in connection/platform.ts.

Closes #15801

🤖 Generated with Claude Code (Claude Opus 5.5, in T3 Code)

[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	2	2	0 (0.0%)	8	✅

Baseline: de09c75 · PR result: c7fe5cc · 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.

[macroscopeapp]

Approvability

Verdict: Approved at 237bb20

Macroscope's review found this PR approvable — This is a contained mobile bug fix that replaces ambiguous global send errors with a dismissible, thread-scoped notice and cleans up stale messages across delivery and recovery paths. The state transitions are message-scoped and covered by focused tests, with no schema, deployment, security, billing, default, or lint-suppression impact.

No code changes detected at c7fe5cc. Prior analysis still applies.

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• apps/mobile/src/connection/platform.ts

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📝 Walkthrough

Walkthrough

Composer and outbox paths now store errors by thread. The selected thread displays and clears its error through a dismissible notice. Environment cleanup removes composer errors associated with that environment.

Changes

Thread composer errors

Layer / File(s)	Summary
Define and manage thread-scoped errors apps/mobile/src/state/thread-composer-error.ts, apps/mobile/src/state/thread-composer-error.test.ts, apps/mobile/src/connection/platform.ts	A keep-alive atom stores errors by thread key and optional message ID. Functions set errors, clear them conditionally, or clear errors for an environment. Tests cover message matching and environment-specific clearing.
Connect composer and outbox outcomes apps/mobile/src/state/use-thread-composer-state.ts, apps/mobile/src/state/use-thread-outbox-drain.ts, apps/mobile/src/state/use-thread-outbox-drain.test.ts	Composer and outbox paths set errors for the affected thread. New sends and successful delivery clear applicable errors. Tests cover delivery cleanup and recovery outcomes.
Display and dismiss thread errors apps/mobile/src/features/threads/ComposerErrorNotice.tsx, apps/mobile/src/features/threads/ThreadDetailScreen.tsx	The selected thread displays an accessible notice when it has an error. Dismissing the notice clears that thread’s error.

Priority: ⬇️ Low

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

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge

Merge Risk: 🔵 Low · up to 2997f

In the unusual case of overlapping colon-containing environment IDs, removing one environment can hide another thread’s failed-send reason. The impact is limited to that feedback, so the change is mergeable with follow-up awareness.

Architecture Summary

Architecture risk: 🔵 Low · up to 2997f

The change affects 1 system.

Changed systems: apps/mobile

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — apps/mobile (service) was modified; 8 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in apps/mobile/src/features/threads/ComposerErrorNotice.tsx: Adds the imports and exported ComposerErrorNotice declaration. When Platform.OS is "ios", changes to message trigger an accessibility announcement.
• observed — Modified behavior in apps/mobile/src/features/threads/ComposerErrorNotice.tsx: Adds a styled error notice displaying the message and an alert icon, plus a button labeled “Dismiss error” that invokes onDismiss.
• observed — Modified behavior in apps/mobile/src/features/threads/ThreadDetailScreen.tsx: Adds the useAtomValue import used to read composer-error state.
• observed — Modified behavior in apps/mobile/src/features/threads/ThreadDetailScreen.tsx: Imports the composer-error atom and its thread-specific clearing function.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Out of Scope Changes check	⚠️ Warning	The PR also adds unrelated route-management and connectivity features. Examples include pairing with an expected environment ID in connection/onboarding.ts, network-path wakeups in `connection/platf…	Remove the route-management, pairing, and network-path changes from this PR, or move them to a separate PR.
Docstring Coverage	⚠️ Warning	Docstring coverage is 57.14% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 8 files.	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 clearly summarizes the main change: mobile threads now explain why a message failed to send. It is specific and uses a conventional commit format.
Description check	✅ Passed	The description covers the problem, change, scope and approval, and verification. It includes focused test results, UI evidence, unverified cases, and the agent and harness attribution.
Linked Issues check	✅ Passed	[15801] The PR stores rejection reasons per thread and shows a dismissible notice above that thread’s composer. It associates errors with messages, clears an error when its message is delivered, and p…

Full details: Out of Scope Changes check

Explanation

The PR also adds unrelated route-management and connectivity features. Examples include pairing with an expected environment ID in connection/onboarding.ts, network-path wakeups in connection/platform.ts, route persistence in connection/storage.ts, and the new EnvironmentRoutesSection.tsx. These changes do not support [15801]’s thread send-error feedback objective.

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Inline comments:
Review comments at @apps/mobile/src/features/threads/ComposerErrorNotice.tsx:
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• apps/mobile/src/features/threads/ComposerErrorNotice.tsx
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• apps/mobile/src/state/thread-composer-error.ts
• apps/mobile/src/state/use-thread-composer-state.ts
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Inline comments:
Review comments at @apps/mobile/src/state/use-thread-outbox-drain.ts:
- Line 575: Update the creation recovery flow in useThreadOutboxDrain to clear
the matching thread error for queuedMessage.messageId once restoration succeeds,
including when a previously blocked restoration becomes unblocked. Preserve the
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• apps/mobile/src/connection/platform.ts
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• apps/mobile/src/state/thread-composer-error.ts
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