fix(mobile): a stuck attachment upload no longer holds the whole outbox

[deathemperor]

Problem

The mobile outbox dispatches one message at a time, across every thread (dispatchingQueuedMessageIdAtom). uploadFileBytes has no upper bound, and the drain passes no signal, so one transfer that never settles holds every queued reply and new thread behind it.

I hit this on iOS sending a 7.7 MB PNG through a tunnel that cuts a request at about two minutes. From the server's traces:

Upload from the phone	Size	Result
screenshot A	0.9 MB	204 in about 5 s
screenshot B	2.6 MB	204 in 69 s
screenshot C	7.7 MB	499 at about 125 s, every attempt

The server also saw the same signed upload URL re-posted up to 22 minutes after it expired. The app mints a fresh URL per attempt, so those replays came from iOS: expo-file-system uploads on a background URLSession, which retries a failed transfer on its own. Text-only replies in other threads stayed "Pending" for over an hour, while inbound messages kept arriving. The stuck message could not be pulled back, because the edit pencil is hidden for the message currently being dispatched.

Fix

uploadFileBytes bounds one transfer with ATTACHMENT_UPLOAD_TIMEOUT_MS (3 minutes). At the bound it aborts the native task through a linked AbortController, and rejects by itself via Promise.race, so the bound holds even if the native side never reports the cancellation.

The rejection is a plain Error, so shouldRetryThreadOutboxDelivery is false and the drain's existing path restores the message to the composer with the error shown. No outbox change. A user cancel still aborts the outer signal and is still reported as abandoned.

I left the session type at its background default so an upload still survives a locked phone.

Verification

• vp test run src/lib/attachmentUpload.test.ts: 31 pass. The new test drives a never-settling upload on fake timers and asserts the rejection and the aborted native signal.
• tsc --noEmit in apps/mobile, lint and format on the two touched files.
• Not run on a device.

No UI change. Two files, 48 lines.

Model and harness: Claude Fable 5.1 in Claude Code.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Attachment uploads now time out after 180 seconds if they do not complete.
  • Timed-out uploads stop cleanly, preventing them from continuing indefinitely.
  • Users now see a clear error message when an attachment upload exceeds the time limit.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This changes the default behavior of all mobile attachment uploads by imposing a new 180-second deadline, rather than adding an opt-in path. Unresolved Medium findings also identify lifecycle and cancellation-error risks on iOS.

Not approved because:

• 2 blocking correctness issues found at or above your repo's Minimum Blocking Severity

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ℹ️ Recent review info

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Reviewing files that changed from the base of the PR and between 866d0a1 and 8afdece.

📒 Files selected for processing (2)

• apps/mobile/src/lib/attachmentUpload.test.ts
• apps/mobile/src/lib/attachmentUpload.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• apps/mobile/src/lib/attachmentUpload.ts
• apps/mobile/src/lib/attachmentUpload.test.ts

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📝 Walkthrough

Walkthrough

Attachment uploads now use a 180-second timeout. Timed-out transfers are aborted and return a filename-specific error. Tests verify the timeout rejection and native abort signal.

Changes

Attachment upload timeout

Layer / File(s)	Summary
Transfer timeout handling apps/mobile/src/lib/attachmentUpload.ts	Adds ATTACHMENT_UPLOAD_TIMEOUT_MS and applies it to each upload. Timed-out uploads abort through an internal AbortController, reject with a filename-specific error, and clean up timers and listeners.
Stalled upload validation apps/mobile/src/lib/attachmentUpload.test.ts	Adds a fake-timer test for a never-settling upload. The test verifies that the timeout error wins over the abort rejection and that the native AbortSignal is aborted.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing a stuck mobile attachment upload from blocking the outbox.
Description check	✅ Passed	The description explains the problem, solution, verification, UI impact, and scope. It does not use the template headings or include the checklist, but it provides the required information in equivale…
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.

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Inline comments:
In `@apps/mobile/src/lib/attachmentUpload.ts`:
- Around line 287-288: In the attachment upload timeout handler, update the
ordering around timedOut.reject and transfer.abort so the timeout promise
rejects before aborting the transfer. Preserve the existing timeout error
message and timer behavior.

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📒 Files selected for processing (2)

• apps/mobile/src/lib/attachmentUpload.test.ts
• apps/mobile/src/lib/attachmentUpload.ts

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[deathemperor]

Addressed in 8afdece.

Timeout error vs cancellation error (both bots): correct, and the hardened test proved it. With a fake upload that rejects on abort synchronously, the old order surfaced "Upload cancelled." for a timeout. The timer now settles the timeout rejection first, then aborts.

setTimeout does not run while the app is suspended (Macroscope): true, but nothing waits on the outbox lock while JavaScript is suspended, because the outbox is JavaScript too. When the app resumes, the timer fires and the bound applies. A native deadline would end an upload iOS is legitimately finishing in the background, which is the opposite of what the bound is for.

A bound by default rather than opt-in: the default is the bug. Every caller of this helper is a sender waiting on the result, and an unbounded wait holds the serialized outbox for every other message. There is no caller that wants no bound.