[Bug]: Mobile has no way to stop background work after the turn settles #14655

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/mobile

Steps to reproduce

1. On a Claude thread, ask the agent to start something that outlives the turn: a Monitor-tool watch loop, a background shell, or background subagents.
2. Wait for the parent turn to finish. On web/desktop the composer now shows a Monitoring (or N agents working) banner with a Stop button.
3. Open the same thread in the mobile app (iOS or Android) and try to stop the background work.

Expected behavior

Mobile offers a Stop control for background work that outlives the turn, the same as the web/desktop banner. Pressing it stops the background tasks and the thread returns to idle.

Actual behavior

Mobile has no stop control in this state. The composer shows the normal send/dictation actions, and nothing else on the thread screen can stop the work. The only way to stop it is to switch to web or desktop.

This is separate from the missing status label tracked in #10372 and #4962. #13803 fixes those by adding the Working/Monitoring label to the mobile list and the open-thread pill, but its diff has no stop or interrupt changes, so after it merges mobile will show Monitoring and still not be able to stop it.

Impact

Major degradation or frequent failure

It happens every time background work outlives a turn, and the phone is often the only client at hand when a user wants to stop a runaway watch loop or subagent fleet.

Version or commit

main @ 094fb23

Environment

Source-level finding against main; not reproduced on a device for this report. The code involved is shared React Native code, so it applies to both iOS and Android. The device reports on #10372 and #4962 (iOS, Pixel 9, Galaxy S25 Ultra) describe the same thread state.

Source evidence

Web deliberately gives this state its own stop control, and says why:

• ChatView.tsx#L6237-L6243: "once it settles, the composer stop button is gone, so this banner is the only visible stop affordance. Stop routes through the stop-everything interrupt ... and works by session, so no active turn is needed."
• ChatView.tsx#L6278-L6313: the banner and its Stop button.
• ChatView.logic.ts#L530-L539: the interrupt input is built with threadId only when no turn is running.

Mobile blocks the same action in two places:

• ThreadComposer.tsx#L301-L304: showStopAction is true only while session.status is running or starting, so the "Stop agent" button is hidden once the turn settles.
• ThreadRouteScreen.tsx#L632-L649: handleStopThread returns early unless the session is running or starting. Showing a button is therefore not enough; the handler also has to allow a settled session with background work.

The server side already supports it. backgroundLiveness is on the thread shell mobile receives (orchestration.ts#L928), and the Claude adapter's interrupt stops the whole session regardless of turn (ClaudeAdapter.ts#L5363-L5371). No contract or server change should be needed.

apps/mobile has no references to backgroundLiveness on main.

Suggested fix

When backgroundLiveness is non-null and no turn is running, show a Stop control on the mobile thread screen and send the interrupt with threadId only, as buildThreadTurnInterruptInput does on web. Hold a "Stopping..." state until the liveness clears, since the command returning only means the request was accepted.

Workaround

Open the thread on web or desktop and press Stop on the Monitoring banner.

Related

• [Bug]: iOS does not show Monitoring status displayed on desktop and web #10372: mobile does not show Monitoring
• [Bug]: Mobile looks idle while background subagents are still working #4962: mobile looks idle while background subagents work
• fix(mobile): show Working and Monitoring when background work outlives the turn #13803: open fix for the two above (label only)
• [Feature]: Mobile: sub-agent visibility parity — spawn indicator, Agents surface, and background liveness #6402: closed parity request that listed "no stop affordance for that background work"

Investigated from source with Claude Opus 5.5 in T3 Code.