Wake a thread when a command it started exits, even after its turn ends

[shootingallday]

The gap

An agent often starts something long (a build, a test suite, a deploy, a script on another machine) and wants to hear back when it exits. Today that only works while the provider session is alive and only for providers with their own background tasks. If the turn ends, the session closes, or T3 restarts, nobody wakes the thread when the command finishes. Agents either sit in a foreground wait loop to keep the thread in Working, or hand-roll a detached job that posts a message into the thread on exit.

I run the second kind myself: a small CLI that runs a command detached and, on exit, sends the exit code and last lines into the thread through orchestration.dispatchCommand. It works, but it lives outside T3, so T3 can't show it, stop it, or recover it after a restart.

What I'd like

• A thread-owned command with a wake on exit. An MCP tool, say t3_thread_run, takes a command, cwd, an optional log file, and a deadline. T3 runs it outside the provider session and records it on the thread. When it exits, T3 posts a message into the thread with the exit code and the last lines of output, queued after any active turn.
• Optional matched wakes. A wakeOn regex wakes the thread on matching output lines, batched, plus always on exit.
• Visible and stoppable. It shows in the waiting strip like other background work (Show what each background monitor and command is running in the waiting strip #15584), keeps the thread in Working (Should background commands keep a thread in the Working section? #15433, fix(client-runtime): background commands keep threads in Working #15413), and Stop ends it (as fix(server): Stop also stops delegated tasks and pull request watches #16002 did for delegated tasks and PR watches).
• Survives restarts. On startup T3 re-attaches to a command that is still running, or reports that it was lost.
• Works the same for every provider, since it doesn't depend on the provider's own background tasks.

Related

• [Feature]: Scheduled Prompts #6748 Scheduled Prompts and [Feature]: Add model options and custom recurrence to Scheduled Tasks #15565 custom recurrence cover waking at a time. This is waking on an event.
• [Feature]: Let an agent or tool mark a thread as waiting on outside work #14072 lets a tool mark a thread as waiting on outside work. This would be one built-in source of that.
• Proposal: expose thread-aware process launch and disposal hooks #13081 asks for thread-aware process launch and disposal hooks for hosts. This is the agent-facing side.

Drafted with Opus 5.5 in Claude Code.