A chat agent already has a way to start a worker — the harness gives it one.
Nothing else does. A watcher loop, a plugin, a background job, a cron entry: none
can reach that tool, which is exactly why a commander's loop shells out to
`claude -p` by hand and then invents its own record-keeping for what it started.
So this is the door Officer defines. `POST /sub-agents/spawn` takes a prompt and an
optional cwd and model, and returns either the session key immediately or the
result if asked to wait. Verified both ways against the live server: the
synchronous call came back with the four words it was told to say, and the async
call returned in milliseconds and the agent had written its file within five
seconds.
The budget check comes BEFORE the spawn, and refuses with a 429 naming the window.
The windows belong to the Anthropic account and every `claude` on the machine
spends them, so an endpoint that could start work without asking would burn the
last of one and cut off the turn the owner is sitting in — a failure that lands on
somebody else's conversation, which is the worst place for it.
`confined`, and confined in FACT on the day it was added rather than ahead of
itself — the registry test's comment records that `chat` sat on that list for a day
before it was true. The identity comes from `chatIdentity` on the caller's token
and `member: { osUser, home }` goes to the sidecar, which is the mechanism chat
already runs under. There is no path in the endpoint that chooses a directory, so
there is nothing for a caller to point elsewhere. `member` is passed explicitly
because it is required-but-may-be-undefined on purpose: optional let a call site
forget it, and forgetting means a member's agent running as the owner.
Not a queue, not a supervisor, not a retry. One call starts one agent; a caller
that wants three tries writes three calls, because a retry in here would be a
policy nobody chose applied to work this endpoint cannot read.
Closes todo/sub-agents/an-api-endpoint-for-spawning-an-agent-with-a.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The failure this prevents is specific — a sub-agent burns the end of a limit window and the session the
owner is actually sitting in dies mid-turn, because the credits went somewhere nobody was watching. So
it is a condition on spawning rather than a refinement: an endpoint that can start unattended work
without checking is wrong from its first call, and the symptom lands on someone else's conversation.
Wired into POST /command-hq/commanders/new, which — this is the finding — already IS the spawn
mechanism the sub-agents item was asking for. It starts a turn with ws: null, waits only for
session:claude, and returns the transcript id, with command_hq_sessions naming, listing and costing it.
So "commander or something lighter" answers itself: a commander costs nothing extra and a lighter thing
would need its own registry to be visible at all. What is still missing is only the agent-callable
surface.
Refuses rather than queues or downgrades. Queueing means holding work against a window Officer does not
control, and the reset it would wait for is a claim about a shared pool — every claude on the machine
spends these, including terminals and pipelines. A refusal naming the window, the percentage and the
reset is something a caller can act on now.
The floor is 15% and the reasoning is in the file: the interactive failure is not "cannot start a chat",
it is "a turn already in flight is cut off", and a turn costs a fraction of a window.
Fails OPEN, deliberately. The numbers come from an external endpoint with a credential Officer does not
own, so a blip or a signed-out CLI must not stop every spawn on the machine with an error about usage
that has nothing to do with usage. The problem is reported so a caller can say "started, but unchecked".
Seven tests on the pure rule — tightest window decides rather than the average, no limits allowed rather
than blocked, exactly-at-the-ceiling refuses. Verified against the live account, where it correctly
refuses right now at Session 90%.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
pastilhasandClaude Opus 5