subagent-external-wait-orchestrator-takeover

Subagent external-wait → orchestrator-takeover

Problem

You dispatch a subagent with a brief that includes both substantive work AND a final verification step gated on an external event:

"1. Implement … 2. Open PR … 3. Merge … 4. Verify auto-deploy: poll GHA workflow + gcloud run revisions list until new revision is active."

Step 4 is wait work — the subagent has nothing to compute, only to wait and check. The harness keeps the agent task open during this wait, and each heartbeat / external signal wakes the agent for a tiny no-op cycle:

status: completed · tool_uses: 0 · duration_ms: 2000 · result: "Still polling."
status: completed · tool_uses: 0 · duration_ms: 2200 · result: "In progress."
status: completed · tool_uses: 0 · duration_ms: 1800 · result: "Continuing to wait."
... × 10-20 ...

Each cycle costs:

• Subagent: ~100-300 tokens of additional context per wake (small but accumulates)
• Orchestrator: ~one full turn to acknowledge the notification (large — the orchestrator's context is bigger and every reply costs)

The orchestrator's response cost dwarfs the subagent's polling cost. Over a 13-minute Cloud Build wait, this can be ~10-20 orchestrator turns of "still polling, will report when done" — a non-trivial budget tax for zero work.

Context / Trigger Conditions

ALL of the following:

1. You dispatched a subagent (Task tool with run_in_background: true)
2. The subagent's brief includes a "wait + verify" step at the end
3. You're seeing repeated <task-notification> events from that agent with:
   • status: completed
   • tool_uses: 0
   • Short duration_ms (1-30s)
   • result saying some variant of "still polling / in progress / waiting"

The earlier in the wait you notice this, the more orchestrator budget you save by taking over.

Solution

The instruction that causes this most often is a PROHIBITION the agent reads as a command

The brief in the section above at least asks for the polling. The commoner and more expensive case is a line you wrote to stop an agent doing something, which it reads as an instruction to stand and watch: