## Why
`wait_agent` can block for a long timeout while waiting for sub-agent
mailbox activity. Although same-turn user steer is accepted during that
tool call, the input remains pending until the wait returns, so an
explicit request to change direction can appear unresponsive.
## What changed
- Notify active `wait_agent` calls when user input is steered into the
current turn.
- Check for already-pending steer input when subscribing so input that
races with tool startup is not missed.
- Distinguish mailbox activity, steered input, and timeout outcomes,
returning `Wait interrupted by new input.` for the steer path.
- Update the `wait_agent` tool description to document the early-return
behavior.
## Testing
- `just test -p codex-core input_queue_`
- `just test -p codex-core wait_agent`
The coverage includes steer notification before and after subscription,
plus an end-to-end test that verifies the interrupted wait result and
steered user input are both included exactly once in the follow-up model
request.
jif
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