Feature Request: Async exec callback — inject result back to session when process exits #18237
Description
Problem
When an agent launches a long-running process (e.g., Claude Code via exec), there is no way to receive the result without either:
- Blocking the agent turn — The agent sits idle waiting for the process (wastes resources, and sub-agent sessions get killed by system lifetime limits before the process finishes)
- Polling — The agent repeatedly checks process status via
process poll/log(wastes tokens, unreliable) - External workarounds — Fire-and-forget with hook scripts, signal files, fswatch, etc. (fragile, complex)
This is a fundamental gap for any workflow that needs to run an external tool for 10-60 minutes (coding agents, build pipelines, test suites, etc.).
Proposed Solution
Add an async exec callback mode:
exec command="claude -p '...' --dangerously-skip-permissions" timeout=3600 callback=true
Behavior:
callback=true→ exec launches the process, agent turn ends immediately (likebackground=true)- When the process exits, the result (stdout, exit code) is automatically injected back into the same session as a system event or tool result
- The agent wakes up and processes the result in a new turn
This is similar to how webhook callbacks work — the agent does not need to stay alive or poll; the system handles the lifecycle.
Why This Matters
We have been building a programming task workflow (Claude Code + Spec Kit + GitHub PRs) and tried every available pattern:
| Approach | Result |
|---|---|
| Sub-agent + blocking exec | Sub-agent killed by session lifetime limits (even with generous runTimeoutSeconds) |
| Sub-agent + yieldMs=3600000 | Sub-agent still killed after ~2 min |
| Sub-agent + polling | Burns 30-100K tokens on useless poll loops |
| Sub-agent + fswatch blocking | Sub-agent token budget exhausted (100K+), orphans CC process |
| Fire-and-forget + hook wake | Works but requires external hook scripts, signal files, task-meta routing — fragile |
With async exec callback, all of these reduce to a single exec call. No sub-agents needed, no polling, no external hooks, no orphaned processes.
Desired Behavior
# Agent launches long-running process
exec command="some-long-task" timeout=3600 callback=true
# → Agent turn ends immediately
# → Agent is free for other conversations
# ... 20 minutes later, process exits ...
# → System injects result into session:
# { "type": "execCallback", "sessionId": "xxx", "exitCode": 0, "stdout": "...", "stderr": "..." }
# → Agent wakes up and processes the result
Additional Context
- This would make OpenClaw a first-class orchestrator for coding agents (Claude Code, Codex CLI, etc.)
- The hook mechanism (
/hooks/wake,/hooks/agent) already provides similar functionality but requires external scripts and manual routing - A native callback would be simpler, more reliable, and work out of the box