| name | heartbeat-extension-authoring |
| description | Create or modify hidden per-workdir heartbeat extensions for this harness. Use when asked to add pre-heartbeat prompt injection, post-heartbeat accounting/export/audit, or customize heartbeat lifecycle behavior for this deployed agent. |
heartbeat-extension-authoring
Heartbeat extensions are runtime files, not agent-facing skills. Put them under .harness/heartbeat.
Layout
.harness/heartbeat/
pre/*.json
post/*.json
scripts/*
Manifest
Pre manifests inject stdout into the next heartbeat prompt:
{
"name": "custom-context",
"command": ["uv", "run", "python", ".harness/heartbeat/scripts/custom_context.py"],
"timeout_ms": 5000,
"inject_as": "prompt_section"
}
Post manifests receive the heartbeat result through HEARTBEAT_PAYLOAD_FILE and do not inject prompt text:
{
"name": "usage-export",
"command": ["uv", "run", "python", ".harness/heartbeat/scripts/usage_export.py"],
"timeout_ms": 5000
}
Script Contract
- Read JSON from
HEARTBEAT_PAYLOAD_FILE.
- Use
AGENT_DIR, HEARTBEAT_PHASE, and HEARTBEAT_EXTENSION_NAME if needed.
- For pre scripts, print only the prompt section to stdout.
- For post scripts, write only extension-owned files and keep stdout short.
- Do not modify
Runtime/metrics.json, Runtime/events.jsonl, or pending message markers.
