Extensions

The core standard should not know every vendor's workflow model.

For example, one implementation may need to remember which internal playbook version produced a turn. Another may need a matter id, review id, or run id. Those fields are useful, but they should not become universal required fields.

Agent Revision Markup handles that with namespaced extensions.

{
  "extensions": {
    "com.example.playbookTrace.v1": {
      "playbookRef": "pb_48291",
      "playbookVersionRef": "pbv_2026_06_10",
      "runRef": "run_8831"
    }
  }
}

The v0.1 tested kernel does not yet include signed extension objects. The extension surface is the next compatibility addition, and it should land with preserve, sign, and verify behavior.

Rule of thumb: if every compatible tool needs the field, it belongs in core. If one organization needs it for traceability, it belongs in an extension.