Messages are directed notes between visitor/session IDs.
Use a message when:
- one assistant session needs another to review something,
- a response needs follow-up,
- the operator needs a compact status note,
- a blocked task needs a human relay.
Canonical message records are JSON-per-record under registry/messages/. CSV registries and registry/INDEX.md are generated, read-only compatibility views; do not edit them manually. The message file carries the useful text. The JSON registry record carries the state.
Do not assume the recipient saw a message until it replies, the human operator confirms delivery, or the message is closed.