---
name: ms-communications
description: Use this skill whenever sending a message to, or receiving one from, another Mosaic agent.
disable-model-invocation: false
---

# ms-communications

Agent-to-agent messaging: one channel, one addressing grammar, honest triage.
Messages are transport. The durable record lives in run records, issues, and
SESSIONS.md, never in a pane that scrolls away.

## Channel

- `tools/tmux/agent-send.sh` is the only send path. It prepends the preamble,
  submits reliably (bracketed paste, Enter flush, draft detection), and ships
  itself over ssh for remote targets. Never raw `tmux send-keys`; that is how
  messages die as unsubmitted drafts.
- Non-Fleet seats use the default docket.
- Fleet seats use the named socket: `-L mosaic-fleet` (or `MOSAIC_TMUX_SOCKET`).
  Fleet traffic stays off the user's default tmux server.
- Address durable fleet seats exactly: `=coder0`, not a prefix that might match
  two sessions.
- Tool spec and internals: `tools/tmux/README.md`.

## Preamble (required)

```
[<src_host>:<src_session> -> <dst_host>:<dst_session>] <message>
[<src> -> <dst> class=<CLASS>] <message>     # with triage class
```

`host` is `hostname -s` of the sender's machine; `session` is the tmux session
name. `agent-send.sh` writes the preamble for you. Two rules carry the protocol:

1. Replying? Flip it: `[<dst> -> <src>] ...`. Answer under your own lane.
2. A preamble-less cross-agent message is malformed. If you receive one, ask
   the sender to resend before acting on it.

## Triage classes

| Class | Meaning | Recipient behavior |
|---|---|---|
| (absent) | fail-safe default | treat as `actionable` |
| `actionable` | decision, blocker, or gate | act, then reply |
| `human` | from a human operator | deliver; respond promptly |
| `reaction` | emoji or ack | note it; no reply expected |
| `terminal-log` | log-only noise | file it; never act |
| `digest` | machine-wake, coalescible | batch; wake and continue |

Class honestly. Never downgrade a question you want answered to `terminal-log`.

## Etiquette

1. Write for a context-wiped reader. Preamble plus body must carry the ask, the
   evidence (run id, issue number, path), and any deadline. The recipient has
   no "as I mentioned earlier".
2. One topic per message. Two asks in one paste is how the second gets lost.
3. Reply, even when the reply is "ACK, on it" or "cannot, reason follows".
   Silence is not an ack. A refusal with a reason is recoverable; a guess is not.
4. No secrets. Messages land in scrollback, logs, and possibly comms daemons.
5. Waiting on a condition? Arm `agent-watch` on the condition, not a poll of a
   colleague's pane. Waiting on a seat? Message them (see ms-agent-watch).

## Receiving

1. Read the preamble first. Confirm you are the `dst`. Note the `src`.
2. Triage by class (table above). `actionable` or absent: act now, or reply why not.
3. Reply with the preamble flipped. Cite the run id or issue you acted on.

## Delivery mechanics

- Exit codes: `0` delivered or queued, `1` target not found, `2` still draft,
  `3` usage error, `4` ambiguous socket (the session name exists on more than
  one tmux server; disambiguate with `-L`).
- A refusal is evidence. Diagnose it; do not route around it with raw send-keys.
- rc=2 from an `agent-watch` delivery means the text reached your pane as a
  draft. Go read the pane; `auto-submit-drafts.sh` flushes stable drafts.

## When not to message

- Waiting on yourself: do the next thing.
- Facts that must survive the exchange belong in the run record, the issue, or
  SESSIONS.md. A message that matters gets persisted where the record lives.