# Inter-Agent tmux Comms — Standard & Tooling

Reliable, self-identifying messaging between Mosaic agents running in tmux panes
(Claude Code / Codex / OpenCode REPLs), across hosts.

## The addressing standard (required)

Every cross-agent tmux message MUST begin with an addressing preamble:

```
[<src_host>:<src_session> -> <dst_host>:<dst_session>] <message>
```

- `host` = `hostname -s` of the machine the agent runs on (e.g. `web1`, `sb-it-mgr-0-lt`).
- `session` = the tmux session name (e.g. `mos-claude`, `rev0-4`, `installer-1`).
- **Replies FLIP the preamble**: the recipient answers with `[<dst> -> <src>] ...`.

Why: a fresh or context-wiped agent always knows who sent a message and to whom.
No ambiguity about origin or lane after a tmux wipe / session restart.

Example exchange:

```
[web1:mos-claude -> sb-it-mgr-0-lt:installer-1] status on #29?
[sb-it-mgr-0-lt:installer-1 -> web1:mos-claude] Q2 done, opening PR #34.
```

## The helper: `agent-send.sh`

Prepends the preamble automatically (auto-detecting your own `host:session`) and
delivers reliably to local OR remote panes.

```bash
# Local target (same host, default tmux server)
agent-send.sh -s <dst_session> -m "message"

# Local target on a Mosaic fleet socket
agent-send.sh -L mosaic-fleet -s '=coder0' -m "message"

# Remote target (over ssh)
agent-send.sh -H user@host -s <dst_session> -m "message"

# From a file / stdin
agent-send.sh -H user@host -s <dst_session> -f msg.txt
echo "msg" | agent-send.sh -s <dst_session>
```

Key flags: `-L` named tmux socket · `-s` dst session (required) · `-H` ssh target for remote · `-n` dst
hostname for the preamble (else auto-resolved) · `-m`/`-f`/stdin body · `-S`
override source label · `-v` verbose · `-r N` Enter-flush attempts.

For durable fleet use, prefer exact tmux targets such as `=coder0`. The helper
normalizes exact session targets to pane-qualified targets internally so pane
commands do not fall back to tmux's prefix matching behavior.

## Named socket isolation

Durable Mosaic fleets should use a dedicated tmux socket, for example:

```bash
tmux -L mosaic-fleet ls
agent-send.sh -L mosaic-fleet -s '=coder0' -m "status?"
send-message.sh -L mosaic-fleet -t '=coder0' -m "raw pane message"
```

This keeps fleet operations away from the user's default tmux server. It is the
safe rollout path on hosts that already have manual tmux sessions.

## Why a helper exists (the submission gotcha)

Pasting into an interactive REPL via raw `tmux send-keys` is unreliable: a
trailing `Enter` is frequently swallowed and the message sits as an **unsubmitted
draft** ("Press up to edit queued messages"). Over an `ssh -> nested tmux` hop the
plain `Enter` keyname often does not register at all — `C-m` is needed.

`send-message.sh` solves this for a **local** pane: bracketed-paste the body
(so multi-line content doesn't submit early), pause, then send `Enter` as its own
keystroke and flush with a second, verifying against a draft heuristic.

`agent-send.sh` solves the **remote** case by _shipping `send-message.sh` over ssh_
(`ssh host bash -s -- ... < send-message.sh`) and running it local to the target
pane — so the reliable send-keys always happens on the pane's own host. The remote
needs only `bash` + `tmux` + `base64`; **no mosaic install required there**. The
message crosses the wire as base64 (`-b`) to avoid all shell-quoting hazards.

## Files

- `agent-send.sh` — inter-agent wrapper (preamble + local/remote dispatch).
- `send-message.sh` — low-level reliable single-pane submitter (`-b` base64 input).
- `auto-submit-drafts.sh` — watchdog that flushes stable unsubmitted prompt
  drafts on a coordinator pane (default target `mos-claude`); run it as a
  long-lived process alongside the coordinator session.
- `agent-send.test.sh` — regression + grammar lock for `agent-send.sh`.
- `test-send-message-socket.sh` — smoke test for named-socket isolation.

## Distribution

These live in the installed framework copy at
`~/.config/mosaic/tools/tmux/`. `install.sh` rsyncs the framework **source tree**
to each host, so to propagate permanently, land both files in the framework
source repo and re-run the installer on each host. Until then, `agent-send.sh`
already works against any reachable host because it ships `send-message.sh` over
ssh per-send — no pre-install on the target host is needed to _send to_ it.
