# Fleet onboarding-injection — comms cheat-sheet + peer roster (#620)

- **Issue:** #620 · **Branch:** `feat/fleet-comms-onboarding` (off main). Root cause of Mos's failed first send.

## What

Inject a `# Fleet Comms` block into each spawned fleet agent's system prompt (via composeContract — the
runtime-agnostic path every `mosaic yolo <runtime>` agent hits), so it boots knowing how to reach peers.

- `src/fleet/comms-onboarding.ts` (standalone, no fleet.ts coupling):
  - `parseRosterAgents` (name/class/host/ssh, lenient), `renderPeerReach` (same-host `-s` vs cross-host
    `-H <ssh> -s`), `buildFleetCommsBlock` (self [host:session] identity + agent-send path + peer table +
    FLIP-to-reply + `agent send --verify`=ACCEPTED), `readFleetCommsBlock` (reads roster.yaml; '' if not a member).
  - `composeContract` appends it only when MOSAIC_AGENT_NAME is set + the agent is in the roster.
- `roster.schema.json`: optional per-agent `host` + `ssh` (cross-host addresses; manual = pre-federation
  stopgap, federation/W1 auto-discovers later).

## Acceptance criteria (Mos) — all covered

1. own [host:session] + agent-send path + peer roster ✓
2. cross-host correctness: local→`-s` (no -H); remote→`-H <ssh> -s` ✓ (concrete coder0-0@dragon-lin)
3. FLIP-the-preamble reply rule ✓
4. `agent send --verify` = ACCEPTED ✓
5. no `-L` (default socket); matches live tooling ✓

## Verification

- 10 onboarding unit tests (parse, render local/remote/fallback/equal-host, build, situational read) +
  2 composeContract situational tests (injects for fleet agent w/ correct cross-host addr; no-op when
  MOSAIC_AGENT_NAME unset). tsc/eslint/prettier/sanitize clean.
- Post-merge validation: Mos spawns a real w-jarvis agent → first-try reach to coder0-0@dragon-lin + a local peer.
