feat(fleet): comms-block emitter + FLEET-LAUNCH runbook (#633)

Add `mosaic fleet comms-block <role> [--host]` — an explicit-arg, comms-only
emitter wrapping a new resolveCommsBlock() over readFleetCommsBlock. Unlike the
launch-time reader (which returns '' on any miss so composeContract can no-op
silently), the emitter fails loud: unknown role / missing roster → stderr +
exit 1, so an operator can safely preview any peer's view and a typo is never
a silent no-op.

Add docs/fleet/FLEET-LAUNCH.md: the canonical roster-driven launch path
(worker + orchestrator .env fold via MOSAIC_AGENT_COMMAND, which short-circuits
the line-44 yolo hardcode), 3 launch gotchas (flag conflict, MOSAIC_AGENT_NAME
baking, launchRuntime guards), the #632 preserve-list note, and the North-Star
A→B→webUI launch-config arc.

PATH A of the orchestrator-launch fix; PATH B (roster-native launch-config:
yolo toggle + command/channels emission) tracked as #636.

TDD: 6 new resolveCommsBlock cases; 177 fleet+comms tests green; typecheck,
eslint, prettier clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EsgTQzV5YUGk1JtCLP4B83

docs/TASKS.md

@@ -86,3 +86,7 @@ Active workstream is **W1 — Federation v1**. Workers should:
 ## #631 — re-seed preserves user fleet data (CRITICAL) — fix/631-reseed-preserves-fleet-data
 
 - Status: implemented + tested. PRIMARY: install.sh PRESERVE_PATHS += fleet/\*.yaml + fleet/agents + fleet/run (glob-aware cp-fallback); TS parity. SECONDARY: refreshActiveFleetUnits propagates unit fixes to ~/.config/systemd/user on mosaic update. bash F6 + TS + unit tests green. Detail: scratchpads/631-reseed-preserves-fleet.md.
+
+## #633 — comms-block emitter + FLEET-LAUNCH runbook — feat/633-comms-block-runbook
+
+- Status: implemented + tested (TDD). `mosaic fleet comms-block <role> [--host]` wraps resolveCommsBlock → readFleetCommsBlock; fails loud (stderr + exit 1) on unknown role / missing roster instead of silent empty. docs/fleet/FLEET-LAUNCH.md runbook: worker path + orchestrator .env fold (MOSAIC_AGENT_COMMAND; line-41 [-z] short-circuits line-44 yolo hardcode) + 3 launch gotchas + #632 preserve note + North-Star 4-field arc (harness ✅/model ✅ roster-native today; yolo + command/channels = PATH B #636). 177 fleet+comms tests green (6 new resolveCommsBlock cases). PATH A of the A→B→webUI arc. Detail: scratchpads/633-comms-block-runbook.md.

docs/fleet/FLEET-LAUNCH.md

@@ -0,0 +1,114 @@
+# Fleet Launch Runbook
+
+How every Mosaic fleet agent — workers **and** the orchestrator — is launched, and how to
+configure each one. The guiding principle: **one roster-driven launcher**. There is no bespoke
+per-agent launch script; the roster plus per-agent `.env` files are the single source of launch
+config.
+
+## The launch chain
+
+| Layer            | File                                              | Responsibility                                                                                                                                              |
+| ---------------- | ------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| systemd unit     | `mosaic-agent@<role>.service`                     | One templated unit per role; `ExecStart` runs the session launcher with the instance name `%i`. Defaults `MOSAIC_AGENT_RUNTIME=pi`, `MOSAIC_AGENT_NAME=%i`. |
+| session launcher | `tools/fleet/start-agent-session.sh <role>`       | Builds the launch command, opens the tmux pane, wires the heartbeat.                                                                                        |
+| launch command   | `mosaic yolo <runtime>` (or a per-agent override) | Replaces the pane's foreground process with the runtime, fully seeded.                                                                                      |
+| seeding          | `mosaic`'s `composeContract()`                    | Injects the Constitution/USER/TOOLS/runtime contract, `*.local` overlays, **and** the Fleet-Comms cheat-sheet — all via `--append-system-prompt`.           |
+
+Per-agent overrides live in `fleet/agents/<role>.env`, generated from `roster.yaml` by
+`generateAgentEnv` (`packages/mosaic/src/commands/fleet.ts`) and consumed by the launcher.
+
+## Worker launch path (default)
+
+1. `roster.yaml` carries each agent's `runtime` and optional `model_hint`.
+2. `generateAgentEnv` emits `fleet/agents/<role>.env` with `MOSAIC_AGENT_NAME`,
+   `MOSAIC_AGENT_RUNTIME`, and `MOSAIC_AGENT_MODEL`.
+3. `start-agent-session.sh` has no `MOSAIC_AGENT_COMMAND` set, so it falls through to the default
+   (line ~44):
+   ```sh
+   MOSAIC_AGENT_COMMAND="mosaic yolo $MOSAIC_AGENT_RUNTIME${MOSAIC_AGENT_MODEL:+ --model $MOSAIC_AGENT_MODEL}"
+   ```
+4. The launcher bakes `MOSAIC_AGENT_NAME` into the pane command (line ~118), so `composeContract`
+   can inject the Fleet-Comms cheat-sheet for that role.
+
+That is the whole worker path: roster → `.env` → `mosaic yolo <runtime>` → seeded pane.
+
+## Orchestrator fold (PATH A — ships today)
+
+The orchestrator is **just another roster agent** launched through the canonical path — not a
+snowflake script.
+
+| Piece              | Value                               |
+| ------------------ | ----------------------------------- |
+| host-side launcher | `orchestrator-launch.sh`            |
+| systemd unit       | `mosaic-fleet-orchestrator.service` |
+| tmux session       | `orchestrator` (role-named)         |
+
+Set its launch command via `fleet/agents/orchestrator.env`:
+
+```sh
+MOSAIC_AGENT_COMMAND='mosaic yolo claude --channels plugin:discord@<channel>'
+```
+
+When `MOSAIC_AGENT_COMMAND` is set, `start-agent-session.sh`'s `if [ -z "$MOSAIC_AGENT_COMMAND" ]`
+guard (line ~41) is false, so the line-44 default — **including its hardcoded `yolo`** — is skipped
+entirely. The override fully controls the runtime and flags. Routing through `mosaic yolo claude`
+(rather than a raw `claude` invocation) is what gives the orchestrator the same full
+`composeContract` seeding + Fleet-Comms cheat-sheet as every worker, with `--channels` and any
+other flags passed straight through to the `claude` binary.
+
+## Launch gotchas
+
+1. **Flag conflict.** `mosaic yolo claude` already injects `--dangerously-skip-permissions`. Do
+   **not** also pass `--permission-mode bypassPermissions` — the `claude` binary would receive both.
+   Use `mosaic yolo claude …` alone (yolo covers the unattended posture), **or** non-yolo
+   `mosaic claude --permission-mode bypassPermissions …`. Never mix the two.
+2. **`MOSAIC_AGENT_NAME` must reach the pane.** The launcher bakes it from the instance name, and
+   `composeContract` gates the Fleet-Comms block on it (`launch.ts`, in `composeContract`) — **and**
+   the role must be a member of `roster.yaml`, or the block resolves empty.
+3. **`launchRuntime` guards.** `mosaic yolo claude` runs `checkSoul` / `checkRuntime` /
+   `checkSequentialThinking`. The host needs `SOUL.md` and the sequential-thinking MCP, or the
+   launch aborts (a raw `claude` invocation skipped these checks). Dry-run the composed command in a
+   throwaway tmux session before swapping a live launcher.
+
+## Why per-agent `.env` survives upgrades (#632)
+
+`install.sh` `PRESERVE_PATHS` includes `fleet/*.yaml`, `fleet/agents`, and `fleet/run`, so
+`mosaic update`'s framework re-seed **preserves** your roster and per-agent `.env` overrides
+(glob-aware `cp` fallback; matching TS parity in `file-adapter.ts`). Before #632, an auto re-seed
+could wipe them — which is exactly why PATH A's `.env` override is safe to rely on now.
+
+## Inspecting the comms wiring
+
+- `mosaic fleet comms-block <role>` prints the Fleet-Comms cheat-sheet a given role receives at
+  launch — its `[host:session]` identity, the exact `agent-send.sh` command for each peer, and the
+  FLIP / `--verify` conventions. `--host <h>` previews a cross-host view. An unknown role or missing
+  roster **fails loud** (stderr + non-zero exit), so a typo is never a silent no-op.
+- Versus `mosaic compose-contract <runtime>`: that emits the **whole** system prompt and reads the
+  role from `MOSAIC_AGENT_NAME` (a full-prompt smoke test). `comms-block` is the targeted,
+  explicit-arg, comms-only view — e.g. `mosaic fleet comms-block coder0-0` to preview a peer.
+
+## North Star / future direction
+
+**Vision:** a webUI lets the user edit each agent's launch config — switch **harness**
+(claude / pi / codex / opencode), toggle **yolo**, pick a **model**, set a **command/channels**
+override — with no terminal.
+
+**Continuity — this is not a new launch path.** It is a data-model + UI-binding layer over the
+existing roster-driven launcher. Field-by-field status today:
+
+| Launch-config field      | Roster-native today? | Mechanism / gap                                                                                                                                          |
+| ------------------------ | -------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| **harness** (`runtime`)  | ✅ end-to-end        | `roster.runtime` → `generateAgentEnv` emits `MOSAIC_AGENT_RUNTIME` → launcher line 44. UI just writes the field.                                         |
+| **model** (`model_hint`) | ✅ end-to-end        | `roster.model_hint` → `MOSAIC_AGENT_MODEL` → launcher line 44 `--model`. UI just writes the field.                                                       |
+| **yolo**                 | ❌ new               | Launcher line 44 **hardcodes** `mosaic yolo`. A non-yolo toggle needs a roster `yolo` field → emit `MOSAIC_AGENT_YOLO` → make line 44 conditional.       |
+| **command / channels**   | ❌ new               | `MOSAIC_AGENT_COMMAND` is **consumed** (launcher line ~12) but `generateAgentEnv` does not emit it. Needs a roster `command`/`channels` field → emitted. |
+
+**The arc:**
+
+- **A** — `.env` `MOSAIC_AGENT_COMMAND` hatch: manual, ships now, kept safe across upgrades by #632.
+- **B** — roster-native launch-config: harness + model are already there; add the **yolo** toggle
+  (line-44 conditional) and **command/channels** emission to complete the data model.
+- **webUI** — binds dropdowns/toggles directly to those four roster fields.
+
+PATH A's `.env` override is the **manual form** of exactly what PATH B makes roster-native and the
+webUI edits — one continuous arc, not three separate features. PATH B is tracked as #636.

docs/scratchpads/633-comms-block-runbook.md

@@ -0,0 +1,54 @@
+# #633 — comms-block emitter + FLEET-LAUNCH runbook
+
+Branch: `feat/633-comms-block-runbook` (off `bf2a6745`, post-#632 merge)
+Issue: #633 · Follow-up filed: #636 (PATH B)
+
+## Goal
+
+PATH A of the orchestrator-launch fix: give every launch path the Fleet-Comms onboarding, and
+document the canonical roster-driven launcher so the orchestrator stops being a bespoke snowflake.
+
+## Deliverables
+
+1. **`mosaic fleet comms-block <role> [--host <h>]`** — explicit-arg, comms-block-only emitter.
+   - Backed by new `resolveCommsBlock(mosaicHome, role, fleetHost?)` in `fleet/comms-onboarding.ts`
+     returning `{ ok, output, error }`.
+   - Unlike `readFleetCommsBlock` (returns `''` on any miss so `composeContract` can no-op silently
+     during launch), the emitter **fails loud**: unknown role / missing roster → `ok:false` → CLI
+     prints to stderr + sets `process.exitCode = 1`. A typo is never a silent no-op.
+   - Distinct from `mosaic compose-contract <runtime>` (whole prompt, env-coupled via
+     `MOSAIC_AGENT_NAME`); comms-block is the targeted, explicit-arg, comms-only view.
+2. **`docs/fleet/FLEET-LAUNCH.md`** — worker path + orchestrator `.env` fold + 3 launch gotchas +
+   #632 preserve note + North-Star 4-field arc.
+
+## Key findings (drove the design)
+
+- `mosaic yolo claude` **already** forwards `--channels`/`--permission-mode` to the binary
+  (`launch.ts` claude case `cliArgs.push(...args)`) AND injects the comms block via
+  `composeContract` → `readFleetCommsBlock(home, env.MOSAIC_AGENT_NAME)`. So no `launch.ts` change
+  was needed — PATH A is `.env` + doc only.
+- `start-agent-session.sh` line ~41 `[ -z "$MOSAIC_AGENT_COMMAND" ]` short-circuits the line-44
+  default, so an `.env` `MOSAIC_AGENT_COMMAND` override bypasses the hardcoded `yolo` entirely — the
+  yolo-conditional is therefore a PATH B (default-path) concern, not PATH A.
+- `generateAgentEnv` (`fleet.ts` ~202-207) emits NAME/RUNTIME/MODEL but **not** `MOSAIC_AGENT_COMMAND`
+  — the seam PATH B (#636) closes.
+
+## A → B → webUI arc (North Star)
+
+- A = `.env` `MOSAIC_AGENT_COMMAND` hatch (manual, ships now, #632-safe).
+- B (#636) = roster-native launch-config: harness ✅ + model ✅ already there; add **yolo** (line-44
+  conditional `MOSAIC_AGENT_YOLO`) + **command/channels** (`generateAgentEnv` emission).
+- webUI binds dropdowns/toggles to those four roster fields. One launcher, no new launch path.
+
+## Results
+
+- TDD: spec first (`comms-onboarding.spec.ts`, 6 new `resolveCommsBlock` cases) → red → implement → green.
+- `fleet.spec.ts` subcommand-list assertion extended with `comms-block`.
+- 177 fleet+comms tests green; typecheck clean; eslint clean; prettier clean.
+
+## Risks / notes
+
+- Pre-existing local-only failure `uninstall.spec.ts > removeFramework > handles missing mosaicHome
+gracefully` (EACCES on `/nonexistent` as non-root) — unrelated to #633, passes in CI as root.
+- Did NOT run `mosaic update` / anything auto-reseed: installed CLI still 0.0.40 (roster-wipe live
+  until mos-claude-0 ships 0.0.41). All work is in-repo + vitest, never touches the live mosaic home.

packages/mosaic/src/commands/fleet.spec.ts

@@ -95,6 +95,7 @@ describe('registerFleetCommand', () => {
     expect(agent).toBeDefined();
     expect(agent!.options.map((option) => option.long)).toContain('--list');
     expect(agent!.commands.map((command) => command.name()).sort()).toEqual([
+      'comms-block',
       'reset',
       'roster',
       'send',

packages/mosaic/src/commands/fleet.ts

@@ -7,6 +7,7 @@ import { spawn } from 'node:child_process';
 import * as readline from 'node:readline';
 import type { Command } from 'commander';
 import YAML from 'yaml';
+import { resolveCommsBlock } from '../fleet/comms-onboarding.js';
 
 /**
  * A function that spawns a command with inherited stdio (TTY passthrough).
@@ -1359,6 +1360,23 @@ export function registerFleetAgentCommands(
       }
     });
 
+  agentCommand
+    .command('comms-block <role>')
+    .description(
+      "Print the Fleet Comms cheat-sheet for a roster role (preview a peer's peer-reach view)",
+    )
+    .option('--host <host>', 'Override the fleet host (preview a cross-host peer view)')
+    .action((role: string, opts: { host?: string }) => {
+      const mosaicHome = resolveMosaicHomeFromCommand(agentCommand, deps.mosaicHome);
+      const res = resolveCommsBlock(mosaicHome, role, opts.host);
+      if (!res.ok) {
+        console.error(`[mosaic] comms-block: ${res.error}`);
+        process.exitCode = 1;
+        return;
+      }
+      console.log(res.output);
+    });
+
   agentCommand
     .command('status [agent]')
     .description('Show tmux status for the local fleet or one agent')

packages/mosaic/src/fleet/comms-onboarding.spec.ts

@@ -7,6 +7,7 @@ import {
   buildFleetCommsBlock,
   renderPeerReach,
   readFleetCommsBlock,
+  resolveCommsBlock,
   type CommsPeer,
 } from './comms-onboarding.js';
 
@@ -185,3 +186,53 @@ describe('readFleetCommsBlock — situational (the context a spawned agent gets)
     expect(readFleetCommsBlock(mkdtempSync(join(tmpdir(), 'noroster-')), 'orchestrator')).toBe('');
   });
 });
+
+describe('resolveCommsBlock — `mosaic fleet comms-block <role>` emitter semantics', () => {
+  // The emitter wraps readFleetCommsBlock but must NEVER print an empty string silently:
+  // an unknown role / missing roster has to fail loud (caller maps !ok → stderr + exit 1)
+  // so `mosaic fleet comms-block bogus` is a visible error, not a confusing no-op. The
+  // success path returns the block verbatim for `mosaic fleet comms-block <peer>` previews.
+  let home: string;
+  beforeEach(() => {
+    home = mkdtempSync(join(tmpdir(), 'mosaic-commsblk-'));
+    mkdirSync(join(home, 'fleet'), { recursive: true });
+    writeFileSync(join(home, 'fleet', 'roster.yaml'), ROSTER);
+  });
+  afterEach(() => rmSync(home, { recursive: true, force: true }));
+
+  it('returns ok + the cheat-sheet for a roster member', () => {
+    const res = resolveCommsBlock(home, 'orchestrator', 'w-jarvis');
+    expect(res.ok).toBe(true);
+    expect(res.output).toContain('# Fleet Comms');
+    expect(res.output).toContain('| enhancer |');
+    expect(res.error).toBeUndefined();
+  });
+
+  it('fails loud (not ok + error naming the role) for a non-member — never silently empty', () => {
+    const res = resolveCommsBlock(home, 'stranger', 'w-jarvis');
+    expect(res.ok).toBe(false);
+    expect(res.output).toBe('');
+    expect(res.error).toContain('stranger');
+  });
+
+  it('fails loud when no roster exists at the mosaic home', () => {
+    const noRoster = mkdtempSync(join(tmpdir(), 'mosaic-noroster-'));
+    const res = resolveCommsBlock(noRoster, 'orchestrator', 'w-jarvis');
+    expect(res.ok).toBe(false);
+    expect(res.error).toBeTruthy();
+    rmSync(noRoster, { recursive: true, force: true });
+  });
+
+  it('fails loud for a missing role argument', () => {
+    const res = resolveCommsBlock(home, undefined, 'w-jarvis');
+    expect(res.ok).toBe(false);
+    expect(res.error).toBeTruthy();
+  });
+
+  it('honors a host override so a peer can preview its own cross-host view', () => {
+    // coder0-0 viewing with its own host → its self-identity line uses that host.
+    const res = resolveCommsBlock(home, 'coder0-0', '10.1.10.37');
+    expect(res.ok).toBe(true);
+    expect(res.output).toContain('`[10.1.10.37:coder0-0]`');
+  });
+});

packages/mosaic/src/fleet/comms-onboarding.ts

@@ -179,5 +179,48 @@ export function readFleetCommsBlock(
   });
 }
 
+/** Result of resolving a comms-block emit request — see `mosaic fleet comms-block`. */
+export interface CommsBlockResult {
+  /** True when a cheat-sheet was produced; false maps to stderr + non-zero exit. */
+  ok: boolean;
+  /** The Fleet-Comms cheat-sheet (empty unless ok). */
+  output: string;
+  /** Operator-facing reason when !ok. */
+  error?: string;
+}
+
+/**
+ * Resolve the Fleet-Comms cheat-sheet for an explicit <role>, backing the
+ * `mosaic fleet comms-block <role>` command. Unlike readFleetCommsBlock — which
+ * returns '' on any miss so composeContract can no-op silently during a launch —
+ * this NEVER silently emits empty: an unknown role or missing roster yields
+ * ok:false + an operator-facing reason, so the CLI surfaces it (stderr + exit 1)
+ * rather than printing nothing. That makes it safe to preview any peer's view,
+ * e.g. `mosaic fleet comms-block coder0-0`.
+ */
+export function resolveCommsBlock(
+  mosaicHome: string,
+  role: string | undefined,
+  fleetHost?: string,
+): CommsBlockResult {
+  if (!role) {
+    return { ok: false, output: '', error: 'comms-block requires a <role> argument' };
+  }
+  const block = fleetHost
+    ? readFleetCommsBlock(mosaicHome, role, fleetHost)
+    : readFleetCommsBlock(mosaicHome, role);
+  if (!block) {
+    const rosterPath = join(mosaicHome, 'fleet', 'roster.yaml');
+    return {
+      ok: false,
+      output: '',
+      error: existsSync(rosterPath)
+        ? `role "${role}" is not a member of the fleet roster at ${rosterPath}`
+        : `no fleet roster at ${rosterPath}`,
+    };
+  }
+  return { ok: true, output: block };
+}
+
 /** Default mosaic home (mirrors launch.ts), for callers that don't pass one. */
 export const DEFAULT_MOSAIC_HOME_FOR_COMMS = join(homedir(), '.config', 'mosaic');