fix(fleet): consume model_hint + fix socket-default trap (stand-up fixes) (#627)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

packages/mosaic/src/commands/fleet.ts

@@ -117,10 +117,26 @@ export interface FleetPaths {
 
 type FleetServiceAction = 'start' | 'stop' | 'restart' | 'status';
 
-const DEFAULT_SOCKET_NAME = 'mosaic-factory';
+/**
+ * The named tmux socket the canonical fleet uses. Kept as a public constant for
+ * rosters/callers that explicitly want isolation; it is NO LONGER the silent
+ * fallback for a socket-less roster (that now resolves to the default socket).
+ */
+export const DEFAULT_SOCKET_NAME = 'mosaic-factory';
 const DEFAULT_HOLDER_SESSION = '_holder';
 const DEFAULT_WORKING_DIRECTORY = '~/src';
 
+/**
+ * tmux `-L` args for a socket name. An empty/absent socket ⇒ the LITERAL default
+ * tmux socket (no `-L`), so spawn, observe (`fleet ps`/watch), and the onboarding
+ * cheat-sheet all agree. A named socket ⇒ `-L <name>`. `DEFAULT_SOCKET_NAME`
+ * remains a constant for callers that explicitly want mosaic-factory; it is no
+ * longer the silent fallback for a socket-less roster.
+ */
+export function socketArgs(socketName: string): string[] {
+  return socketName ? ['-L', socketName] : [];
+}
+
 /**
  * Default poll interval (ms) between capture-pane checks in `send --verify`.
  * Kept short enough to react quickly while not hammering tmux on busy hosts.
@@ -185,6 +201,10 @@ export function generateAgentEnv(roster: FleetRoster, agent: FleetAgent): string
   return [
     `MOSAIC_AGENT_NAME=${shellEnvValue(agent.name)}`,
     `MOSAIC_AGENT_RUNTIME=${shellEnvValue(agent.runtime)}`,
+    // Per-agent model hint → start-agent-session.sh appends `--model <hint>` to
+    // the `mosaic yolo` launch so workers run on the roster's model (e.g. pi on
+    // openai-codex/gpt-5.5:high). Empty when the agent declares no model_hint.
+    `MOSAIC_AGENT_MODEL=${shellEnvValue(agent.modelHint ?? '')}`,
     `MOSAIC_AGENT_WORKDIR=${shellEnvValue(expandHome(workingDirectory))}`,
     `MOSAIC_TMUX_SOCKET=${shellEnvValue(roster.tmux.socketName)}`,
     '',
@@ -319,13 +339,12 @@ export function buildAgentSendCommand(
   paths: FleetPaths,
   agentName: string,
   message: string,
-  socketName = DEFAULT_SOCKET_NAME,
+  socketName = '',
   sourceLabel = getDefaultOperatorSourceLabel(),
 ): string[] {
   return [
     join(paths.tmuxToolsDir, 'agent-send.sh'),
-    '-L',
-    socketName,
+    ...socketArgs(socketName),
     '-S',
     sourceLabel,
     '-s',
@@ -344,12 +363,11 @@ export function buildAgentResetCommand(
   paths: FleetPaths,
   agentName: string,
   resetCommand: string,
-  socketName = DEFAULT_SOCKET_NAME,
+  socketName = '',
 ): string[] {
   return [
     join(paths.tmuxToolsDir, 'send-message.sh'),
-    '-L',
-    socketName,
+    ...socketArgs(socketName),
     '-t',
     `=${agentName}`,
     '-m',
@@ -357,15 +375,10 @@ export function buildAgentResetCommand(
   ];
 }
 
-export function buildAgentTailCommand(
-  agentName: string,
-  lines: number,
-  socketName = DEFAULT_SOCKET_NAME,
-): string[] {
+export function buildAgentTailCommand(agentName: string, lines: number, socketName = ''): string[] {
   return [
     'tmux',
-    '-L',
-    socketName,
+    ...socketArgs(socketName),
     'capture-pane',
     '-t',
     `=${agentName}:0.0`,
@@ -449,14 +462,10 @@ export function buildSystemdShowCommand(agentName: string): string[] {
  * Returns the tmux list-panes command for an agent pane.
  * Format: `#{pane_pid} #{pane_current_command} #{pane_dead} #{pane_activity}`
  */
-export function buildTmuxListPanesCommand(
-  agentName: string,
-  socketName = DEFAULT_SOCKET_NAME,
-): string[] {
+export function buildTmuxListPanesCommand(agentName: string, socketName = ''): string[] {
   return [
     'tmux',
-    '-L',
-    socketName,
+    ...socketArgs(socketName),
     'list-panes',
     '-t',
     `=${agentName}:0.0`,
@@ -470,8 +479,8 @@ export function buildTmuxListPanesCommand(
  * Format: `tmux -L <socket> list-sessions -F '#{session_name}'`
  * Used to discover ad-hoc sessions that are not in the roster.
  */
-export function buildTmuxListSessionsCommand(socketName = DEFAULT_SOCKET_NAME): string[] {
-  return ['tmux', '-L', socketName, 'list-sessions', '-F', '#{session_name}'];
+export function buildTmuxListSessionsCommand(socketName = ''): string[] {
+  return ['tmux', ...socketArgs(socketName), 'list-sessions', '-F', '#{session_name}'];
 }
 
 /**
@@ -653,12 +662,11 @@ export function getDefaultTenantAndHost(): { tenant_id: string; host: string } {
 export function buildAgentWatchCreateViewerCommand(
   agentName: string,
   viewerSessionName: string,
-  socketName = DEFAULT_SOCKET_NAME,
+  socketName = '',
 ): string[] {
   return [
     'tmux',
-    '-L',
-    socketName,
+    ...socketArgs(socketName),
     'new-session',
     '-d',
     '-t',
@@ -672,11 +680,8 @@ export function buildAgentWatchCreateViewerCommand(
  * Builds the interactive attach command for a viewer session (read-only).
  * Must be run via interactiveRunner (stdio: 'inherit').
  */
-export function buildAgentWatchAttachCommand(
-  viewerSessionName: string,
-  socketName = DEFAULT_SOCKET_NAME,
-): string[] {
-  return ['tmux', '-L', socketName, 'attach', '-r', '-t', viewerSessionName];
+export function buildAgentWatchAttachCommand(viewerSessionName: string, socketName = ''): string[] {
+  return ['tmux', ...socketArgs(socketName), 'attach', '-r', '-t', viewerSessionName];
 }
 
 /**
@@ -685,9 +690,9 @@ export function buildAgentWatchAttachCommand(
  */
 export function buildAgentWatchKillViewerCommand(
   viewerSessionName: string,
-  socketName = DEFAULT_SOCKET_NAME,
+  socketName = '',
 ): string[] {
-  return ['tmux', '-L', socketName, 'kill-session', '-t', viewerSessionName];
+  return ['tmux', ...socketArgs(socketName), 'kill-session', '-t', viewerSessionName];
 }
 
 /**
@@ -705,11 +710,8 @@ export function buildViewerSessionName(agentName: string): string {
  *
  * Kept for backward compatibility only.
  */
-export function buildAgentWatchCommand(
-  agentName: string,
-  socketName = DEFAULT_SOCKET_NAME,
-): string[] {
-  return ['tmux', '-L', socketName, 'attach', '-r', '-t', `=${agentName}`];
+export function buildAgentWatchCommand(agentName: string, socketName = ''): string[] {
+  return ['tmux', ...socketArgs(socketName), 'attach', '-r', '-t', `=${agentName}`];
 }
 
 /**
@@ -719,13 +721,12 @@ export function buildAgentWatchCommand(
  */
 export function buildAgentVerifyAcceptedCommand(
   agentName: string,
-  socketName = DEFAULT_SOCKET_NAME,
+  socketName = '',
   lines = 5,
 ): string[] {
   return [
     'tmux',
-    '-L',
-    socketName,
+    ...socketArgs(socketName),
     'capture-pane',
     '-t',
     `=${agentName}:0.0`,
@@ -989,8 +990,7 @@ export function registerFleetCommand(program: Command, deps: FleetCommandDeps =
       const socketName = roster.tmux.socketName;
       await runChecked(runner, [
         'tmux',
-        '-L',
-        socketName,
+        ...socketArgs(socketName),
         'has-session',
         '-t',
         `=${roster.tmux.holderSession}:0.0`,
@@ -998,8 +998,7 @@ export function registerFleetCommand(program: Command, deps: FleetCommandDeps =
       for (const agent of roster.agents) {
         await runChecked(runner, [
           'tmux',
-          '-L',
-          socketName,
+          ...socketArgs(socketName),
           'has-session',
           '-t',
           `=${agent.name}:0.0`,
@@ -1370,8 +1369,8 @@ export function registerFleetAgentCommands(
         getRosterAgent(roster, agent);
       }
       const command = agent
-        ? ['tmux', '-L', roster.tmux.socketName, 'has-session', '-t', `=${agent}:0.0`]
-        : ['tmux', '-L', roster.tmux.socketName, 'ls'];
+        ? ['tmux', ...socketArgs(roster.tmux.socketName), 'has-session', '-t', `=${agent}:0.0`]
+        : ['tmux', ...socketArgs(roster.tmux.socketName), 'ls'];
       const result = await runner(...splitCommand(command));
       if (opts.json) {
         console.log(
@@ -1689,9 +1688,12 @@ function normalizeRoster(raw: RawFleetRoster): FleetRoster {
     version: 1,
     transport: 'tmux',
     tmux: {
+      // Absent socket_name ⇒ '' (the literal default tmux socket, no -L) — NOT
+      // mosaic-factory. Shipped presets set socket_name explicitly, so they are
+      // unaffected; only socket-less rosters get default-socket behavior.
       socketName: stringValue(
         raw.tmux?.socket_name ?? raw.tmux?.socketName,
-        DEFAULT_SOCKET_NAME,
+        '',
         'Fleet roster tmux socket_name',
       ),
       holderSession: stringValue(
@@ -1857,6 +1859,12 @@ function expandHome(path: string): string {
 }
 
 function shellEnvValue(value: string): string {
+  // Empty ⇒ a bare `VAR=` (unambiguous empty in a systemd EnvironmentFile and
+  // when shell-sourced). Quoting it as '' risks a literal two-char value (e.g.
+  // a tmux socket named "''"), which would defeat the default-socket behavior.
+  if (value === '') {
+    return '';
+  }
   if (/^[A-Za-z0-9_./:=@+-]+$/.test(value)) {
     return value;
   }