feat(fleet): engine picker offers only engines the factory advertises

Add GET /fleet/factories (lists a product's factory docs with capabilities) —
also fixes the fleet map's empty factory cards (listFactories had no route and
silently returned []). The New-Job form now loads the selected factory's
engine:* capabilities and constrains the engine dropdown to those (e.g. hides
codex when the host doesn't have it), keeping the current pick valid; falls back
to all engines when capabilities are unknown.

Generated with [Devin](https://cli.devin.ai/docs)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

dashboards/tracker-web/src/app/dashboard/fleet/jobs/page.tsx

@@ -8,6 +8,7 @@ import { useAuth } from '@/lib/auth-context';
 import {
   listJobs,
   submitJob,
+  availableEnginesForProduct,
   FLEET_ENGINES,
   type FleetJob,
   type FleetEngine,
@@ -99,6 +100,9 @@ export default function FleetJobsPage() {
   const [body, setBody] = useState('');
   const [priority, setPriority] = useState<'critical' | 'high' | 'medium' | 'low'>('high');
   const [engine, setEngine] = useState<FleetEngine>('devin');
+  // Engines the selected factory's product actually advertises ([] ⇒ unknown,
+  // offer all). Keeps users from picking an engine the host can't run.
+  const [engineOptions, setEngineOptions] = useState<FleetEngine[]>([]);
   // Empty by default: no agent-queue factory advertises a `build` capability
   // (caps are os:* / engine:* / node:* / has:*), so a non-empty default here makes
   // the job unroutable. Leave blank ⇒ any capable factory for the product claims it.
@@ -133,6 +137,31 @@ export default function FleetJobsPage() {
   useEffect(() => {
     setHideShipped(localStorage.getItem('fleet_hide_shipped') === '1');
   }, []);
+
+  // When the target factory changes, learn which engines its product advertises
+  // and constrain the picker (so you can't pick an engine the host can't run).
+  useEffect(() => {
+    if (!token || !showForm) return;
+    const factory = FLEET_FACTORIES.find(f => f.id === factoryId) ?? FLEET_FACTORIES[0];
+    let cancelled = false;
+    availableEnginesForProduct(factory.productId)
+      .then(engines => {
+        if (cancelled) return;
+        setEngineOptions(engines);
+        // Keep the selection valid: prefer the current pick, else devin, else first.
+        if (engines.length > 0) {
+          setEngine(prev =>
+            engines.includes(prev) ? prev : engines.includes('devin') ? 'devin' : engines[0]!
+          );
+        }
+      })
+      .catch(() => {
+        if (!cancelled) setEngineOptions([]);
+      });
+    return () => {
+      cancelled = true;
+    };
+  }, [token, showForm, factoryId]);
   const toggleHideShipped = useCallback((next: boolean) => {
     setHideShipped(next);
     localStorage.setItem('fleet_hide_shipped', next ? '1' : '0');
@@ -290,12 +319,15 @@ export default function FleetJobsPage() {
                   onChange={e => setEngine(e.target.value as FleetEngine)}
                   className="rounded border bg-background px-2 py-1 text-sm"
                 >
-                  {FLEET_ENGINES.map(e => (
+                  {(engineOptions.length > 0 ? engineOptions : FLEET_ENGINES).map(e => (
                     <option key={e} value={e}>
                       {e}
                     </option>
                   ))}
                 </select>
+                {engineOptions.length > 0 && (
+                  <p className="mt-1 text-xs text-muted-foreground">advertised by this factory</p>
+                )}
               </div>
               <div>
                 <label htmlFor="job-caps" className="mb-1 block text-sm font-medium">

dashboards/tracker-web/src/lib/fleet-client.ts

@@ -520,14 +520,32 @@ export async function getJobExplain(jobId: string): Promise<JobExplain | null> {
 
 // ── Factories ───────────────────────────────────────────────────────────────
 
-export async function listFactories(): Promise<{ factories: FleetFactory[] }> {
+export async function listFactories(productId?: string): Promise<{ factories: FleetFactory[] }> {
+  const headers = productId ? { 'x-product-id': productId } : undefined;
   try {
-    return await apiFetch('/factories');
+    return await apiFetch('/factories', headers ? { headers } : undefined);
   } catch {
     return { factories: [] };
   }
 }
 
+/** Concrete engines a product's live factories advertise (`engine:*` capabilities),
+ * intersected with the known engine set. Empty ⇒ unknown (caller should not filter). */
+export async function availableEnginesForProduct(productId?: string): Promise<FleetEngine[]> {
+  const { factories } = await listFactories(productId);
+  const seen = new Set<FleetEngine>();
+  for (const f of factories) {
+    if (f.health === 'down') continue;
+    for (const cap of f.capabilities ?? []) {
+      if (cap.startsWith('engine:')) {
+        const e = cap.slice('engine:'.length) as FleetEngine;
+        if ((FLEET_ENGINES as readonly string[]).includes(e)) seen.add(e);
+      }
+    }
+  }
+  return [...seen];
+}
+
 // ── Budgets ─────────────────────────────────────────────────────────────────
 
 /**

services/platform-service/src/modules/fleet/routes.ts

@@ -332,6 +332,14 @@ export async function fleetRoutes(app: FastifyInstance) {
     return { ok: true, factory };
   });
 
+  // ── List factories for the product (powers the fleet map + engine picker) ──
+  app.get('/fleet/factories', async req => {
+    await extractAuth(req);
+    const pid = getRequestProductId(req);
+    const factories = await repo.listFactories(pid);
+    return { factories };
+  });
+
   // ── Runs ──
   app.get('/fleet/jobs/:id/runs', async req => {
     await extractAuth(req);