feat(backend): Ollama embeddings preflight on session create/resume (503 hard-fail)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/app.ts

@@ -43,7 +43,10 @@ export function buildApp(config: AppConfig, deps?: BuildAppDeps): FastifyInstanc
 
   app.addHook("preHandler", authPreHandler(config.authMode));
   app.get("/health", async () => ({ status: "ok" }));
-  sessionRoutes(app, { mgr, tht: tht as ThtRunner, hub, getSettings });
+  sessionRoutes(app, {
+    mgr, tht: tht as ThtRunner, hub, getSettings,
+    ollamaEnsureTimeoutSec: Math.round(config.ollamaEnsureTimeoutMs / 1000),
+  });
   sqlRoutes(app, { tht: tht as ThtRunner });
   metaRoutes(app, { harnessDir: config.harnessDir, listModels });
   settingsRoutes(app, { cfg: config, listModels });

backend/src/config.ts

@@ -4,6 +4,7 @@ export interface AppConfig {
   defaults: { provider?: string; model?: string; thinking?: string };
   maxPiProcesses: number;
   settingsFile: string;
+  ollamaEnsureTimeoutMs: number;
 }
 export function loadConfig(env: Record<string, string | undefined>): AppConfig {
   return {
@@ -15,5 +16,6 @@ export function loadConfig(env: Record<string, string | undefined>): AppConfig {
     defaults: { provider: env.PI_PROVIDER, model: env.PI_MODEL, thinking: env.PI_THINKING },
     maxPiProcesses: Number(env.MAX_PI_PROCESSES ?? 4),
     settingsFile: env.SETTINGS_FILE ?? "data/settings.json",
+    ollamaEnsureTimeoutMs: Number(env.OLLAMA_ENSURE_TIMEOUT_MS ?? 60000),
   };
 }

backend/src/routes/sessions.ts

@@ -7,11 +7,13 @@ import { getUser } from "../auth/auth.js";
 
 export function sessionRoutes(
   app: FastifyInstance,
-  d: { mgr: PiProcessManager; tht: ThtRunner; hub: SseHub; getSettings: () => Settings },
+  d: { mgr: PiProcessManager; tht: ThtRunner; hub: SseHub; getSettings: () => Settings; ollamaEnsureTimeoutSec: number },
 ) {
   app.post("/sessions", async (req, reply) => {
     const b = req.body as { question: string; name?: string };
     const s = d.getSettings();
+    const ensure = await d.tht.ollamaEnsure(s.workspace ?? "", d.ollamaEnsureTimeoutSec);
+    if (!ensure.ok) return reply.code(503).send({ error: ensure.error ?? "Ollama/embeddings non disponibili" });
     // Settings (global) supply workspace/provider/model/thinking. The new-question
     // form sends only the question text. `workspace` selects the tht `-c <config>`.
     const { id } = await d.tht.sessionNew({
@@ -48,6 +50,8 @@ export function sessionRoutes(
   });
   app.post("/sessions/:id/resume", async (req, reply) => {
     const id = (req.params as any).id;
+    const ensure = await d.tht.ollamaEnsure(d.getSettings().workspace ?? "", d.ollamaEnsureTimeoutSec);
+    if (!ensure.ok) return reply.code(503).send({ error: ensure.error ?? "Ollama/embeddings non disponibili" });
     const manifest = (await d.tht.sessionShow(id)) as { status?: string; archived?: boolean } | null;
     if (manifest?.status === "finalized" || manifest?.archived) {
       return reply.code(409).send({ error: "sessione in sola lettura (finalizzata o archiviata)" });