fix: make join approval atomic

backend/test/routes-sessions.test.ts

@@ -106,6 +106,33 @@ test("POST /sessions/:id/resume configura Pi con il thinking persistito", async
   expect(configured.thinking).toBe("medium");
 });
 
+test("POST /sessions/:id/resume usa il thinking globale se manca nel manifest", async () => {
+  let configured: any;
+  const bridge = { onClientEvent: () => {}, emitClientEvent: () => {} };
+  const runtime = { bridge } as any;
+  const mgr = {
+    get: () => undefined,
+    createFor: () => runtime,
+    configure: async (_rt: any, options: any) => { configured = options; },
+    start: () => {},
+    teardown: () => {},
+  } as any;
+  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
+    mgr,
+    thtRunner: {
+      ollamaEnsure: async () => ({ ok: true }),
+      sessionShow: async () => ({ status: "open", archived: false }),
+      reopenSession: async () => {},
+    } as any,
+    getSettings: () => ({ workspace: "psd", thinking: "low" }) as any,
+  });
+
+  await app.inject({ method: "POST", url: "/sessions/s-thinking/resume" });
+  await new Promise((resolve) => setImmediate(resolve));
+
+  expect(configured.thinking).toBe("low");
+});
+
 test("POST /sessions/:id/response inoltra al bridge (no error)", async () => {
   const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
     thtRunner: {