feat: harden runtime readiness and session workflow

backend/test/pi-process-manager.test.ts

@@ -36,27 +36,30 @@ test("l'exit del child rimuove il runtime dalla mappa (exit handler)", async ()
   expect(mgr.get("exit-test")).toBeUndefined();
 });
 
-test("spawnFor sullo STESSO id uccide il vecchio child e sostituisce il runtime (count resta 1)", async () => {
+test("spawnFor sullo STESSO id rifiuta il duplicato senza interrompere il runtime attivo", async () => {
   const cfg = loadConfig({ THT_HARNESS_DIR: "../harness" });
   const mgr = new PiProcessManager(cfg, { spawnFn: () => spawn("node", [FAKE, SCRIPT]) as any });
   const first = await mgr.spawnFor("dup-id", {});
   expect(mgr.count()).toBe(1);
-  const firstExited = new Promise<void>((res) => first.child.on("exit", () => res()));
-  const second = await mgr.spawnFor("dup-id", {});
-  await firstExited; // the old child was killed by the idempotent respawn
+  await expect(mgr.spawnFor("dup-id", {})).rejects.toThrow(
+    "session runtime already active: dup-id",
+  );
   expect(mgr.count()).toBe(1);
-  expect(mgr.get("dup-id")).toBe(second);
-  expect(second).not.toBe(first);
+  expect(mgr.get("dup-id")).toBe(first);
   mgr.teardown("dup-id");
 });
 
 test("l'exit del VECCHIO child non elimina il nuovo runtime (exit identity-checked)", async () => {
   const cfg = loadConfig({ THT_HARNESS_DIR: "../harness" });
-  const mgr = new PiProcessManager(cfg, { spawnFn: () => spawn("node", [FAKE, SCRIPT]) as any });
-  const first = await mgr.spawnFor("respawn-id", {});
-  const second = await mgr.spawnFor("respawn-id", {});
+  const firstChild = recordingChild();
+  const secondChild = recordingChild();
+  const children = [firstChild, secondChild];
+  const mgr = new PiProcessManager(cfg, { spawnFn: () => children.shift() as any });
+  const first = mgr.createFor("respawn-id", {});
+  mgr.teardown("respawn-id");
+  const second = mgr.createFor("respawn-id", {});
   // The old child's exit handler fires after the respawn; it must NOT evict `second`.
-  await new Promise((res) => setImmediate(res));
+  firstChild.emit("exit", 0);
   expect(mgr.get("respawn-id")).toBe(second);
   expect(mgr.count()).toBe(1);
   void first;
@@ -91,6 +94,7 @@ test("un exit INATTESO del child notifica il client (info error + agent_end)", a
   child.emit("exit", 137);
   expect(seen).toEqual([
     { type: "info", level: "error", text: expect.stringContaining("137") },
+    { type: "system_event", event: "session_failed" },
     { type: "system_event", event: "agent_end" },
   ]);
   expect(mgr.count()).toBe(0);
@@ -138,6 +142,19 @@ test("spawnFor new mode forwards the real question instead of kickoff", async ()
   mgr.teardown("sid-question");
 });
 
+test("createFor does not prompt until start is called", async () => {
+  const cfg = loadConfig({});
+  const child = recordingChild();
+  const mgr = new PiProcessManager(cfg, { spawnFn: () => child as any });
+  const rt = mgr.createFor("sid-deferred", { question: "q" });
+  expect(child._writes).toEqual([]);
+  await mgr.configure(rt, {});
+  expect(child._writes).toEqual([]);
+  mgr.start("sid-deferred", rt, { question: "q" });
+  expect(JSON.parse(child._writes.at(-1)!).message).toBe('/nuova-domanda "q"');
+  mgr.teardown("sid-deferred");
+});
+
 test("production spawn uses explicit Pi path and passes portable data root without rewriting PATH", async () => {
   vi.stubEnv("PATH", "/usr/local/bin:/usr/bin");
   vi.stubEnv("PI_PROVIDER_API_KEY", "provider-secret");