diff --git a/backend/src/pi/pi-process-manager.ts b/backend/src/pi/pi-process-manager.ts
index cb0daf15..c9701d58 100644
--- a/backend/src/pi/pi-process-manager.ts
+++ b/backend/src/pi/pi-process-manager.ts
@@ -47,7 +47,7 @@ export class PiProcessManager {
 
   async spawnFor(
     sessionId: string,
-    o: { provider?: string; model?: string; thinking?: string; author?: string },
+    o: { provider?: string; model?: string; thinking?: string; author?: string; mode?: "new" | "resume" },
   ): Promise<SessionRuntime> {
     // Idempotent per session id: tear down any existing runtime for this id
     // first (before the cap check) so a resume/respawn neither leaks the old
@@ -80,7 +80,10 @@ export class PiProcessManager {
       await rpc.request({ type: "set_thinking_level", level: thinking } as object & { type: string });
     }
 
-    rpc.send({ type: "prompt", message: `/nuova-domanda "kickoff"` });
+    const message = o.mode === "resume"
+      ? `/riprendi-sessione ${sessionId}`
+      : `/nuova-domanda "kickoff"`;
+    rpc.send({ type: "prompt", message });
     return rt;
   }
 
@@ -90,6 +93,7 @@ export class PiProcessManager {
       provider: manifest?.provider,
       model: manifest?.model,
       thinking: manifest?.thinking,
+      mode: "resume",
     });
   }
 
diff --git a/backend/test/pi-process-manager.test.ts b/backend/test/pi-process-manager.test.ts
index fb53bbfb..b983d660 100644
--- a/backend/test/pi-process-manager.test.ts
+++ b/backend/test/pi-process-manager.test.ts
@@ -2,6 +2,7 @@ import { test, expect } from "vitest";
 import { spawn } from "node:child_process";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
+import { EventEmitter } from "node:events";
 import { PiProcessManager } from "../src/pi/pi-process-manager.js";
 import { loadConfig } from "../src/config.js";
 
@@ -68,3 +69,32 @@ test("oltre maxPiProcesses solleva errore", async () => {
   await expect(mgr.spawnFor("b", {})).rejects.toThrow(/max/i);
   mgr.teardown("a");
 });
+
+function recordingChild() {
+  const ch: any = new EventEmitter();
+  ch.stdout = new EventEmitter();
+  ch.stderr = new EventEmitter();
+  ch._writes = [] as string[];
+  ch.stdin = { write: (d: any) => { ch._writes.push(String(d)); return true; } };
+  ch.kill = () => {};
+  return ch;
+}
+
+test("spawnFor resume mode sends /riprendi-sessione <id>", async () => {
+  const cfg = loadConfig({}); // no provider/model/thinking -> no rpc.request handshakes
+  const child = recordingChild();
+  const mgr = new PiProcessManager(cfg, { spawnFn: () => child as any });
+  await mgr.spawnFor("sid-9", { mode: "resume" });
+  expect(child._writes.join("")).toContain("/riprendi-sessione sid-9");
+  expect(child._writes.join("")).not.toContain("/nuova-domanda");
+  mgr.teardown("sid-9");
+});
+
+test("spawnFor default (new) mode sends /nuova-domanda", async () => {
+  const cfg = loadConfig({});
+  const child = recordingChild();
+  const mgr = new PiProcessManager(cfg, { spawnFn: () => child as any });
+  await mgr.spawnFor("sid-10", {});
+  expect(child._writes.join("")).toContain("/nuova-domanda");
+  mgr.teardown("sid-10");
+});