diff --git a/packages/shared/src/agent/pi-rpc-client.ts b/packages/shared/src/agent/pi-rpc-client.ts
index 7190503..d335ef4 100644
--- a/packages/shared/src/agent/pi-rpc-client.ts
+++ b/packages/shared/src/agent/pi-rpc-client.ts
@@ -576,18 +576,23 @@ export class PiRpcClient {
       return;
     }
 
-    const pending = this.findPending(event);
     const control = this.findControl(event);
     if (control) {
       clearTimeout(control.timeout);
       this.pendingControls.delete(control.id);
-      if (event.type === 'error') {
-        control.reject(createCodeError('PI_RUNTIME_ERROR', String(event.message ?? 'Pi runtime error.')));
+      if (event.type === 'error' || event.success === false) {
+        control.reject(createCodeError(
+          'PI_RUNTIME_ERROR',
+          String(event.error ?? event.message ?? 'Pi runtime error.')
+        ));
       } else {
         control.resolve(event.data);
       }
+      return;
     }
 
+    const pending = this.findPending(event);
+
     if (!pending) return;
 
     pending.trace.push({
@@ -684,6 +689,7 @@ export class PiRpcClient {
   private findPending(event: Record<string, unknown>) {
     const id = typeof event.id === 'string' ? event.id : typeof event.requestId === 'string' ? event.requestId : undefined;
     if (id && this.pendingPrompts.has(id)) return this.pendingPrompts.get(id);
+    if (event.type === 'response') return undefined;
     if (this.pendingPrompts.size === 1) return Array.from(this.pendingPrompts.values())[0];
     return undefined;
   }
diff --git a/packages/shared/src/agent/pi-runtime-agent-backend.test.ts b/packages/shared/src/agent/pi-runtime-agent-backend.test.ts
index 0425ff5..33b0ccf 100644
--- a/packages/shared/src/agent/pi-runtime-agent-backend.test.ts
+++ b/packages/shared/src/agent/pi-runtime-agent-backend.test.ts
@@ -249,11 +249,65 @@ describe('PiRpcClient', () => {
     await stream.abort();
     await consume;
 
-    expect(events).toContain('message_update');
+    expect(events).toEqual(['message_update']);
+    expect(events).not.toContain('response');
+    expect(events).not.toContain('abort');
     expect(result).toMatchObject({ aborted: true });
     expect((result as { answer: string }).answer).toBe('Partial');
   });
 
+  it('ignores stale prompt responses while a prompt is active', async () => {
+    const client = new PiRpcClient({
+      spawnProcess: createSpawn(() =>
+        new FakePiProcess((line, proc) => {
+          if (line.type !== 'prompt') return;
+
+          proc.writeEvent({
+            id: 'stale-prompt-id',
+            type: 'response',
+            command: 'prompt',
+            success: false,
+            error: 'stale prompt response',
+          });
+          proc.writeEvent({
+            id: line.id,
+            type: 'response',
+            command: 'prompt',
+            success: true,
+          });
+          proc.writeEvent({
+            id: line.id,
+            type: 'agent_end',
+            messages: [{ role: 'assistant', content: [{ type: 'text', text: 'completed' }] }],
+          });
+        })
+      ),
+    });
+
+    await expect(client.prompt('hello')).resolves.toMatchObject({ answer: 'completed' });
+  });
+
+  it('falls back to the only active prompt for id-less agent events', async () => {
+    const client = new PiRpcClient({
+      spawnProcess: createSpawn(() =>
+        new FakePiProcess((line, proc) => {
+          if (line.type !== 'prompt') return;
+
+          proc.writeEvent({
+            type: 'message_update',
+            assistantMessageEvent: { type: 'text_delta', delta: 'id-less ' },
+          });
+          proc.writeEvent({
+            type: 'agent_end',
+            messages: [{ role: 'assistant', content: [{ type: 'text', text: 'event' }] }],
+          });
+        })
+      ),
+    });
+
+    await expect(client.prompt('hello')).resolves.toMatchObject({ answer: 'event' });
+  });
+
   it('rejects when Pi refuses a prompt before execution', async () => {
     const client = new PiRpcClient({
       spawnProcess: createSpawn(() =>