feat: surface parent message ids in streams

examples/fork-session.ts

@@ -21,7 +21,9 @@ async function streamText(
   prompt: string
 ): Promise<string> {
   let text = '';
-  for await (const msg of session.stream(prompt)) {
+  for await (const msg of session.stream(prompt, {
+    includePartialMessages: true,
+  })) {
     if (msg.type === DroidMessageType.AssistantTextDelta) {
       text += msg.text;
     }

examples/interrupt-session.ts

@@ -11,9 +11,9 @@ const session = await createSession({ cwd: process.cwd() });
 let deltaCount = 0;
 
 try {
-  for await (const msg of session.stream(
-    'Write a long history of computing.'
-  )) {
+  for await (const msg of session.stream('Write a long history of computing.', {
+    includePartialMessages: true,
+  })) {
     if (msg.type !== DroidMessageType.AssistantTextDelta) {
       continue;
     }

examples/multi-turn-session.ts

@@ -12,7 +12,9 @@ async function streamText(
   prompt: string
 ): Promise<string> {
   let text = '';
-  for await (const msg of session.stream(prompt)) {
+  for await (const msg of session.stream(prompt, {
+    includePartialMessages: true,
+  })) {
     if (msg.type === DroidMessageType.AssistantTextDelta) {
       text += msg.text;
     }

examples/sdk-mcp-tool.ts

@@ -30,7 +30,8 @@ const session = await createSession({
 
 try {
   for await (const msg of session.stream(
-    'Use the favorite_number tool for Ada and tell me the answer.'
+    'Use the favorite_number tool for Ada and tell me the answer.',
+    { includePartialMessages: true }
   )) {
     if (msg.type === DroidMessageType.AssistantTextDelta) {
       process.stdout.write(msg.text);

src/stream.ts

@@ -110,12 +110,14 @@ export interface DroidToolCallMessage extends DroidStreamBase {
 export interface DroidAssistantMessage extends DroidStreamBase {
   readonly type: 'assistant';
   readonly message: FactoryDroidMessage;
+  readonly parentMessageId?: string;
   readonly text: string;
 }
 
 export interface DroidUserMessage extends DroidStreamBase {
   readonly type: 'user';
   readonly message: FactoryDroidMessage;
+  readonly parentMessageId?: string;
 }
 
 export interface ToolResult extends DroidStreamBase {
@@ -458,13 +460,15 @@ export function convertNotificationToStreamMessage(
           type: DroidMessageType.Assistant,
           sessionId,
           message: msg,
+          parentMessageId: notification.parentId ?? msg.parentId,
           text: extractTextFromMessage(msg),
         });
       } else if (msg.role === FactoryDroidMessageRole.User) {
         messages.push({
           type: DroidMessageType.User,
           sessionId,
           message: msg,
+          parentMessageId: notification.parentId ?? msg.parentId,
         });
       } else {
         messages.push({

tests/stream.test.ts

@@ -932,6 +932,58 @@ describe('convertNotificationToStreamMessage', () => {
       expect(messages[0].type).toBe('assistant');
     });
 
+    it('sets parentMessageId on user messages', () => {
+      const notification = makeNotification(
+        SessionNotificationType.CREATE_MESSAGE,
+        {
+          message: {
+            id: 'user-id-1',
+            role: 'user',
+            parentId: 'message-parent-id',
+            createdAt: 1000,
+            updatedAt: 1000,
+            content: [{ type: 'text', text: 'hello' }],
+          },
+          parentId: 'notification-parent-id',
+          requestId: 'req-1',
+        }
+      );
+
+      const result = convertNotificationToStreamMessage(notification);
+      expect(Array.isArray(result)).toBe(true);
+      const messages = result as DroidMessage[];
+      expect(messages).toHaveLength(1);
+      expect(messages[0]).toMatchObject({
+        type: 'user',
+        parentMessageId: 'notification-parent-id',
+      });
+    });
+
+    it('sets parentMessageId on assistant messages', () => {
+      const notification = makeNotification(
+        SessionNotificationType.CREATE_MESSAGE,
+        {
+          message: {
+            id: 'assistant-id-1',
+            role: 'assistant',
+            parentId: 'user-id-1',
+            createdAt: 1000,
+            updatedAt: 1000,
+            content: [{ type: 'text', text: 'hello' }],
+          },
+        }
+      );
+
+      const result = convertNotificationToStreamMessage(notification);
+      expect(Array.isArray(result)).toBe(true);
+      const messages = result as DroidMessage[];
+      expect(messages).toHaveLength(1);
+      expect(messages[0]).toMatchObject({
+        type: 'assistant',
+        parentMessageId: 'user-id-1',
+      });
+    });
+
     it('handles empty content array', () => {
       const notification = makeNotification(
         SessionNotificationType.CREATE_MESSAGE,