fix(cli): filter subagent sessions from resume history (#19698)

packages/cli/src/utils/sessionUtils.test.ts

@@ -445,9 +445,76 @@ describe('SessionSelector', () => {
     const sessionSelector = new SessionSelector(config);
     const sessions = await sessionSelector.listSessions();
 
+    // Should list the session with gemini message
     expect(sessions.length).toBe(1);
     expect(sessions[0].id).toBe(sessionIdGeminiOnly);
   });
+
+  it('should not list sessions marked as subagent', async () => {
+    const mainSessionId = randomUUID();
+    const subagentSessionId = randomUUID();
+
+    // Create test session files
+    const chatsDir = path.join(tmpDir, 'chats');
+    await fs.mkdir(chatsDir, { recursive: true });
+
+    // Main session - should be listed
+    const mainSession = {
+      sessionId: mainSessionId,
+      projectHash: 'test-hash',
+      startTime: '2024-01-01T10:00:00.000Z',
+      lastUpdated: '2024-01-01T10:30:00.000Z',
+      messages: [
+        {
+          type: 'user',
+          content: 'Hello world',
+          id: 'msg1',
+          timestamp: '2024-01-01T10:00:00.000Z',
+        },
+      ],
+      kind: 'main',
+    };
+
+    // Subagent session - should NOT be listed
+    const subagentSession = {
+      sessionId: subagentSessionId,
+      projectHash: 'test-hash',
+      startTime: '2024-01-01T11:00:00.000Z',
+      lastUpdated: '2024-01-01T11:30:00.000Z',
+      messages: [
+        {
+          type: 'user',
+          content: 'Internal subagent task',
+          id: 'msg1',
+          timestamp: '2024-01-01T11:00:00.000Z',
+        },
+      ],
+      kind: 'subagent',
+    };
+
+    await fs.writeFile(
+      path.join(
+        chatsDir,
+        `${SESSION_FILE_PREFIX}2024-01-01T10-00-${mainSessionId.slice(0, 8)}.json`,
+      ),
+      JSON.stringify(mainSession, null, 2),
+    );
+
+    await fs.writeFile(
+      path.join(
+        chatsDir,
+        `${SESSION_FILE_PREFIX}2024-01-01T11-00-${subagentSessionId.slice(0, 8)}.json`,
+      ),
+      JSON.stringify(subagentSession, null, 2),
+    );
+
+    const sessionSelector = new SessionSelector(config);
+    const sessions = await sessionSelector.listSessions();
+
+    // Should only list the main session
+    expect(sessions.length).toBe(1);
+    expect(sessions[0].id).toBe(mainSessionId);
+  });
 });
 
 describe('extractFirstUserMessage', () => {

packages/cli/src/utils/sessionUtils.ts

@@ -276,6 +276,12 @@ export const getAllSessionFiles = async (
             return { fileName: file, sessionInfo: null };
           }
 
+          // Skip subagent sessions - these are implementation details of a tool call
+          // and shouldn't be surfaced for resumption in the main agent history.
+          if (content.kind === 'subagent') {
+            return { fileName: file, sessionInfo: null };
+          }
+
           const firstUserMessage = extractFirstUserMessage(content.messages);
           const isCurrentSession = currentSessionId
             ? file.includes(currentSessionId.slice(0, 8))