From b80234aa3ecf75d71dbf1e136f5c1aafe43b3545 Mon Sep 17 00:00:00 2001
From: Sri Pasumarthi <111310667+sripasg@users.noreply.github.com>
Date: Thu, 2 Apr 2026 10:16:36 -0700
Subject: [PATCH] fix(acp): handle all InvalidStreamError types gracefully in
 prompt (#24540)

---
 packages/cli/src/acp/acpClient.test.ts | 26 ++++++++++++++++++++++++++
 packages/cli/src/acp/acpClient.ts      |  5 ++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/packages/cli/src/acp/acpClient.test.ts b/packages/cli/src/acp/acpClient.test.ts
index f077b0ef4b..470ff38351 100644
--- a/packages/cli/src/acp/acpClient.test.ts
+++ b/packages/cli/src/acp/acpClient.test.ts
@@ -875,6 +875,32 @@ describe('Session', () => {
     expect(result).toMatchObject({ stopReason: 'end_turn' });
   });
 
+  it('should handle prompt with no finish reason (InvalidStreamError)', async () => {
+    mockChat.sendMessageStream.mockRejectedValue(
+      new InvalidStreamError('No finish reason', 'NO_FINISH_REASON'),
+    );
+
+    const result = await session.prompt({
+      sessionId: 'session-1',
+      prompt: [{ type: 'text', text: 'Hi' }],
+    });
+
+    expect(mockChat.sendMessageStream).toHaveBeenCalled();
+    expect(result).toMatchObject({ stopReason: 'end_turn' });
+  });
+
+  it('should handle prompt with no finish reason (NO_FINISH_REASON anomaly)', async () => {
+    mockChat.sendMessageStream.mockRejectedValue({ type: 'NO_FINISH_REASON' });
+
+    const result = await session.prompt({
+      sessionId: 'session-1',
+      prompt: [{ type: 'text', text: 'Hi' }],
+    });
+
+    expect(mockChat.sendMessageStream).toHaveBeenCalled();
+    expect(result).toMatchObject({ stopReason: 'end_turn' });
+  });
+
   it('should handle /memory command', async () => {
     const handleCommandSpy = vi
       .spyOn(
diff --git a/packages/cli/src/acp/acpClient.ts b/packages/cli/src/acp/acpClient.ts
index 14761d7162..e0a352e0d1 100644
--- a/packages/cli/src/acp/acpClient.ts
+++ b/packages/cli/src/acp/acpClient.ts
@@ -863,7 +863,10 @@ export class Session {
           (error &&
             typeof error === 'object' &&
             'type' in error &&
-            error.type === 'NO_RESPONSE_TEXT')
+            (error.type === 'NO_RESPONSE_TEXT' ||
+              error.type === 'NO_FINISH_REASON' ||
+              error.type === 'MALFORMED_FUNCTION_CALL' ||
+              error.type === 'UNEXPECTED_TOOL_CALL'))
         ) {
           // The stream ended with an empty response or malformed tool call.
           // Treat this as a graceful end to the model's turn rather than a crash.