From 6c9f6444178e64d128c13f913188d3fff6a4a6a6 Mon Sep 17 00:00:00 2001
From: Adam Weidman <adamfweidman@gmail.com>
Date: Fri, 20 Mar 2026 10:58:58 -0400
Subject: [PATCH] refactor(core): treat max session turns as stream end

---
 .../core/src/agent/event-translator.test.ts   | 38 +++++++++++++++----
 packages/core/src/agent/event-translator.ts   | 15 +++++---
 2 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/packages/core/src/agent/event-translator.test.ts b/packages/core/src/agent/event-translator.test.ts
index 596bc23f6b..a7a6a50711 100644
--- a/packages/core/src/agent/event-translator.test.ts
+++ b/packages/core/src/agent/event-translator.test.ts
@@ -181,7 +181,13 @@ describe('translateEvent', () => {
     it('stringifies object resultDisplay correctly', () => {
       state.streamStartEmitted = true;
       state.pendingToolNames.set('call-3', 'diff_tool');
-      const objectDisplay = { type: 'FileDiff', before: 'a', after: 'b' };
+      const objectDisplay = {
+        fileDiff: '@@ -1 +1 @@\n-a\n+b',
+        fileName: 'test.txt',
+        filePath: '/tmp/test.txt',
+        originalContent: 'a',
+        newContent: 'b',
+      };
       const event: ServerGeminiStreamEvent = {
         type: GeminiEventType.ToolCallResponse,
         value: {
@@ -402,19 +408,17 @@ describe('translateEvent', () => {
   });
 
   describe('MaxSessionTurns events', () => {
-    it('emits a non-fatal max-turns error event', () => {
+    it('emits stream_end with max_turns', () => {
       state.streamStartEmitted = true;
       const event: ServerGeminiStreamEvent = {
         type: GeminiEventType.MaxSessionTurns,
       };
       const result = translateEvent(event, state);
       expect(result).toHaveLength(1);
-      const err = result[0] as AgentEvent<'error'>;
-      expect(err.type).toBe('error');
-      expect(err.fatal).toBe(false);
-      expect(err.status).toBe('RESOURCE_EXHAUSTED');
-      expect(err._meta?.['code']).toBe('MAX_TURNS_EXCEEDED');
-      expect(err.message).toBe('Maximum session turns exceeded');
+      const streamEnd = result[0] as AgentEvent<'stream_end'>;
+      expect(streamEnd.type).toBe('stream_end');
+      expect(streamEnd.reason).toBe('max_turns');
+      expect(streamEnd.data).toEqual({ code: 'MAX_TURNS_EXCEEDED' });
     });
   });
 
@@ -628,6 +632,24 @@ describe('mapFinishReason', () => {
   it('maps PROHIBITED_CONTENT to refusal', () => {
     expect(mapFinishReason(FinishReason.PROHIBITED_CONTENT)).toBe('refusal');
   });
+
+  it('maps IMAGE_SAFETY to refusal', () => {
+    expect(mapFinishReason(FinishReason.IMAGE_SAFETY)).toBe('refusal');
+  });
+
+  it('maps IMAGE_PROHIBITED_CONTENT to refusal', () => {
+    expect(mapFinishReason(FinishReason.IMAGE_PROHIBITED_CONTENT)).toBe(
+      'refusal',
+    );
+  });
+
+  it('maps UNEXPECTED_TOOL_CALL to failed', () => {
+    expect(mapFinishReason(FinishReason.UNEXPECTED_TOOL_CALL)).toBe('failed');
+  });
+
+  it('maps NO_IMAGE to failed', () => {
+    expect(mapFinishReason(FinishReason.NO_IMAGE)).toBe('failed');
+  });
 });
 
 describe('mapHttpToGrpcStatus', () => {
diff --git a/packages/core/src/agent/event-translator.ts b/packages/core/src/agent/event-translator.ts
index 7f0381eb38..63307c1685 100644
--- a/packages/core/src/agent/event-translator.ts
+++ b/packages/core/src/agent/event-translator.ts
@@ -157,11 +157,11 @@ export function translateEvent(
     case GeminiEventType.MaxSessionTurns:
       ensureStreamStart(state, out);
       out.push(
-        makeEvent('error', state, {
-          status: 'RESOURCE_EXHAUSTED',
-          message: 'Maximum session turns exceeded',
-          fatal: false,
-          _meta: { code: 'MAX_TURNS_EXCEEDED' },
+        makeEvent('stream_end', state, {
+          reason: 'max_turns',
+          data: {
+            code: 'MAX_TURNS_EXCEEDED',
+          },
         }),
       );
       break;
@@ -338,12 +338,15 @@ export function mapFinishReason(
     case 'BLOCKLIST':
     case 'PROHIBITED_CONTENT':
     case 'SPII':
+    case 'IMAGE_SAFETY':
+    case 'IMAGE_PROHIBITED_CONTENT':
       return 'refusal';
     case 'MALFORMED_FUNCTION_CALL':
     case 'OTHER':
+    case 'UNEXPECTED_TOOL_CALL':
+    case 'NO_IMAGE':
       return 'failed';
     default:
-      ((_x: never) => {})(reason);
       return 'failed';
   }
 }