From f0c3c81e94f04720daf0661b28369e8699a1266a Mon Sep 17 00:00:00 2001
From: Sandy Tao <sandytao520@icloud.com>
Date: Mon, 3 Nov 2025 18:06:22 -0800
Subject: [PATCH] fix(core): Improve loop detection for longer repeating
 patterns (#12505)

---
 .../src/services/loopDetectionService.test.ts | 76 +++++++++++++++++++
 .../core/src/services/loopDetectionService.ts |  6 +-
 2 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/packages/core/src/services/loopDetectionService.test.ts b/packages/core/src/services/loopDetectionService.test.ts
index 41cb10a1fb..ce8c1bbb8d 100644
--- a/packages/core/src/services/loopDetectionService.test.ts
+++ b/packages/core/src/services/loopDetectionService.test.ts
@@ -207,6 +207,82 @@ describe('LoopDetectionService', () => {
       expect(isLoop).toBe(false);
       expect(loggers.logLoopDetected).not.toHaveBeenCalled();
     });
+
+    it('should detect a loop with longer repeating patterns (e.g. ~150 chars)', () => {
+      service.reset('');
+      const longPattern = createRepetitiveContent(1, 150);
+      expect(longPattern.length).toBe(150);
+
+      let isLoop = false;
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD + 2; i++) {
+        isLoop = service.addAndCheck(createContentEvent(longPattern));
+        if (isLoop) break;
+      }
+      expect(isLoop).toBe(true);
+      expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
+    });
+
+    it('should detect the specific user-provided loop example', () => {
+      service.reset('');
+      const userPattern = `I will not output any text.
+  I will just end the turn.
+  I am done.
+  I will not do anything else.
+  I will wait for the user's next command.
+`;
+
+      let isLoop = false;
+      // Loop enough times to trigger the threshold
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD + 5; i++) {
+        isLoop = service.addAndCheck(createContentEvent(userPattern));
+        if (isLoop) break;
+      }
+      expect(isLoop).toBe(true);
+      expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
+    });
+
+    it('should detect the second specific user-provided loop example', () => {
+      service.reset('');
+      const userPattern =
+        'I have added all the requested logs and verified the test file. I will now mark the task as complete.\n  ';
+
+      let isLoop = false;
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD + 5; i++) {
+        isLoop = service.addAndCheck(createContentEvent(userPattern));
+        if (isLoop) break;
+      }
+      expect(isLoop).toBe(true);
+      expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
+    });
+
+    it('should detect a loop of alternating short phrases', () => {
+      service.reset('');
+      const alternatingPattern = 'Thinking... Done. ';
+
+      let isLoop = false;
+      // Needs more iterations because the pattern is short relative to chunk size,
+      // so it takes a few slides of the window to find the exact alignment.
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD * 3; i++) {
+        isLoop = service.addAndCheck(createContentEvent(alternatingPattern));
+        if (isLoop) break;
+      }
+      expect(isLoop).toBe(true);
+      expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
+    });
+
+    it('should detect a loop of repeated complex thought processes', () => {
+      service.reset('');
+      const thoughtPattern =
+        'I need to check the file. The file does not exist. I will create the file. ';
+
+      let isLoop = false;
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD + 5; i++) {
+        isLoop = service.addAndCheck(createContentEvent(thoughtPattern));
+        if (isLoop) break;
+      }
+      expect(isLoop).toBe(true);
+      expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
+    });
   });
 
   describe('Content Loop Detection with Code Blocks', () => {
diff --git a/packages/core/src/services/loopDetectionService.ts b/packages/core/src/services/loopDetectionService.ts
index a850816648..3448b6c0c6 100644
--- a/packages/core/src/services/loopDetectionService.ts
+++ b/packages/core/src/services/loopDetectionService.ts
@@ -28,7 +28,7 @@ import { debugLogger } from '../utils/debugLogger.js';
 const TOOL_CALL_LOOP_THRESHOLD = 5;
 const CONTENT_LOOP_THRESHOLD = 10;
 const CONTENT_CHUNK_SIZE = 50;
-const MAX_HISTORY_LENGTH = 1000;
+const MAX_HISTORY_LENGTH = 5000;
 
 /**
  * The number of recent conversation turns to include in the history when asking the LLM to check for a loop.
@@ -328,7 +328,7 @@ export class LoopDetectionService {
    * 2. Verify actual content matches to prevent hash collisions
    * 3. Track all positions where this chunk appears
    * 4. A loop is detected when the same chunk appears CONTENT_LOOP_THRESHOLD times
-   *    within a small average distance (≤ 1.5 * chunk size)
+   *    within a small average distance (≤ 5 * chunk size)
    */
   private isLoopDetectedForChunk(chunk: string, hash: string): boolean {
     const existingIndices = this.contentStats.get(hash);
@@ -353,7 +353,7 @@ export class LoopDetectionService {
     const totalDistance =
       recentIndices[recentIndices.length - 1] - recentIndices[0];
     const averageDistance = totalDistance / (CONTENT_LOOP_THRESHOLD - 1);
-    const maxAllowedDistance = CONTENT_CHUNK_SIZE * 1.5;
+    const maxAllowedDistance = CONTENT_CHUNK_SIZE * 5;
 
     return averageDistance <= maxAllowedDistance;
   }