Skip and reset loop checking around code blocks (#5144)

packages/core/src/services/loopDetectionService.test.ts

@@ -56,6 +56,15 @@ describe('LoopDetectionService', () => {
     value: content,
   });
 
+  const createRepetitiveContent = (id: number, length: number): string => {
+    const baseString = `This is a unique sentence, id=${id}. `;
+    let content = '';
+    while (content.length < length) {
+      content += baseString;
+    }
+    return content.slice(0, length);
+  };
+
   describe('Tool Call Loop Detection', () => {
     it(`should not detect a loop for fewer than TOOL_CALL_LOOP_THRESHOLD identical calls`, () => {
       const event = createToolCallRequestEvent('testTool', { param: 'value' });
@@ -149,13 +158,11 @@ describe('LoopDetectionService', () => {
 
     it('should detect a loop when a chunk of content repeats consecutively', () => {
       service.reset('');
-      const repeatedContent = 'a'.repeat(CONTENT_CHUNK_SIZE);
+      const repeatedContent = createRepetitiveContent(1, CONTENT_CHUNK_SIZE);
 
       let isLoop = false;
       for (let i = 0; i < CONTENT_LOOP_THRESHOLD; i++) {
-        for (const char of repeatedContent) {
+        isLoop = service.addAndCheck(createContentEvent(repeatedContent));
-          isLoop = service.addAndCheck(createContentEvent(char));
-        }
       }
       expect(isLoop).toBe(true);
       expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
@@ -163,23 +170,119 @@ describe('LoopDetectionService', () => {
 
     it('should not detect a loop if repetitions are very far apart', () => {
       service.reset('');
-      const repeatedContent = 'b'.repeat(CONTENT_CHUNK_SIZE);
+      const repeatedContent = createRepetitiveContent(1, CONTENT_CHUNK_SIZE);
       const fillerContent = generateRandomString(500);
 
       let isLoop = false;
       for (let i = 0; i < CONTENT_LOOP_THRESHOLD; i++) {
-        for (const char of repeatedContent) {
+        isLoop = service.addAndCheck(createContentEvent(repeatedContent));
-          isLoop = service.addAndCheck(createContentEvent(char));
+        isLoop = service.addAndCheck(createContentEvent(fillerContent));
-        }
-        for (const char of fillerContent) {
-          isLoop = service.addAndCheck(createContentEvent(char));
-        }
       }
       expect(isLoop).toBe(false);
       expect(loggers.logLoopDetected).not.toHaveBeenCalled();
     });
   });
 
+  describe('Content Loop Detection with Code Blocks', () => {
+    it('should not detect a loop when repetitive content is inside a code block', () => {
+      service.reset('');
+      const repeatedContent = createRepetitiveContent(1, CONTENT_CHUNK_SIZE);
+
+      service.addAndCheck(createContentEvent('```\n'));
+
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD; i++) {
+        const isLoop = service.addAndCheck(createContentEvent(repeatedContent));
+        expect(isLoop).toBe(false);
+      }
+
+      const isLoop = service.addAndCheck(createContentEvent('\n```'));
+      expect(isLoop).toBe(false);
+      expect(loggers.logLoopDetected).not.toHaveBeenCalled();
+    });
+
+    it('should detect a loop when repetitive content is outside a code block', () => {
+      service.reset('');
+      const repeatedContent = createRepetitiveContent(1, CONTENT_CHUNK_SIZE);
+
+      service.addAndCheck(createContentEvent('```'));
+      service.addAndCheck(createContentEvent('\nsome code\n'));
+      service.addAndCheck(createContentEvent('```'));
+
+      let isLoop = false;
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD; i++) {
+        isLoop = service.addAndCheck(createContentEvent(repeatedContent));
+      }
+      expect(isLoop).toBe(true);
+      expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
+    });
+
+    it('should handle content with multiple code blocks and no loops', () => {
+      service.reset('');
+      service.addAndCheck(createContentEvent('```\ncode1\n```'));
+      service.addAndCheck(createContentEvent('\nsome text\n'));
+      const isLoop = service.addAndCheck(createContentEvent('```\ncode2\n```'));
+
+      expect(isLoop).toBe(false);
+      expect(loggers.logLoopDetected).not.toHaveBeenCalled();
+    });
+
+    it('should handle content with mixed code blocks and looping text', () => {
+      service.reset('');
+      const repeatedContent = createRepetitiveContent(1, CONTENT_CHUNK_SIZE);
+
+      service.addAndCheck(createContentEvent('```'));
+      service.addAndCheck(createContentEvent('\ncode1\n'));
+      service.addAndCheck(createContentEvent('```'));
+
+      let isLoop = false;
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD; i++) {
+        isLoop = service.addAndCheck(createContentEvent(repeatedContent));
+      }
+
+      expect(isLoop).toBe(true);
+      expect(loggers.logLoopDetected).toHaveBeenCalledTimes(1);
+    });
+
+    it('should not detect a loop for a long code block with some repeating tokens', () => {
+      service.reset('');
+      const repeatingTokens =
+        'for (let i = 0; i < 10; i++) { console.log(i); }';
+
+      service.addAndCheck(createContentEvent('```\n'));
+
+      for (let i = 0; i < 20; i++) {
+        const isLoop = service.addAndCheck(createContentEvent(repeatingTokens));
+        expect(isLoop).toBe(false);
+      }
+
+      const isLoop = service.addAndCheck(createContentEvent('\n```'));
+      expect(isLoop).toBe(false);
+      expect(loggers.logLoopDetected).not.toHaveBeenCalled();
+    });
+
+    it('should reset tracking when a code fence is found', () => {
+      service.reset('');
+      const repeatedContent = createRepetitiveContent(1, CONTENT_CHUNK_SIZE);
+
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD - 1; i++) {
+        service.addAndCheck(createContentEvent(repeatedContent));
+      }
+
+      // This should not trigger a loop because of the reset
+      service.addAndCheck(createContentEvent('```'));
+
+      // We are now in a code block, so loop detection should be off.
+      // Let's add the repeated content again, it should not trigger a loop.
+      let isLoop = false;
+      for (let i = 0; i < CONTENT_LOOP_THRESHOLD; i++) {
+        isLoop = service.addAndCheck(createContentEvent(repeatedContent));
+        expect(isLoop).toBe(false);
+      }
+
+      expect(loggers.logLoopDetected).not.toHaveBeenCalled();
+    });
+  });
+
   describe('Edge Cases', () => {
     it('should handle empty content', () => {
       const event = createContentEvent('');

packages/core/src/services/loopDetectionService.ts

@@ -61,6 +61,7 @@ export class LoopDetectionService {
   private contentStats = new Map<string, number[]>();
   private lastContentIndex = 0;
   private loopDetected = false;
+  private inCodeBlock = false;
 
   // LLM loop track tracking
   private turnsInCurrentPrompt = 0;
@@ -156,8 +157,27 @@ export class LoopDetectionService {
    * 2. Truncating history if it exceeds the maximum length
    * 3. Analyzing content chunks for repetitive patterns using hashing
    * 4. Detecting loops when identical chunks appear frequently within a short distance
+   * 5. Disabling loop detection within code blocks to prevent false positives,
+   *    as repetitive code structures are common and not necessarily loops.
    */
   private checkContentLoop(content: string): boolean {
+    // Code blocks can often contain repetitive syntax that is not indicative of a loop.
+    // To avoid false positives, we detect when we are inside a code block and
+    // temporarily disable loop detection.
+    const numFences = (content.match(/```/g) ?? []).length;
+    if (numFences) {
+      // Reset tracking when a code fence is detected to avoid analyzing content
+      // that spans across code block boundaries.
+      this.resetContentTracking();
+    }
+
+    const wasInCodeBlock = this.inCodeBlock;
+    this.inCodeBlock =
+      numFences % 2 === 0 ? this.inCodeBlock : !this.inCodeBlock;
+    if (wasInCodeBlock) {
+      return false;
+    }
+
     this.streamContentHistory += content;
 
     this.truncateAndUpdate();