chore(core): remove legacy fallback flags and migrate loop detection (#15213)

packages/core/src/config/flashFallback.test.ts

@@ -37,27 +37,6 @@ describe('Flash Model Fallback Configuration', () => {
     };
   });
 
-  // These tests do not actually test fallback. isInFallbackMode() only returns true,
-  // when setFallbackMode is marked as true. This is to decouple setting a model
-  // with the fallback mechanism. This will be necessary we introduce more
-  // intelligent model routing.
-  describe('setModel', () => {
-    it('should only mark as switched if contentGeneratorConfig exists', () => {
-      // Create config without initializing contentGeneratorConfig
-      const newConfig = new Config({
-        sessionId: 'test-session-2',
-        targetDir: '/test',
-        debugMode: false,
-        cwd: '/test',
-        model: DEFAULT_GEMINI_MODEL,
-      });
-
-      // Should not crash when contentGeneratorConfig is undefined
-      newConfig.setModel(DEFAULT_GEMINI_FLASH_MODEL);
-      expect(newConfig.isInFallbackMode()).toBe(false);
-    });
-  });
-
   describe('getModel', () => {
     it('should return contentGeneratorConfig model if available', () => {
       // Simulate initialized content generator config
@@ -78,26 +57,4 @@ describe('Flash Model Fallback Configuration', () => {
       expect(newConfig.getModel()).toBe('custom-model');
     });
   });
-
-  describe('isInFallbackMode', () => {
-    it('should start as false for new session', () => {
-      expect(config.isInFallbackMode()).toBe(false);
-    });
-
-    it('should remain false if no model switch occurs', () => {
-      // Perform other operations that don't involve model switching
-      expect(config.isInFallbackMode()).toBe(false);
-    });
-
-    it('should persist switched state throughout session', () => {
-      config.setModel(DEFAULT_GEMINI_FLASH_MODEL);
-      // Setting state for fallback mode as is expected of clients
-      config.setFallbackMode(true);
-      expect(config.isInFallbackMode()).toBe(true);
-
-      // Should remain true even after getting model
-      config.getModel();
-      expect(config.isInFallbackMode()).toBe(true);
-    });
-  });
 });