bug(core): Add default chat compression config. (#13766)

Author: joshualitt

docs/get-started/configuration.md

@@ -510,6 +510,11 @@ their corresponding top-level category object in your `settings.json` file.
         "modelConfig": {
           "model": "gemini-2.5-flash-lite"
         }
+      },
+      "chat-compression-default": {
+        "modelConfig": {
+          "model": "gemini-2.5-pro"
+        }
       }
     }
     ```

packages/core/src/config/defaultModelConfigs.ts

@@ -203,5 +203,10 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
         model: 'gemini-2.5-flash-lite',
       },
     },
+    'chat-compression-default': {
+      modelConfig: {
+        model: 'gemini-2.5-pro',
+      },
+    },
   },
 };

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

@@ -16,7 +16,6 @@ import { tokenLimit } from '../core/tokenLimits.js';
 import type { GeminiChat } from '../core/geminiChat.js';
 import type { Config } from '../config/config.js';
 import { getInitialChatHistory } from '../utils/environmentContext.js';
-import { DEFAULT_GEMINI_MODEL } from '../config/models.js';
 
 vi.mock('../core/tokenLimits.js');
 vi.mock('../telemetry/loggers.js');
@@ -105,7 +104,7 @@ describe('findCompressSplitPoint', () => {
 describe('modelStringToModelConfigAlias', () => {
   it('should return the default model for unexpected aliases', () => {
     expect(modelStringToModelConfigAlias('gemini-flash-flash')).toBe(
-      DEFAULT_GEMINI_MODEL,
+      'chat-compression-default',
     );
   });
 

packages/core/src/services/chatCompressionService.ts

@@ -92,7 +92,7 @@ export function modelStringToModelConfigAlias(model: string): string {
     case DEFAULT_GEMINI_FLASH_LITE_MODEL:
       return 'chat-compression-2.5-flash-lite';
     default:
-      return DEFAULT_GEMINI_MODEL;
+      return 'chat-compression-default';
   }
 }
 

packages/core/src/services/test-data/resolved-aliases.golden.json

@@ -214,5 +214,9 @@
   "chat-compression-2.5-flash-lite": {
     "model": "gemini-2.5-flash-lite",
     "generateContentConfig": {}
+  },
+  "chat-compression-default": {
+    "model": "gemini-2.5-pro",
+    "generateContentConfig": {}
   }
 }