bug(core): fix issue with overrides to bases. (#15255)

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

@@ -5,7 +5,10 @@
  */
 
 import { describe, it, expect } from 'vitest';
-import type { ModelConfigServiceConfig } from './modelConfigService.js';
+import type {
+  ModelConfigAlias,
+  ModelConfigServiceConfig,
+} from './modelConfigService.js';
 import { ModelConfigService } from './modelConfigService.js';
 
 describe('ModelConfigService', () => {
@@ -470,6 +473,21 @@ describe('ModelConfigService', () => {
         'Alias "non-existent" not found.',
       );
     });
+
+    it('should throw an error if the alias chain is too deep', () => {
+      const aliases: Record<string, ModelConfigAlias> = {};
+      for (let i = 0; i < 101; i++) {
+        aliases[`alias-${i}`] = {
+          extends: i === 100 ? undefined : `alias-${i + 1}`,
+          modelConfig: i === 100 ? { model: 'gemini-pro' } : {},
+        };
+      }
+      const config: ModelConfigServiceConfig = { aliases };
+      const service = new ModelConfigService(config);
+      expect(() => service.getResolvedConfig({ model: 'alias-0' })).toThrow(
+        'Alias inheritance chain exceeded maximum depth of 100.',
+      );
+    });
   });
 
   describe('deep merging', () => {
@@ -889,5 +907,50 @@ describe('ModelConfigService', () => {
       });
       expect(retry.generateContentConfig.temperature).toBe(1.0);
     });
+
+    it('should apply overrides to parents in the alias hierarchy', () => {
+      const config: ModelConfigServiceConfig = {
+        aliases: {
+          'base-alias': {
+            modelConfig: {
+              model: 'gemini-test',
+              generateContentConfig: {
+                temperature: 0.5,
+              },
+            },
+          },
+          'child-alias': {
+            extends: 'base-alias',
+            modelConfig: {
+              generateContentConfig: {
+                topP: 0.9,
+              },
+            },
+          },
+        },
+        overrides: [
+          {
+            match: { model: 'base-alias', isRetry: true },
+            modelConfig: {
+              generateContentConfig: {
+                temperature: 1.0,
+              },
+            },
+          },
+        ],
+      };
+      const service = new ModelConfigService(config);
+
+      // Normal request
+      const normal = service.getResolvedConfig({ model: 'child-alias' });
+      expect(normal.generateContentConfig.temperature).toBe(0.5);
+
+      // Retry request - should match override on parent
+      const retry = service.getResolvedConfig({
+        model: 'child-alias',
+        isRetry: true,
+      });
+      expect(retry.generateContentConfig.temperature).toBe(1.0);
+    });
   });
 });