feat(core): Plumbing for late resolution of model configs. (#14597)

docs/get-started/configuration.md

@@ -524,6 +524,11 @@ their corresponding top-level category object in your `settings.json` file.
     with (and override) the built-in aliases.
   - **Default:** `{}`
 
+- **`modelConfigs.customOverrides`** (array):
+  - **Description:** Custom model config overrides. These are merged with (and
+    added to) the built-in overrides.
+  - **Default:** `[]`
+
 - **`modelConfigs.overrides`** (array):
   - **Description:** Apply specific configuration overrides based on matches,
     with a primary key of model (or alias). The most specific match will be

packages/cli/src/config/settingsSchema.ts

@@ -742,6 +742,16 @@ const SETTINGS_SCHEMA = {
           'Custom named presets for model configs. These are merged with (and override) the built-in aliases.',
         showInDialog: false,
       },
+      customOverrides: {
+        type: 'array',
+        label: 'Custom Model Config Overrides',
+        category: 'Model',
+        requiresRestart: false,
+        default: [],
+        description:
+          'Custom model config overrides. These are merged with (and added to) the built-in overrides.',
+        showInDialog: false,
+      },
       overrides: {
         type: 'array',
         label: 'Model Config Overrides',

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

@@ -1344,6 +1344,30 @@ describe('Generation Config Merging (HACK)', () => {
     expect(serviceConfig.overrides).toEqual(userOverrides);
   });
 
+  it('should merge default overrides when user provides only aliases', () => {
+    const userAliases = {
+      'my-alias': {
+        modelConfig: { model: 'my-model' },
+      },
+    };
+
+    const params: ConfigParameters = {
+      ...baseParams,
+      modelConfigServiceConfig: {
+        aliases: userAliases,
+      },
+    };
+
+    const config = new Config(params);
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const serviceConfig = (config.modelConfigService as any).config;
+
+    // Assert that the user's aliases are present
+    expect(serviceConfig.aliases).toEqual(userAliases);
+    // Assert that the default overrides are present
+    expect(serviceConfig.overrides).toEqual(DEFAULT_MODEL_CONFIGS.overrides);
+  });
+
   it('should use user-provided aliases if they exist', () => {
     const userAliases = {
       'my-alias': {

packages/core/src/config/config.ts

@@ -629,12 +629,20 @@ export class Config {
     // TODO(12593): Fix the settings loading logic to properly merge defaults and
     // remove this hack.
     let modelConfigServiceConfig = params.modelConfigServiceConfig;
-    if (modelConfigServiceConfig && !modelConfigServiceConfig.aliases) {
+    if (modelConfigServiceConfig) {
+      if (!modelConfigServiceConfig.aliases) {
         modelConfigServiceConfig = {
           ...modelConfigServiceConfig,
           aliases: DEFAULT_MODEL_CONFIGS.aliases,
         };
       }
+      if (!modelConfigServiceConfig.overrides) {
+        modelConfigServiceConfig = {
+          ...modelConfigServiceConfig,
+          overrides: DEFAULT_MODEL_CONFIGS.overrides,
+        };
+      }
+    }
 
     this.modelConfigService = new ModelConfigService(
       modelConfigServiceConfig ?? DEFAULT_MODEL_CONFIGS,

packages/core/src/config/defaultModelConfigs.ts

@@ -209,4 +209,14 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
       },
     },
   },
+  overrides: [
+    {
+      match: { model: 'chat-base', isRetry: true },
+      modelConfig: {
+        generateContentConfig: {
+          temperature: 1,
+        },
+      },
+    },
+  ],
 };

packages/core/src/services/modelConfig.golden.test.ts

@@ -18,6 +18,14 @@ const GOLDEN_FILE_PATH = path.resolve(
   'resolved-aliases.golden.json',
 );
 
+const RETRY_GOLDEN_FILE_PATH = path.resolve(
+  process.cwd(),
+  'src',
+  'services',
+  'test-data',
+  'resolved-aliases-retry.golden.json',
+);
+
 describe('ModelConfigService Golden Test', () => {
   it('should match the golden file for resolved default aliases', async () => {
     const service = new ModelConfigService(DEFAULT_MODEL_CONFIGS);
@@ -60,4 +68,49 @@ describe('ModelConfigService Golden Test', () => {
       'Golden file mismatch. If the new resolved aliases are correct, run the test with `UPDATE_GOLDENS=true` to regenerate the golden file.',
     ).toEqual(goldenData);
   });
+
+  it('should match the golden file for resolved default aliases with isRetry=true', async () => {
+    const service = new ModelConfigService(DEFAULT_MODEL_CONFIGS);
+    const aliases = Object.keys(DEFAULT_MODEL_CONFIGS.aliases ?? {});
+
+    const resolvedAliases: Record<string, unknown> = {};
+    for (const alias of aliases) {
+      resolvedAliases[alias] =
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        (service as any).internalGetResolvedConfig({
+          model: alias,
+          isRetry: true,
+        });
+    }
+
+    if (process.env['UPDATE_GOLDENS']) {
+      await fs.mkdir(path.dirname(RETRY_GOLDEN_FILE_PATH), { recursive: true });
+      await fs.writeFile(
+        RETRY_GOLDEN_FILE_PATH,
+        JSON.stringify(resolvedAliases, null, 2),
+        'utf-8',
+      );
+      // In update mode, we pass the test after writing the file.
+      return;
+    }
+
+    let goldenContent: string;
+    try {
+      goldenContent = await fs.readFile(RETRY_GOLDEN_FILE_PATH, 'utf-8');
+    } catch (e) {
+      if ((e as NodeJS.ErrnoException).code === 'ENOENT') {
+        throw new Error(
+          'Golden file not found. Run with `UPDATE_GOLDENS=true` to create it.',
+        );
+      }
+      throw e;
+    }
+
+    const goldenData = JSON.parse(goldenContent);
+
+    expect(
+      resolvedAliases,
+      'Golden file mismatch. If the new resolved aliases are correct, run the test with `UPDATE_GOLDENS=true` to regenerate the golden file.',
+    ).toEqual(goldenData);
+  });
 });

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

@@ -697,4 +697,122 @@ describe('ModelConfigService', () => {
       });
     });
   });
+
+  describe('custom overrides', () => {
+    it('should apply custom overrides on top of defaults', () => {
+      const config: ModelConfigServiceConfig = {
+        aliases: {
+          'test-alias': {
+            modelConfig: {
+              model: 'gemini-test',
+              generateContentConfig: { temperature: 0.5 },
+            },
+          },
+        },
+        overrides: [
+          {
+            match: { model: 'test-alias' },
+            modelConfig: { generateContentConfig: { temperature: 0.6 } },
+          },
+        ],
+        customOverrides: [
+          {
+            match: { model: 'test-alias' },
+            modelConfig: { generateContentConfig: { temperature: 0.7 } },
+          },
+        ],
+      };
+      const service = new ModelConfigService(config);
+      const resolved = service.getResolvedConfig({ model: 'test-alias' });
+
+      // Custom overrides should be appended to overrides, so they win
+      expect(resolved.generateContentConfig.temperature).toBe(0.7);
+    });
+  });
+
+  describe('retry behavior', () => {
+    it('should apply retry-specific overrides when isRetry is true', () => {
+      const config: ModelConfigServiceConfig = {
+        aliases: {
+          'test-model': {
+            modelConfig: {
+              model: 'gemini-test',
+              generateContentConfig: {
+                temperature: 0.5,
+              },
+            },
+          },
+        },
+        overrides: [
+          {
+            match: { model: 'test-model', isRetry: true },
+            modelConfig: {
+              generateContentConfig: {
+                temperature: 1.0,
+              },
+            },
+          },
+        ],
+      };
+      const service = new ModelConfigService(config);
+
+      // Normal request
+      const normal = service.getResolvedConfig({ model: 'test-model' });
+      expect(normal.generateContentConfig.temperature).toBe(0.5);
+
+      // Retry request
+      const retry = service.getResolvedConfig({
+        model: 'test-model',
+        isRetry: true,
+      });
+      expect(retry.generateContentConfig.temperature).toBe(1.0);
+    });
+
+    it('should prioritize retry overrides over generic overrides', () => {
+      const config: ModelConfigServiceConfig = {
+        aliases: {
+          'test-model': {
+            modelConfig: {
+              model: 'gemini-test',
+              generateContentConfig: {
+                temperature: 0.5,
+              },
+            },
+          },
+        },
+        overrides: [
+          // Generic override for this model
+          {
+            match: { model: 'test-model' },
+            modelConfig: {
+              generateContentConfig: {
+                temperature: 0.7,
+              },
+            },
+          },
+          // Retry-specific override
+          {
+            match: { model: 'test-model', isRetry: true },
+            modelConfig: {
+              generateContentConfig: {
+                temperature: 1.0,
+              },
+            },
+          },
+        ],
+      };
+      const service = new ModelConfigService(config);
+
+      // Normal request - hits generic override
+      const normal = service.getResolvedConfig({ model: 'test-model' });
+      expect(normal.generateContentConfig.temperature).toBe(0.7);
+
+      // Retry request - hits retry override (more specific)
+      const retry = service.getResolvedConfig({
+        model: 'test-model',
+        isRetry: true,
+      });
+      expect(retry.generateContentConfig.temperature).toBe(1.0);
+    });
+  });
 });

packages/core/src/services/modelConfigService.ts

@@ -21,6 +21,11 @@ export interface ModelConfigKey {
   // model calls made by this specific subagent, and no others, while still
   // ensuring model configs are fully orthogonal to the agents who use them.
   overrideScope?: string;
+
+  // Indicates whether this configuration request is happening during a retry attempt.
+  // This allows overrides to specify different settings (e.g., higher temperature)
+  // specifically for retry scenarios.
+  isRetry?: boolean;
 }
 
 export interface ModelConfig {
@@ -32,6 +37,7 @@ export interface ModelConfigOverride {
   match: {
     model?: string; // Can be a model name or an alias
     overrideScope?: string;
+    isRetry?: boolean;
   };
   modelConfig: ModelConfig;
 }
@@ -45,6 +51,7 @@ export interface ModelConfigServiceConfig {
   aliases?: Record<string, ModelConfigAlias>;
   customAliases?: Record<string, ModelConfigAlias>;
   overrides?: ModelConfigOverride[];
+  customOverrides?: ModelConfigOverride[];
 }
 
 export type ResolvedModelConfig = _ResolvedModelConfig & {
@@ -105,12 +112,18 @@ export class ModelConfigService {
     generateContentConfig: GenerateContentConfig;
   } {
     const config = this.config || {};
-    const { aliases = {}, customAliases = {}, overrides = [] } = config;
+    const {
+      aliases = {},
+      customAliases = {},
+      overrides = [],
+      customOverrides = [],
+    } = config;
     const allAliases = {
       ...aliases,
       ...customAliases,
       ...this.runtimeAliases,
     };
+    const allOverrides = [...overrides, ...customOverrides];
     let baseModel: string | undefined = context.model;
     let resolvedConfig: GenerateContentConfig = {};
 
@@ -135,7 +148,7 @@ export class ModelConfigService {
     };
 
     // Step 2: Override Application
-    const matches = overrides
+    const matches = allOverrides
       .map((override, index) => {
         const matchEntries = Object.entries(override.match);
         if (matchEntries.length === 0) {

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

@@ -0,0 +1,222 @@
+{
+  "base": {
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1
+    }
+  },
+  "chat-base": {
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true
+      },
+      "topK": 64
+    }
+  },
+  "chat-base-2.5": {
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true,
+        "thinkingBudget": 8192
+      },
+      "topK": 64
+    }
+  },
+  "chat-base-3": {
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true,
+        "thinkingLevel": "HIGH"
+      },
+      "topK": 64
+    }
+  },
+  "gemini-3-pro-preview": {
+    "model": "gemini-3-pro-preview",
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true,
+        "thinkingLevel": "HIGH"
+      },
+      "topK": 64
+    }
+  },
+  "gemini-2.5-pro": {
+    "model": "gemini-2.5-pro",
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true,
+        "thinkingBudget": 8192
+      },
+      "topK": 64
+    }
+  },
+  "gemini-2.5-flash": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true,
+        "thinkingBudget": 8192
+      },
+      "topK": 64
+    }
+  },
+  "gemini-2.5-flash-lite": {
+    "model": "gemini-2.5-flash-lite",
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true,
+        "thinkingBudget": 8192
+      },
+      "topK": 64
+    }
+  },
+  "gemini-2.5-flash-base": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1
+    }
+  },
+  "classifier": {
+    "model": "gemini-2.5-flash-lite",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1,
+      "maxOutputTokens": 1024,
+      "thinkingConfig": {
+        "thinkingBudget": 512
+      }
+    }
+  },
+  "prompt-completion": {
+    "model": "gemini-2.5-flash-lite",
+    "generateContentConfig": {
+      "temperature": 0.3,
+      "topP": 1,
+      "maxOutputTokens": 16000,
+      "thinkingConfig": {
+        "thinkingBudget": 0
+      }
+    }
+  },
+  "edit-corrector": {
+    "model": "gemini-2.5-flash-lite",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1,
+      "thinkingConfig": {
+        "thinkingBudget": 0
+      }
+    }
+  },
+  "summarizer-default": {
+    "model": "gemini-2.5-flash-lite",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1,
+      "maxOutputTokens": 2000
+    }
+  },
+  "summarizer-shell": {
+    "model": "gemini-2.5-flash-lite",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1,
+      "maxOutputTokens": 2000
+    }
+  },
+  "web-search": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1,
+      "tools": [
+        {
+          "googleSearch": {}
+        }
+      ]
+    }
+  },
+  "web-fetch": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1,
+      "tools": [
+        {
+          "urlContext": {}
+        }
+      ]
+    }
+  },
+  "web-fetch-fallback": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1
+    }
+  },
+  "loop-detection": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1
+    }
+  },
+  "loop-detection-double-check": {
+    "model": "gemini-2.5-pro",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1
+    }
+  },
+  "llm-edit-fixer": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1
+    }
+  },
+  "next-speaker-checker": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {
+      "temperature": 0,
+      "topP": 1
+    }
+  },
+  "chat-compression-3-pro": {
+    "model": "gemini-3-pro-preview",
+    "generateContentConfig": {}
+  },
+  "chat-compression-2.5-pro": {
+    "model": "gemini-2.5-pro",
+    "generateContentConfig": {}
+  },
+  "chat-compression-2.5-flash": {
+    "model": "gemini-2.5-flash",
+    "generateContentConfig": {}
+  },
+  "chat-compression-2.5-flash-lite": {
+    "model": "gemini-2.5-flash-lite",
+    "generateContentConfig": {}
+  },
+  "chat-compression-default": {
+    "model": "gemini-2.5-pro",
+    "generateContentConfig": {}
+  }
+}