feat(core): Wire up chat code path for model configs. (#12850)

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

@@ -231,4 +231,42 @@ describe('ModelConfigService Integration', () => {
       topP: 0.95, // from base
     });
   });
+
+  it('should correctly merge static aliases, runtime aliases, and overrides', () => {
+    // Re-instantiate service for this isolated test to not pollute other tests
+    const service = new ModelConfigService(complexConfig);
+
+    // Register a runtime alias, simulating what AgentExecutor does.
+    // This alias extends a static base and provides its own settings.
+    service.registerRuntimeModelConfig('agent-runtime:my-agent', {
+      extends: 'creative-writer', // extends a multi-level alias
+      modelConfig: {
+        generateContentConfig: {
+          temperature: 0.1, // Overrides parent
+          maxOutputTokens: 8192, // Adds a new property
+        },
+      },
+    });
+
+    // Resolve the configuration for the runtime alias, with a matching agent scope
+    const resolved = service.getResolvedConfig({
+      model: 'agent-runtime:my-agent',
+      overrideScope: 'core',
+    });
+
+    // Assert the final merged configuration.
+    expect(resolved.model).toBe('gemini-1.5-pro-latest'); // from 'default-text-model'
+    expect(resolved.generateContentConfig).toEqual({
+      // from 'core' agent override, wins over runtime alias's 0.1 and creative-writer's 0.9
+      temperature: 0.5,
+      // from 'base' alias
+      topP: 0.95,
+      // from 'creative-writer' alias
+      topK: 50,
+      // from runtime alias
+      maxOutputTokens: 8192,
+      // from 'core' agent override
+      stopSequences: ['AGENT_STOP'],
+    });
+  });
 });

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

@@ -550,4 +550,30 @@ describe('ModelConfigService', () => {
       ]);
     });
   });
+
+  describe('runtime aliases', () => {
+    it('should resolve a simple runtime-registered alias', () => {
+      const config: ModelConfigServiceConfig = {
+        aliases: {},
+        overrides: [],
+      };
+      const service = new ModelConfigService(config);
+
+      service.registerRuntimeModelConfig('runtime-alias', {
+        modelConfig: {
+          model: 'gemini-runtime-model',
+          generateContentConfig: {
+            temperature: 0.123,
+          },
+        },
+      });
+
+      const resolved = service.getResolvedConfig({ model: 'runtime-alias' });
+
+      expect(resolved.model).toBe('gemini-runtime-model');
+      expect(resolved.generateContentConfig).toEqual({
+        temperature: 0.123,
+      });
+    });
+  });
 });

packages/core/src/services/modelConfigService.ts

@@ -56,9 +56,15 @@ export interface _ResolvedModelConfig {
 }
 
 export class ModelConfigService {
+  private readonly runtimeAliases: Record<string, ModelConfigAlias> = {};
+
   // TODO(12597): Process config to build a typed alias hierarchy.
   constructor(private readonly config: ModelConfigServiceConfig) {}
 
+  registerRuntimeModelConfig(aliasName: string, alias: ModelConfigAlias): void {
+    this.runtimeAliases[aliasName] = alias;
+  }
+
   private resolveAlias(
     aliasName: string,
     aliases: Record<string, ModelConfigAlias>,
@@ -99,12 +105,13 @@ export class ModelConfigService {
   } {
     const config = this.config || {};
     const { aliases = {}, overrides = [] } = config;
+    const allAliases = { ...aliases, ...this.runtimeAliases };
     let baseModel: string | undefined = context.model;
     let resolvedConfig: GenerateContentConfig = {};
 
     // Step 1: Alias Resolution
-    if (aliases[context.model]) {
-      const resolvedAlias = this.resolveAlias(context.model, aliases);
+    if (allAliases[context.model]) {
+      const resolvedAlias = this.resolveAlias(context.model, allAliases);
       baseModel = resolvedAlias.modelConfig.model; // This can now be undefined
       resolvedConfig = this.deepMerge(
         resolvedConfig,

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

@@ -11,7 +11,19 @@
       "topP": 0.95,
       "thinkingConfig": {
         "includeThoughts": true,
-        "thinkingBudget": -1
+        "thinkingBudget": 8192
+      },
+      "topK": 64
+    }
+  },
+  "gemini-3-pro-preview": {
+    "model": "gemini-3-pro-preview",
+    "generateContentConfig": {
+      "temperature": 1,
+      "topP": 0.95,
+      "thinkingConfig": {
+        "includeThoughts": true,
+        "thinkingBudget": 8192
       },
       "topK": 64
     }
@@ -23,7 +35,7 @@
       "topP": 0.95,
       "thinkingConfig": {
         "includeThoughts": true,
-        "thinkingBudget": -1
+        "thinkingBudget": 8192
       },
       "topK": 64
     }
@@ -35,7 +47,7 @@
       "topP": 0.95,
       "thinkingConfig": {
         "includeThoughts": true,
-        "thinkingBudget": -1
+        "thinkingBudget": 8192
       },
       "topK": 64
     }
@@ -47,7 +59,7 @@
       "topP": 0.95,
       "thinkingConfig": {
         "includeThoughts": true,
-        "thinkingBudget": -1
+        "thinkingBudget": 8192
       },
       "topK": 64
     }