feat: launch Gemini 3 Flash in Gemini CLI ⚡️⚡️⚡️ (#15196)

Co-authored-by: gemini-cli-robot <gemini-cli-robot@google.com>
Co-authored-by: joshualitt <joshualitt@google.com>
Co-authored-by: Sehoon Shon <sshon@google.com>
Co-authored-by: Adam Weidman <65992621+adamfweidman@users.noreply.github.com>
Co-authored-by: Adib234 <30782825+Adib234@users.noreply.github.com>
Co-authored-by: Jenna Inouye <jinouye@google.com>

packages/core/src/agents/codebase-investigator.test.ts

@@ -12,7 +12,7 @@ import {
   LS_TOOL_NAME,
   READ_FILE_TOOL_NAME,
 } from '../tools/tool-names.js';
-import { GEMINI_MODEL_ALIAS_PRO } from '../config/models.js';
+import { DEFAULT_GEMINI_MODEL } from '../config/models.js';
 
 describe('CodebaseInvestigatorAgent', () => {
   it('should have the correct agent definition', () => {
@@ -26,7 +26,7 @@ describe('CodebaseInvestigatorAgent', () => {
     ).toBe(true);
     expect(CodebaseInvestigatorAgent.outputConfig?.outputName).toBe('report');
     expect(CodebaseInvestigatorAgent.modelConfig?.model).toBe(
-      GEMINI_MODEL_ALIAS_PRO,
+      DEFAULT_GEMINI_MODEL,
     );
     expect(CodebaseInvestigatorAgent.toolConfig?.tools).toEqual([
       LS_TOOL_NAME,

packages/core/src/agents/codebase-investigator.ts

@@ -11,7 +11,7 @@ import {
   LS_TOOL_NAME,
   READ_FILE_TOOL_NAME,
 } from '../tools/tool-names.js';
-import { GEMINI_MODEL_ALIAS_PRO } from '../config/models.js';
+import { DEFAULT_GEMINI_MODEL } from '../config/models.js';
 import { z } from 'zod';
 
 // Define a type that matches the outputConfig schema for type safety.
@@ -70,7 +70,7 @@ export const CodebaseInvestigatorAgent: LocalAgentDefinition<
   processOutput: (output) => JSON.stringify(output, null, 2),
 
   modelConfig: {
-    model: GEMINI_MODEL_ALIAS_PRO,
+    model: DEFAULT_GEMINI_MODEL,
     temp: 0.1,
     top_p: 0.95,
     thinkingBudget: -1,

packages/core/src/agents/registry.test.ts

@@ -10,6 +10,13 @@ import { makeFakeConfig } from '../test-utils/config.js';
 import type { AgentDefinition, LocalAgentDefinition } from './types.js';
 import type { Config } from '../config/config.js';
 import { debugLogger } from '../utils/debugLogger.js';
+import {
+  DEFAULT_GEMINI_FLASH_LITE_MODEL,
+  GEMINI_MODEL_ALIAS_AUTO,
+  PREVIEW_GEMINI_FLASH_MODEL,
+  PREVIEW_GEMINI_MODEL,
+  PREVIEW_GEMINI_MODEL_AUTO,
+} from '../config/models.js';
 
 // A test-only subclass to expose the protected `registerAgent` method.
 class TestableAgentRegistry extends AgentRegistry {
@@ -74,12 +81,12 @@ describe('AgentRegistry', () => {
       );
     });
 
-    it('should use preview model for codebase investigator if main model is preview', async () => {
+    it('should use preview flash model for codebase investigator if main model is preview pro', async () => {
       const previewConfig = makeFakeConfig({
-        model: 'gemini-3-pro-preview',
+        model: PREVIEW_GEMINI_MODEL,
         codebaseInvestigatorSettings: {
           enabled: true,
-          model: 'pro',
+          model: GEMINI_MODEL_ALIAS_AUTO,
         },
       });
       const previewRegistry = new TestableAgentRegistry(previewConfig);
@@ -88,10 +95,52 @@ describe('AgentRegistry', () => {
 
       const investigatorDef = previewRegistry.getDefinition(
         'codebase_investigator',
-      );
+      ) as LocalAgentDefinition;
       expect(investigatorDef).toBeDefined();
-      expect((investigatorDef as LocalAgentDefinition).modelConfig.model).toBe(
-        'gemini-3-pro-preview',
+      expect(investigatorDef?.modelConfig.model).toBe(
+        PREVIEW_GEMINI_FLASH_MODEL,
+      );
+    });
+
+    it('should use preview flash model for codebase investigator if main model is preview auto', async () => {
+      const previewConfig = makeFakeConfig({
+        model: PREVIEW_GEMINI_MODEL_AUTO,
+        codebaseInvestigatorSettings: {
+          enabled: true,
+          model: GEMINI_MODEL_ALIAS_AUTO,
+        },
+      });
+      const previewRegistry = new TestableAgentRegistry(previewConfig);
+
+      await previewRegistry.initialize();
+
+      const investigatorDef = previewRegistry.getDefinition(
+        'codebase_investigator',
+      ) as LocalAgentDefinition;
+      expect(investigatorDef).toBeDefined();
+      expect(investigatorDef?.modelConfig.model).toBe(
+        PREVIEW_GEMINI_FLASH_MODEL,
+      );
+    });
+
+    it('should use the model from the investigator settings', async () => {
+      const previewConfig = makeFakeConfig({
+        model: PREVIEW_GEMINI_MODEL,
+        codebaseInvestigatorSettings: {
+          enabled: true,
+          model: DEFAULT_GEMINI_FLASH_LITE_MODEL,
+        },
+      });
+      const previewRegistry = new TestableAgentRegistry(previewConfig);
+
+      await previewRegistry.initialize();
+
+      const investigatorDef = previewRegistry.getDefinition(
+        'codebase_investigator',
+      ) as LocalAgentDefinition;
+      expect(investigatorDef).toBeDefined();
+      expect(investigatorDef?.modelConfig.model).toBe(
+        DEFAULT_GEMINI_FLASH_LITE_MODEL,
       );
     });
   });

packages/core/src/agents/registry.ts

@@ -10,11 +10,13 @@ import { CodebaseInvestigatorAgent } from './codebase-investigator.js';
 import { type z } from 'zod';
 import { debugLogger } from '../utils/debugLogger.js';
 import {
-  DEFAULT_GEMINI_MODEL_AUTO,
-  GEMINI_MODEL_ALIAS_PRO,
-  PREVIEW_GEMINI_MODEL,
+  DEFAULT_GEMINI_MODEL,
+  GEMINI_MODEL_ALIAS_AUTO,
+  PREVIEW_GEMINI_FLASH_MODEL,
+  isPreviewModel,
 } from '../config/models.js';
 import type { ModelConfigAlias } from '../services/modelConfigService.js';
+import { coreEvents, CoreEvent } from '../utils/events.js';
 
 /**
  * Returns the model config alias for a given agent definition.
@@ -41,6 +43,10 @@ export class AgentRegistry {
   async initialize(): Promise<void> {
     this.loadBuiltInAgents();
 
+    coreEvents.on(CoreEvent.ModelChanged, () => {
+      this.loadBuiltInAgents();
+    });
+
     if (this.config.getDebugMode()) {
       debugLogger.log(
         `[AgentRegistry] Initialized with ${this.agents.size} agents.`,
@@ -53,19 +59,17 @@ export class AgentRegistry {
 
     // Only register the agent if it's enabled in the settings.
     if (investigatorSettings?.enabled) {
-      let model =
-        investigatorSettings.model ??
-        CodebaseInvestigatorAgent.modelConfig.model;
-
-      // If the user is using the preview model for the main agent, force the sub-agent to use it too
-      // if it's configured to use 'pro' or 'auto'.
-      if (this.config.getModel() === PREVIEW_GEMINI_MODEL) {
-        if (
-          model === GEMINI_MODEL_ALIAS_PRO ||
-          model === DEFAULT_GEMINI_MODEL_AUTO
-        ) {
-          model = PREVIEW_GEMINI_MODEL;
-        }
+      let model;
+      const settingsModel = investigatorSettings.model;
+      // Check if the user explicitly set a model in the settings.
+      if (settingsModel && settingsModel !== GEMINI_MODEL_ALIAS_AUTO) {
+        model = settingsModel;
+      } else {
+        // Use Preview Flash model if the main model is any of the preview models
+        // If the main model is not preview model, use default pro model.
+        model = isPreviewModel(this.config.getModel())
+          ? PREVIEW_GEMINI_FLASH_MODEL
+          : DEFAULT_GEMINI_MODEL;
       }
 
       const agentDef = {