fix(acp) refactor(core,cli): centralize model discovery logic in ModelConfigService (#24392)

packages/cli/src/acp/acpClient.test.ts

@@ -27,6 +27,7 @@ import {
   type MessageBus,
   LlmRole,
   type GitService,
+  type ModelRouterService,
   processSingleFileContent,
   InvalidStreamError,
 } from '@google/gemini-cli-core';
@@ -102,17 +103,7 @@ vi.mock(
       ...actual,
       updatePolicy: vi.fn(),
       createPolicyUpdater: vi.fn(),
-      ReadManyFilesTool: vi.fn().mockImplementation(() => ({
-        name: 'read_many_files',
-        kind: 'read',
-        build: vi.fn().mockReturnValue({
-          getDescription: () => 'Read files',
-          toolLocations: () => [],
-          execute: vi.fn().mockResolvedValue({
-            llmContent: ['--- file.txt ---\n\nFile content\n\n'],
-          }),
-        }),
-      })),
+      ReadManyFilesTool: vi.fn(),
       logToolCall: vi.fn(),
       LlmRole: {
         MAIN: 'main',
@@ -421,6 +412,26 @@ describe('GeminiAgent', () => {
     );
   });
 
+  it('should include gemini-3.1-flash-lite when useGemini31FlashLite is true', async () => {
+    mockConfig.getHasAccessToPreviewModel = vi.fn().mockReturnValue(true);
+    mockConfig.getGemini31LaunchedSync = vi.fn().mockReturnValue(true);
+    mockConfig.getGemini31FlashLiteLaunchedSync = vi.fn().mockReturnValue(true);
+
+    const response = await agent.newSession({
+      cwd: '/tmp',
+      mcpServers: [],
+    });
+
+    expect(response.models?.availableModels).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          modelId: 'gemini-3.1-flash-lite-preview',
+          name: 'gemini-3.1-flash-lite-preview',
+        }),
+      ]),
+    );
+  });
+
   it('should return modes with plan mode when plan is enabled', async () => {
     mockConfig.getContentGeneratorConfig = vi.fn().mockReturnValue({
       apiKey: 'test-key',
@@ -646,6 +657,7 @@ describe('Session', () => {
       sendMessageStream: vi.fn(),
       addHistory: vi.fn(),
       recordCompletedToolCalls: vi.fn(),
+      getHistory: vi.fn().mockReturnValue([]),
     } as unknown as Mocked<GeminiChat>;
     mockTool = {
       kind: 'read',
@@ -667,6 +679,9 @@ describe('Session', () => {
     mockConfig = {
       getModel: vi.fn().mockReturnValue('gemini-pro'),
       getActiveModel: vi.fn().mockReturnValue('gemini-pro'),
+      getModelRouterService: vi.fn().mockReturnValue({
+        route: vi.fn().mockResolvedValue({ model: 'resolved-model' }),
+      }),
       getToolRegistry: vi.fn().mockReturnValue(mockToolRegistry),
       getMcpServers: vi.fn(),
       getFileService: vi.fn().mockReturnValue({
@@ -713,10 +728,22 @@ describe('Session', () => {
       },
       errors: [],
     } as unknown as LoadedSettings);
+
+    (ReadManyFilesTool as unknown as Mock).mockImplementation(() => ({
+      name: 'read_many_files',
+      kind: 'read',
+      build: vi.fn().mockReturnValue({
+        getDescription: () => 'Read files',
+        toolLocations: () => [],
+        execute: vi.fn().mockResolvedValue({
+          llmContent: ['--- file.txt ---\n\nFile content\n\n'],
+        }),
+      }),
+    }));
   });
 
   afterEach(() => {
-    vi.clearAllMocks();
+    vi.restoreAllMocks();
   });
 
   it('should send available commands', async () => {
@@ -786,6 +813,42 @@ describe('Session', () => {
     expect(result).toMatchObject({ stopReason: 'end_turn' });
   });
 
+  it('should use model router to determine model', async () => {
+    const mockRouter = {
+      route: vi.fn().mockResolvedValue({ model: 'routed-model' }),
+    } as unknown as ModelRouterService;
+    mockConfig.getModelRouterService.mockReturnValue(mockRouter);
+
+    const stream = createMockStream([
+      {
+        type: StreamEventType.CHUNK,
+        value: {
+          candidates: [{ content: { parts: [{ text: 'Hello' }] } }],
+        },
+      },
+    ]);
+    mockChat.sendMessageStream.mockResolvedValue(stream);
+
+    await session.prompt({
+      sessionId: 'session-1',
+      prompt: [{ type: 'text', text: 'Hi' }],
+    });
+
+    expect(mockRouter.route).toHaveBeenCalledWith(
+      expect.objectContaining({
+        requestedModel: 'gemini-pro',
+        request: [{ text: 'Hi' }],
+      }),
+    );
+    expect(mockChat.sendMessageStream).toHaveBeenCalledWith(
+      expect.objectContaining({ model: 'routed-model' }),
+      expect.any(Array),
+      expect.any(String),
+      expect.any(Object),
+      expect.any(String),
+    );
+  });
+
   it('should handle prompt with empty response (InvalidStreamError)', async () => {
     mockChat.sendMessageStream.mockRejectedValue(
       new InvalidStreamError('Empty response', 'NO_RESPONSE_TEXT'),

packages/cli/src/acp/acpClient.ts

@@ -28,7 +28,7 @@ import {
   debugLogger,
   ReadManyFilesTool,
   REFERENCE_CONTENT_START,
-  resolveModel,
+  type RoutingContext,
   createWorkingStdio,
   startupProfiler,
   Kind,
@@ -42,6 +42,7 @@ import {
   DEFAULT_GEMINI_FLASH_LITE_MODEL,
   PREVIEW_GEMINI_MODEL,
   PREVIEW_GEMINI_3_1_MODEL,
+  PREVIEW_GEMINI_3_1_FLASH_LITE_MODEL,
   PREVIEW_GEMINI_3_1_CUSTOM_TOOLS_MODEL,
   PREVIEW_GEMINI_FLASH_MODEL,
   DEFAULT_GEMINI_MODEL_AUTO,
@@ -758,10 +759,15 @@ export class Session {
       const functionCalls: FunctionCall[] = [];
 
       try {
-        const model = resolveModel(
-          this.context.config.getModel(),
-          (await this.context.config.getGemini31Launched?.()) ?? false,
-        );
+        const routingContext: RoutingContext = {
+          history: chat.getHistory(/*curated=*/ true),
+          request: nextMessage?.parts ?? [],
+          signal: pendingSend.signal,
+          requestedModel: this.context.config.getModel(),
+        };
+
+        const router = this.context.config.getModelRouterService();
+        const { model } = await router.route(routingContext);
         const responseStream = await chat.sendMessageStream(
           { model },
           nextMessage?.parts ?? [],
@@ -2009,10 +2015,31 @@ function buildAvailableModels(
   const preferredModel = config.getModel() || DEFAULT_GEMINI_MODEL_AUTO;
   const shouldShowPreviewModels = config.getHasAccessToPreviewModel();
   const useGemini31 = config.getGemini31LaunchedSync?.() ?? false;
+  const useGemini31FlashLite =
+    config.getGemini31FlashLiteLaunchedSync?.() ?? false;
   const selectedAuthType = settings.merged.security.auth.selectedType;
   const useCustomToolModel =
     useGemini31 && selectedAuthType === AuthType.USE_GEMINI;
 
+  // --- DYNAMIC PATH ---
+  if (
+    config.getExperimentalDynamicModelConfiguration?.() === true &&
+    config.getModelConfigService
+  ) {
+    const options = config.getModelConfigService().getAvailableModelOptions({
+      useGemini3_1: useGemini31,
+      useGemini3_1FlashLite: useGemini31FlashLite,
+      useCustomTools: useCustomToolModel,
+      hasAccessToPreview: shouldShowPreviewModels,
+    });
+
+    return {
+      availableModels: options,
+      currentModelId: preferredModel,
+    };
+  }
+
+  // --- LEGACY PATH ---
   const mainOptions = [
     {
       value: DEFAULT_GEMINI_MODEL_AUTO,
@@ -2056,7 +2083,7 @@ function buildAvailableModels(
       ? PREVIEW_GEMINI_3_1_CUSTOM_TOOLS_MODEL
       : previewProModel;
 
-    manualOptions.unshift(
+    const previewOptions = [
       {
         value: previewProValue,
         title: getDisplayString(previewProModel),
@@ -2065,7 +2092,16 @@ function buildAvailableModels(
         value: PREVIEW_GEMINI_FLASH_MODEL,
         title: getDisplayString(PREVIEW_GEMINI_FLASH_MODEL),
       },
-    );
+    ];
+
+    if (useGemini31FlashLite) {
+      previewOptions.push({
+        value: PREVIEW_GEMINI_3_1_FLASH_LITE_MODEL,
+        title: getDisplayString(PREVIEW_GEMINI_3_1_FLASH_LITE_MODEL),
+      });
+    }
+
+    manualOptions.unshift(...previewOptions);
   }
 
   const scaleOptions = (