feat: allow custom filename for context files (#654)

Co-authored-by: N. Taylor Mullen <[email protected]>

5 files changed, 623 insertions, 3 deletions

diff --git a/packages/cli/src/config/config.ts b/packages/cli/src/config/config.ts
index 04347427..44057fad 100644
--- a/packages/cli/src/config/config.ts
+++ b/packages/cli/src/config/config.ts
@@ -13,6 +13,8 @@ import {
   createServerConfig,
   loadServerHierarchicalMemory,
   ConfigParameters,
+  setGeminiMdFilename as setServerGeminiMdFilename,
+  getCurrentGeminiMdFilename,
 } from '@gemini-code/core';
 import { Settings } from './settings.js';
 import { readPackageUp } from 'read-package-up';
@@ -132,6 +134,17 @@ export async function loadCliConfig(settings: Settings): Promise<Config> {
   const argv = await parseArguments();
   const debugMode = argv.debug || false;
 
+  // Set the context filename in the server's memoryTool module BEFORE loading memory
+  // TODO(b/343434939): This is a bit of a hack. The contextFileName should ideally be passed
+  // directly to the Config constructor in core, and have core handle setGeminiMdFilename.
+  // However, loadHierarchicalGeminiMemory is called *before* createServerConfig.
+  if (settings.contextFileName) {
+    setServerGeminiMdFilename(settings.contextFileName);
+  } else {
+    // Reset to default if not provided in settings.
+    setServerGeminiMdFilename(getCurrentGeminiMdFilename());
+  }
+
   // Call the (now wrapper) loadHierarchicalGeminiMemory which calls the server's version
   const { memoryContent, fileCount } = await loadHierarchicalGeminiMemory(
     process.cwd(),
@@ -159,7 +172,8 @@ export async function loadCliConfig(settings: Settings): Promise<Config> {
     userMemory: memoryContent,
     geminiMdFileCount: fileCount,
     vertexai: useVertexAI,
-    showMemoryUsage: argv.show_memory_usage || false,
+    showMemoryUsage:
+      argv.show_memory_usage || settings.showMemoryUsage || false,
   };
 
   return createServerConfig(configParams);
diff --git a/packages/cli/src/config/settings.test.ts b/packages/cli/src/config/settings.test.ts
new file mode 100644
index 00000000..4d61ed8b
--- /dev/null
+++ b/packages/cli/src/config/settings.test.ts
@@ -0,0 +1,309 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/// <reference types="vitest/globals" />
+
+const MOCK_HOME_DIR = '/mock/home/user'; // MUST BE FIRST
+
+// Mock 'os' first. Its factory uses MOCK_HOME_DIR.
+import * as osActual from 'os'; // Import for type info for the mock factory
+vi.mock('os', async (importOriginal) => {
+  const actualOs = await importOriginal<typeof osActual>();
+  return {
+    ...actualOs,
+    homedir: vi.fn(() => MOCK_HOME_DIR),
+  };
+});
+
+// Mock './settings.js' to ensure it uses the mocked 'os.homedir()' for its internal constants.
+vi.mock('./settings.js', async (importActual) => {
+  const originalModule = await importActual<typeof import('./settings.js')>();
+  return {
+    __esModule: true, // Ensure correct module shape
+    ...originalModule, // Re-export all original members
+    // We are relying on originalModule's USER_SETTINGS_PATH being constructed with mocked os.homedir()
+  };
+});
+
+// NOW import everything else, including the (now effectively re-exported) settings.js
+import * as pathActual from 'path'; // Restored for MOCK_WORKSPACE_SETTINGS_PATH
+import {
+  describe,
+  it,
+  expect,
+  vi,
+  beforeEach,
+  afterEach,
+  type Mocked,
+  type Mock,
+} from 'vitest';
+import * as fs from 'fs'; // fs will be mocked separately
+import stripJsonComments from 'strip-json-comments'; // Will be mocked separately
+
+// These imports will get the versions from the vi.mock('./settings.js', ...) factory.
+import {
+  LoadedSettings,
+  loadSettings,
+  USER_SETTINGS_PATH, // This IS the mocked path.
+  SETTINGS_DIRECTORY_NAME, // This is from the original module, but used by the mock.
+  SettingScope,
+} from './settings.js';
+
+const MOCK_WORKSPACE_DIR = '/mock/workspace';
+// Use the (mocked) SETTINGS_DIRECTORY_NAME for consistency
+const MOCK_WORKSPACE_SETTINGS_PATH = pathActual.join(
+  MOCK_WORKSPACE_DIR,
+  SETTINGS_DIRECTORY_NAME,
+  'settings.json',
+);
+
+vi.mock('fs');
+vi.mock('strip-json-comments', () => ({
+  default: vi.fn((content) => content),
+}));
+
+describe('Settings Loading and Merging', () => {
+  let mockFsExistsSync: Mocked<typeof fs.existsSync>;
+  let mockStripJsonComments: Mocked<typeof stripJsonComments>;
+  let mockFsMkdirSync: Mocked<typeof fs.mkdirSync>;
+
+  beforeEach(() => {
+    vi.resetAllMocks();
+
+    mockFsExistsSync = vi.mocked(fs.existsSync);
+    mockFsMkdirSync = vi.mocked(fs.mkdirSync);
+    mockStripJsonComments = vi.mocked(stripJsonComments);
+
+    vi.mocked(osActual.homedir).mockReturnValue(MOCK_HOME_DIR);
+    (mockStripJsonComments as unknown as Mock).mockImplementation(
+      (jsonString: string) => jsonString,
+    );
+    (mockFsExistsSync as Mock).mockReturnValue(false);
+    (fs.readFileSync as Mock).mockReturnValue('{}'); // Return valid empty JSON
+    (mockFsMkdirSync as Mock).mockImplementation(() => undefined);
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  describe('loadSettings', () => {
+    it('should load empty settings if no files exist', () => {
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.user.settings).toEqual({});
+      expect(settings.workspace.settings).toEqual({});
+      expect(settings.merged).toEqual({});
+    });
+
+    it('should load user settings if only user file exists', () => {
+      const expectedUserSettingsPath = USER_SETTINGS_PATH; // Use the path actually resolved by the (mocked) module
+
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === expectedUserSettingsPath,
+      );
+      const userSettingsContent = {
+        theme: 'dark',
+        contextFileName: 'USER_CONTEXT.md',
+      };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === expectedUserSettingsPath)
+            return JSON.stringify(userSettingsContent);
+          return '{}';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(fs.readFileSync).toHaveBeenCalledWith(
+        expectedUserSettingsPath,
+        'utf-8',
+      );
+      expect(settings.user.settings).toEqual(userSettingsContent);
+      expect(settings.workspace.settings).toEqual({});
+      expect(settings.merged).toEqual(userSettingsContent);
+    });
+
+    it('should load workspace settings if only workspace file exists', () => {
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === MOCK_WORKSPACE_SETTINGS_PATH,
+      );
+      const workspaceSettingsContent = {
+        sandbox: true,
+        contextFileName: 'WORKSPACE_CONTEXT.md',
+      };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(fs.readFileSync).toHaveBeenCalledWith(
+        MOCK_WORKSPACE_SETTINGS_PATH,
+        'utf-8',
+      );
+      expect(settings.user.settings).toEqual({});
+      expect(settings.workspace.settings).toEqual(workspaceSettingsContent);
+      expect(settings.merged).toEqual(workspaceSettingsContent);
+    });
+
+    it('should merge user and workspace settings, with workspace taking precedence', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(true);
+      const userSettingsContent = {
+        theme: 'dark',
+        sandbox: false,
+        contextFileName: 'USER_CONTEXT.md',
+      };
+      const workspaceSettingsContent = {
+        sandbox: true,
+        coreTools: ['tool1'],
+        contextFileName: 'WORKSPACE_CONTEXT.md',
+      };
+
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === USER_SETTINGS_PATH)
+            return JSON.stringify(userSettingsContent);
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(settings.user.settings).toEqual(userSettingsContent);
+      expect(settings.workspace.settings).toEqual(workspaceSettingsContent);
+      expect(settings.merged).toEqual({
+        theme: 'dark',
+        sandbox: true,
+        coreTools: ['tool1'],
+        contextFileName: 'WORKSPACE_CONTEXT.md',
+      });
+    });
+
+    it('should handle contextFileName correctly when only in user settings', () => {
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === USER_SETTINGS_PATH,
+      );
+      const userSettingsContent = { contextFileName: 'CUSTOM.md' };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === USER_SETTINGS_PATH)
+            return JSON.stringify(userSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.merged.contextFileName).toBe('CUSTOM.md');
+    });
+
+    it('should handle contextFileName correctly when only in workspace settings', () => {
+      (mockFsExistsSync as Mock).mockImplementation(
+        (p: fs.PathLike) => p === MOCK_WORKSPACE_SETTINGS_PATH,
+      );
+      const workspaceSettingsContent = {
+        contextFileName: 'PROJECT_SPECIFIC.md',
+      };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.merged.contextFileName).toBe('PROJECT_SPECIFIC.md');
+    });
+
+    it('should default contextFileName to undefined if not in any settings file', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(true);
+      const userSettingsContent = { theme: 'dark' };
+      const workspaceSettingsContent = { sandbox: true };
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          if (p === USER_SETTINGS_PATH)
+            return JSON.stringify(userSettingsContent);
+          if (p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return JSON.stringify(workspaceSettingsContent);
+          return '';
+        },
+      );
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+      expect(settings.merged.contextFileName).toBeUndefined();
+    });
+
+    it('should handle JSON parsing errors gracefully', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(true);
+      (fs.readFileSync as Mock).mockImplementation(
+        (p: fs.PathOrFileDescriptor) => {
+          // Make it return invalid json for the paths it will try to read
+          if (p === USER_SETTINGS_PATH || p === MOCK_WORKSPACE_SETTINGS_PATH)
+            return 'invalid json';
+          return '';
+        },
+      );
+      const consoleErrorSpy = vi
+        .spyOn(console, 'error')
+        .mockImplementation(() => {});
+
+      const settings = loadSettings(MOCK_WORKSPACE_DIR);
+
+      expect(settings.user.settings).toEqual({});
+      expect(settings.workspace.settings).toEqual({});
+      expect(settings.merged).toEqual({});
+      expect(consoleErrorSpy).toHaveBeenCalledTimes(2);
+
+      consoleErrorSpy.mockRestore();
+    });
+  });
+
+  describe('LoadedSettings class', () => {
+    it('setValue should update the correct scope and recompute merged settings', () => {
+      (mockFsExistsSync as Mock).mockReturnValue(false);
+      const loadedSettings = loadSettings(MOCK_WORKSPACE_DIR) as LoadedSettings;
+
+      vi.mocked(fs.writeFileSync).mockImplementation(() => {});
+      // mkdirSync is mocked in beforeEach to return undefined, which is fine for void usage
+
+      loadedSettings.setValue(SettingScope.User, 'theme', 'matrix');
+      expect(loadedSettings.user.settings.theme).toBe('matrix');
+      expect(loadedSettings.merged.theme).toBe('matrix');
+      expect(fs.writeFileSync).toHaveBeenCalledWith(
+        USER_SETTINGS_PATH,
+        JSON.stringify({ theme: 'matrix' }, null, 2),
+        'utf-8',
+      );
+
+      loadedSettings.setValue(
+        SettingScope.Workspace,
+        'contextFileName',
+        'MY_AGENTS.md',
+      );
+      expect(loadedSettings.workspace.settings.contextFileName).toBe(
+        'MY_AGENTS.md',
+      );
+      expect(loadedSettings.merged.contextFileName).toBe('MY_AGENTS.md');
+      expect(loadedSettings.merged.theme).toBe('matrix');
+      expect(fs.writeFileSync).toHaveBeenCalledWith(
+        MOCK_WORKSPACE_SETTINGS_PATH,
+        JSON.stringify({ contextFileName: 'MY_AGENTS.md' }, null, 2),
+        'utf-8',
+      );
+
+      loadedSettings.setValue(SettingScope.Workspace, 'theme', 'ocean');
+      expect(loadedSettings.workspace.settings.theme).toBe('ocean');
+      expect(loadedSettings.merged.theme).toBe('ocean');
+    });
+  });
+});
diff --git a/packages/cli/src/config/settings.ts b/packages/cli/src/config/settings.ts
index 1aabc127..5d51ba15 100644
--- a/packages/cli/src/config/settings.ts
+++ b/packages/cli/src/config/settings.ts
@@ -30,6 +30,7 @@ export interface Settings {
   mcpServerCommand?: string;
   mcpServers?: Record<string, MCPServerConfig>;
   showMemoryUsage?: boolean;
+  contextFileName?: string;
   // Add other settings here.
 }
 
diff --git a/packages/cli/src/ui/App.test.tsx b/packages/cli/src/ui/App.test.tsx
new file mode 100644
index 00000000..a7811f6a
--- /dev/null
+++ b/packages/cli/src/ui/App.test.tsx
@@ -0,0 +1,289 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach, Mock } from 'vitest';
+import { render } from 'ink-testing-library';
+import { App } from './App.js';
+import { Config as ServerConfig, MCPServerConfig } from '@gemini-code/core';
+import type { ToolRegistry } from '@gemini-code/core';
+import { LoadedSettings, SettingsFile, Settings } from '../config/settings.js';
+
+// Define a more complete mock server config based on actual Config
+interface MockServerConfig {
+  apiKey: string;
+  model: string;
+  sandbox: boolean | string;
+  targetDir: string;
+  debugMode: boolean;
+  question?: string;
+  fullContext: boolean;
+  coreTools?: string[];
+  toolDiscoveryCommand?: string;
+  toolCallCommand?: string;
+  mcpServerCommand?: string;
+  mcpServers?: Record<string, MCPServerConfig>; // Use imported MCPServerConfig
+  userAgent: string;
+  userMemory: string;
+  geminiMdFileCount: number;
+  alwaysSkipModificationConfirmation: boolean;
+  vertexai?: boolean;
+  showMemoryUsage?: boolean;
+
+  getApiKey: Mock<() => string>;
+  getModel: Mock<() => string>;
+  getSandbox: Mock<() => boolean | string>;
+  getTargetDir: Mock<() => string>;
+  getToolRegistry: Mock<() => ToolRegistry>; // Use imported ToolRegistry type
+  getDebugMode: Mock<() => boolean>;
+  getQuestion: Mock<() => string | undefined>;
+  getFullContext: Mock<() => boolean>;
+  getCoreTools: Mock<() => string[] | undefined>;
+  getToolDiscoveryCommand: Mock<() => string | undefined>;
+  getToolCallCommand: Mock<() => string | undefined>;
+  getMcpServerCommand: Mock<() => string | undefined>;
+  getMcpServers: Mock<() => Record<string, MCPServerConfig> | undefined>;
+  getUserAgent: Mock<() => string>;
+  getUserMemory: Mock<() => string>;
+  setUserMemory: Mock<(newUserMemory: string) => void>;
+  getGeminiMdFileCount: Mock<() => number>;
+  setGeminiMdFileCount: Mock<(count: number) => void>;
+  getAlwaysSkipModificationConfirmation: Mock<() => boolean>;
+  setAlwaysSkipModificationConfirmation: Mock<(skip: boolean) => void>;
+  getVertexAI: Mock<() => boolean | undefined>;
+  getShowMemoryUsage: Mock<() => boolean>;
+}
+
+// Mock @gemini-code/core and its Config class
+vi.mock('@gemini-code/core', async (importOriginal) => {
+  const actualCore = await importOriginal<typeof import('@gemini-code/core')>();
+  const ConfigClassMock = vi
+    .fn()
+    .mockImplementation((optionsPassedToConstructor) => {
+      const opts = { ...optionsPassedToConstructor }; // Clone
+      // Basic mock structure, will be extended by the instance in tests
+      return {
+        apiKey: opts.apiKey || 'test-key',
+        model: opts.model || 'test-model-in-mock-factory',
+        sandbox: typeof opts.sandbox === 'boolean' ? opts.sandbox : false,
+        targetDir: opts.targetDir || '/test/dir',
+        debugMode: opts.debugMode || false,
+        question: opts.question,
+        fullContext: opts.fullContext ?? false,
+        coreTools: opts.coreTools,
+        toolDiscoveryCommand: opts.toolDiscoveryCommand,
+        toolCallCommand: opts.toolCallCommand,
+        mcpServerCommand: opts.mcpServerCommand,
+        mcpServers: opts.mcpServers,
+        userAgent: opts.userAgent || 'test-agent',
+        userMemory: opts.userMemory || '',
+        geminiMdFileCount: opts.geminiMdFileCount || 0,
+        alwaysSkipModificationConfirmation:
+          opts.alwaysSkipModificationConfirmation ?? false,
+        vertexai: opts.vertexai,
+        showMemoryUsage: opts.showMemoryUsage ?? false,
+
+        getApiKey: vi.fn(() => opts.apiKey || 'test-key'),
+        getModel: vi.fn(() => opts.model || 'test-model-in-mock-factory'),
+        getSandbox: vi.fn(() =>
+          typeof opts.sandbox === 'boolean' ? opts.sandbox : false,
+        ),
+        getTargetDir: vi.fn(() => opts.targetDir || '/test/dir'),
+        getToolRegistry: vi.fn(() => ({}) as ToolRegistry), // Simple mock
+        getDebugMode: vi.fn(() => opts.debugMode || false),
+        getQuestion: vi.fn(() => opts.question),
+        getFullContext: vi.fn(() => opts.fullContext ?? false),
+        getCoreTools: vi.fn(() => opts.coreTools),
+        getToolDiscoveryCommand: vi.fn(() => opts.toolDiscoveryCommand),
+        getToolCallCommand: vi.fn(() => opts.toolCallCommand),
+        getMcpServerCommand: vi.fn(() => opts.mcpServerCommand),
+        getMcpServers: vi.fn(() => opts.mcpServers),
+        getUserAgent: vi.fn(() => opts.userAgent || 'test-agent'),
+        getUserMemory: vi.fn(() => opts.userMemory || ''),
+        setUserMemory: vi.fn(),
+        getGeminiMdFileCount: vi.fn(() => opts.geminiMdFileCount || 0),
+        setGeminiMdFileCount: vi.fn(),
+        getAlwaysSkipModificationConfirmation: vi.fn(
+          () => opts.alwaysSkipModificationConfirmation ?? false,
+        ),
+        setAlwaysSkipModificationConfirmation: vi.fn(),
+        getVertexAI: vi.fn(() => opts.vertexai),
+        getShowMemoryUsage: vi.fn(() => opts.showMemoryUsage ?? false),
+      };
+    });
+  return {
+    ...actualCore,
+    Config: ConfigClassMock,
+    MCPServerConfig: actualCore.MCPServerConfig,
+  };
+});
+
+// Mock heavy dependencies or those with side effects
+vi.mock('./hooks/useGeminiStream', () => ({
+  useGeminiStream: vi.fn(() => ({
+    streamingState: 'Idle',
+    submitQuery: vi.fn(),
+    initError: null,
+    pendingHistoryItems: [],
+  })),
+}));
+
+vi.mock('./hooks/useLogger', () => ({
+  useLogger: vi.fn(() => ({
+    getPreviousUserMessages: vi.fn().mockResolvedValue([]),
+  })),
+}));
+
+vi.mock('../config/config.js', async (importOriginal) => {
+  const actual = await importOriginal();
+  return {
+    // @ts-expect-error - this is fine
+    ...actual,
+    loadHierarchicalGeminiMemory: vi
+      .fn()
+      .mockResolvedValue({ memoryContent: '', fileCount: 0 }),
+  };
+});
+
+describe('App UI', () => {
+  let mockConfig: MockServerConfig;
+  let mockSettings: LoadedSettings;
+  let currentUnmount: (() => void) | undefined;
+
+  const createMockSettings = (
+    settings: Partial<Settings> = {},
+  ): LoadedSettings => {
+    const userSettingsFile: SettingsFile = {
+      path: '/user/settings.json',
+      settings: {},
+    };
+    const workspaceSettingsFile: SettingsFile = {
+      path: '/workspace/.gemini/settings.json',
+      settings,
+    };
+    return new LoadedSettings(userSettingsFile, workspaceSettingsFile);
+  };
+
+  beforeEach(() => {
+    const ServerConfigMocked = vi.mocked(ServerConfig, true);
+    mockConfig = new ServerConfigMocked({
+      apiKey: 'test-key',
+      model: 'test-model-in-options',
+      sandbox: false,
+      targetDir: '/test/dir',
+      debugMode: false,
+      userAgent: 'test-agent',
+      userMemory: '',
+      geminiMdFileCount: 0,
+      showMemoryUsage: false,
+      // Provide other required fields for ConfigParameters if necessary
+    }) as unknown as MockServerConfig;
+
+    // Ensure the getShowMemoryUsage mock function is specifically set up if not covered by constructor mock
+    if (!mockConfig.getShowMemoryUsage) {
+      mockConfig.getShowMemoryUsage = vi.fn(() => false);
+    }
+    mockConfig.getShowMemoryUsage.mockReturnValue(false); // Default for most tests
+
+    mockSettings = createMockSettings();
+  });
+
+  afterEach(() => {
+    if (currentUnmount) {
+      currentUnmount();
+      currentUnmount = undefined;
+    }
+    vi.clearAllMocks(); // Clear mocks after each test
+  });
+
+  it('should display default "GEMINI.md" in footer when contextFileName is not set and count is 1', async () => {
+    mockConfig.getGeminiMdFileCount.mockReturnValue(1);
+    // For this test, ensure showMemoryUsage is false or debugMode is false if it relies on that
+    mockConfig.getDebugMode.mockReturnValue(false);
+    mockConfig.getShowMemoryUsage.mockReturnValue(false);
+
+    const { lastFrame, unmount } = render(
+      <App
+        config={mockConfig as unknown as ServerConfig}
+        settings={mockSettings}
+        cliVersion="1.0.0"
+      />,
+    );
+    currentUnmount = unmount;
+    await Promise.resolve(); // Wait for any async updates
+    expect(lastFrame()).toContain('Using 1 GEMINI.md file');
+  });
+
+  it('should display default "GEMINI.md" with plural when contextFileName is not set and count is > 1', async () => {
+    mockConfig.getGeminiMdFileCount.mockReturnValue(2);
+    mockConfig.getDebugMode.mockReturnValue(false);
+    mockConfig.getShowMemoryUsage.mockReturnValue(false);
+
+    const { lastFrame, unmount } = render(
+      <App
+        config={mockConfig as unknown as ServerConfig}
+        settings={mockSettings}
+        cliVersion="1.0.0"
+      />,
+    );
+    currentUnmount = unmount;
+    await Promise.resolve();
+    expect(lastFrame()).toContain('Using 2 GEMINI.md files');
+  });
+
+  it('should display custom contextFileName in footer when set and count is 1', async () => {
+    mockSettings = createMockSettings({ contextFileName: 'AGENTS.MD' });
+    mockConfig.getGeminiMdFileCount.mockReturnValue(1);
+    mockConfig.getDebugMode.mockReturnValue(false);
+    mockConfig.getShowMemoryUsage.mockReturnValue(false);
+
+    const { lastFrame, unmount } = render(
+      <App
+        config={mockConfig as unknown as ServerConfig}
+        settings={mockSettings}
+        cliVersion="1.0.0"
+      />,
+    );
+    currentUnmount = unmount;
+    await Promise.resolve();
+    expect(lastFrame()).toContain('Using 1 AGENTS.MD file');
+  });
+
+  it('should display custom contextFileName with plural when set and count is > 1', async () => {
+    mockSettings = createMockSettings({ contextFileName: 'MY_NOTES.TXT' });
+    mockConfig.getGeminiMdFileCount.mockReturnValue(3);
+    mockConfig.getDebugMode.mockReturnValue(false);
+    mockConfig.getShowMemoryUsage.mockReturnValue(false);
+
+    const { lastFrame, unmount } = render(
+      <App
+        config={mockConfig as unknown as ServerConfig}
+        settings={mockSettings}
+        cliVersion="1.0.0"
+      />,
+    );
+    currentUnmount = unmount;
+    await Promise.resolve();
+    expect(lastFrame()).toContain('Using 3 MY_NOTES.TXT files');
+  });
+
+  it('should not display context file message if count is 0, even if contextFileName is set', async () => {
+    mockSettings = createMockSettings({ contextFileName: 'ANY_FILE.MD' });
+    mockConfig.getGeminiMdFileCount.mockReturnValue(0);
+    mockConfig.getDebugMode.mockReturnValue(false);
+    mockConfig.getShowMemoryUsage.mockReturnValue(false);
+
+    const { lastFrame, unmount } = render(
+      <App
+        config={mockConfig as unknown as ServerConfig}
+        settings={mockSettings}
+        cliVersion="1.0.0"
+      />,
+    );
+    currentUnmount = unmount;
+    await Promise.resolve();
+    expect(lastFrame()).not.toContain('ANY_FILE.MD');
+  });
+});
diff --git a/packages/cli/src/ui/App.tsx b/packages/cli/src/ui/App.tsx
index e1657984..2f216db7 100644
--- a/packages/cli/src/ui/App.tsx
+++ b/packages/cli/src/ui/App.tsx
@@ -39,7 +39,11 @@ import { DetailedMessagesDisplay } from './components/DetailedMessagesDisplay.js
 import { HistoryItemDisplay } from './components/HistoryItemDisplay.js';
 import { useHistory } from './hooks/useHistoryManager.js';
 import process from 'node:process';
-import { getErrorMessage, type Config } from '@gemini-code/core';
+import {
+  getErrorMessage,
+  type Config,
+  getCurrentGeminiMdFilename,
+} from '@gemini-code/core';
 import { useLogger } from './hooks/useLogger.js';
 import { StreamingContext } from './contexts/StreamingContext.js';
 import { useGitBranchName } from './hooks/useGitBranchName.js';
@@ -398,7 +402,10 @@ export const App = ({
                     </Text>
                   ) : geminiMdFileCount > 0 ? (
                     <Text color={Colors.SubtleComment}>
-                      Using {geminiMdFileCount} GEMINI.md file
+                      Using {geminiMdFileCount}{' '}
+                      {settings.merged.contextFileName ||
+                        getCurrentGeminiMdFilename()}{' '}
+                      file
                       {geminiMdFileCount > 1 ? 's' : ''}
                     </Text>
                   ) : (