feat: Introduce session context and add session duration stat for `/stats` command (#854)

packages/cli/src/gemini.tsx

@@ -6,7 +6,7 @@
 
 import React from 'react';
 import { render } from 'ink';
-import { App } from './ui/App.js';
+import { AppWrapper } from './ui/App.js';
 import { loadCliConfig } from './config/config.js';
 import { readStdin } from './utils/readStdin.js';
 import { sandbox_command, start_sandbox } from './utils/sandbox.js';
@@ -95,7 +95,7 @@ export async function main() {
   if (process.stdin.isTTY && input?.length === 0) {
     render(
       <React.StrictMode>
-        <App
+        <AppWrapper
           config={config}
           settings={settings}
           startupWarnings={startupWarnings}

packages/cli/src/ui/App.test.tsx

@@ -6,7 +6,7 @@
 
 import { describe, it, expect, vi, beforeEach, afterEach, Mock } from 'vitest';
 import { render } from 'ink-testing-library';
-import { App } from './App.js';
+import { AppWrapper as App } from './App.js';
 import {
   Config as ServerConfig,
   MCPServerConfig,

packages/cli/src/ui/App.tsx

@@ -48,6 +48,7 @@ import {
 } from '@gemini-cli/core';
 import { useLogger } from './hooks/useLogger.js';
 import { StreamingContext } from './contexts/StreamingContext.js';
+import { SessionProvider } from './contexts/SessionContext.js';
 import { useGitBranchName } from './hooks/useGitBranchName.js';
 
 const CTRL_C_PROMPT_DURATION_MS = 1000;
@@ -58,7 +59,13 @@ interface AppProps {
   startupWarnings?: string[];
 }
 
-export const App = ({ config, settings, startupWarnings = [] }: AppProps) => {
+export const AppWrapper = (props: AppProps) => (
+  <SessionProvider>
+    <App {...props} />
+  </SessionProvider>
+);
+
+const App = ({ config, settings, startupWarnings = [] }: AppProps) => {
   const { history, addItem, clearItems } = useHistory();
   const {
     consoleMessages,

packages/cli/src/ui/contexts/SessionContext.test.tsx

@@ -0,0 +1,29 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { render } from 'ink-testing-library';
+import { Text } from 'ink';
+import { SessionProvider, useSession } from './SessionContext.js';
+import { describe, it, expect } from 'vitest';
+
+const TestComponent = () => {
+  const { startTime } = useSession();
+  return <Text>{startTime.toISOString()}</Text>;
+};
+
+describe('SessionContext', () => {
+  it('should provide a start time', () => {
+    const { lastFrame } = render(
+      <SessionProvider>
+        <TestComponent />
+      </SessionProvider>,
+    );
+
+    const frameText = lastFrame();
+    // Check if the output is a valid ISO string, which confirms it's a Date object.
+    expect(new Date(frameText!).toString()).not.toBe('Invalid Date');
+  });
+});

packages/cli/src/ui/contexts/SessionContext.tsx

@@ -0,0 +1,38 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import React, { createContext, useContext, useState, useMemo } from 'react';
+
+interface SessionContextType {
+  startTime: Date;
+}
+
+const SessionContext = createContext<SessionContextType | null>(null);
+
+export const SessionProvider: React.FC<{ children: React.ReactNode }> = ({
+  children,
+}) => {
+  const [startTime] = useState(new Date());
+
+  const value = useMemo(
+    () => ({
+      startTime,
+    }),
+    [startTime],
+  );
+
+  return (
+    <SessionContext.Provider value={value}>{children}</SessionContext.Provider>
+  );
+};
+
+export const useSession = () => {
+  const context = useContext(SessionContext);
+  if (!context) {
+    throw new Error('useSession must be used within a SessionProvider');
+  }
+  return context;
+};

packages/cli/src/ui/hooks/slashCommandProcessor.test.ts

@@ -61,10 +61,15 @@ import {
   MCPServerStatus,
   getMCPServerStatus,
 } from '@gemini-cli/core';
+import { useSession } from '../contexts/SessionContext.js';
 
 import * as ShowMemoryCommandModule from './useShowMemoryCommand.js';
 import { GIT_COMMIT_INFO } from '../../generated/git-commit.js';
 
+vi.mock('../contexts/SessionContext.js', () => ({
+  useSession: vi.fn(),
+}));
+
 vi.mock('./useShowMemoryCommand.js', () => ({
   SHOW_MEMORY_COMMAND_NAME: '/memory show',
   createShowMemoryAction: vi.fn(() => vi.fn()),
@@ -84,6 +89,7 @@ describe('useSlashCommandProcessor', () => {
   let mockPerformMemoryRefresh: ReturnType<typeof vi.fn>;
   let mockConfig: Config;
   let mockCorgiMode: ReturnType<typeof vi.fn>;
+  const mockUseSession = useSession as Mock;
 
   beforeEach(() => {
     mockAddItem = vi.fn();
@@ -99,6 +105,9 @@ describe('useSlashCommandProcessor', () => {
       getModel: vi.fn(() => 'test-model'),
     } as unknown as Config;
     mockCorgiMode = vi.fn();
+    mockUseSession.mockReturnValue({
+      startTime: new Date('2025-01-01T00:00:00.000Z'),
+    });
 
     (open as Mock).mockClear();
     mockProcessExit.mockClear();
@@ -230,6 +239,34 @@ describe('useSlashCommandProcessor', () => {
     });
   });
 
+  describe('/stats command', () => {
+    it('should show the session duration', async () => {
+      const { handleSlashCommand } = getProcessor();
+      let commandResult: SlashCommandActionReturn | boolean = false;
+
+      // Mock current time
+      const mockDate = new Date('2025-01-01T00:01:05.000Z');
+      vi.setSystemTime(mockDate);
+
+      await act(async () => {
+        commandResult = handleSlashCommand('/stats');
+      });
+
+      expect(mockAddItem).toHaveBeenNthCalledWith(
+        2,
+        expect.objectContaining({
+          type: MessageType.INFO,
+          text: 'Session duration: 1m 5s',
+        }),
+        expect.any(Number),
+      );
+      expect(commandResult).toBe(true);
+
+      // Restore system time
+      vi.useRealTimers();
+    });
+  });
+
   describe('Other commands', () => {
     it('/help should open help and return true', async () => {
       const { handleSlashCommand } = getProcessor();

packages/cli/src/ui/hooks/slashCommandProcessor.ts

@@ -11,6 +11,7 @@ import process from 'node:process';
 import { UseHistoryManagerReturn } from './useHistoryManager.js';
 import { Config, MCPServerStatus, getMCPServerStatus } from '@gemini-cli/core';
 import { Message, MessageType, HistoryItemWithoutId } from '../types.js';
+import { useSession } from '../contexts/SessionContext.js';
 import { createShowMemoryAction } from './useShowMemoryCommand.js';
 import { GIT_COMMIT_INFO } from '../../generated/git-commit.js';
 import { formatMemoryUsage } from '../utils/formatters.js';
@@ -49,6 +50,8 @@ export const useSlashCommandProcessor = (
   toggleCorgiMode: () => void,
   showToolDescriptions: boolean = false,
 ) => {
+  const session = useSession();
+
   const addMessage = useCallback(
     (message: Message) => {
       // Convert Message to HistoryItemWithoutId
@@ -138,6 +141,33 @@ export const useSlashCommandProcessor = (
           openThemeDialog();
         },
       },
+      {
+        name: 'stats',
+        altName: 'usage',
+        description: 'check session stats',
+        action: (_mainCommand, _subCommand, _args) => {
+          const now = new Date();
+          const duration = now.getTime() - session.startTime.getTime();
+          const durationInSeconds = Math.floor(duration / 1000);
+          const hours = Math.floor(durationInSeconds / 3600);
+          const minutes = Math.floor((durationInSeconds % 3600) / 60);
+          const seconds = durationInSeconds % 60;
+
+          const durationString = [
+            hours > 0 ? `${hours}h` : '',
+            minutes > 0 ? `${minutes}m` : '',
+            `${seconds}s`,
+          ]
+            .filter(Boolean)
+            .join(' ');
+
+          addMessage({
+            type: MessageType.INFO,
+            content: `Session duration: ${durationString}`,
+            timestamp: new Date(),
+          });
+        },
+      },
       {
         name: 'mcp',
         description: 'list configured MCP servers and tools',
@@ -447,6 +477,7 @@ Add any other context about the problem here.
       toggleCorgiMode,
       config,
       showToolDescriptions,
+      session.startTime,
     ],
   );