3 files changed, 398 insertions, 0 deletions
diff --git a/packages/cli/src/ui/commands/restoreCommand.test.ts b/packages/cli/src/ui/commands/restoreCommand.test.ts
new file mode 100644
index 00000000..53cd7d18
--- /dev/null
+++ b/packages/cli/src/ui/commands/restoreCommand.test.ts
@@ -0,0 +1,237 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  vi,
+  describe,
+  it,
+  expect,
+  beforeEach,
+  afterEach,
+  Mocked,
+  Mock,
+} from 'vitest';
+import * as fs from 'fs/promises';
+import { restoreCommand } from './restoreCommand.js';
+import { type CommandContext } from './types.js';
+import { createMockCommandContext } from '../../test-utils/mockCommandContext.js';
+import { Config, GitService } from '@google/gemini-cli-core';
+
+vi.mock('fs/promises', () => ({
+  readdir: vi.fn(),
+  readFile: vi.fn(),
+  mkdir: vi.fn(),
+}));
+
+describe('restoreCommand', () => {
+  let mockContext: CommandContext;
+  let mockConfig: Config;
+  let mockGitService: GitService;
+  const mockFsPromises = fs as Mocked<typeof fs>;
+  let mockSetHistory: ReturnType<typeof vi.fn>;
+
+  beforeEach(() => {
+    mockSetHistory = vi.fn().mockResolvedValue(undefined);
+    mockGitService = {
+      restoreProjectFromSnapshot: vi.fn().mockResolvedValue(undefined),
+    } as unknown as GitService;
+
+    mockConfig = {
+      getCheckpointingEnabled: vi.fn().mockReturnValue(true),
+      getProjectTempDir: vi.fn().mockReturnValue('/tmp/gemini'),
+      getGeminiClient: vi.fn().mockReturnValue({
+        setHistory: mockSetHistory,
+      }),
+    } as unknown as Config;
+
+    mockContext = createMockCommandContext({
+      services: {
+        config: mockConfig,
+        git: mockGitService,
+      },
+    });
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('should return null if checkpointing is not enabled', () => {
+    (mockConfig.getCheckpointingEnabled as Mock).mockReturnValue(false);
+    const command = restoreCommand(mockConfig);
+    expect(command).toBeNull();
+  });
+
+  it('should return the command if checkpointing is enabled', () => {
+    const command = restoreCommand(mockConfig);
+    expect(command).not.toBeNull();
+    expect(command?.name).toBe('restore');
+    expect(command?.description).toBeDefined();
+    expect(command?.action).toBeDefined();
+    expect(command?.completion).toBeDefined();
+  });
+
+  describe('action', () => {
+    it('should return an error if temp dir is not found', async () => {
+      (mockConfig.getProjectTempDir as Mock).mockReturnValue(undefined);
+      const command = restoreCommand(mockConfig);
+      const result = await command?.action?.(mockContext, '');
+      expect(result).toEqual({
+        type: 'message',
+        messageType: 'error',
+        content: 'Could not determine the .gemini directory path.',
+      });
+    });
+
+    it('should inform when no checkpoints are found if no args are passed', async () => {
+      mockFsPromises.readdir.mockResolvedValue([]);
+      const command = restoreCommand(mockConfig);
+      const result = await command?.action?.(mockContext, '');
+      expect(result).toEqual({
+        type: 'message',
+        messageType: 'info',
+        content: 'No restorable tool calls found.',
+      });
+      expect(mockFsPromises.mkdir).toHaveBeenCalledWith(
+        '/tmp/gemini/checkpoints',
+        {
+          recursive: true,
+        },
+      );
+    });
+
+    it('should list available checkpoints if no args are passed', async () => {
+      mockFsPromises.readdir.mockResolvedValue([
+        'test1.json',
+        'test2.json',
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      ] as any);
+      const command = restoreCommand(mockConfig);
+      const result = await command?.action?.(mockContext, '');
+      expect(result).toEqual({
+        type: 'message',
+        messageType: 'info',
+        content: 'Available tool calls to restore:\n\ntest1\ntest2',
+      });
+    });
+
+    it('should return an error if the specified file is not found', async () => {
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      mockFsPromises.readdir.mockResolvedValue(['test1.json'] as any);
+      const command = restoreCommand(mockConfig);
+      const result = await command?.action?.(mockContext, 'test2');
+      expect(result).toEqual({
+        type: 'message',
+        messageType: 'error',
+        content: 'File not found: test2.json',
+      });
+    });
+
+    it('should handle file read errors gracefully', async () => {
+      const readError = new Error('Read failed');
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      mockFsPromises.readdir.mockResolvedValue(['test1.json'] as any);
+      mockFsPromises.readFile.mockRejectedValue(readError);
+      const command = restoreCommand(mockConfig);
+      const result = await command?.action?.(mockContext, 'test1');
+      expect(result).toEqual({
+        type: 'message',
+        messageType: 'error',
+        content: `Could not read restorable tool calls. This is the error: ${readError}`,
+      });
+    });
+
+    it('should restore a tool call and project state', async () => {
+      const toolCallData = {
+        history: [{ type: 'user', text: 'do a thing' }],
+        clientHistory: [{ role: 'user', parts: [{ text: 'do a thing' }] }],
+        commitHash: 'abcdef123',
+        toolCall: { name: 'run_shell_command', args: 'ls' },
+      };
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      mockFsPromises.readdir.mockResolvedValue(['my-checkpoint.json'] as any);
+      mockFsPromises.readFile.mockResolvedValue(JSON.stringify(toolCallData));
+
+      const command = restoreCommand(mockConfig);
+      const result = await command?.action?.(mockContext, 'my-checkpoint');
+
+      // Check history restoration
+      expect(mockContext.ui.loadHistory).toHaveBeenCalledWith(
+        toolCallData.history,
+      );
+      expect(mockSetHistory).toHaveBeenCalledWith(toolCallData.clientHistory);
+
+      // Check git restoration
+      expect(mockGitService.restoreProjectFromSnapshot).toHaveBeenCalledWith(
+        toolCallData.commitHash,
+      );
+      expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+        {
+          type: 'info',
+          text: 'Restored project to the state before the tool call.',
+        },
+        expect.any(Number),
+      );
+
+      // Check returned action
+      expect(result).toEqual({
+        type: 'tool',
+        toolName: 'run_shell_command',
+        toolArgs: 'ls',
+      });
+    });
+
+    it('should restore even if only toolCall is present', async () => {
+      const toolCallData = {
+        toolCall: { name: 'run_shell_command', args: 'ls' },
+      };
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      mockFsPromises.readdir.mockResolvedValue(['my-checkpoint.json'] as any);
+      mockFsPromises.readFile.mockResolvedValue(JSON.stringify(toolCallData));
+
+      const command = restoreCommand(mockConfig);
+      const result = await command?.action?.(mockContext, 'my-checkpoint');
+
+      expect(mockContext.ui.loadHistory).not.toHaveBeenCalled();
+      expect(mockSetHistory).not.toHaveBeenCalled();
+      expect(mockGitService.restoreProjectFromSnapshot).not.toHaveBeenCalled();
+
+      expect(result).toEqual({
+        type: 'tool',
+        toolName: 'run_shell_command',
+        toolArgs: 'ls',
+      });
+    });
+  });
+
+  describe('completion', () => {
+    it('should return an empty array if temp dir is not found', async () => {
+      (mockConfig.getProjectTempDir as Mock).mockReturnValue(undefined);
+      const command = restoreCommand(mockConfig);
+      const result = await command?.completion?.(mockContext, '');
+      expect(result).toEqual([]);
+    });
+
+    it('should return an empty array on readdir error', async () => {
+      mockFsPromises.readdir.mockRejectedValue(new Error('ENOENT'));
+      const command = restoreCommand(mockConfig);
+      const result = await command?.completion?.(mockContext, '');
+      expect(result).toEqual([]);
+    });
+
+    it('should return a list of checkpoint names', async () => {
+      mockFsPromises.readdir.mockResolvedValue([
+        'test1.json',
+        'test2.json',
+        'not-a-checkpoint.txt',
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      ] as any);
+      const command = restoreCommand(mockConfig);
+      const result = await command?.completion?.(mockContext, '');
+      expect(result).toEqual(['test1', 'test2']);
+    });
+  });
+});
diff --git a/packages/cli/src/ui/commands/restoreCommand.ts b/packages/cli/src/ui/commands/restoreCommand.ts
new file mode 100644
index 00000000..3d744189
--- /dev/null
+++ b/packages/cli/src/ui/commands/restoreCommand.ts
@@ -0,0 +1,155 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as fs from 'fs/promises';
+import path from 'path';
+import {
+  type CommandContext,
+  type SlashCommand,
+  type SlashCommandActionReturn,
+} from './types.js';
+import { Config } from '@google/gemini-cli-core';
+
+async function restoreAction(
+  context: CommandContext,
+  args: string,
+): Promise<void | SlashCommandActionReturn> {
+  const { services, ui } = context;
+  const { config, git: gitService } = services;
+  const { addItem, loadHistory } = ui;
+
+  const checkpointDir = config?.getProjectTempDir()
+    ? path.join(config.getProjectTempDir(), 'checkpoints')
+    : undefined;
+
+  if (!checkpointDir) {
+    return {
+      type: 'message',
+      messageType: 'error',
+      content: 'Could not determine the .gemini directory path.',
+    };
+  }
+
+  try {
+    // Ensure the directory exists before trying to read it.
+    await fs.mkdir(checkpointDir, { recursive: true });
+    const files = await fs.readdir(checkpointDir);
+    const jsonFiles = files.filter((file) => file.endsWith('.json'));
+
+    if (!args) {
+      if (jsonFiles.length === 0) {
+        return {
+          type: 'message',
+          messageType: 'info',
+          content: 'No restorable tool calls found.',
+        };
+      }
+      const truncatedFiles = jsonFiles.map((file) => {
+        const components = file.split('.');
+        if (components.length <= 1) {
+          return file;
+        }
+        components.pop();
+        return components.join('.');
+      });
+      const fileList = truncatedFiles.join('\n');
+      return {
+        type: 'message',
+        messageType: 'info',
+        content: `Available tool calls to restore:\n\n${fileList}`,
+      };
+    }
+
+    const selectedFile = args.endsWith('.json') ? args : `${args}.json`;
+
+    if (!jsonFiles.includes(selectedFile)) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: `File not found: ${selectedFile}`,
+      };
+    }
+
+    const filePath = path.join(checkpointDir, selectedFile);
+    const data = await fs.readFile(filePath, 'utf-8');
+    const toolCallData = JSON.parse(data);
+
+    if (toolCallData.history) {
+      if (!loadHistory) {
+        // This should not happen
+        return {
+          type: 'message',
+          messageType: 'error',
+          content: 'loadHistory function is not available.',
+        };
+      }
+      loadHistory(toolCallData.history);
+    }
+
+    if (toolCallData.clientHistory) {
+      await config?.getGeminiClient()?.setHistory(toolCallData.clientHistory);
+    }
+
+    if (toolCallData.commitHash) {
+      await gitService?.restoreProjectFromSnapshot(toolCallData.commitHash);
+      addItem(
+        {
+          type: 'info',
+          text: 'Restored project to the state before the tool call.',
+        },
+        Date.now(),
+      );
+    }
+
+    return {
+      type: 'tool',
+      toolName: toolCallData.toolCall.name,
+      toolArgs: toolCallData.toolCall.args,
+    };
+  } catch (error) {
+    return {
+      type: 'message',
+      messageType: 'error',
+      content: `Could not read restorable tool calls. This is the error: ${error}`,
+    };
+  }
+}
+
+async function completion(
+  context: CommandContext,
+  _partialArg: string,
+): Promise<string[]> {
+  const { services } = context;
+  const { config } = services;
+  const checkpointDir = config?.getProjectTempDir()
+    ? path.join(config.getProjectTempDir(), 'checkpoints')
+    : undefined;
+  if (!checkpointDir) {
+    return [];
+  }
+  try {
+    const files = await fs.readdir(checkpointDir);
+    return files
+      .filter((file) => file.endsWith('.json'))
+      .map((file) => file.replace('.json', ''));
+  } catch (_err) {
+    return [];
+  }
+}
+
+export const restoreCommand = (config: Config | null): SlashCommand | null => {
+  if (!config?.getCheckpointingEnabled()) {
+    return null;
+  }
+
+  return {
+    name: 'restore',
+    description:
+      'Restore a tool call. This will reset the conversation and file history to the state it was in when the tool call was suggested',
+    action: restoreAction,
+    completion,
+  };
+};
diff --git a/packages/cli/src/ui/commands/types.ts b/packages/cli/src/ui/commands/types.ts
index d3d5ee8a..51b66fb4 100644
--- a/packages/cli/src/ui/commands/types.ts
+++ b/packages/cli/src/ui/commands/types.ts
@@ -41,6 +41,12 @@ export interface CommandContext {
      * @param item The history item to display as pending, or `null` to clear.
      */
     setPendingItem: (item: HistoryItemWithoutId | null) => void;
+    /**
+     * Loads a new set of history items, replacing the current history.
+     *
+     * @param history The array of history items to load.
+     */
+    loadHistory: UseHistoryManagerReturn['loadHistory'];
   };
   // Session-specific data
   session: {