feat: Add /undo command to revert last conversation turn #18708

packages/cli/src/services/BuiltinCommandLoader.ts

@@ -34,6 +34,7 @@ import { extensionsCommand } from '../ui/commands/extensionsCommand.js';
 import { helpCommand } from '../ui/commands/helpCommand.js';
 import { shortcutsCommand } from '../ui/commands/shortcutsCommand.js';
 import { rewindCommand } from '../ui/commands/rewindCommand.js';
+import { undoCommand } from '../ui/commands/undoCommand.js';
 import { hooksCommand } from '../ui/commands/hooksCommand.js';
 import { ideCommand } from '../ui/commands/ideCommand.js';
 import { initCommand } from '../ui/commands/initCommand.js';
@@ -122,6 +123,7 @@ export class BuiltinCommandLoader implements ICommandLoader {
       shortcutsCommand,
       ...(this.config?.getEnableHooksUI() ? [hooksCommand] : []),
       rewindCommand,
+      undoCommand,
       await ideCommand(),
       initCommand,
       ...(isNightlyBuild ? [oncallCommand] : []),

packages/cli/src/ui/commands/rewindCommand.tsx

@@ -37,7 +37,7 @@ import {
  * @param messageId The ID of the message to rewind to.
  * @param newText The new text for the input field after rewinding.
  */
-async function rewindConversation(
+export async function rewindConversation(
   context: CommandContext,
   client: GeminiClient,
   recordingService: ChatRecordingService,

packages/cli/src/ui/commands/undoCommand.tsx

@@ -0,0 +1,57 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { CommandKind, type SlashCommand } from './types.js';
+import { rewindConversation } from './rewindCommand.js';
+import { partToString } from '@google/gemini-cli-core';
+
+export const undoCommand: SlashCommand = {
+  name: 'undo',
+  description: 'Revert the last conversation turn',
+  kind: CommandKind.BUILT_IN,
+  action: async (context) => {
+    const client = context.services.config?.getGeminiClient();
+    const recordingService = client?.getChatRecordingService();
+    const conversation = recordingService?.getConversation();
+
+    if (!client || !recordingService || !conversation) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: 'Undo unavailable.',
+      };
+    }
+
+    const messages = conversation.messages;
+    const lastUserIndex = messages.findLastIndex((m) => m.type === 'user');
+
+    // User message and a model response to undo turn
+    if (messages.length < 2) {
+      return {
+        type: 'message',
+        messageType: 'info',
+        content: 'Nothing to undo.',
+      };
+    }
+
+    const targetId = messages[lastUserIndex].id;
+    const lastUserPrompt = messages[lastUserIndex].content;
+
+    await rewindConversation(
+      context,
+      client,
+      recordingService,
+      targetId,
+      partToString(lastUserPrompt),
+    );
+
+    return {
+      type: 'message',
+      messageType: 'info',
+      content: 'Undid last turn.',
+    };
+  },
+};