feat(cli): add /note slash command to append or view notes

packages/cli/src/services/BuiltinCommandLoader.ts

@@ -42,6 +42,7 @@ import { initCommand } from '../ui/commands/initCommand.js';
 import { mcpCommand } from '../ui/commands/mcpCommand.js';
 import { memoryCommand } from '../ui/commands/memoryCommand.js';
 import { modelCommand } from '../ui/commands/modelCommand.js';
+import { noteCommand } from '../ui/commands/noteCommand.js';
 import { oncallCommand } from '../ui/commands/oncallCommand.js';
 import { permissionsCommand } from '../ui/commands/permissionsCommand.js';
 import { planCommand } from '../ui/commands/planCommand.js';
@@ -184,6 +185,7 @@ export class BuiltinCommandLoader implements ICommandLoader {
         : [mcpCommand]),
       memoryCommand,
       modelCommand,
+      noteCommand,
       ...(this.config?.getFolderTrust() ? [permissionsCommand] : []),
       ...(this.config?.isPlanEnabled() ? [planCommand] : []),
       policiesCommand,

packages/cli/src/ui/commands/noteCommand.test.ts

@@ -0,0 +1,75 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import fs from 'node:fs/promises';
+import path from 'node:path';
+import { noteCommand } from './noteCommand.js';
+import { type CommandContext } from './types.js';
+
+vi.mock('node:fs/promises');
+
+describe('noteCommand', () => {
+  const mockContext = {} as CommandContext;
+  const notesPath = path.join(process.cwd(), 'notes.md');
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('should return notes content when no args provided and file exists', async () => {
+    vi.mocked(fs.readFile).mockResolvedValue('existing note\n');
+
+    const result = await noteCommand.action!(mockContext, '');
+
+    expect(fs.readFile).toHaveBeenCalledWith(notesPath, 'utf8');
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'info',
+      content: expect.stringContaining('existing note'),
+    });
+  });
+
+  it('should return info message when no args provided and file does not exist', async () => {
+    vi.mocked(fs.readFile).mockRejectedValue(new Error('File not found'));
+
+    const result = await noteCommand.action!(mockContext, '  ');
+
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'info',
+      content: 'No notes found. Use "/note <text>" to add one.',
+    });
+  });
+
+  it('should append note to file when args are provided', async () => {
+    const note = 'this is a new note';
+    vi.mocked(fs.appendFile).mockResolvedValue(undefined);
+
+    const result = await noteCommand.action!(mockContext, note);
+
+    expect(fs.appendFile).toHaveBeenCalledWith(notesPath, `${note}\n`);
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'info',
+      content: expect.stringContaining('Note added'),
+    });
+  });
+
+  it('should return error message when append fails', async () => {
+    vi.mocked(fs.appendFile).mockRejectedValue(new Error('Permission denied'));
+
+    const result = await noteCommand.action!(mockContext, 'some note');
+
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'error',
+      content: expect.stringContaining(
+        'Failed to save note: Permission denied',
+      ),
+    });
+  });
+});

packages/cli/src/ui/commands/noteCommand.ts

@@ -0,0 +1,51 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import fs from 'node:fs/promises';
+import path from 'node:path';
+import { CommandKind, type SlashCommand } from './types.js';
+
+export const noteCommand: SlashCommand = {
+  name: 'note',
+  description: 'Append a note to notes.md or view current notes',
+  kind: CommandKind.BUILT_IN,
+  autoExecute: true,
+  action: async (_context, args) => {
+    const notesPath = path.join(process.cwd(), 'notes.md');
+
+    if (!args || args.trim().length === 0) {
+      try {
+        const content = await fs.readFile(notesPath, 'utf8');
+        return {
+          type: 'message',
+          messageType: 'info',
+          content: `Current notes in ${notesPath}:\n\n${content}`,
+        };
+      } catch {
+        return {
+          type: 'message',
+          messageType: 'info',
+          content: 'No notes found. Use "/note <text>" to add one.',
+        };
+      }
+    }
+
+    try {
+      await fs.appendFile(notesPath, `${args}\n`);
+      return {
+        type: 'message',
+        messageType: 'info',
+        content: `Note added to ${notesPath}`,
+      };
+    } catch (error) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: `Failed to save note: ${error instanceof Error ? error.message : String(error)}`,
+      };
+    }
+  },
+};