5 files changed, 85 insertions, 9 deletions
diff --git a/packages/cli/src/ui/commands/themeCommand.test.ts b/packages/cli/src/ui/commands/themeCommand.test.ts
new file mode 100644
index 00000000..2a537bcc
--- /dev/null
+++ b/packages/cli/src/ui/commands/themeCommand.test.ts
@@ -0,0 +1,38 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest';
+import { themeCommand } from './themeCommand.js';
+import { type CommandContext } from './types.js';
+import { createMockCommandContext } from '../../test-utils/mockCommandContext.js';
+
+describe('themeCommand', () => {
+  let mockContext: CommandContext;
+
+  beforeEach(() => {
+    mockContext = createMockCommandContext();
+  });
+
+  it('should return a dialog action to open the theme dialog', () => {
+    // Ensure the command has an action to test.
+    if (!themeCommand.action) {
+      throw new Error('The theme command must have an action.');
+    }
+
+    const result = themeCommand.action(mockContext, '');
+
+    // Assert that the action returns the correct object to trigger the theme dialog.
+    expect(result).toEqual({
+      type: 'dialog',
+      dialog: 'theme',
+    });
+  });
+
+  it('should have the correct name and description', () => {
+    expect(themeCommand.name).toBe('theme');
+    expect(themeCommand.description).toBe('change the theme');
+  });
+});
diff --git a/packages/cli/src/ui/commands/themeCommand.ts b/packages/cli/src/ui/commands/themeCommand.ts
new file mode 100644
index 00000000..29e9a491
--- /dev/null
+++ b/packages/cli/src/ui/commands/themeCommand.ts
@@ -0,0 +1,16 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { OpenDialogActionReturn, SlashCommand } from './types.js';
+
+export const themeCommand: SlashCommand = {
+  name: 'theme',
+  description: 'change the theme',
+  action: (_context, _args): OpenDialogActionReturn => ({
+    type: 'dialog',
+    dialog: 'theme',
+  }),
+};
diff --git a/packages/cli/src/ui/commands/types.ts b/packages/cli/src/ui/commands/types.ts
index 09682d7a..9aad3399 100644
--- a/packages/cli/src/ui/commands/types.ts
+++ b/packages/cli/src/ui/commands/types.ts
@@ -66,7 +66,7 @@ export interface MessageActionReturn {
 export interface OpenDialogActionReturn {
   type: 'dialog';
   // TODO: Add 'theme' | 'auth' | 'editor' | 'privacy' as migration happens.
-  dialog: 'help';
+  dialog: 'help' | 'theme';
 }
 
 export type SlashCommandActionReturn =
diff --git a/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts b/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
index 45f52074..563092a2 100644
--- a/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
+++ b/packages/cli/src/ui/hooks/slashCommandProcessor.test.ts
@@ -507,6 +507,32 @@ describe('useSlashCommandProcessor', () => {
       expect(commandResult).toEqual({ type: 'handled' });
     });
 
+    it('should open the theme dialog when a new command returns a theme dialog action', async () => {
+      const mockAction = vi.fn().mockResolvedValue({
+        type: 'dialog',
+        dialog: 'theme',
+      });
+      const newCommand: SlashCommand = { name: 'test', action: mockAction };
+      const mockLoader = async () => [newCommand];
+      const commandServiceInstance = new ActualCommandService(mockLoader);
+      vi.mocked(CommandService).mockImplementation(
+        () => commandServiceInstance,
+      );
+
+      const { result } = getProcessorHook();
+      await vi.waitFor(() => {
+        expect(
+          result.current.slashCommands.some((c) => c.name === 'test'),
+        ).toBe(true);
+      });
+
+      const commandResult = await result.current.handleSlashCommand('/test');
+
+      expect(mockAction).toHaveBeenCalledTimes(1);
+      expect(mockOpenThemeDialog).toHaveBeenCalledWith();
+      expect(commandResult).toEqual({ type: 'handled' });
+    });
+
     it('should show help for a parent command with no action', async () => {
       const parentCommand: SlashCommand = {
         name: 'parent',
diff --git a/packages/cli/src/ui/hooks/slashCommandProcessor.ts b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
index f53bdc12..59f748bf 100644
--- a/packages/cli/src/ui/hooks/slashCommandProcessor.ts
+++ b/packages/cli/src/ui/hooks/slashCommandProcessor.ts
@@ -243,13 +243,6 @@ export const useSlashCommandProcessor = (
         },
       },
       {
-        name: 'theme',
-        description: 'change the theme',
-        action: (_mainCommand, _subCommand, _args) => {
-          openThemeDialog();
-        },
-      },
-      {
         name: 'auth',
         description: 'change the auth method',
         action: (_mainCommand, _subCommand, _args) => openAuthDialog(),
@@ -1034,7 +1027,6 @@ export const useSlashCommandProcessor = (
     return commands;
   }, [
     addMessage,
-    openThemeDialog,
     openAuthDialog,
     openEditorDialog,
     openPrivacyNotice,
@@ -1133,6 +1125,9 @@ export const useSlashCommandProcessor = (
                   case 'help':
                     setShowHelp(true);
                     return { type: 'handled' };
+                  case 'theme':
+                    openThemeDialog();
+                    return { type: 'handled' };
                   default: {
                     const unhandled: never = result.dialog;
                     throw new Error(
@@ -1214,6 +1209,7 @@ export const useSlashCommandProcessor = (
       legacyCommands,
       commandContext,
       addMessage,
+      openThemeDialog,
     ],
   );