diff --git a/src/resources/apps.ts b/src/resources/apps.ts
index b695501..c4ef381 100644
--- a/src/resources/apps.ts
+++ b/src/resources/apps.ts
@@ -1,5 +1,5 @@
 import type { HttpClient } from '../http-client';
-import type { AppType, PaginationOptions } from '../types';
+import type { AppType, BuildStack, PaginationOptions } from '../types';
 import { AutomationsResource } from './automations';
 import { BaseResource } from './base';
 import { BuildSourcesResource } from './build-sources';
@@ -30,6 +30,11 @@ export interface App {
    * The id of the default environment.
    */
   appEnvironmentId: string | null;
+  /**
+   * The default build stack for builds that do not specify one. `null` uses
+   * the Capawesome Cloud default.
+   */
+  buildStack: BuildStack | null;
   createdAt: string;
   updatedAt: string;
 }
@@ -65,6 +70,11 @@ export interface UpdateAppOptions {
   type?: AppType;
   appChannelId?: string | null;
   appEnvironmentId?: string | null;
+  /**
+   * The default build stack for builds that do not specify one. `null` uses
+   * the Capawesome Cloud default.
+   */
+  buildStack?: BuildStack | null;
   appChannelDiscoveryEnabled?: boolean;
   nextAppBuildNumber?: number;
 }
diff --git a/src/resources/automations.ts b/src/resources/automations.ts
index 4c4ab01..8cac5b3 100644
--- a/src/resources/automations.ts
+++ b/src/resources/automations.ts
@@ -74,9 +74,16 @@ export interface CreateAutomationOptions {
   appEnvironmentName?: string;
 }
 
-export interface UpdateAutomationOptions extends Partial<CreateAutomationOptions> {
+export interface UpdateAutomationOptions extends Omit<
+  Partial<CreateAutomationOptions>,
+  'buildStack'
+> {
   appId: string;
   automationId: string;
+  /**
+   * The build stack to use. `null` uses the app's default build stack.
+   */
+  buildStack?: BuildStack | null;
   enabled?: boolean;
 }
 
diff --git a/src/types.ts b/src/types.ts
index bd5ad13..d010dfd 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -21,7 +21,7 @@ export type GitProvider = 'azure_devops' | 'bitbucket' | 'gitea' | 'git_http' |
 /**
  * The macOS stack used to run a native build.
  */
-export type BuildStack = 'macos-sequoia' | 'macos-tahoe';
+export type BuildStack = 'macos-sequoia' | 'macos-tahoe' | 'macos-golden-gate';
 
 /**
  * The type of a native build.
diff --git a/test/resources.test.ts b/test/resources.test.ts
index 033b565..9fb798c 100644
--- a/test/resources.test.ts
+++ b/test/resources.test.ts
@@ -188,6 +188,18 @@ describe('resources', () => {
     expect(url.searchParams.get('name')).toBe('My App');
   });
 
+  it('clears the default build stack of an app', async () => {
+    const { getLastRequest } = mockFetchJson({ id: 'app-1', buildStack: null });
+    const client = new CapawesomeCloud({ token: 't' });
+
+    await client.apps.update({ appId: 'app-1', buildStack: null });
+
+    const { url, init } = getLastRequest();
+    expect(init.method).toBe('PATCH');
+    expect(url).toBe('https://api.cloud.capawesome.io/v1/apps/app-1');
+    expect(JSON.parse(init.body as string)).toEqual({ buildStack: null });
+  });
+
   it('filters teams by name', async () => {
     const { getLastRequest } = mockFetchJson([]);
     const client = new CapawesomeCloud({ token: 't' });