fix(sea-builder): make --node's omitted default match its docs

packages/sea-builder/CHANGELOG.md

@@ -38,6 +38,12 @@ project adheres to
   permanent download cache (#72).
 - Stopped `devPreinstall` from executing unpinned `pnpm dlx` packages
   (#76).
+- Made `--node`'s omitted default match its documentation: `sea-builder`
+  now actually resolves the latest patch of the oldest supported LTS
+  line when the option isn't passed, instead of silently embedding
+  whatever Node.js version happened to run the build, making SEA
+  builds reproducible across machines. The resolved version is now
+  also shown in the build output (#59).
 
 ## [0.21.0] - 2025-10-03
 

packages/sea-builder/README.md

@@ -45,7 +45,8 @@ as `linux-x64` or `win32-x64`. `sea-builder` automatically invokes
 `sea-builder` also accepts a `--node` option to choose the Node.js version.
 Omitting this option uses the latest patch of the oldest supported LTS line.
 Passing `--node=22` is equivalent to specifying `^22`, while
-`--node=22.23` behaves like `~22.23`.
+`--node=22.23` behaves like `~22.23`. The resolved version is shown in
+the build output.
 
 ### Cache directory
 

packages/sea-builder/src/listr2/createBuildTasks.mts

@@ -27,7 +27,7 @@ export const createBuildTasks = async (
   options: BuildTasksOptions,
 ): Promise<Listr> => {
   const { arch, platform = process.platform, projectRoot } = options;
-  const { basename, download, execa, existsSync, mkdir, nodeVersion, targets } =
+  const { basename, download, execa, existsSync, mkdir, targets } =
     await normalizeBuildOptions(options);
   return new Listr([
     createBuildTask(execa),
@@ -36,7 +36,7 @@ export const createBuildTasks = async (
       download,
       existsSync,
       mkdir,
-      nodeVersion: await resolveNodeVersion(nodeVersion),
+      nodeVersion: await resolveNodeVersion(options.nodeVersion),
       platform,
       projectRoot,
       targets,

packages/sea-builder/src/listr2/createBuildTasks.spec.mts

@@ -0,0 +1,66 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { createBuildTasks } from './createBuildTasks.mjs';
+
+const mocks = vi.hoisted(() => ({
+  createBuildTask: vi.fn(() => ({ task: vi.fn(), title: 'Build' })),
+  createCacheTask: vi.fn(() => ({ task: vi.fn(), title: 'Cache' })),
+  createSeaTask: vi.fn(() => ({ task: vi.fn(), title: 'Sea' })),
+  normalizeBuildOptions: vi.fn(),
+  resolveNodeVersion: vi.fn(),
+}));
+
+vi.mock('../tasks/createBuildTask.mjs', () => ({
+  createBuildTask: mocks.createBuildTask,
+}));
+
+vi.mock('../tasks/createCacheTask.mjs', () => ({
+  createCacheTask: mocks.createCacheTask,
+}));
+
+vi.mock('../tasks/createSeaTask.mjs', () => ({
+  createSeaTask: mocks.createSeaTask,
+}));
+
+vi.mock('../tasks/normalizeBuildOptions.mjs', () => ({
+  normalizeBuildOptions: mocks.normalizeBuildOptions,
+}));
+
+vi.mock('../utils/resolveNodeVersion.mjs', () => ({
+  resolveNodeVersion: mocks.resolveNodeVersion,
+}));
+
+describe('createBuildTasks', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mocks.normalizeBuildOptions.mockResolvedValue({
+      basename: 'foo',
+      download: vi.fn(),
+      execa: vi.fn(),
+      existsSync: vi.fn(),
+      mkdir: vi.fn(),
+      // A pre-defaulted value, distinct from the raw option, so a
+      // regression that resolves this instead of the raw option is
+      // caught by the assertions below.
+      nodeVersion: 'v20.19.5',
+      targets: ['linux-x64'],
+    });
+    mocks.resolveNodeVersion.mockResolvedValue('v22.23.2');
+  });
+
+  it('resolves the node version from the raw option, not the pre-defaulted one', async () => {
+    await createBuildTasks({ basename: 'foo' });
+    expect(mocks.resolveNodeVersion).toHaveBeenCalledWith(undefined);
+  });
+
+  it('passes an explicit --node spec through untouched', async () => {
+    await createBuildTasks({ basename: 'foo', nodeVersion: '20' });
+    expect(mocks.resolveNodeVersion).toHaveBeenCalledWith('20');
+  });
+
+  it('passes the resolved node version to createCacheTask', async () => {
+    await createBuildTasks({ basename: 'foo' });
+    expect(mocks.createCacheTask).toHaveBeenCalledWith(
+      expect.objectContaining({ nodeVersion: 'v22.23.2' }),
+    );
+  });
+});

packages/sea-builder/src/tasks/createCacheTask.mts

@@ -8,6 +8,8 @@ import type { Task } from './createTaskFactory.mjs';
  * @returns Listr task object.
  */
 export const createCacheTask = (opts: CacheOptions): Task => ({
-  title: 'Download the Node.js archives',
+  title: opts.nodeVersion
+    ? `Download the Node.js archives (${opts.nodeVersion})`
+    : 'Download the Node.js archives',
   task: () => createListrCacheTasks(opts).run(),
 });

packages/sea-builder/src/tasks/createCacheTask.spec.mts

@@ -15,4 +15,9 @@ describe('createCacheTask', () => {
 
   it('sets title', () =>
     expect(createCacheTask(opts).title).toBe('Download the Node.js archives'));
+
+  it('includes the resolved Node.js version in the title when provided', () =>
+    expect(createCacheTask({ ...opts, nodeVersion: 'v22.23.2' }).title).toBe(
+      'Download the Node.js archives (v22.23.2)',
+    ));
 });