diff --git a/packages/shims/package.json b/packages/shims/package.json
index a257b5b88..120ae5f53 100644
--- a/packages/shims/package.json
+++ b/packages/shims/package.json
@@ -26,7 +26,7 @@
     "changelog:validate": "../../scripts/validate-changelog.sh @ocap/shims",
     "clean": "rimraf --glob ./dist './*.tsbuildinfo'",
     "publish:preview": "yarn npm publish --tag preview",
-    "test": "vitest run --config vitest.config.ts --passWithNoTests",
+    "test": "yarn build && vitest run --config vitest.config.ts --passWithNoTests",
     "test:clean": "yarn test --no-cache --coverage.clean",
     "test:dev": "yarn test --coverage false",
     "test:verbose": "yarn test --reporter verbose",
@@ -42,6 +42,7 @@
     "@metamask/auto-changelog": "^3.4.4",
     "deepmerge": "^4.3.1",
     "rimraf": "^6.0.1",
+    "vite": "^5.3.5",
     "vitest": "^2.0.5"
   },
   "engines": {
diff --git a/packages/shims/scripts/bundle.js b/packages/shims/scripts/bundle.js
index 45157d98d..b27a9f6d7 100644
--- a/packages/shims/scripts/bundle.js
+++ b/packages/shims/scripts/bundle.js
@@ -2,41 +2,47 @@ import 'ses';
 import '@endo/lockdown/commit.js';
 
 import bundleSource from '@endo/bundle-source';
-import { copyFile, mkdir, writeFile } from 'fs/promises';
+import { createReadStream, createWriteStream } from 'fs';
+import { mkdir } from 'fs/promises';
 import path from 'path';
 import { rimraf } from 'rimraf';
+import { Readable } from 'stream';
 import { fileURLToPath } from 'url';
 
 console.log('Bundling shims...');
 
-const rootDir = path.resolve(import.meta.dirname, '..');
+const rootDir = fileURLToPath(new URL('..', import.meta.url));
 const src = path.resolve(rootDir, 'src');
 const dist = path.resolve(rootDir, 'dist');
-const fileNames = {
-  endoify: 'endoify.mjs',
-  eventualSend: 'eventual-send.mjs',
-  applyLockdown: 'apply-lockdown.mjs',
-};
 
 await mkdir(dist, { recursive: true });
-await rimraf(`${dist}/*`);
-
-for (const fileName of [fileNames.endoify, fileNames.applyLockdown]) {
-  await copyFile(path.resolve(src, fileName), path.resolve(dist, fileName));
-}
-
-const eventualSendSourcePath = fileURLToPath(
-  import.meta.resolve('@endo/eventual-send/shim.js'),
-);
+await rimraf(`${dist}/*`, { glob: true });
+
+/**
+ * Bundles the target file as endoScript and returns the content as a readable stream.
+ *
+ * @param {string} specifier - Import path to the file to bundle, e.g. `'@endo/eventual-send/shim.js'`.
+ * @returns {Promise<Readable>} The bundled file contents as a Readable stream.
+ */
+const createEndoBundleReadStream = async (specifier) => {
+  const filePath = fileURLToPath(import.meta.resolve(specifier));
+  const { source: bundle } = await bundleSource(filePath, {
+    format: 'endoScript',
+  });
+  return Readable.from(bundle);
+};
 
-const { source: eventualSendBundleSource } = await bundleSource(
-  eventualSendSourcePath,
-  { format: 'endoScript' },
-);
+const sources = {
+  ses: createReadStream(
+    path.resolve(rootDir, '../../node_modules/ses/dist/ses.mjs'),
+  ),
+  eventualSend: await createEndoBundleReadStream('@endo/eventual-send/shim.js'),
+  shim: createReadStream(path.resolve(src, 'endoify.mjs')),
+};
 
-await writeFile(
-  path.resolve(dist, fileNames.eventualSend),
-  eventualSendBundleSource,
-);
+const target = createWriteStream(path.resolve(dist, 'endoify.mjs'));
 
-console.log('Success!');
+sources.ses.pipe(target, { end: false });
+sources.ses.on('end', () => sources.eventualSend.pipe(target, { end: false }));
+sources.eventualSend.on('end', () => sources.shim.pipe(target, { end: true }));
+sources.shim.on('end', () => console.log('Success!'));
diff --git a/packages/shims/src/endoify.mjs b/packages/shims/src/endoify.mjs
index 824aa9c32..40124f6f0 100644
--- a/packages/shims/src/endoify.mjs
+++ b/packages/shims/src/endoify.mjs
@@ -1,5 +1,6 @@
-import './ses.mjs';
-import './eventual-send.mjs';
+/* eslint-disable import-x/unambiguous */
+// @inline './ses.mjs';
+// @inline './eventual-send.mjs';
 
 lockdown({
   consoleTaming: 'unsafe',
@@ -9,3 +10,5 @@ lockdown({
   domainTaming: 'unsafe',
   overrideTaming: 'severe',
 });
+
+/* eslint-enable import-x/unambiguous */
diff --git a/packages/shims/src/endoify.test.ts b/packages/shims/src/endoify.test.ts
new file mode 100644
index 000000000..de8618c6c
--- /dev/null
+++ b/packages/shims/src/endoify.test.ts
@@ -0,0 +1,12 @@
+import { HandledPromise } from '@endo/eventual-send';
+import { describe, expect, it } from 'vitest';
+
+describe('endoified', () => {
+  it('calls lockdown', () => {
+    expect(Object.isFrozen(Array.prototype)).toBe(true); // Due to `lockdown()`, and therefore `ses`
+  });
+
+  it('loads eventual-send', () => {
+    expect(typeof HandledPromise).not.toBe('undefined'); // Due to eventual send
+  });
+});
diff --git a/packages/shims/src/vitest-environment-endoified.ts b/packages/shims/src/vitest-environment-endoified.ts
new file mode 100644
index 000000000..63a817387
--- /dev/null
+++ b/packages/shims/src/vitest-environment-endoified.ts
@@ -0,0 +1,25 @@
+import type { Context } from 'node:vm';
+import type { Environment } from 'vitest/environments';
+
+export default {
+  name: 'endoified',
+  transformMode: 'ssr',
+  async setupVM() {
+    const vm = await import('node:vm');
+    return {
+      getVmContext(): Context {
+        return vm.createContext({
+          setTimeout,
+          clearTimeout,
+        });
+      },
+      // eslint-disable-next-line no-empty-function
+      teardown(): void {},
+    };
+  },
+  async setup() {
+    throw new Error(
+      'endoified environment requires vitest option --pool=vmThreads or --pool=vmForks',
+    );
+  },
+} as Environment;
diff --git a/packages/shims/vitest.config.ts b/packages/shims/vitest.config.ts
index 2709902e1..4d7480d27 100644
--- a/packages/shims/vitest.config.ts
+++ b/packages/shims/vitest.config.ts
@@ -1,9 +1,23 @@
 // eslint-disable-next-line spaced-comment
 /// <reference types="vitest" />
 
+import { defineConfig, mergeConfig } from 'vite';
+
 import { getDefaultConfig } from '../../vitest.config.packages.js';
 
-const config = getDefaultConfig();
+const defaultConfig = getDefaultConfig();
+
+const config = mergeConfig(
+  defaultConfig,
+  defineConfig({
+    test: {
+      pool: 'vmThreads',
+      environment: './vitest-environment-endoified.ts',
+      setupFiles: '../dist/endoify.mjs',
+    },
+  }),
+);
+
 // @ts-expect-error We can and will delete this.
 delete config.test.coverage.thresholds;
 export default config;
diff --git a/yarn.lock b/yarn.lock
index d5df286f8..7dfab2953 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1324,6 +1324,7 @@ __metadata:
     deepmerge: "npm:^4.3.1"
     rimraf: "npm:^6.0.1"
     ses: "npm:^1.7.0"
+    vite: "npm:^5.3.5"
     vitest: "npm:^2.0.5"
   languageName: unknown
   linkType: soft