diff --git a/packages/dev-test/package.json b/packages/dev-test/package.json
index c836614..339306b 100644
--- a/packages/dev-test/package.json
+++ b/packages/dev-test/package.json
@@ -15,7 +15,7 @@
   },
   "sideEffects": false,
   "type": "module",
-  "version": "0.86.7",
+  "version": "0.86.8",
   "main": "./index.js",
   "exports": {
     "./globals.d.ts": "./src/globals.d.ts"
diff --git a/packages/dev-test/src/env/browser.spec.ts b/packages/dev-test/src/env/browser.spec.ts
index 47f0018..690ff88 100644
--- a/packages/dev-test/src/env/browser.spec.ts
+++ b/packages/dev-test/src/env/browser.spec.ts
@@ -1,6 +1,9 @@
 // Copyright 2017-2026 @pezkuwi/dev-test authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
+import { createHash } from 'node:crypto';
+import { createServer } from 'node:http';
+
 import { browser } from './browser.js';
 
 const all = browser();
@@ -18,6 +21,7 @@ describe('browser', () => {
   it('contains the top-level objects', () => {
     expect(all.document).toBeDefined();
     expect(all.navigator).toBeDefined();
+    expect(location.href).toBe('http://localhost/');
   });
 
   it('contains HTML*Element', () => {
@@ -61,4 +65,49 @@ describe('browser', () => {
     expect(() => window.dispatchEvent(new CustomEvent('custom', { detail: 1 }))).not.toThrow();
     expect(() => window.dispatchEvent(new Event('plain'))).not.toThrow();
   });
+
+  it('opens a WebSocket and exchanges a message', async () => {
+    // the smallest server that completes the RFC 6455 handshake and sends one text frame
+    const server = createServer();
+    // an upgraded socket leaves the server's tracking, so it is closed here
+    const sockets: { destroy: () => void }[] = [];
+
+    server.on('upgrade', (req, socket) => {
+      sockets.push(socket);
+
+      const accept = createHash('sha1')
+        .update(`${String(req.headers['sec-websocket-key'])}258EAFA5-E914-47DA-95CA-C5AB0DC85B11`)
+        .digest('base64');
+
+      socket.write(`HTTP/1.1 101 Switching Protocols\r\nUpgrade: websocket\r\nConnection: Upgrade\r\nSec-WebSocket-Accept: ${accept}\r\n\r\n`);
+      socket.write(Buffer.from([0x81, 0x02, 0x68, 0x69]));
+    });
+
+    await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve));
+
+    const { port } = server.address() as { port: number };
+    const ws = new WebSocket(`ws://127.0.0.1:${port}`);
+
+    try {
+      const received = await new Promise<string>((resolve, reject) => {
+        const timer = setTimeout(() => reject(new Error('no message within 5s')), 5_000);
+
+        ws.onmessage = (event) => {
+          clearTimeout(timer);
+          resolve(String(event.data));
+        };
+
+        ws.onerror = () => {
+          clearTimeout(timer);
+          reject(new Error('WebSocket error'));
+        };
+      });
+
+      expect(received).toBe('hi');
+    } finally {
+      ws.close();
+      sockets.forEach((socket) => socket.destroy());
+      await new Promise((resolve) => server.close(resolve));
+    }
+  });
 });
diff --git a/packages/dev-test/src/env/browser.ts b/packages/dev-test/src/env/browser.ts
index fda9a8b..07d079d 100644
--- a/packages/dev-test/src/env/browser.ts
+++ b/packages/dev-test/src/env/browser.ts
@@ -9,8 +9,13 @@ import { JSDOM } from 'jsdom';
  * Constructors that Node defines as well. A DOM node only accepts an event
  * created in its own realm, so in the browser environment the JSDOM ones
  * replace Node's, as they do under jest-environment-jsdom.
+ *
+ * WebSocket follows from that: Node's own dispatches its events through
+ * Node's EventTarget, which rejects the JSDOM Event that replaced Node's, so
+ * no open, message or error ever reaches a listener and a connection never
+ * comes up. JSDOM's WebSocket dispatches events from its own realm.
  */
-export const BROWSER_OVERRIDES: readonly string[] = ['CustomEvent', 'Event'];
+export const BROWSER_OVERRIDES: readonly string[] = ['CustomEvent', 'Event', 'WebSocket'];
 
 /**
  * JSDOM does no layout, so no element ever changes size and the callback
@@ -62,6 +67,13 @@ function events (window: DOMWindow) {
   };
 }
 
+/** Network, see BROWSER_OVERRIDES for why WebSocket is JSDOM's */
+function network (window: DOMWindow) {
+  return {
+    WebSocket: window.WebSocket
+  };
+}
+
 /** Styles, geometry and the observers */
 function layout (window: DOMWindow) {
   return {
@@ -90,6 +102,7 @@ export function browser () {
     ...nodes(window),
     ...events(window),
     ...layout(window),
+    ...network(window),
     // All HTML Elements that are defined on the JSDOM window object.
     // (we copied as-is from the types definition). We cannot get this
     // via Object.keys(window).filter(...) so we have to specify explicitly
@@ -168,6 +181,7 @@ export function browser () {
     crypto: window.crypto,
     document: window.document,
     localStorage: window.localStorage,
+    location: window.location,
     navigator: window.navigator,
     // window...
     window
diff --git a/packages/dev-test/src/packageInfo.ts b/packages/dev-test/src/packageInfo.ts
index d67254e..5ba5961 100644
--- a/packages/dev-test/src/packageInfo.ts
+++ b/packages/dev-test/src/packageInfo.ts
@@ -3,4 +3,4 @@
 
 // Do not edit, auto-generated by @pezkuwi/dev
 
-export const packageInfo = { name: '@pezkuwi/dev-test', path: 'auto', type: 'auto', version: '0.86.7' };
+export const packageInfo = { name: '@pezkuwi/dev-test', path: 'auto', type: 'auto', version: '0.86.8' };
diff --git a/packages/dev-ts/package.json b/packages/dev-ts/package.json
index e63fa69..5679996 100644
--- a/packages/dev-ts/package.json
+++ b/packages/dev-ts/package.json
@@ -15,7 +15,7 @@
   },
   "sideEffects": false,
   "type": "module",
-  "version": "0.86.7",
+  "version": "0.86.8",
   "main": "./index.js",
   "exports": {
     "./globals.d.ts": "./src/globals.d.ts"
diff --git a/packages/dev-ts/src/packageInfo.ts b/packages/dev-ts/src/packageInfo.ts
index b6cff06..1f9f3ca 100644
--- a/packages/dev-ts/src/packageInfo.ts
+++ b/packages/dev-ts/src/packageInfo.ts
@@ -3,4 +3,4 @@
 
 // Do not edit, auto-generated by @pezkuwi/dev
 
-export const packageInfo = { name: '@pezkuwi/dev-ts', path: 'auto', type: 'auto', version: '0.86.7' };
+export const packageInfo = { name: '@pezkuwi/dev-ts', path: 'auto', type: 'auto', version: '0.86.8' };
diff --git a/packages/dev/package.json b/packages/dev/package.json
index 6b1d0de..26e898f 100644
--- a/packages/dev/package.json
+++ b/packages/dev/package.json
@@ -15,7 +15,7 @@
   },
   "sideEffects": false,
   "type": "module",
-  "version": "0.86.7",
+  "version": "0.86.8",
   "bin": {
     "pezkuwi-ci-ghact-build": "./scripts/pezkuwi-ci-ghact-build.mjs",
     "pezkuwi-ci-ghact-docs": "./scripts/pezkuwi-ci-ghact-docs.mjs",
@@ -52,8 +52,8 @@
   "dependencies": {
     "@eslint/compat": "^2.1.1",
     "@eslint/js": "^10.0.1",
-    "@pezkuwi/dev-test": "^0.86.7",
-    "@pezkuwi/dev-ts": "^0.86.7",
+    "@pezkuwi/dev-test": "^0.86.8",
+    "@pezkuwi/dev-ts": "^0.86.8",
     "@rollup/plugin-alias": "^5.1.1",
     "@rollup/plugin-commonjs": "^29.0.3",
     "@rollup/plugin-dynamic-import-vars": "^2.1.5",
diff --git a/packages/dev/scripts/pezkuwi-dev-build-ts.mjs b/packages/dev/scripts/pezkuwi-dev-build-ts.mjs
index c1a1ff6..428494a 100755
--- a/packages/dev/scripts/pezkuwi-dev-build-ts.mjs
+++ b/packages/dev/scripts/pezkuwi-dev-build-ts.mjs
@@ -4,6 +4,7 @@
 
 import JSON5 from 'json5';
 import fs from 'node:fs';
+import { builtinModules } from 'node:module';
 import path from 'node:path';
 import process from 'node:process';
 import ts from 'typescript';
@@ -32,8 +33,9 @@ const TARGET_TSES = ts.ScriptTarget.ES2022;
 const TARGET_NODE = '>=18';
 
 const IGNORE_IMPORTS = [
-  // node (new-style)
-  ...['assert', 'child_process', 'crypto', 'fs', 'module', 'os', 'path', 'process', 'readline', 'test', 'url', 'util'].map((m) => `node:${m}`),
+  // node (new-style): every builtin, none of them is a package.json dependency.
+  // Some are listed with the prefix already (node:test, node:sqlite).
+  ...builtinModules.map((m) => m.startsWith('node:') ? m : `node:${m}`),
   // other
   '@testing-library/react',
   'react', 'react-native', 'styled-components'
diff --git a/packages/dev/src/packageInfo.ts b/packages/dev/src/packageInfo.ts
index e138bc1..51a0879 100644
--- a/packages/dev/src/packageInfo.ts
+++ b/packages/dev/src/packageInfo.ts
@@ -3,4 +3,4 @@
 
 // Do not edit, auto-generated by @pezkuwi/dev
 
-export const packageInfo = { name: '@pezkuwi/dev', path: 'auto', type: 'auto', version: '0.86.7' };
+export const packageInfo = { name: '@pezkuwi/dev', path: 'auto', type: 'auto', version: '0.86.8' };
diff --git a/yarn.lock b/yarn.lock
index a7720ca..08fd13d 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1189,7 +1189,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@pezkuwi/dev-test@npm:^0.86.7, @pezkuwi/dev-test@workspace:packages/dev-test":
+"@pezkuwi/dev-test@npm:^0.86.8, @pezkuwi/dev-test@workspace:packages/dev-test":
   version: 0.0.0-use.local
   resolution: "@pezkuwi/dev-test@workspace:packages/dev-test"
   dependencies:
@@ -1205,7 +1205,7 @@ __metadata:
   languageName: unknown
   linkType: soft
 
-"@pezkuwi/dev-ts@npm:^0.86.7, @pezkuwi/dev-ts@workspace:packages/dev-ts":
+"@pezkuwi/dev-ts@npm:^0.86.8, @pezkuwi/dev-ts@workspace:packages/dev-ts":
   version: 0.0.0-use.local
   resolution: "@pezkuwi/dev-ts@workspace:packages/dev-ts"
   dependencies:
@@ -1221,8 +1221,8 @@ __metadata:
   dependencies:
     "@eslint/compat": "npm:^2.1.1"
     "@eslint/js": "npm:^10.0.1"
-    "@pezkuwi/dev-test": "npm:^0.86.7"
-    "@pezkuwi/dev-ts": "npm:^0.86.7"
+    "@pezkuwi/dev-test": "npm:^0.86.8"
+    "@pezkuwi/dev-ts": "npm:^0.86.8"
     "@rollup/plugin-alias": "npm:^5.1.1"
     "@rollup/plugin-commonjs": "npm:^29.0.3"
     "@rollup/plugin-dynamic-import-vars": "npm:^2.1.5"