diff --git a/packages/php-wasm/node/src/lib/node-fs-mount.ts b/packages/php-wasm/node/src/lib/node-fs-mount.ts
index 7f7ab08106..e75adeac0a 100644
--- a/packages/php-wasm/node/src/lib/node-fs-mount.ts
+++ b/packages/php-wasm/node/src/lib/node-fs-mount.ts
@@ -1,7 +1,7 @@
 import type { MountHandler } from '@php-wasm/universal';
 
 export function createNodeFsMountHandler(localPath: string): MountHandler {
-	return async function (php, FS, vfsMountPoint) {
+	return function (php, FS, vfsMountPoint) {
 		FS.mount(FS.filesystems['NODEFS'], { root: localPath }, vfsMountPoint);
 		return () => {
 			FS!.unmount(vfsMountPoint);
diff --git a/packages/php-wasm/universal/src/lib/index.ts b/packages/php-wasm/universal/src/lib/index.ts
index 8fb02068b9..5ec07dcf71 100644
--- a/packages/php-wasm/universal/src/lib/index.ts
+++ b/packages/php-wasm/universal/src/lib/index.ts
@@ -76,6 +76,7 @@ export {
 
 export { isExitCode } from './is-exit-code';
 export { proxyFileSystem } from './proxy-file-system';
+export { sandboxedSpawnHandlerFactory } from './sandboxed-spawn-handler-factory';
 
 export * from './api';
 export type { WithAPIState as WithIsReady } from './api';
diff --git a/packages/php-wasm/universal/src/lib/sandboxed-spawn-handler-factory.ts b/packages/php-wasm/universal/src/lib/sandboxed-spawn-handler-factory.ts
new file mode 100644
index 0000000000..c61024337f
--- /dev/null
+++ b/packages/php-wasm/universal/src/lib/sandboxed-spawn-handler-factory.ts
@@ -0,0 +1,96 @@
+import { createSpawnHandler } from '@php-wasm/util';
+import type { PHPProcessManager } from './php-process-manager';
+
+/**
+ * An isomorphic proc_open() handler that implements typical shell in TypeScript
+ * without relying on a server runtime. It can be used in the browser and Node.js
+ * alike whenever you need to spawn a PHP subprocess, query the terminal size, etc.
+ * It is open for future expansion if more shell or busybox calls are needed, but
+ * advanced shell features such as piping, stream redirection etc. are outside of
+ * the scope of this minimal handler. If they become vital at any point, let's
+ * explore bringing in an actual shell implementation or at least a proper command
+ * parser.
+ */
+export function sandboxedSpawnHandlerFactory(
+	processManager: PHPProcessManager
+) {
+	return createSpawnHandler(async function (args, processApi, options) {
+		processApi.notifySpawn();
+		if (args[0] === 'exec') {
+			args.shift();
+		}
+
+		if (args[0].endsWith('.php') || args[0].endsWith('.phar')) {
+			args.unshift('php');
+		}
+
+		const binaryName = args[0].split('/').pop();
+
+		// Mock programs required by wp-cli:
+		if (
+			args[0] === '/usr/bin/env' &&
+			args[1] === 'stty' &&
+			args[2] === 'size'
+		) {
+			// These numbers are hardcoded because this
+			// spawnHandler is transmitted as a string to
+			// the PHP backend and has no access to local
+			// scope. It would be nice to find a way to
+			// transfer / proxy a live object instead.
+			// @TODO: Do not hardcode this
+			processApi.stdout(`18 140`);
+			processApi.exit(0);
+		} else if (binaryName === 'tput' && args[1] === 'cols') {
+			processApi.stdout(`140`);
+			processApi.exit(0);
+		} else if (binaryName === 'less') {
+			processApi.on('stdin', (data: Uint8Array) => {
+				processApi.stdout(data.buffer as ArrayBuffer);
+			});
+			processApi.exit(0);
+		} else if (binaryName === 'php') {
+			const { php, reap } = await processManager.acquirePHPInstance({
+				considerPrimary: false,
+			});
+
+			php.chdir(options.cwd as string);
+			try {
+				// Figure out more about setting env, putenv(), etc.
+				const result = await php.cli(args, {
+					env: {
+						...options.env,
+						SCRIPT_PATH: args[1],
+						// Set SHELL_PIPE to 0 to ensure WP-CLI formats
+						// the output as ASCII tables.
+						// @see https://github.com/wp-cli/wp-cli/issues/1102
+						SHELL_PIPE: '0',
+					},
+				});
+
+				result.stdout.pipeTo(
+					new WritableStream({
+						write(chunk) {
+							processApi.stdout(chunk.buffer as ArrayBuffer);
+						},
+					})
+				);
+				result.stderr.pipeTo(
+					new WritableStream({
+						write(chunk) {
+							processApi.stderr(chunk.buffer as ArrayBuffer);
+						},
+					})
+				);
+				processApi.exit(await result.exitCode);
+			} catch (e) {
+				// An exception here means the PHP runtime has crashed.
+				processApi.exit(1);
+				throw e;
+			} finally {
+				reap();
+			}
+		} else {
+			processApi.exit(1);
+		}
+	});
+}
diff --git a/packages/playground/cli/src/worker-thread.ts b/packages/playground/cli/src/worker-thread.ts
index 94e11003be..23ce53df41 100644
--- a/packages/playground/cli/src/worker-thread.ts
+++ b/packages/playground/cli/src/worker-thread.ts
@@ -7,6 +7,7 @@ import {
 	consumeAPI,
 	consumeAPISync,
 	exposeAPI,
+	sandboxedSpawnHandlerFactory,
 } from '@php-wasm/universal';
 import { sprintf } from '@php-wasm/util';
 import { bootWordPress } from '@wp-playground/wordpress';
@@ -186,6 +187,7 @@ export class PlaygroundCliWorker extends PHPWorker {
 				},
 				cookieStore: internalCookieStore ? undefined : false,
 				dataSqlPath,
+				spawnHandler: sandboxedSpawnHandlerFactory,
 			});
 			this.__internal_setRequestHandler(requestHandler);
 
diff --git a/packages/playground/wordpress/src/boot.ts b/packages/playground/wordpress/src/boot.ts
index 6cfa7826f2..e3c6df47b8 100644
--- a/packages/playground/wordpress/src/boot.ts
+++ b/packages/playground/wordpress/src/boot.ts
@@ -11,6 +11,7 @@ import {
 	PHPRequestHandler,
 	proxyFileSystem,
 	rotatePHPRuntime,
+	sandboxedSpawnHandlerFactory,
 	setPhpIniEntries,
 	withPHPIniValues,
 	writeFiles,
@@ -190,6 +191,7 @@ export async function bootWordPress(options: BootOptions) {
 }
 
 export async function bootRequestHandler(options: BootOptions) {
+	const spawnHandler = options.spawnHandler ?? sandboxedSpawnHandlerFactory;
 	async function createPhp(
 		requestHandler: PHPRequestHandler,
 		isPrimary: boolean
@@ -233,9 +235,9 @@ export async function bootRequestHandler(options: BootOptions) {
 
 		// Spawn handler is responsible for spawning processes for all the
 		// `popen()`, `proc_open()` etc. calls.
-		if (options.spawnHandler) {
+		if (spawnHandler) {
 			await php.setSpawnHandler(
-				options.spawnHandler(requestHandler.processManager)
+				spawnHandler(requestHandler.processManager)
 			);
 		}