diff --git a/mock-server/README.md b/mock-server/README.md
index 29ef9b12..6ab62d25 100644
--- a/mock-server/README.md
+++ b/mock-server/README.md
@@ -2,4 +2,17 @@
 
 This is a simple mock server for use in client tests. It just serves a bunch of static files from `sdk-test-data` at the appropriate locations.
 
-See `prepare.sh` for the list of files served.
+The mock server may serve multiple "environments" at the same time at different prefixes, so the base URL format is `http://localhost:8378/{env_name}/api`.
+
+We currently have three:
+- `ufc` is the default `flags-v1.json`.
+- `obfuscated` is the obfuscated version of `ufc`.
+- `bandits` is bandit flags and bandit models.
+
+See `prepare.js` for the full list of files and environments served.
+
+# Q&A
+
+## Why port 8378?
+
+8378 is "test" in T9.
diff --git a/mock-server/package.json b/mock-server/package.json
index 21332d2e..3aa3c894 100644
--- a/mock-server/package.json
+++ b/mock-server/package.json
@@ -1,7 +1,8 @@
 {
   "private": true,
+  "type": "module",
   "scripts": {
-    "prestart": "./prepare.sh",
+    "prestart": "node ./prepare.js",
     "start": "http-server -p 8378 -a 127.0.0.1 --cors"
   },
   "dependencies": {
diff --git a/mock-server/prepare.js b/mock-server/prepare.js
new file mode 100644
index 00000000..d9ee7b5b
--- /dev/null
+++ b/mock-server/prepare.js
@@ -0,0 +1,45 @@
+// This is a prepare script that is automatically run before "start" command.
+//
+// It is repsonsible to copy files from sdk-test-data into the proper
+import fs from 'node:fs/promises';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+// The format here is:
+// env name -> { api path -> file relative to sdk-test-data }
+const envs = {
+  ufc: {
+    'api/flag-config/v1/config': 'ufc/flags-v1.json',
+  },
+  obfuscated: {
+    'api/flag-config/v1/config': 'ufc/flags-v1-obfuscated.json',
+  },
+  bandit: {
+    'api/flag-config/v1/config': 'ufc/bandit-flags-v1.json',
+    'api/flag-config/v1/bandits': 'ufc/bandit-models-v1.json',
+  }
+}
+
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const sdkTestDataPath = path.join(__dirname, '../sdk-test-data/')
+const publicPath = path.join(__dirname, './public/')
+
+try {
+  await fs.rm(path.join(__dirname, 'public'), {recursive: true});
+} catch {
+  // ignore if it's not present
+}
+
+for (const [env, links] of Object.entries(envs)) {
+  for (const [target, source] of Object.entries(links)) {
+    const sourcePath = path.join(sdkTestDataPath, source);
+    const targetPath = path.join(publicPath, env, target);
+
+    console.log(sourcePath, '->', targetPath);
+
+    await fs.mkdir(path.dirname(targetPath), { recursive: true });
+    console.log('mkdir', path.dirname(targetPath));
+    await fs.copyFile(sourcePath, targetPath);
+  }
+}
diff --git a/mock-server/prepare.sh b/mock-server/prepare.sh
deleted file mode 100755
index f1eaafbc..00000000
--- a/mock-server/prepare.sh
+++ /dev/null
@@ -1,12 +0,0 @@
-#!/usr/bin/env sh
-set -e
-
-cd "$(dirname "$0")"
-rm -rf ./public
-mkdir -p ./public/ufc/api/flag-config/v1/
-mkdir -p ./public/obfuscated/api/flag-config/v1/
-mkdir -p ./public/bandit/api/flag-config/v1/
-ln -s ../../../../../../sdk-test-data/ufc/flags-v1.json ./public/ufc/api/flag-config/v1/config
-ln -s ../../../../../../sdk-test-data/ufc/flags-v1-obfuscated.json ./public/obfuscated/api/flag-config/v1/config
-ln -s ../../../../../../sdk-test-data/ufc/bandit-flags-v1.json ./public/bandit/api/flag-config/v1/config
-ln -s ../../../../../../sdk-test-data/ufc/bandit-models-v1.json ./public/bandit/api/flag-config/v1/bandits