diff --git a/app/game-frontend/src/config/viteEnv.ts b/app/game-frontend/src/config/viteEnv.ts
new file mode 100644
index 00000000..1e3b33bc
--- /dev/null
+++ b/app/game-frontend/src/config/viteEnv.ts
@@ -0,0 +1,7 @@
+export const mergeViteEnv = (
+    fileEnv: Record<string, string>,
+    runtimeEnv: NodeJS.ProcessEnv
+): Record<string, string | undefined> => ({
+    ...fileEnv,
+    ...runtimeEnv,
+});
diff --git a/app/game-frontend/test/viteConfig.test.ts b/app/game-frontend/test/viteConfig.test.ts
index 01a8abe6..6ebe9cf7 100644
--- a/app/game-frontend/test/viteConfig.test.ts
+++ b/app/game-frontend/test/viteConfig.test.ts
@@ -1,6 +1,6 @@
 import assert from 'node:assert/strict';
 import { describe, it } from 'node:test';
-import { mergeViteEnv } from '../vite.config.ts';
+import { mergeViteEnv } from '../src/config/viteEnv.ts';
 
 void describe('game frontend Vite config', () => {
     void it('prefers managed runtime values over values loaded from env files', () => {
diff --git a/app/game-frontend/vite.config.ts b/app/game-frontend/vite.config.ts
index 96f42431..2930af53 100644
--- a/app/game-frontend/vite.config.ts
+++ b/app/game-frontend/vite.config.ts
@@ -2,6 +2,7 @@ import { defineConfig, loadEnv } from 'vite';
 import vue from '@vitejs/plugin-vue';
 import tailwindcss from '@tailwindcss/vite';
 import path from 'path';
+import { mergeViteEnv } from './src/config/viteEnv';
 
 const normalizeBasePath = (value: string | undefined): string => {
     const pathValue = (value ?? '/').trim();
@@ -23,14 +24,6 @@ const resolvePreviewAllowedHosts = (value: string | undefined): true | string[]
     return hosts;
 };
 
-export const mergeViteEnv = (
-    fileEnv: Record<string, string>,
-    runtimeEnv: NodeJS.ProcessEnv
-): Record<string, string | undefined> => ({
-    ...fileEnv,
-    ...runtimeEnv,
-});
-
 // https://vitejs.dev/config/
 export default defineConfig(({ mode }) => {
     const env = mergeViteEnv(loadEnv(mode, process.cwd(), ''), process.env);