diff --git a/src/core/configuration/ConfigLoader.ts b/src/core/configuration/ConfigLoader.ts
index 4987da1c3..82e5f66b5 100644
--- a/src/core/configuration/ConfigLoader.ts
+++ b/src/core/configuration/ConfigLoader.ts
@@ -9,14 +9,6 @@ import { prodConfig } from "./ProdConfig";
 
 export let cachedSC: ServerConfig | null = null;
 
-declare global {
-  interface Window {
-    BOOTSTRAP_CONFIG?: {
-      gameEnv?: string;
-    };
-  }
-}
-
 export async function getConfig(
   gameConfig: GameConfig,
   userSettings: UserSettings | null,
@@ -39,12 +31,13 @@ export async function getServerConfigFromClient(): Promise<ServerConfig> {
     return cachedSC;
   }
 
-  const bootstrapGameEnv = window.BOOTSTRAP_CONFIG?.gameEnv;
-  if (!bootstrapGameEnv) {
-    throw new Error("Missing bootstrap server config");
+  // Vite replaces this in browser and worker bundles at build time.
+  const gameEnv = process.env.GAME_ENV;
+  if (!gameEnv) {
+    throw new Error("Missing client server config");
   }
 
-  cachedSC = getServerConfig(bootstrapGameEnv);
+  cachedSC = getServerConfig(gameEnv);
   return cachedSC;
 }
 export function getServerConfigFromServer(): ServerConfig {
diff --git a/tests/core/configuration/ConfigLoader.test.ts b/tests/core/configuration/ConfigLoader.test.ts
index 65fd81757..6bf14163e 100644
--- a/tests/core/configuration/ConfigLoader.test.ts
+++ b/tests/core/configuration/ConfigLoader.test.ts
@@ -6,14 +6,16 @@ import {
 } from "../../../src/core/configuration/ConfigLoader";
 
 describe("ConfigLoader", () => {
+  const originalGameEnv = process.env.GAME_ENV;
+
   beforeEach(() => {
     vi.restoreAllMocks();
-    window.BOOTSTRAP_CONFIG = undefined;
+    process.env.GAME_ENV = originalGameEnv;
     clearCachedServerConfig();
   });
 
-  test("uses bootstrap config without fetching /api/env", async () => {
-    window.BOOTSTRAP_CONFIG = { gameEnv: "prod" };
+  test("uses bundled GAME_ENV without fetching /api/env", async () => {
+    process.env.GAME_ENV = "prod";
     const fetchSpy = vi.spyOn(globalThis, "fetch");
 
     const config = await getServerConfigFromClient();