diff --git a/config/vitest.config.ts b/config/vitest.config.ts
index 7f6fde0f0ca..ee791d96b78 100644
--- a/config/vitest.config.ts
+++ b/config/vitest.config.ts
@@ -15,6 +15,8 @@ export default defineConfig({
   },
   test: {
     environment: 'node',
+    // Why: Node 26's undefined Web Storage globals prevent Vitest from installing happy-dom's.
+    execArgv: ['--no-experimental-webstorage'],
     include: [
       'src/**/*.test.ts',
       'src/**/*.test.tsx',