diff --git a/frontend/src/api/client.ts b/frontend/src/api/client.ts
index 96104a9..ccbd951 100644
--- a/frontend/src/api/client.ts
+++ b/frontend/src/api/client.ts
@@ -1,7 +1,14 @@
 const BASE = '/api';
 
+function withDevUser(path: string): string {
+  const devUser = new URLSearchParams(window.location.search).get('devUser');
+  if (!devUser) return path;
+  const sep = path.includes('?') ? '&' : '?';
+  return `${path}${sep}devUser=${devUser}`;
+}
+
 async function request<T>(path: string, options?: RequestInit): Promise<T> {
-  const res = await fetch(`${BASE}${path}`, {
+  const res = await fetch(`${BASE}${withDevUser(path)}`, {
     ...options,
     headers: {
       'Content-Type': 'application/json',