diff --git a/frontend/client/lib/api/auth.ts b/frontend/client/lib/api/auth.ts
index 93315ce..1880062 100644
--- a/frontend/client/lib/api/auth.ts
+++ b/frontend/client/lib/api/auth.ts
@@ -21,8 +21,6 @@ export type RefreshTokenResponse = {
   refreshToken: string;
 };
 
-const baseURL = apiBaseUrl();
-
 export async function login(data: LoginRequest): Promise<AuthResponse> {
   const { data: res } = await apiClient.post<AuthResponse>("/api/v1/auth/login", data);
   return res;
@@ -72,7 +70,7 @@ export async function changePassword(
 }
 
 export async function refreshToken(token: string): Promise<RefreshTokenResponse> {
-  const { data } = await axios.post<RefreshTokenResponse>(`${baseURL}/api/v1/auth/refresh`, {
+  const { data } = await axios.post<RefreshTokenResponse>(`${apiBaseUrl()}/api/v1/auth/refresh`, {
     refreshToken: token,
   });
   return data;
diff --git a/frontend/client/lib/api/client.ts b/frontend/client/lib/api/client.ts
index f51d31c..bc0388c 100644
--- a/frontend/client/lib/api/client.ts
+++ b/frontend/client/lib/api/client.ts
@@ -14,15 +14,15 @@ export type ApiError = {
 
 type RetryableConfig = InternalAxiosRequestConfig & { _retry?: boolean };
 
-const baseURL = apiBaseUrl();
-
 export const apiClient: AxiosInstance = axios.create({
-  baseURL,
   headers: { "Content-Type": "application/json" },
 });
 
-// Attach access token from in-memory Zustand store on every request.
+// Resolve the API base per-request + attach the access token. window.__ENV (runtime config)
+// may not be populated at module-load on a hard page load (e.g. the OAuth callback), which
+// would otherwise cache the localhost fallback and send requests to the wrong origin.
 apiClient.interceptors.request.use((config) => {
+  config.baseURL = apiBaseUrl();
   const token = useAuthStore.getState().token;
   if (token) {
     config.headers.set("Authorization", `Bearer ${token}`);
@@ -97,7 +97,7 @@ apiClient.interceptors.response.use(
 
     try {
       const { data } = await axios.post<{ accessToken: string; refreshToken: string }>(
-        `${baseURL}/api/v1/auth/refresh`,
+        `${apiBaseUrl()}/api/v1/auth/refresh`,
         { refreshToken },
       );
       setToken(data.accessToken);
diff --git a/frontend/client/lib/auth/token.ts b/frontend/client/lib/auth/token.ts
index 17179bb..ac5c033 100644
--- a/frontend/client/lib/auth/token.ts
+++ b/frontend/client/lib/auth/token.ts
@@ -55,8 +55,6 @@ function isExpiredSoon(token: string | null, bufferMs = 30_000): boolean {
   return exp * 1000 < Date.now() + bufferMs;
 }
 
-const BASE_URL = apiBaseUrl();
-
 export async function getValidAccessToken(force = false): Promise<string | null> {
   const token = getAccessToken();
   // `force` refreshes even a still-valid token — used by the idle keep-alive timer so
@@ -68,7 +66,7 @@ export async function getValidAccessToken(force = false): Promise<string | null>
     const { refreshToken, setToken, setRefreshToken, logout } = useAuthStore.getState();
     if (!refreshToken) { logout(); return null; }
 
-    const res = await fetch(`${BASE_URL}/api/v1/auth/refresh`, {
+    const res = await fetch(`${apiBaseUrl()}/api/v1/auth/refresh`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify({ refreshToken }),