diff --git a/apps/pwa/src/api/client.ts b/apps/pwa/src/api/client.ts
index 7067342..743acd9 100644
--- a/apps/pwa/src/api/client.ts
+++ b/apps/pwa/src/api/client.ts
@@ -219,11 +219,15 @@ export async function fetchAdminResetPassword(
 /**
  * POST /api/me/link-oidc — initiate the OIDC-link flow for the current local user (Surface 13).
  *
- * The server returns a redirect URL to begin the OIDC authorization-code flow with a
- * state parameter encoding the linkUserId claim. The caller should follow the redirect
- * via top-level navigation (window.location.href = result.redirectUrl).
+ * The server returns the OIDC authorization endpoint URL (with a signed `state` parameter
+ * encoding the linkUserId claim) to begin the authorization-code flow. The caller should
+ * follow it via top-level navigation (window.location.href = authorizationUrl) when present.
+ *
+ * authorizationUrl is null when OIDC is not configured in env (the server cannot build the
+ * URL); callers MUST handle that case and surface an error instead of navigating to null.
+ * The server contract is { signedState, authorizationUrl } (see apps/api/src/routes/me.ts).
  */
-export async function fetchLinkOidc(): Promise<{ redirectUrl: string }> {
+export async function fetchLinkOidc(): Promise<{ authorizationUrl: string | null }> {
   const res = await fetch('/api/me/link-oidc', {
     method: 'POST',
     credentials: 'include',
@@ -234,7 +238,7 @@ export async function fetchLinkOidc(): Promise<{ redirectUrl: string }> {
   if (!res.ok) {
     throw new Error(`fetchLinkOidc failed: ${res.status}`);
   }
-  return res.json() as Promise<{ redirectUrl: string }>;
+  return res.json() as Promise<{ signedState: string; authorizationUrl: string | null }>;
 }
 
 // ── /api/me ────────────────────────────────────────────────────────────────
diff --git a/apps/pwa/src/components/SettingsSheet.tsx b/apps/pwa/src/components/SettingsSheet.tsx
index 287af72..59f5b1a 100644
--- a/apps/pwa/src/components/SettingsSheet.tsx
+++ b/apps/pwa/src/components/SettingsSheet.tsx
@@ -859,9 +859,15 @@ function LinkOidcSheet({ isOpen, onClose }: LinkOidcSheetProps) {
   const linkMutation = useMutation({
     mutationFn: fetchLinkOidc,
     onSuccess: (data) => {
-      // Close the sheet and initiate OIDC link flow
+      // authorizationUrl is null when OIDC is not configured in env (server could not
+      // build the URL). Do NOT navigate to null — surface an error and keep the sheet open.
+      if (!data.authorizationUrl) {
+        setError('Something went wrong. Please try again.');
+        return;
+      }
+      // Close the sheet and initiate the OIDC link flow via top-level navigation.
       onClose();
-      window.location.href = data.redirectUrl;
+      window.location.href = data.authorizationUrl;
     },
     onError: () => {
       setError('Something went wrong. Please try again.');