diff --git a/frontend/src/api.ts b/frontend/src/api.ts
index 319d37d..778cbaa 100644
--- a/frontend/src/api.ts
+++ b/frontend/src/api.ts
@@ -7,6 +7,10 @@ async function req<T>(method: string, path: string, body?: unknown): Promise<T>
     headers: body ? { 'Content-Type': 'application/json' } : undefined,
     body: body ? JSON.stringify(body) : undefined,
   })
+  if (res.status === 401) {
+    ;(window.top ?? window).location.href = '/login'
+    throw new Error('Unauthenticated')
+  }
   if (!res.ok) {
     const err = await res.json().catch(() => ({ error: res.statusText }))
     throw new Error((err as { error?: string }).error || res.statusText)
@@ -36,6 +40,10 @@ export async function uploadAttachment(
     credentials: 'include',
     body: fd,
   })
+  if (res.status === 401) {
+    ;(window.top ?? window).location.href = '/login'
+    throw new Error('Unauthenticated')
+  }
   if (!res.ok) {
     const err = await res.json().catch(() => ({ error: res.statusText }))
     throw new Error((err as { error?: string }).error || res.statusText)