diff --git a/.phase30-state.json b/.phase30-state.json
index ba88c02..c4fb984 100644
--- a/.phase30-state.json
+++ b/.phase30-state.json
@@ -1,5 +1,8 @@
 {
   "completed_features": [],
-  "current_feature": "404-not-found-page",
-  "started_at": "2026-05-23T09:23:38.401372"
+  "current_feature": "api-error-pages",
+  "started_at": "2026-05-23T09:23:38.401372",
+  "attempted_features": [
+    "404-not-found-page"
+  ]
 }
\ No newline at end of file
diff --git a/GENERATION_LOG.md b/GENERATION_LOG.md
index bc9ef47..74475b2 100644
--- a/GENERATION_LOG.md
+++ b/GENERATION_LOG.md
@@ -3399,3 +3399,23 @@ src/index.ts(27,25): error TS2769: No overload matches this call.
   Overload 1 of 3, '(plugin: FastifyPluginCallback<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
     Argument of type 'Promise<FastifyMultipartPlugin>' is not assignable to parameter of type 'FastifyPluginCallback<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>'.
       Type 'Promise<FastifyMultipartPlugin>' provides no match for the signature '(instance: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, 
+- `09:24:53` **INFO**   Committed feature 404-not-found-page
+- `09:24:53` **INFO**   Pushed: rc=0
+
+## Phase-3 Feature: api-error-pages (2026-05-23 09:24:53)
+
+- `09:24:53` **INFO** Description: 500-Error-Page bei API-Down
+- `09:24:53` **INFO**   Generating apps/web/src/components/ApiErrorBanner.tsx (ApiErrorBanner-Component. useQuery('health', () => api.health(), {refe…)
+- `09:24:59` **INFO**     wrote 592 chars in 6.0s (attempt 1)
+- `09:24:59` **INFO**   Generating apps/web/src/App.tsx (ERWEITERT — mount <ApiErrorBanner /> direkt unter Nav (vor Outlet). Be…)
+- `09:26:04` **INFO**     wrote 7942 chars in 64.4s (attempt 1)
+- `09:26:04` **INFO** Running tsc --noEmit on api…
+- `09:26:06` **WARN**   tsc errors:
+src/db/schema.ts(37,14): error TS7022: 'customers' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+src/db/schema.ts(45,59): error TS7024: Function implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.
+src/db/schema.ts(49,14): error TS7022: 'projects' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+src/db/schema.ts(53,56): error TS7024: Function implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions.
+src/index.ts(27,25): error TS2769: No overload matches this call.
+  Overload 1 of 3, '(plugin: FastifyPluginCallback<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
+    Argument of type 'Promise<FastifyMultipartPlugin>' is not assignable to parameter of type 'FastifyPluginCallback<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>'.
+      Type 'Promise<FastifyMultipartPlugin>' provides no match for the signature '(instance: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, 
diff --git a/apps/web/src/App.tsx b/apps/web/src/App.tsx
index 05e0a7e..24e69d1 100644
--- a/apps/web/src/App.tsx
+++ b/apps/web/src/App.tsx
@@ -34,6 +34,7 @@ import VersionBadge from "./components/VersionBadge"
 import QuickAdd from "./components/QuickAdd"
 import IdleDetector from "./components/IdleDetector"
 import UndoStack from "./components/UndoStack"
+import ApiErrorBanner from "./components/ApiErrorBanner"
 import { ToastProvider } from "./components/Toast"
 import ErrorBoundary from "./components/ErrorBoundary"
 import { api } from "./lib/api"
@@ -47,6 +48,7 @@ const rootRoute = createRootRoute({
           <div className="flex-grow">
             <IdleDetector />
             <Nav />
+            <ApiErrorBanner />
             <CommandPalette />
             <KeyboardHelp />
             <OnboardingTour />
@@ -136,11 +138,18 @@ const timeEntryTemplatesRoute = createRoute({
   component: TimeEntryTemplates
 })
 
-const projectTemplatesRoute = createRoute({
+const customersRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/project-templates",
+  path: "/customers",
   beforeLoad: authCheck,
-  component: ProjectTemplates
+  component: Customers
+})
+
+const customerDetailRoute = createRoute({
+  getParentRoute: () => rootRoute,
+  path: "/customers/$customerId",
+  beforeLoad: authCheck,
+  component: CustomerDetail
 })
 
 const projectsRoute = createRoute({
@@ -157,18 +166,11 @@ const projectDetailRoute = createRoute({
   component: ProjectDetail
 })
 
-const customersRoute = createRoute({
+const projectTemplatesRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/customers",
+  path: "/project-templates",
   beforeLoad: authCheck,
-  component: Customers
-})
-
-const customerDetailRoute = createRoute({
-  getParentRoute: () => rootRoute,
-  path: "/customers/$customerId",
-  beforeLoad: authCheck,
-  component: CustomerDetail
+  component: ProjectTemplates
 })
 
 const profileRoute = createRoute({
@@ -185,6 +187,20 @@ const settingsRoute = createRoute({
   component: Settings
 })
 
+const twoFactorRoute = createRoute({
+  getParentRoute: () => rootRoute,
+  path: "/settings/2fa",
+  beforeLoad: authCheck,
+  component: TwoFactorAuth
+})
+
+const apiKeysRoute = createRoute({
+  getParentRoute: () => rootRoute,
+  path: "/settings/api-keys",
+  beforeLoad: authCheck,
+  component: ApiKeys
+})
+
 const calendarRoute = createRoute({
   getParentRoute: () => rootRoute,
   path: "/calendar",
@@ -192,13 +208,6 @@ const calendarRoute = createRoute({
   component: Calendar
 })
 
-const invoicesRoute = createRoute({
-  getParentRoute: () => rootRoute,
-  path: "/invoices",
-  beforeLoad: authCheck,
-  component: Invoices
-})
-
 const holidaysRoute = createRoute({
   getParentRoute: () => rootRoute,
   path: "/holidays",
@@ -206,34 +215,25 @@ const holidaysRoute = createRoute({
   component: Holidays
 })
 
-const adminUsersRoute = createRoute({
+const invoicesRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/admin/users",
-  beforeLoad: async () => {
-    await authCheck()
-    await adminCheck()
-  },
-  component: AdminUsers
+  path: "/invoices",
+  beforeLoad: authCheck,
+  component: Invoices
 })
 
-const auditLogRoute = createRoute({
+const billingRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/admin/audit-log",
-  beforeLoad: async () => {
-    await authCheck()
-    await adminCheck()
-  },
-  component: AuditLog
+  path: "/billing",
+  beforeLoad: authCheck,
+  component: Billing
 })
 
-const rolePermissionsRoute = createRoute({
+const integrationsRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/admin/permissions",
-  beforeLoad: async () => {
-    await authCheck()
-    await adminCheck()
-  },
-  component: RolePermissions
+  path: "/integrations",
+  beforeLoad: authCheck,
+  component: Integrations
 })
 
 const documentsRoute = createRoute({
@@ -246,42 +246,35 @@ const documentsRoute = createRoute({
 const webhooksRoute = createRoute({
   getParentRoute: () => rootRoute,
   path: "/webhooks",
-  beforeLoad: async () => {
-    await authCheck()
-    await adminCheck()
-  },
+  beforeLoad: authCheck,
   component: Webhooks
 })
 
-const twoFactorAuthRoute = createRoute({
+const adminUsersRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/settings/2fa",
-  beforeLoad: authCheck,
-  component: TwoFactorAuth
+  path: "/admin/users",
+  beforeLoad: adminCheck,
+  component: AdminUsers
 })
 
-const billingRoute = createRoute({
+const rolePermissionsRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/billing",
-  beforeLoad: async () => {
-    await authCheck()
-    await adminCheck()
-  },
-  component: Billing
+  path: "/admin/permissions",
+  beforeLoad: adminCheck,
+  component: RolePermissions
 })
 
-const integrationsRoute = createRoute({
+const auditLogRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/integrations",
-  beforeLoad: authCheck,
-  component: Integrations
+  path: "/admin/audit-log",
+  beforeLoad: adminCheck,
+  component: AuditLog
 })
 
-const apiKeysRoute = createRoute({
+const notFoundRoute = createRoute({
   getParentRoute: () => rootRoute,
-  path: "/settings/api-keys",
-  beforeLoad: authCheck,
-  component: ApiKeys
+  path: "*",
+  component: NotFound
 })
 
 const routeTree = [
@@ -292,30 +285,30 @@ const routeTree = [
   acceptInviteRoute,
   timeEntriesRoute,
   timeEntryTemplatesRoute,
-  projectTemplatesRoute,
-  projectsRoute,
-  projectDetailRoute,
   customersRoute,
   customerDetailRoute,
+  projectsRoute,
+  projectDetailRoute,
+  projectTemplatesRoute,
   profileRoute,
   settingsRoute,
+  twoFactorRoute,
+  apiKeysRoute,
   calendarRoute,
-  invoicesRoute,
   holidaysRoute,
-  adminUsersRoute,
-  auditLogRoute,
-  rolePermissionsRoute,
-  documentsRoute,
-  webhooksRoute,
-  twoFactorAuthRoute,
+  invoicesRoute,
   billingRoute,
   integrationsRoute,
-  apiKeysRoute
+  documentsRoute,
+  webhooksRoute,
+  adminUsersRoute,
+  rolePermissionsRoute,
+  auditLogRoute,
+  notFoundRoute
 ]
 
-const router = createRouter({
+const router = createRouter({ 
   routeTree,
-  notFoundComponent: NotFound,
   defaultPreload: 'intent'
 })
 
@@ -326,10 +319,5 @@ declare module "@tanstack/react-router" {
 }
 
 export default function App() {
-  return (
-    <RouterProvider 
-      router={router} 
-      defaultErrorBoundary={<ErrorBoundary />} 
-    />
-  )
+  return <RouterProvider router={router} />
 }
\ No newline at end of file
diff --git a/apps/web/src/components/ApiErrorBanner.tsx b/apps/web/src/components/ApiErrorBanner.tsx
new file mode 100644
index 0000000..39a5270
--- /dev/null
+++ b/apps/web/src/components/ApiErrorBanner.tsx
@@ -0,0 +1,20 @@
+import React from 'react';
+import { useQuery } from '@tanstack/react-query';
+import { api } from '@emberclone/shared/api';
+
+export const ApiErrorBanner: React.FC = () => {
+  const { isError } = useQuery({
+    queryKey: ['health'],
+    queryFn: () => api.health(),
+    refetchInterval: 30000,
+    retry: 0,
+  });
+
+  if (!isError) return null;
+
+  return (
+    <div className="fixed top-0 left-0 right-0 z-50 bg-red-600 text-white text-center py-2 px-4 text-sm font-medium animate-in fade-in slide-in-from-top duration-300">
+      API nicht erreichbar — versuche erneut in 30s
+    </div>
+  );
+};
\ No newline at end of file