fix: frontend error handling — ErrorBoundary, type-safe errors, stable keys

- React ErrorBoundary wrapping entire app for graceful crash recovery
- fetchJSON error handling uses try/catch instead of .catch() chain
- CertificateDetailPage: instanceof checks replace unsafe type casts
- DataTable: keyField prop replaces array index keys

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/api/client.ts

@@ -33,8 +33,14 @@ async function fetchJSON<T>(url: string, init?: RequestInit): Promise<T> {
     throw new Error('Authentication required');
   }
   if (!res.ok) {
-    const body = await res.json().catch(() => ({ message: res.statusText }));
-    throw new Error(body.message || body.error || `HTTP ${res.status}`);
+    let errorMsg = res.statusText;
+    try {
+      const body = await res.json();
+      errorMsg = body.message || body.error || errorMsg;
+    } catch {
+      // Response body is not JSON, use status text
+    }
+    throw new Error(errorMsg || `HTTP ${res.status}`);
   }
   return res.json();
 }

web/src/components/DataTable.tsx

@@ -11,9 +11,10 @@ interface DataTableProps<T> {
   onRowClick?: (item: T) => void;
   emptyMessage?: string;
   isLoading?: boolean;
+  keyField?: string;
 }
 
-export default function DataTable<T>({ columns, data, onRowClick, emptyMessage, isLoading }: DataTableProps<T>) {
+export default function DataTable<T>({ columns, data, onRowClick, emptyMessage, isLoading, keyField = 'id' }: DataTableProps<T>) {
   if (isLoading) {
     return (
       <div className="flex items-center justify-center py-16 text-slate-400">
@@ -49,7 +50,7 @@ export default function DataTable<T>({ columns, data, onRowClick, emptyMessage,
         <tbody>
           {data.map((item, i) => (
             <tr
-              key={i}
+              key={(item as Record<string, unknown>)[keyField] as string ?? `row-${i}`}
               onClick={() => onRowClick?.(item)}
               className={`border-b border-slate-700/50 transition-colors hover:bg-blue-500/5 ${onRowClick ? 'cursor-pointer' : ''}`}
             >

web/src/components/ErrorBoundary.tsx

@@ -0,0 +1,50 @@
+import { Component, type ErrorInfo, type ReactNode } from 'react';
+
+interface Props {
+  children: ReactNode;
+}
+
+interface State {
+  hasError: boolean;
+  error: Error | null;
+}
+
+export default class ErrorBoundary extends Component<Props, State> {
+  constructor(props: Props) {
+    super(props);
+    this.state = { hasError: false, error: null };
+  }
+
+  static getDerivedStateFromError(error: Error): State {
+    return { hasError: true, error };
+  }
+
+  componentDidCatch(error: Error, errorInfo: ErrorInfo) {
+    console.error('Uncaught component error:', error, errorInfo);
+  }
+
+  render() {
+    if (this.state.hasError) {
+      return (
+        <div className="flex items-center justify-center min-h-screen bg-slate-900">
+          <div className="text-center p-8">
+            <h1 className="text-xl font-semibold text-red-400 mb-2">Something went wrong</h1>
+            <p className="text-sm text-slate-400 mb-4">
+              {this.state.error?.message || 'An unexpected error occurred'}
+            </p>
+            <button
+              onClick={() => {
+                this.setState({ hasError: false, error: null });
+                window.location.reload();
+              }}
+              className="px-4 py-2 bg-blue-600 text-white rounded-lg text-sm hover:bg-blue-500"
+            >
+              Reload Page
+            </button>
+          </div>
+        </div>
+      );
+    }
+    return this.props.children;
+  }
+}

web/src/main.tsx

@@ -2,6 +2,7 @@ import { StrictMode } from 'react';
 import { createRoot } from 'react-dom/client';
 import { BrowserRouter, Routes, Route } from 'react-router-dom';
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import ErrorBoundary from './components/ErrorBoundary';
 import AuthProvider from './components/AuthProvider';
 import AuthGate from './components/AuthGate';
 import Layout from './components/Layout';
@@ -30,28 +31,30 @@ const queryClient = new QueryClient({
 
 createRoot(document.getElementById('root')!).render(
   <StrictMode>
-    <QueryClientProvider client={queryClient}>
-      <AuthProvider>
-        <AuthGate>
-          <BrowserRouter>
-            <Routes>
-              <Route element={<Layout />}>
-                <Route index element={<DashboardPage />} />
-                <Route path="certificates" element={<CertificatesPage />} />
-                <Route path="certificates/:id" element={<CertificateDetailPage />} />
-                <Route path="agents" element={<AgentsPage />} />
-                <Route path="agents/:id" element={<AgentDetailPage />} />
-                <Route path="jobs" element={<JobsPage />} />
-                <Route path="notifications" element={<NotificationsPage />} />
-                <Route path="policies" element={<PoliciesPage />} />
-                <Route path="issuers" element={<IssuersPage />} />
-                <Route path="targets" element={<TargetsPage />} />
-                <Route path="audit" element={<AuditPage />} />
-              </Route>
-            </Routes>
-          </BrowserRouter>
-        </AuthGate>
-      </AuthProvider>
-    </QueryClientProvider>
+    <ErrorBoundary>
+      <QueryClientProvider client={queryClient}>
+        <AuthProvider>
+          <AuthGate>
+            <BrowserRouter>
+              <Routes>
+                <Route element={<Layout />}>
+                  <Route index element={<DashboardPage />} />
+                  <Route path="certificates" element={<CertificatesPage />} />
+                  <Route path="certificates/:id" element={<CertificateDetailPage />} />
+                  <Route path="agents" element={<AgentsPage />} />
+                  <Route path="agents/:id" element={<AgentDetailPage />} />
+                  <Route path="jobs" element={<JobsPage />} />
+                  <Route path="notifications" element={<NotificationsPage />} />
+                  <Route path="policies" element={<PoliciesPage />} />
+                  <Route path="issuers" element={<IssuersPage />} />
+                  <Route path="targets" element={<TargetsPage />} />
+                  <Route path="audit" element={<AuditPage />} />
+                </Route>
+              </Routes>
+            </BrowserRouter>
+          </AuthGate>
+        </AuthProvider>
+      </QueryClientProvider>
+    </ErrorBoundary>
   </StrictMode>
 );

web/src/pages/CertificateDetailPage.tsx

@@ -130,7 +130,7 @@ export default function CertificateDetailPage() {
         )}
         {renewMutation.isError && (
           <div className="bg-red-500/10 border border-red-500/20 text-red-400 rounded-lg px-4 py-3 text-sm">
-            Failed to trigger renewal: {(renewMutation.error as Error).message}
+            Failed to trigger renewal: {renewMutation.error instanceof Error ? renewMutation.error.message : 'Unknown error'}
           </div>
         )}
         {deployMutation.isSuccess && (
@@ -140,12 +140,12 @@ export default function CertificateDetailPage() {
         )}
         {deployMutation.isError && (
           <div className="bg-red-500/10 border border-red-500/20 text-red-400 rounded-lg px-4 py-3 text-sm">
-            Failed to deploy: {(deployMutation.error as Error).message}
+            Failed to deploy: {deployMutation.error instanceof Error ? deployMutation.error.message : 'Unknown error'}
           </div>
         )}
         {archiveMutation.isError && (
           <div className="bg-red-500/10 border border-red-500/20 text-red-400 rounded-lg px-4 py-3 text-sm">
-            Failed to archive: {(archiveMutation.error as Error).message}
+            Failed to archive: {archiveMutation.error instanceof Error ? archiveMutation.error.message : 'Unknown error'}
           </div>
         )}
 
@@ -226,7 +226,7 @@ export default function CertificateDetailPage() {
             <h2 className="text-lg font-semibold text-slate-200 mb-4">Deploy Certificate</h2>
             {deployMutation.isError && (
               <div className="bg-red-500/10 border border-red-500/20 text-red-400 rounded-lg px-3 py-2 text-sm mb-3">
-                {(deployMutation.error as Error).message}
+                {deployMutation.error instanceof Error ? deployMutation.error.message : 'Unknown error'}
               </div>
             )}
             <label className="text-xs text-slate-400 block mb-2">Select Target</label>