diff --git a/frontend/src/app/Main.tsx b/frontend/src/app/Main.tsx
index bdea6784..ffbd040b 100644
--- a/frontend/src/app/Main.tsx
+++ b/frontend/src/app/Main.tsx
@@ -21,18 +21,58 @@ import AppShell from './components/Layout/AppShell';
 import DashboardSelection from './pages/DashboardSelection/DashboardSelection';
 import ErrorBoundary from './components/feedback/ErrorBoundary';
 import { setPanelMode, disableOnboardingAfterCrash } from '@/shared/state/onboardingProgressSlice';
-const Skills = lazy(() => import('./pages/Skills/Skills'));
-const Tools = lazy(() => import('./pages/Tools/Tools'));
-const Modes = lazy(() => import('./pages/Modes/Modes'));
-const Views = lazy(() => import('./pages/Views/Views'));
-const Customization = lazy(() => import('./pages/Customization/Customization'));
-const Analytics = lazy(() => import('./pages/Analytics/Analytics'));
-const OnboardingRoot = lazy(() =>
+// Wrap every lazy() so each chunk load (request, success, failure) emits a diag line. Chunk-split race against React commit is one of the candidate causes of the packaged-only segfault, so this surfaces if a chunk failed to load in the moment leading up to a crash.
+function diagLazy<T extends React.ComponentType<any>>(name: string, loader: () => Promise<{ default: T } | T>): React.LazyExoticComponent<T> {
+  return lazy(() => {
+    // eslint-disable-next-line no-console
+    console.log('[diag][lazy:requested]', name);
+    return Promise.resolve()
+      .then(loader)
+      .then((mod: any) => {
+        // eslint-disable-next-line no-console
+        console.log('[diag][lazy:loaded]', name);
+        return mod && 'default' in mod ? mod : { default: mod };
+      })
+      .catch((err) => {
+        // eslint-disable-next-line no-console
+        console.error('[diag][lazy:failed]', name, err && err.message, err && err.stack);
+        throw err;
+      });
+  });
+}
+
+const Skills = diagLazy('Skills', () => import('./pages/Skills/Skills'));
+const Tools = diagLazy('Tools', () => import('./pages/Tools/Tools'));
+const Modes = diagLazy('Modes', () => import('./pages/Modes/Modes'));
+const Views = diagLazy('Views', () => import('./pages/Views/Views'));
+const Customization = diagLazy('Customization', () => import('./pages/Customization/Customization'));
+const Analytics = diagLazy('Analytics', () => import('./pages/Analytics/Analytics'));
+const OnboardingRoot = diagLazy('OnboardingRoot', () =>
   import('./components/Onboarding').then((m) => ({ default: m.OnboardingRoot })),
 );
-const SignInGate = lazy(() => import('./components/overlays/SignInGate'));
+const SignInGate = diagLazy('SignInGate', () => import('./components/overlays/SignInGate'));
 
 if (typeof window !== 'undefined') {
+  // Boot-time env snapshot targets candidates #2 (React prod mode) and #3 (tree-shaking removed side-effectful import): we log NODE_ENV, React version, presence of Emotion's cache stylesheet, and any pre-existing emotion/MUI globals so a post-crash trace shows whether the runtime env matched what the bundle expected.
+  try {
+    // eslint-disable-next-line no-console
+    console.log('[diag][env] NODE_ENV=', (typeof process !== 'undefined' && process.env && process.env.NODE_ENV) || 'undefined',
+      'React=', (React as any).version,
+      'origin=', window.location.origin,
+      'href=', window.location.href);
+    setTimeout(() => {
+      try {
+        const emotionStyles = document.querySelectorAll('style[data-emotion]');
+        const muiStyles = document.querySelectorAll('style[data-styled],style[data-mui]');
+        // eslint-disable-next-line no-console
+        console.log('[diag][env] emotion_styles=', emotionStyles.length, 'mui_styles=', muiStyles.length, 'all_styles=', document.styleSheets.length);
+      } catch (err) {
+        // eslint-disable-next-line no-console
+        console.error('[diag][env] style probe failed:', err && (err as Error).message);
+      }
+    }, 100);
+  } catch { /* never let the diag block crash */ }
+
   // Diagnostic global error capture. The packaged bundle has no source maps, so without these handlers the only thing that reaches main-process stderr is "Uncaught TypeError: ... (bundle.js:2)" with zero stack context. Forward error.stack and Redux action.type when available so we can pinpoint the offender across the chat-spawn / workflow rendering paths even in minified prod.
   window.addEventListener('error', (e) => {
     try {
diff --git a/frontend/src/app/components/feedback/ErrorBoundary.tsx b/frontend/src/app/components/feedback/ErrorBoundary.tsx
index 4d5e2dbb..7fd5d289 100644
--- a/frontend/src/app/components/feedback/ErrorBoundary.tsx
+++ b/frontend/src/app/components/feedback/ErrorBoundary.tsx
@@ -39,7 +39,8 @@ class ErrorBoundary extends React.Component<Props, State> {
     } catch {}
     try { this.props.onError?.(error, info); } catch {}
     if (typeof console !== 'undefined' && console.error) {
-      console.error('[ErrorBoundary]', error, info);
+      // [diag] prefix so the packaged-build stderr monitor picks this up alongside other diag traces (the renderer-side crash we are hunting does not always reach window.onerror, so an in-React-tree throw needs its own visible breadcrumb).
+      console.error('[diag][ErrorBoundary]', this.props.scope || 'unknown', error && error.message, '\nstack:\n', error && error.stack, '\ncomponent_stack:\n', info && info.componentStack);
     }
   }