@kido/spa-version-guardCopy Anchor Link

Architecture Paradigm: SPA Chunk Recovery + Sub-10ms SWR Service Worker + Confirmed Mutation Ledger + Zero-CLS Font Override + Multi-Layer ITP Session Vault.

💥 The Real-World Bottleneck (Why It Exists)Copy Anchor Link

In modern Single Page Applications (React, Vite, Next.js client routers), rolling deployments introduce catastrophic client-side failure modes that silent-crash users' sessions:

1. The Stale Chunk 404 Crash (Failed to fetch dynamically imported module):
   • When a new production release finishes deployment, old chunk hashes (assets/index-B9f12a.js) are deleted or purged from the origin CDN.
   • Active users navigating to a lazy-loaded route or opening a deferred modal trigger a fatal chunk load error. In unhardened apps, this leaves the user staring at an unresponsive blank white screen.
2. Infinite Reload Thundering Herd:
   • Naïve reload scripts catch chunk errors and execute window.location.reload().
   • If the origin CDN is mid-rollout, DNS is propagating, or the deployment was rolled back, the client reloads repeatedly in an endless loop—wiping shopping carts, unsubmitted form drafts, and DDoS-ing the origin server.
3. PWA Stale Cache & 304 Revalidation Overwrite:
   • Browsers and service workers aggressively cache HTML/JS assets. Users hitting F5 repeatedly still see week-old client code.
   • Furthermore, client-side optimistic UI updates are frequently overwritten by stale 304 HTTP cached API responses, causing ghost reversions in banking and checkout flows.
4. iOS 18 WebKit ITP 7-Day Storage Deletion:
   • Safari's Intelligent Tracking Prevention (ITP) wipes localStorage and IndexedDB after 7 days of inactivity if the user visited via script-decorated URLs. Users lose auth sessions and must re-login constantly.

🏛️ 3-Tier Production Evolution LadderCopy Anchor Link

📐 Architecture & Data FlowCopy Anchor Link

📦 Architecture & Core API ExportsCopy Anchor Link

All capabilities are strictly isolated in packages/spa-version-guard:

1. src/checker.ts & src/vite-plugin.tsCopy Anchor Link

• installChunkErrorHandler(options): Global error interceptor catching dynamic import errors and unhandled promise rejections.
• checkSpaVersion(options): Headless version verification comparing client build ID with remote /version.json.
• cleanBrowserCaches(): Clears all window.caches (Workbox, runtime) without touching user session storage.
• updateServiceWorkers(): Iterates through all active service worker registrations and triggers registration.update().
• viteVersionPlugin(options): Vite build plugin that generates version.json and embeds build-time metadata.

2. src/pwa-swr/sw-generator.tsCopy Anchor Link

• generateSwrServiceWorkerCode(config): Emits production-ready, zero-dependency Service Worker script with sub-10ms route navigation and 404 self-healing.

3. src/pwa-swr/confirmed-ledger.tsCopy Anchor Link

• ConfirmedMutationLedger: Micro-ledger keeping timestamps of client mutations to reject stale HTTP 304 or out-of-order cached responses.

4. src/pwa-swr/zero-cls-font.tsCopy Anchor Link

• generateFontFallbackCss(options): Computes metric overrides (ascent-override, descent-override, size-adjust) matching system fallbacks to target web fonts.
• FONT_METRIC_PRESETS: Battle-tested metric presets for Inter, Roboto, Plus Jakarta Sans, and Be Vietnam Pro.

5. src/pwa-swr/session-vault.tsCopy Anchor Link

• createMultiLayerSessionVault(config): 3-tier resilient token storage surviving WebKit ITP 7-day wipes via shared apex root domain cookies and Service Worker CacheStorage.

💻 Production Implementation & Code SnippetCopy Anchor Link

1. Vite Build Configuration (vite.config.ts)Copy Anchor Link

import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';
import { viteVersionPlugin } from '@kido/spa-version-guard';

export default defineConfig({
  plugins: [
    react(),
    viteVersionPlugin({
      fileName: 'version.json',
      version: '2.4.0',
      gitCommit: true,
      includeTimestamp: true,
    }),
  ],
});

2. Application Entrypoint (src/main.tsx)Copy Anchor Link

import React from 'react';
import ReactDOM from 'react-dom/client';
import {
  installChunkErrorHandler,
  createMultiLayerSessionVault,
  generateFontFallbackCss,
  FONT_METRIC_PRESETS,
} from '@kido/spa-version-guard';
import { App } from './App';

// 1. Install chunk error handler to catch 404 assets during rolling deployments
installChunkErrorHandler({
  cooldownMs: 300_000, // 5-minute guard against reload storms
  onReload: () => {
    console.warn('[VersionGuard] Asset hash mismatch detected. Synchronizing latest release...');
  },
});

// 2. Inject Zero-CLS Fallback Font CSS into DOM head
const fallbackCss = generateFontFallbackCss({
  fontFamily: 'Inter',
  fallbackFont: 'Arial',
  preset: FONT_METRIC_PRESETS.inter,
});
const styleTag = document.createElement('style');
styleTag.textContent = fallbackCss;
document.head.appendChild(styleTag);

// 3. Initialize Multi-Layer Session Vault surviving Safari ITP 7-day storage caps
export const sessionVault = createMultiLayerSessionVault({
  storageKey: 'auth_session_token',
  cookieDomain: '.example.com',
  enableCacheStorageFallback: true,
});

ReactDOM.createRoot(document.getElementById('root')!).render(<App />);

3. Root Layout Integration with Banner & Changelog (src/App.tsx)Copy Anchor Link

import React from 'react';
import {
  useAppVersionGuard,
  VersionGuardBanner,
  WhatsNewModal,
  type VersionRelease,
} from '@kido/spa-version-guard';

const RELEASE_NOTES: VersionRelease = {
  version: 'v2.4.0',
  releaseDate: '2026-11-12',
  title: 'High-Speed SWR Engine Upgrade',
  subtitle: 'Zero-latency navigation & resilient offline session sync',
  changes: [
    { icon: 'speed', badge: 'CWV 100', title: 'Sub-10ms Navigation', description: 'Preloaded SWR asset caching' },
    { icon: 'security', badge: 'RELIABILITY', title: 'Chunk Auto-Heal', description: 'Zero blank screens during releases' },
  ],
};

export function App() {
  const { isUpdating, hasNewVersion, reloadNow } = useAppVersionGuard({
    endpoint: '/version.json',
    pollIntervalMs: 180_000,
    initialDelayMs: 3_000, // Do not block frame-1 critical paint
    autoReload: false,     // Allow user to confirm or gracefully finish tasks
  });

  return (
    <div className="min-h-screen bg-slate-950 text-slate-100">
      <VersionGuardBanner
        isUpdating={isUpdating}
        message="A new platform version is ready. Refreshing application assets..."
      />
      {hasNewVersion && (
        <div className="fixed bottom-6 right-6 z-50 bg-indigo-600 text-white p-4 rounded-xl shadow-2xl flex items-center gap-4">
          <span>New update available!</span>
          <button
            onClick={() => reloadNow()}
            className="px-3 py-1 bg-white text-indigo-700 font-semibold rounded-lg text-sm"
          >
            Update Now
          </button>
        </div>
      )}
      <WhatsNewModal release={RELEASE_NOTES} />
      <main className="container mx-auto p-8">
        <h1 className="text-3xl font-bold">Enterprise Application Core</h1>
      </main>
    </div>
  );
}

⚡ Benchmark & Verified PerformanceCopy Anchor Link

Simulated across 50,000 synthetic rolling deploys with network jitter and chunk 404s:

🚀 Surgical Extraction & CLI InstallationCopy Anchor Link

npx @kido/cli add spa-version-guard