Cloudflare Worker Base

Quick Start (5 Minutes)

# 1. Scaffold project
npm create cloudflare@latest my-worker -- --type hello-world --ts --git --deploy false --framework none

# 2. Install dependencies
cd my-worker
npm install [email protected]
npm install -D @cloudflare/[email protected] [email protected]

# 3. Create wrangler.jsonc
{
  "name": "my-worker",
  "main": "src/index.ts",
  "account_id": "YOUR_ACCOUNT_ID",
  "compatibility_date": "2025-11-11",
  "assets": {
    "directory": "./public/",
    "binding": "ASSETS",
    "not_found_handling": "single-page-application",
    "run_worker_first": ["/api/*"]  // CRITICAL: Prevents SPA fallback from intercepting API routes
  }
}

# 4. Create vite.config.ts
import { defineConfig } from 'vite'
import { cloudflare } from '@cloudflare/vite-plugin'
export default defineConfig({ plugins: [cloudflare()] })

# 5. Create src/index.ts
import { Hono } from 'hono'
type Bindings = { ASSETS: Fetcher }
const app = new Hono<{ Bindings: Bindings }>()
app.get('/api/hello', (c) => c.json({ message: 'Hello!' }))
app.all('*', (c) => c.env.ASSETS.fetch(c.req.raw))
export default app  // CRITICAL: Use this pattern (NOT { fetch: app.fetch })

# 6. Deploy
npm run dev              # Local: http://localhost:8787
wrangler deploy          # Production

Critical Configuration:

• run_worker_first: ["/api/*"] - Without this, SPA fallback intercepts API routes returning index.html instead of JSON (workers-sdk #8879)
• export default app - Using { fetch: app.fetch } causes "Cannot read properties of undefined" (honojs/hono #3955)

Known Issues Prevention

This skill prevents 10 documented issues:

Issue #1: Export Syntax Error

Error: "Cannot read properties of undefined (reading 'map')" Source: honojs/hono #3955 Prevention: Use export default app (NOT { fetch: app.fetch })

Issue #2: Static Assets Routing Conflicts

Error: API routes return index.html instead of JSON Source: workers-sdk #8879 Prevention: Add "run_worker_first": ["/api/*"] to wrangler.jsonc

Issue #3: Scheduled/Cron Not Exported

Error: "Handler does not export a scheduled() function" Source: honojs/vite-plugins #275 Prevention: Use Module Worker format when needed:

export default {
  fetch: app.fetch,
  scheduled: async (event, env, ctx) => { /* ... */ }
}

Issue #4: HMR Race Condition

Error: "A hanging Promise was canceled" during development Source: workers-sdk #9518 Prevention: Use @cloudflare/[email protected] or later

Issue #5: Static Assets Upload Race

Error: Non-deterministic deployment failures in CI/CD Source: workers-sdk #7555 Prevention: Use Wrangler 4.x+ with retry logic (fixed in recent versions)

Issue #6: Service Worker Format Confusion

Error: Using deprecated Service Worker format Source: Cloudflare migration guide Prevention: Always use ES Module format

Issue #7: Gradual Rollouts Asset Mismatch (2025)

Error: 404 errors for fingerprinted assets during gradual deployments Source: Cloudflare Static Assets Docs Why It Happens: Modern frameworks (React/Vue/Angular with Vite) generate fingerprinted filenames (e.g., index-a1b2c3d4.js). During gradual rollouts between versions, a user's initial request may go to Version A (HTML references index-a1b2c3d4.js), but subsequent asset requests route to Version B (only has index-m3n4o5p6.js), causing 404s Prevention:

• Avoid gradual deployments with fingerprinted assets
• Use instant cutover deployments for static sites
• Or implement version-aware routing with custom logic

Issue #8: Free Tier 429 Errors with run_worker_first (2025)

Error: 429 (Too Many Requests) responses on asset requests when exceeding free tier limits Source: Cloudflare Static Assets Billing Docs Why It Happens: When using run_worker_first, requests matching specified patterns ALWAYS invoke your Worker script (counted toward free tier limits). After exceeding limits, these requests receive 429 instead of falling back to free static asset serving Prevention:

• Upgrade to Workers Paid plan ($5/month) for unlimited requests
• Use negative patterns (!/pattern) to exclude paths from Worker invocation
• Minimize run_worker_first patterns to only essential API routes

Issue #9: Vite 8 Breaks nodejs_compat with require()

Error: Calling require for "buffer" in an environment that doesn't expose the require function Source: workers-sdk #11948 Affected Versions: Vite 8.x with @cloudflare/vite-plugin 1.21.0+ Why It Happens: Vite 8 uses Rolldown bundler which doesn't convert require() to import for external modules. Workers don't expose require() function, causing Node built-in module imports to fail at runtime. Prevention:

// vite.config.ts - Add esmExternalRequirePlugin
import { defineConfig } from 'vite'
import { cloudflare } from '@cloudflare/vite-plugin'
import { esmExternalRequirePlugin } from 'vite'
import { builtinModules } from 'node:module'

export default defineConfig({
  plugins: [
    cloudflare(),
    esmExternalRequirePlugin({
      external: [/^node:/, ...builtinModules],
    }),
  ],
})

Status: Workaround available. Vite team working on fix (vitejs/vite#21452).

Issue #10: Vite base Option Breaks SPA Routing (1.13.8+)

Error: curl http://localhost:5173/prefix returns 404 instead of index.html Source: workers-sdk #11857 Affected Versions: @cloudflare/vite-plugin 1.13.8+ Why It Happens: Plugin now passes full URL with base path to Asset Worker (matching prod behavior). Platform support for assets.base not yet available. Prevention (dev-mode workaround):

// worker.ts - Strip base path in development
if (import.meta.env.DEV) {
  url.pathname = url.pathname.replace(import.meta.env.BASE_URL, '');
  if (url.pathname === '/') {
    return this.env.ASSETS.fetch(request);
  }
  request = new Request(url, request);
}

Status: Intentional change to align dev with prod. Platform feature assets.base planned for Q1 2026 (workers-sdk #9885).

Route Priority with run_worker_first

Critical Understanding: "not_found_handling": "single-page-application" returns index.html for unknown routes (enables React Router, Vue Router). Without run_worker_first, this intercepts API routes!

Request Routing with run_worker_first: ["/api/*"]:

1. /api/hello → Worker handles (returns JSON)
2. / → Static Assets serve index.html
3. /styles.css → Static Assets serve styles.css
4. /unknown → Static Assets serve index.html (SPA fallback)

Static Assets Caching: Automatic edge caching. Cache bust with query strings: <link href="/styles.css?v=1.0.0">

Free Tier Warning (2025): run_worker_first patterns count toward free tier limits. After exceeding, requests get 429 instead of falling back to free static assets. Use negative patterns (!/pattern) or upgrade to Paid plan.

Auto-Provisioning (Wrangler 4.45+)

Default Behavior: Wrangler automatically provisions R2 buckets, D1 databases, and KV namespaces when deploying. This eliminates manual resource creation steps.

Critical: Always Specify Resource Names

⚠️ Edge Case (workers-sdk #11870): If you provide only binding without database_name/bucket_name, Wrangler uses the binding name as the resource name. This causes confusing behavior with wrangler dev and subcommands, which prefer database_id → database_name → binding.

// ❌ DON'T: Binding-only creates database named "DB"
{
  "d1_databases": [{ "binding": "DB" }]
}

// ✅ DO: Explicit names prevent confusion
{
  "d1_databases": [
    {
      "binding": "DB",
      "database_name": "my-app-db"  // Always specify!
    }
  ],
  "r2_buckets": [
    {
      "binding": "STORAGE",
      "bucket_name": "my-app-files"  // Always specify!
    }
  ],
  "kv_namespaces": [
    {
      "binding": "CACHE",
      "title": "my-app-cache"  // Always specify!
    }
  ]
}

# Deploy - resources auto-provisioned if they don't exist
wrangler deploy

# Disable auto-provisioning (use existing resources only)
wrangler deploy --no-x-provision

Benefits:

• No separate wrangler d1 create / wrangler r2 create steps needed
• Idempotent - existing resources are used, not recreated
• Works with local dev (wrangler dev creates local emulated resources)

Workers RPC (Service Bindings)

What It Is: JavaScript-native RPC system for calling methods between Workers. Uses Cap'n Proto under the hood for zero-copy message passing.

Use Case: Split your application into multiple Workers (e.g., API Worker + Auth Worker + Email Worker) that call each other with type-safe methods.

Defining an RPC Service:

import { WorkerEntrypoint } from 'cloudflare:workers'

export class AuthService extends WorkerEntrypoint<Env> {
  async verifyToken(token: string): Promise<{ userId: string; valid: boolean }> {
    // Access bindings via this.env
    const session = await this.env.SESSIONS.get(token)
    return session ? { userId: session.userId, valid: true } : { userId: '', valid: false }
  }

  async createSession(userId: string): Promise<string> {
    const token = crypto.randomUUID()
    await this.env.SESSIONS.put(token, JSON.stringify({ userId }), { expirationTtl: 3600 })
    return token
  }
}

// Default export still handles HTTP requests
export default { fetch: ... }

Calling from Another Worker:

// wrangler.jsonc
{
  "services": [
    { "binding": "AUTH", "service": "auth-worker", "entrypoint": "AuthService" }
  ]
}

// In your main Worker
const { valid, userId } = await env.AUTH.verifyToken(authHeader)

Key Points:

• Zero latency: Workers on same account typically run in same thread
• Type-safe: Full TypeScript support for method signatures
• 32 MiB limit: Max serialized RPC message size
• Self-bindings: In wrangler dev, shows as [connected] for same-Worker calls

Troubleshooting

Random "Response Already Sent" Errors in Development

Symptom: Sporadic ResponseSentError: The response has already been sent to the browser and cannot be altered during wrangler dev Source: workers-sdk #11932 Cause: Cache corruption in .wrangler directory or stale Vite cache

Solution:

# Clear all caches
rm -rf .wrangler dist node_modules/.vite

# Rebuild
npm run build

# Recreate local D1 databases if needed
wrangler d1 execute DB --local --file schema.sql

Applies to: Wrangler 4.x full Workers mode (not Cloudflare Pages)

Community Tips

Note: These tips come from community discussions. Verify against your version.

Avoid vite-tsconfig-paths v6 with React SSR

Source: workers-sdk #11825 (Community-sourced)

If using React SSR with @cloudflare/vite-plugin, pin to [email protected]:

npm install [email protected]

Why: Version 6.x doesn't follow path aliases during dependency scan, causing duplicate React instances and "Invalid hook call" errors.

Applies to: Projects using TypeScript path aliases with React SSR

Use crypto.randomUUID() Instead of uuid Package

Source: workers-sdk #11957

The uuid@11 package (ESM) can cause runtime crashes with "fileURLToPath undefined" in Workers. Use the native Web Crypto API instead:

// ✅ Native Workers API (recommended)
const uuid = crypto.randomUUID();

// ❌ Avoid uuid package in Workers
import { v4 as uuidv4 } from 'uuid';  // May crash

Applies to: All Workers projects needing UUIDs

Commands

/deploy - One-Command Deploy Pipeline

Use when: Ready to commit, push, and deploy your Cloudflare Worker in one step.

Does:

1. Pre-flight: Verifies wrangler config, checks for changes, builds, runs TypeScript check
2. Commit & Push: Stages changes, generates conventional commit message, pushes to remote
3. Deploy: Runs wrangler deploy, captures Worker URL
4. Report: Shows commit hash, branch, deployed URL, any warnings

Time savings: 2-3 min per deploy cycle

Edge Cases Handled:

• No changes to commit → skips to deploy
• Build script missing → warns and continues
• No remote configured → reports error with suggestion
• TypeScript errors → stops and reports

Bundled Resources

Templates: Complete setup files in templates/ directory (wrangler.jsonc, vite.config.ts, package.json, tsconfig.json, src/index.ts, public/index.html, styles.css, script.js)

Official Documentation

• Cloudflare Workers: https://developers.cloudflare.com/workers/
• Static Assets: https://developers.cloudflare.com/workers/static-assets/
• Vite Plugin: https://developers.cloudflare.com/workers/vite-plugin/
• Wrangler: https://developers.cloudflare.com/workers/wrangler/
• Hono: https://hono.dev/docs/getting-started/cloudflare-workers
• MCP Tool: Use mcp__cloudflare-docs__search_cloudflare_documentation for latest docs

Dependencies (Latest Verified 2026-01-03)

{
  "dependencies": {
    "hono": "^4.11.3"
  },
  "devDependencies": {
    "@cloudflare/vite-plugin": "^1.17.1",
    "@cloudflare/workers-types": "^4.20260103.0",
    "vite": "^7.3.1",
    "wrangler": "^4.54.0",
    "typescript": "^5.9.3"
  }
}

Production Validation

Live Example: https://cloudflare-worker-base-test.webfonts.workers.dev (build time: 45 min, 0 errors, all 10 issues prevented)

Last verified: 2026-01-20 | Skill version: 3.1.0 | Changes: Added Vite 8 nodejs_compat workaround (Issue #9), Vite base option regression (Issue #10), auto-provisioning edge case warning, troubleshooting section for cache corruption, and community tips for vite-tsconfig-paths v6 and uuid package alternatives. Research conducted by skill-researcher agent covering post-May 2025 Workers SDK updates.