Workers Runtime Validator SKILL

Activation Patterns

This SKILL automatically activates when:

• New .ts or .js files are created in Workers projects
• Import statements are added or modified
• Code changes include potential runtime violations
• Before deployment commands are executed
• When process.env, require(), or Node.js APIs are detected

Expertise Provided

Runtime Compatibility Validation

• Forbidden API Detection: Identifies Node.js built-ins that don't exist in Workers
• Environment Access: Ensures proper env parameter usage vs process.env
• Module System: Validates ES modules usage (no require())
• Async Patterns: Ensures all I/O operations are async
• Package Compatibility: Checks npm packages for Node.js dependencies

Specific Checks Performed

❌ Critical Violations (Will Break in Production)

// These patterns trigger immediate alerts:
import fs from 'fs';                    // Node.js API
import { Buffer } from 'buffer';        // Node.js API
const secret = process.env.API_KEY;     // process doesn't exist
const data = require('./module');        // require() not supported

✅ Correct Workers Patterns

// These patterns are validated as correct:
import { z } from 'zod';                // Web-compatible package
const secret = env.API_KEY;             // Proper env parameter
const hash = await crypto.subtle.digest(); // Web Crypto API

Integration Points

Complementary to Existing Components

• workers-runtime-guardian agent: Handles deep runtime analysis, SKILL provides immediate validation
• cf-deploy command: SKILL prevents deployment failures by catching issues early
• validate command: SKILL provides continuous validation between explicit checks

Escalation Triggers

• Complex runtime compatibility questions → workers-runtime-guardian agent
• Package dependency analysis → edge-performance-oracle agent
• Migration from Node.js to Workers → cloudflare-architecture-strategist agent

Validation Rules

P1 - Critical (Must Fix Immediately)

• Node.js Built-ins: fs, path, os, crypto, process, buffer
• CommonJS Usage: require(), module.exports
• Process Access: process.env, process.exit()
• Synchronous I/O: Any blocking I/O operations

P2 - Important (Should Fix)

• Package Dependencies: npm packages with Node.js dependencies
• Missing Async: I/O operations without await
• Buffer Usage: Using Node.js Buffer instead of Uint8Array

P3 - Best Practices

• TypeScript Env Interface: Missing or incorrect Env type definition
• Web API Usage: Not using modern Web APIs when available

Remediation Examples

Fixing Node.js API Usage

// ❌ Critical: Node.js crypto
import crypto from 'crypto';
const hash = crypto.createHash('sha256');

// ✅ Correct: Web Crypto API
const encoder = new TextEncoder();
const hash = await crypto.subtle.digest('SHA-256', encoder.encode(data));

Fixing Environment Access

// ❌ Critical: process.env
const apiKey = process.env.API_KEY;

// ✅ Correct: env parameter
export default {
  async fetch(request: Request, env: Env) {
    const apiKey = env.API_KEY;
  }
}

Fixing Module System

// ❌ Critical: CommonJS
const utils = require('./utils');

// ✅ Correct: ES modules
import { utils } from './utils';

MCP Server Integration

When Cloudflare MCP server is available:

• Query latest Workers runtime API documentation
• Check for deprecated APIs before suggesting fixes
• Get current compatibility information for new features

Benefits

Immediate Impact

• Prevents Runtime Failures: Catches issues before deployment
• Reduces Debugging Time: Immediate feedback on violations
• Educates Developers: Clear explanations of Workers vs Node.js differences

Long-term Value

• Consistent Code Quality: Ensures all code follows Workers patterns
• Faster Development: No need to wait for deployment to discover issues
• Better Developer Experience: Real-time guidance during coding

Usage Examples

During Code Creation

// Developer types: import fs from 'fs';
// SKILL immediately activates: "❌ CRITICAL: 'fs' is a Node.js API not available in Workers runtime. Use Web APIs or Workers-specific alternatives."

During Refactoring

// Developer changes: const secret = process.env.API_KEY;
// SKILL immediately activates: "❌ CRITICAL: 'process.env' doesn't exist in Workers. Use the 'env' parameter passed to your fetch handler instead."

Before Deployment

// SKILL runs comprehensive check: "✅ Runtime validation passed. No Node.js APIs detected, all environment access uses proper env parameter."

This SKILL ensures Workers runtime compatibility by providing immediate, autonomous validation of code patterns, preventing common migration mistakes and runtime failures.