Type Safety Guardian Skill

I autonomously enforce strict TypeScript typing per ADR-0006. I activate whenever TypeScript code is being written or reviewed.

Core Mission

ZERO TOLERANCE FOR any OR unknown TYPES

When I Activate

I trigger when:

• Writing new TypeScript code
• Reviewing existing code
• Fixing TypeScript compiler errors
• Refactoring code
• Integrating third-party libraries

What I Check

Forbidden Patterns (Auto-Reject)

• any types
• as any casts
• unknown types (except external APIs)
• Property existence checks ('property' in object)
• Optional chaining for type narrowing
• Missing return types on public methods

Required Patterns (Auto-Enforce)

• Explicit return types on public methods
• Strong type assumptions based on context
• Non-null assertions when safe (value!)
• Discriminated unions for variant types
• import type { } for type imports
• Classes over interfaces for entities
• Shared types from types/core.ts

How I Help

1. Proactive Detection

// ❌ I CATCH THIS
function process(data: any) { // FORBIDDEN!
  return data.value;
}

// ✅ I SUGGEST THIS
function process<T extends { value: string }>(data: T): string {
  return data.value;
}

2. Context-Based Typing

// ❌ I CATCH THIS
if ('position' in entity) { // Weak typing!
  entity.position.x = 0;
}

// ✅ I SUGGEST THIS
const player = entity as PlayerEntity; // Strong assumption
player.position.x = 0;

3. Proper Generics

// ❌ I CATCH THIS
function findItem(items: any[], id: string) {
  return items.find(i => i.id === id);
}

// ✅ I SUGGEST THIS
function findItem<T extends { id: string }>(items: T[], id: string): T | undefined {
  return items.find(i => i.id === id);
}

Automatic Actions

When I detect violations:

1. Immediate alert - Flag the violation clearly
2. Root cause analysis - Why did this happen?
3. Proper solution - Show correctly typed version
4. Fix immediately - Don't defer, fix now
5. Educate - Explain why it matters

Integration with Project

• Enforces ADR-0006 standards
• Uses eslint rule: @typescript-eslint/no-explicit-any: 'error'
• References shared types from @hyperscape/shared
• Checks all packages in monorepo
• Fails builds on violations

Success Metrics

Target: ZERO any types in production code

Current violations get fixed immediately, not deferred.

References

• ADR-0006: Enforce TypeScript Strict Typing Standards
• CLAUDE.md coding-standards.mdc
• eslint.config.js

I use Deepwiki to research advanced TypeScript patterns when needed.