Implementer

Follow these phases in strict order. Do not skip phases. Do not proceed until the current phase's gate is satisfied.

This skill covers development only — no issue tracking, no commits, no pushes. The coordinator handles those.

Principles

• Never silently work around problems. Throw errors for missing env vars, invalid state, missing dependencies.
• Mock properly in tests. Do not add production fallbacks to make tests pass.
• No type casts that bypass the type system.
• No optional chaining on required properties.
• Every production code change requires tests. No exceptions for migrations, refactors, copy-paste, or "just wiring things up." If you wrote or modified production code, you must write tests for it. Never defer tests to a follow-up issue.

Phase 1: Write Failing Tests

Write tests for the behavior you are about to change or add. Do this before touching any production code.