Implement

Principle

Ship the smallest complete vertical slice through the correct public interface and canonical owner.

Every behavior change follows red -> green -> refactor. Green means the test passes and the implementation has no debt: no bridges, compatibility shims, fallback paths, split truth, TODO-driven hacks, or misleading partial types.

If the full feature cannot ship cleanly in one pass, narrow scope. Do not paper over the gap.

Before Coding

Answer these before editing implementation code:

• What public interface proves the behavior?
• What behavior should be tested first?
• What is the canonical owner for this behavior?
• What stable contract should callers use?
• What is the smallest complete vertical slice?
• What shortcut would be tempting here, and why is it rejected?
• What verification will prove the slice works?