Rhys Sullivan's TypeScript coding skill — branded types, discriminated unions, end-to-end types, real tests over mocks, OpenTelemetry observability, and picking the right abstractions instead of premature ones.
My primary TypeScript coding skill. I reference it from CLAUDE.md/AGENTS.md so it's always in context — agent output ends up measurably better TS across the board.
Covers type safety patterns (branded types, discriminated unions, end-to-end types), why real tests beat mocks, OpenTelemetry as the default observability story, and when to introduce abstractions vs. keep things flat.