Effect TS Guide

Overview

Use this skill to teach Effect-TS fundamentals and best practices, then apply them to user code and architecture questions.

Teaching workflow

• Clarify context: runtime (node/bun/browser), goal (new app, refactor, review), and constraints.

• Separate core vs shell: identify pure domain logic vs effects and boundaries.

• Model errors and dependencies: define tagged error types and Context.Tag service interfaces.

• Compose with Effect: use pipe/Effect.gen, typed errors, and Layer provisioning.

• Validate inputs at boundaries with @effect/schema before entering core.

• Explain resource safety: acquireRelease, scoped lifetimes, and clean finalizers.

• Provide minimal, runnable examples tailored to the user context.

• If the user asks for version-specific or "latest" details, verify with official docs before answering.

Core practices (short list)

• Use Effect for all side effects; keep core functions pure and total.

• Avoid async/await, raw Promise chains, and try/catch in application logic.

• Use Context.Tag + Layer for dependency injection and testability.

• Use tagged error unions and Match.exhaustive for total handling.

• Decode unknown at the boundary with @effect/schema; never leak unknown into core.

• Use Effect.acquireRelease/Effect.scoped for resource safety.

• Use @effect/platform services instead of host APIs (fetch, fs, child_process, etc.).

References

• Read references/best-practices.md for the extended checklist and examples.

• Read references/platform-map.md when comparing @effect/platform to Node/Bun/Browser APIs.