Effect

Effect is a TypeScript framework that models computations as lazy, typed workflows (Effect<A, E, R>). You describe what should happen, including its possible errors and dependencies, and the runtime handles execution, concurrency, resource cleanup, and observability.

Overview

Contents

Concepts

• The Effect Type - The three-channel Effect<A, E, R> type and why it matters
• Generators and Yield - Effect.gen, yield*, Effect.fn, and the return yield* pattern
• Typed Errors - Schema.TaggedError, Data.TaggedError, and the catch combinator family
• Dependency Injection - Context.Service, Layer, and the v4 service pattern
• Structured Concurrency - Fibers, Effect.all, concurrency options, and racing
• Scope and Resources - Effect.acquireRelease, Scope, and guaranteed cleanup

Architecture

• Runtime and Fibers - Fiber scheduler, structured concurrency model, and runtime configuration
• Layer Composition - Dependency graphs, memoization, and layer lifecycle

Resources

• Effect Docs (v4)
• LLMS.md Guide
• SCHEMA.md Guide
• Effect API Reference
• Effect Discord