Effect v4 (Beta) - Development & Migration

Overview

Comprehensive guidance for Effect v4 development and migration from v3. This skill provides:

v4 Core Patterns - Guide to building new v4 code with Context, layers, generators, schema codecs
v3 → v4 Migration - Step-by-step migration guidance with API renames, behavior changes, and before/after examples

Status: Effect v4 is beta software under active development in effect-smol. The core programming model is stable, but effect/unstable/* modules may receive breaking changes in minor releases. For production use, review official v4 beta guidance and stability notes.

All bundled migration guides are sourced from the official effect-smol migration documentation.

Upstream Changes Since February 22, 2026

The upstream beta changed substantially after this skill was last refreshed. Treat older examples that mention ServiceMap or Schema.makeUnsafe as stale. Current guidance should prefer:

Related skills

More from teeverc/effect-ts-skills

effect-ts
Effect-TS (Effect) guidance for TypeScript. Use when building, refactoring, reviewing, or explaining Effect code, especially for: typed error modeling (expected errors vs defects), Context/Layer/Effect.Service dependency wiring, Scope/resource lifecycles, runtime execution boundaries, schema-based decoding, concurrency/scheduling/streams, @effect/platform APIs, Effect AI workflows, and Promise/async migration.
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Repository

teeverc/effect-ts-skills

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First Seen

Feb 28, 2026

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