Effect v4

Routing

• Do not read this file linearly. Pick one target.
• Match the task to a folder below, then open the file whose title fits.
• Within a folder, the lowest-numbered file is the lead example for that topic; higher numbers add variations.
• fixtures/ folders hold supporting modules for an example, not standalone topics.
• Migrating existing v3 code? Go to Migration first.

Identify the version

Use this skill when the code targets Effect v4:

• effect@4 (or 4.0.0-beta.*) in package.json, with @effect/* packages on the same version.
• Imports from effect/unstable/* (http, httpapi, cli, sql, rpc, cluster, ai, observability, process, ...).
• Context.Service for services, Effect.fn(...) for effectful functions, Schema.TaggedErrorClass for errors.

If it's effect@3 / @effect/platform@0.x style, use ts-effect-v3.