# Effect Program Design

Design, write, review, and test production Effect v4 programs: deep services and...

- Repository: https://github.com/humanlayer/humanlayer (12740 stars)
- Category: Design
- License: Apache-2.0
- Last updated: 2026-10-31
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add humanlayer/humanlayer --skill effect-program-design -g -a claude-code -y`
Codex: `npx skills add humanlayer/humanlayer --skill effect-program-design -g -a codex -y`
Cursor: `npx skills add humanlayer/humanlayer --skill effect-program-design -g -a cursor -y`
Gemini CLI: `npx skills add humanlayer/humanlayer --skill effect-program-design -g -a gemini-cli -y`

## Description

Design, write, review, and test production Effect v4 programs: deep services and layers, schemas, tagged errors, observability, Config, persistence, resources, concurrency, schedules, workers, streams, caches, HTTP clients, Effect platform services (Node filesystem/path/crypto/process/socket), and Effect Atom integrations. Use for any Effect application or adapter work.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Effect Program Design

Build production Effect v4 programs with small domain-shaped interfaces, typed success and error channels,
declared dependencies, observable operation boundaries, and tests that substitute layers at real seams. This skill
combines broad Effect mechanics with HumanLayer's deep-module, capture-before-narrow, and real-seam design standards.

## Source rule

Check these before guessing:

1. the nearest `CLAUDE.md` / `AGENTS.md` and project-local conventions;
2. the installed `effect`, `@effect/*`, and related package versions and declarations;
3. the Effect v4 docs at <https://effect-ts-effect-smol.mintlify.app/>;
4. the pinned/upstream source (`~/projects/effect-smol`) when docs do not settle an API.

unstable-tagged modules (`effect/http`, `effect/rpc`, `effect/process`, ...) can change between beta/minor versions. Typecheck examples against the installed version. Local
project conventions take precedence unless the task explicitly changes them.

## References

Read only the references relevant to the task; read all matching branches when work crosses concerns.

The rest: https://github.com/humanlayer/humanlayer/blob/HEAD/.claude/skills/effect-program-design/SKILL.md