Effect Expert

Use this skill when working with Effect services, layers, schema errors, config, and runtime integration.

Load Triggers

Load this skill when:

• User mentions Effect, Layer, Context.Tag, Schema.TaggedError, Effect.gen, or Effect.fn
• You are editing service files in packages/services/ or agent-tools/*
• You need test strategy for Effect code (@effect/vitest, test layers)
• You need Effect runtime integration (TRPC/server boundaries)

First Step (Always)

Before implementing or reviewing, fetch current recommendations:

effect-solutions list
effect-solutions show tsconfig
effect-solutions show basics
effect-solutions show services-and-layers
effect-solutions show data-modeling
effect-solutions show error-handling
effect-solutions show config
effect-solutions show testing
effect-solutions show cli

Effect guidance evolves. Do not rely on stale memory.

Decision Tree

• Service design or refactor -> references/services-and-layers.md
• Typed errors, Option/Either, recovery -> references/error-handling.md
• TRPC/server runtime boundary -> references/framework-integration.md
• CLI tooling in agent-tools/* -> references/agent-tools-patterns.md
• Testing and mocks -> references/testing-layers.md

Project Rules (Do Not Break)

• Prefer service co-location (Context.Tag + static layer in one file)
• Use Schema.TaggedError for domain errors
• Do not access Option/Either internals via _tag; use helpers (match, isNone, isLeft)
• For Effect dependencies, mock with Layers, not vi.mock()
• Keep one clear provide boundary at entry points

Output Expectations

When advising or implementing, return:

1. Which effect-solutions show ... topics were checked
2. Which reference file(s) were used and why
3. Concrete change proposal following existing project patterns
4. Verification plan (typecheck/tests)

Reference Index

• references/services-and-layers.md
• references/error-handling.md
• references/framework-integration.md
• references/agent-tools-patterns.md
• references/testing-layers.md