---compatibility: name: effect-tsdescription: ---

Effect 3

Apply Effect 3 semantics from project-local architecture, the narrowest relevant reference, and source matching the target's installed packages.

Workflow

Do not activate this workflow merely because a file imports effect. For nontrivial Effect work:

1. Resolve the target package or workspace and its exact installed effect and relevant @effect/* versions. If effect is not 3.x, stop because this skill does not apply.
2. Inspect neighboring services, layers, errors, schemas, runtime boundaries, and tests. Local conventions decide organization; installed package evidence decides API facts.
3. Read references/critical-rules.md, then only the task-specific references below.
4. Verify every uncertain import, signature, or behavior against the package installation visible to the target workspace before editing.
5. Implement the smallest pattern consistent with the project and run the narrowest test or typecheck covering the changed semantics.

Evidence Order

Use the target workspace's manifest and lockfile to identify versions. Prefer, in order:

1. the installed package's src/, README, tests, and changelog;
2. its emitted declarations when source is not shipped;
3. the matching official package artifact or source tag.

Do not install or update dependencies solely to obtain documentation. Do not trust an unrelated checkout or a source branch that does not match the target's installed version. If exact behavior cannot be verified, stop rather than guessing.

Reference Router

Task	Reference
Services, Layers, tags, Effect.fn	references/services-layers.md
Config providers and secrets	references/config.md
Schema, JSON Schema, encoded errors/models	references/schema-jsonschema.md
@effect/vitest, clocks, fibers, retries	references/testing.md
resources, scheduling, refs, concurrency	references/runtime.md
streams and backpressure	references/streams.md
pattern matching and tagged unions	references/pattern-matching.md
@effect/ai	references/ai.md
@effect/sql	references/sql.md
Next.js / @prb/effect-next	references/next-js.md
Effect Atom	references/effect-atom.md
Option at nullable boundaries	references/option-null.md

For platform/RPC APIs, collection utilities, deprecations, or constructor lookup, inspect the installed package source directly instead of loading a local API inventory.

Boundaries

• Keep pure helpers, constants, and path manipulation pure unless an Effect boundary provides a concrete dependency, testability, resource-safety, or error-model benefit.
• Preserve existing domain facades and service/runtime boundaries unless the user requested redesign.
• Prefer typed failures and scoped resources at IO boundaries; choose Schema-backed errors/models only when encoding or boundary validation is needed.
• Do not broaden environment requirements merely to replace a small platform call.

For changes, completion requires code consistent with local Effect architecture, selected references and installed source where needed, and the narrowest test/typecheck that exercises the changed semantics. Read-only work requires evidence for the reported conclusion. Finish with ### ⚡ Effect — ✅ change complete after verified edits or ### ⚡ Effect — 🔎 reviewed, no files written for read-only work, one sentence naming the boundary or pattern used, and ### 🧪 Verification with exact scoped commands/results. If required validation is incomplete, use ### ⚡ Effect — ⛔ blocked instead. Add ### ⚠️ Limitation only for non-blocking caveats. Never decorate typed errors, Schema messages, logs, tests, generated JSON/API responses, or command output.