Effect-TS

Overview

Provide workflows, patterns, and best practices for building Effect-based TypeScript programs, with focused references for errors, dependencies, resources, runtime execution, generators, schema, and testing.

For the most up-to-date documentation, see https://effect.website/docs and https://effect.website/docs/platform. For internal lookups, the effect-docs MCP can be used to search and fetch API references (https://github.com/tim-smart/effect-mcp).

Quick Triage

• If it needs core Effect data types or combinators, open references/core-usage.md.
• If the task is about error modeling or typed failures, open references/error-management.md.
• If it needs error tooling (sandboxing, Cause, error-channel transforms), open references/error-tooling.md.
• If it involves services/dependencies, open references/dependency-management.md.
• If it involves layer construction or test wiring, open references/layer-patterns.md.
• If it involves resource lifecycles, open references/resource-management.md.
• If it involves running effects or runtime choice, open references/runtime-execution.md.
• If it involves fibers or concurrency primitives, open references/concurrency.md.
• If it involves interruption, supervision, or fiber refs, open references/concurrency-advanced.md.
• If it involves schedules or repetition, open references/scheduling.md.
• If it involves retries/backoff or schedule composition, open references/scheduling-retry.md.
• If it involves streams, queues, pubsub, or STM, open references/streams-queues-stm.md.
• If it involves HTTP clients or external APIs, open references/http-client.md.
• If it involves HTTP servers or API definitions, open references/http-server.md.
• If it involves request batching or data loaders, open references/request-resolver.md.
• If it involves caching or memoization, open references/caching.md.
• If it involves configuration or config providers, open references/configuration.md.
• If it involves advanced config or redaction, open references/configuration-advanced.md.
• If it involves logs, metrics, or tracing, open references/observability.md.
• If it needs concrete logger/metrics/tracing setups or exporters, open references/observability-examples.md.
• If it needs wiring of log/metric/trace layers, open references/observability-wiring.md.
• If it needs sequential/branching readability, open references/generators.md.
• If it needs runtime validation/decoding, open references/schema.md.
• If it needs deterministic time in tests, open references/testing.md.
• If it needs broader testing services, open references/testing-stack.md.
• If it involves migrating from Promise/async, open references/migration-async.md.
• If it needs versioning or signature changes, open references/versioning.md.
• If it hits common pitfalls or runtime errors, open references/troubleshooting.md.
• If it needs result inspection or debugging, open references/exit-cause.md.

Core Workflow

1. Clarify boundaries and IO; keep core logic as Effect values.
2. Choose style: use pipelines for simple composition; use Effect.gen for sequential logic.
3. Model errors explicitly: type expected errors; treat defects as unexpected failures.
4. Model dependencies with services, tags, and layers; keep interfaces clean of construction concerns.
5. Manage resource lifecycles with Scope when opening/closing resources.
6. Provide the environment via layers and run effects only at the program edge.

Output Standards

• Show imports and minimal runnable examples.
• Keep dependency graphs explicit (services, layers, context tags).
• Include error channel types and call out expected vs defect errors.
• Avoid running effects inside libraries; show runtime usage in entrypoints or tests.

References

• references/core-usage.md – core data types and common combinators.
• references/error-management.md – expected vs unexpected errors and error-channel guidance.
• references/error-tooling.md – sandboxing, Cause handling, and error-channel transforms.
• references/exit-cause.md – Exit/Cause usage and result handling.
• references/dependency-management.md – services, tags, contexts, layers, and Effect.Service patterns.
• references/layer-patterns.md – layer construction, composition, and test wiring.
• references/resource-management.md – Scope and finalizers.
• references/runtime-execution.md – run* functions and edge execution.
• references/concurrency.md – fibers, forking, and lifetime strategies.
• references/concurrency-advanced.md – interruption, supervision, and fiber refs.
• references/scheduling.md – schedules, repetition, and timing.
• references/scheduling-retry.md – retry policies, backoff, and schedule composition.
• references/streams-queues-stm.md – Stream, Queue, PubSub, and STM touchpoints.
• references/http-client.md – HTTP client patterns and external API calls.
• references/http-server.md – HTTP server and HttpApi patterns.
• references/request-resolver.md – Request/RequestResolver batching patterns.
• references/caching.md – caching and memoization utilities.
• references/configuration.md – Config, ConfigProvider, and runtime configuration.
• references/configuration-advanced.md – nested config, redaction, and test providers.
• references/observability.md – logging, metrics, and tracing overview.
• references/observability-examples.md – concrete logger/metrics/tracing configs and exporters.
• references/observability-wiring.md – how to provide observability layers in apps.
• references/generators.md – Effect.gen patterns.
• references/schema.md – Effect Schema overview and requirements.
• references/testing.md – TestClock guidance.
• references/testing-stack.md – test services, layers, and config in tests.
• references/migration-async.md – guidance for Promise/async migration.
• references/versioning.md – version and signature change notes.
• references/troubleshooting.md – common errors and fixes.