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Effect Documentation

This Week in Effect - 2026-03-27

Davide Scognamiglio
Davide Scognamiglio
Project Manager
 Mirela Prifti
Mirela Prifti
Community Manager
 Michael Arnaldi
Michael Arnaldi
BDFL

Hi Effecters!

Welcome back to This Week In Effect (TWIE) - your weekly update of the latest developments in the Effect community and ecosystem.

Effect is a powerful TypeScript library that helps developers build complex, synchronous, and asynchronous programs. One key feature that sets Effect apart is how it leverages structured concurrency to provide features such as async cancellation and safe resource management, making it easier to build robust, scalable, and efficient programs.

To get started, below you’ll find links to our documentation as well as our guide for installing Effect. Enjoy!

Recent major updates:

 

Technology

Effect v4 Beta updates

Here are the main changes that landed in effect-smol.

  • HttpApi overhaul: Added a code generation module (HttpApi.gen), reworked HttpApiClient so urlBuilder uses schemas and client-shaped APIs, renamed the withResponse option to responseMode, added disableCodecs option to HttpClientEndpoint constructors, fixed security middleware cache reuse, and updated docs to reflect automatic codec coercion for HttpApiEndpoint. Also allowed middleware to accept error arrays and fixed the HttpApi.Any constraint for HttpApiClient.urlBuilder.
  • Schema improvements: Collapsed same-type literal branches into a single enum array in JSON Schema output, fixed compactEnums to support multi-value enum branches, renamed MakeOptions.disableValidation to disableChecks (now also applies constructor defaults when set), and fixed Struct utility return types (e.g. pick) to preserve the simplified shape instead of exposing raw Pick<T, K> types.
  • AI & streaming: Fixed missing finish parts in LanguageModel streaming, fixed tool output persistence in streamed chat history, fixed the OpenRouter client HTTP referer header name, and added Stream.timeoutOrElse.
  • PostgreSQL & runtime: Added a dedicated PG connection for LISTEN, switched to pg_notify instead of raw NOTIFY in PgClient, cleaned up sql-pg constructors and layers, fixed Unify.unify for Effect unions, flushed devtools queued messages on teardown, and tracked ManagedRuntime fibers in a scope.
  • Bug fixes & internals: Fixed Schedule.fixed immediate catch-up for long-running iterations, re-exported core ServiceMap references in effect/References, fixed Queue.takeN example, fixed metro bundler issues, allowed ServiceMap.Key to be covariant, and improved Prompt.select/multiSelect highlight text color.

You can follow the full changelog directly in the effect-smol repository.

 

Here are all the technical changes from the past week.

Effect Core

Effect AI

Effect SQL

 

Community Events

This week, the acemate.ai team, Jan Tiegges, and Tom Favre successfully wrapped up the 3rd edition of Effect Berlin 🇩🇪 meetup! We’re very grateful to acemate.ai for hosting, and to everyone who joined and made it a great, educational evening around Effect!

To stay informed about future events, visit our Effect Community Events calendar and subscribe for updates.

 

Community Highlights

 

 

 

 

  • expect - a tool for letting agents test your code in a real browser. Priject by the Million Software team.

 

  • effect-jetbrains-plugin – JetBrains plugin for @effect/tsgo language-server support and Effect runtime Dev Tools. Project by elpresidank.

 

  • effect-analyzer – static analysis for Effect code. Project by Jag Reehal.

 

  • audius-mcp-atris – a Code Mode MCP server using Effect for the Audius web3 music platform. Project by glassBead.

 

  • The Effect Schema course by Hemanta Kumar Sundaray got 2 new chapters: optional/nullable fields and Standard Schema Integration.

 

Effect Content Update

  • Roasting PRs & ecosystem updates | Effect Office Hours 22 🔥
Play

 

  • Effect.all
Play

 

  • ChEffect 15 - A Local-First Meal Planning App written with Effect & LiveStore
Play

 

  • Effect v4 CLI
Play

 

  • How to use AI Agents with Effect the right way
Play

 

  • LLM usage tips from the Effect Team, Ralph, Lalph
Play

 

  • Effect.Retry
Play

 

Cause & Effect Podcast

Don’t forget to listen to our Cause & Effect podcast hosted by Johannes Schickling and available on YouTube, X(Twitter), and audio platforms like Spotify and Apple Podcast.

Adam Rankin, CTO at Warp, joined Johannes Schickling to talk about using Effect to bring structure and composability to a growing TypeScript codebase, enabling a small, fast-moving team to stay productive while shipping reliable payment & payroll systems.

Play

 

Effect Job Opportunities

More and more companies are adopting Effect in their projects. Here’s a list of companies looking for software engineers with Effect experience:

Disclaimer: Please note that these job postings are shared for informational purposes, and we encourage applicants to verify details directly with the hiring companies.

 

Effect Merch Store

The Effect Merch Store offers a selection of Effect-branded items designed for the community. All orders are processed and fully managed through Printful.

 

Closing Notes

That’s all for this week. Thank you for being a vital part of our community. Your feedback is highly valued as we fine-tune this format. Feel free to share your thoughts, and we’ll do our best to tailor it to the needs of our community.

Effect Community Team

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