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Effect Documentation

This Week in Effect - 2026-05-15

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

The one weird Git trick that makes coding agents more Effect-ive: a practical guide on using Git subtrees to vendor Effect’s source code directly into your project, giving coding agents access to real implementation patterns so they write more idiomatic Effect code. Article by Maxwell Brown.

 

Effect v4 Beta updates

Significant Schema ergonomics improvements, a new durable module port, and continued IndexedDB refinements — here are the most notable changes that landed in effect-smol.

  • Schema defaults & decoding: Allowed schema decoding defaults to require services (enabling context-aware defaults), allowed defaults to fail with SchemaError, switched to eager mapping for schema defaults for more predictable behavior, fixed makeEffect usage, and restored support for passing schema parse options when creating decode/encode helpers. Also renamed SchemaParser.makeUnsafe to SchemaParser.make for consistency.

  • DurableQueue: Ported the DurableQueue module from v3, bringing persistent queue semantics to the v4 beta.

  • IndexedDB: Used Cause.NoSuchElementError for IDB .first queries (aligning with the rest of the Effect error model), and cached base IDB query builders for better performance.

  • HttpApi: Allowed overriding HttpApiTest group base URLs, making it easier to test endpoints against different environments.

  • RPC & HTTP: Fixed RpcServer HTTP finalizer request IDs, and removed the HTTP server log span counter.

  • SQL: Added Sql.unique for queries that must return exactly one row.

  • Developer experience: Fixed schema Struct symbol links to preserve “Go to Definition” (F12) navigation in VSCode, and clarified filter annotation messages in Schema docs.

  • Removals: Removed Effect.Yieldable, continuing the v4 API surface cleanup.

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

 

Here are all the technical changes from the past week.

Effect CLI

 

Community Events

The second Effect Milan Meetup 🇮🇹 is scheduled on June 11 — hosted & co-organized by Datapizza 🍕.

We have two more meetups happening this month: the Effect Vienna 🇦🇹 on May 27, sponsored by Sentry, and Effect Miami 🇺🇸 on May 28, hosted by The LAB Miami.

Visit our Effect Community Events calendar and subscribe for updates on upcoming Effect events and meetups.

 

Community Highlights

 

  • OpenCode migrated from Hono to Effect HttpApi!

    Kit Langton
    Kit Langton
    @kitlangton
    · Follow

    I finally merged and released the Hono → Effect HttpApi migration. With this, the first Effectification pass of the opencode repo is complete. Now for the second and third passes. 🙏😭

    Image
    OpenCode Changelog
    OpenCode Changelog
    @OpenCodeLog

    𝙊𝙥𝙚𝙣𝘾𝙤𝙙𝙚 v1.14.42 released. TL;DR: native LLM core groundwork; interactive opencode run; Effect HTTP API replaces Hono paths; Scout/repo research + provider retry fixes. 𝗖𝗼𝗿𝗲 & 𝗟𝗟𝗠 • Added a new internal @opencode-ai/llm foundation: schema-first requests/events,

    606
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    Read 24 replies

 

 

 

 

 

  • zenbu.js - a TypeScript framework for building applications that users and coding agents can modify at runtime through direct source code editing or plugin injection, without recompilation.

 

  • @wolfcola/treeshake-check - a tree-shakeability analyzer built on Effect and @effect/cli.  

  • effect-http-starter - a project scaffolding tool for spinning up new Effect HTTP server projects with schema-first API design, CRUD endpoints, health checks, Scalar docs, and OpenAPI spec generation out of the box.

 

Effect Content Update

  • effect.fail vs effect.die, Typed Errors vs Defects, Workflows, Effect SQL | Effect Office Hours 28 🔥
Play

 

  • Effect Query Builder: effect-qb
Play

 

  • Effect Workflows & Cluster
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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