Hi Effecters!
Welcome back to This Week in Effect, your weekly update of the latest developments in the Effect community and ecosystem.
Effect is the TypeScript library for the AI era, helping 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 and our guide for installing Effect. Enjoy!
Recent major updates:
- Effect v4 Release Candidate! 🚀
- Effect AI SDK Release.
- Durable workflows in TypeScript with
@effect/workflow- currently in alpha. - Effect Days 2026 ✨.
Technology
Effect v4 updates: RC Announcement.
This week marks a milestone: Effect v4 has officially moved to Release Candidate status.
Effect v4 Release Candidate is here! After months of beta releases, real-world usage, and community feedback, v4 is entering the final stretch before stable. Try it, migrate, test your integrations, and tell us what still breaks before 4.0. ↓↓↓ effect.website/blog/releases/…
The team continued its deep codebase audit, with the focus now squarely on correctness and reliability.
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RC announcement: Effect v4 is now in Release Candidate. The API surface is presumed stable, and the focus has shifted entirely to correctness, reliability, and documentation.
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Cluster & durable execution: Fixed a cluster shutdown hang from abandoned requests, fixed defecting execution-plan observers replacing outcomes and leaving events unpaired, fixed
TxPubSubsubscriber release interrupting after hub shutdown, fixed SQLfindByIdresolvers invokingNonEmptycallbacks with empty batches, fixed SQL resolvers executing empty batches, used migrations for SQL persisted queues, added integration coverage for entity shutdown, replay, workflow owner-loss, and cluster transport failure scenarios. -
AI providers: Corrected max output tokens for Claude Opus 4.6, 4.7, 4.8 and Sonnet 4.6, fixed OpenRouter emitting cumulative tool-parameter prefixes as deltas, fixed OpenRouter reasoning-end metadata casing, fixed OpenRouter streamed citation end offsets overwriting start offsets, fixed OpenAI telemetry response attributes using the request namespace type, fixed batched encrypted event records reusing per-record randomization metadata, and fixed unknown MCP cancellation suppressing a later reused request ID.
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Platform & HTTP: Fixed Bun and Deno
fileWebResponseignoring range options, fixed closing an older Bun server not properly tearing down, fixed client-server-clientFormDataround-trip, fixedrcRefleaking resources acquired before acquisition failure, fixedscopedRef.setorphaning a replacement when old cleanup defects, fixed log annotations overwriting active span correlation identifiers, fixed disabled tracer timing still recording span end times, and fixed buffered worker send failures escaping theWorkerErrorchannel. -
Fiber & runtime: Fixed
fiber.joinAllerasing input fiber error types, fixedNodeTerminalreadline staying alive between prompts. -
SQL & persistence: Migrated
NodeRedisfromioredistoredis(node-redis), addedSQL,HttpApitesting, and CLI schema coverage to AI docs. -
Documentation & examples: Updated
HttpApiexamples to usehandleAll, added AI docs coverage for SQL, HttpApi testing, and CLI schemas.
You can follow the full changelog in the effect repository.
To catch up on more updates, check out Effect v4 Beta updates.
Other technical changes from the past week.
Effect CLI
Effect Adoption Partner
Save your seat for the first Effect Training Workshop by John De Goes!
We're ramping up for the @EffectTS_ Workshop 🚀 Saved your seat? eventbrite.com/e/ziverge-effe… See you there! Thank you @MichaelArnaldi for sitting down with us and having such a fantastic conversation 🙏 More to come! @jdegoes @effectfultech
Community Events
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Effect Days 2026 is back! ✨ Join us in Italy on December 9–11 for three days with the people building Effect and the people building with it.
Effect Days is back 🇮🇹 Join us on December 9–11 for three days with the people building Effect and the people building with it. Workshops. Talks. Community. Early Bird tickets are now live ↓ effect.website/effect-days
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The first Effect Warsaw meetup is scheduled on September 15!
Effect is coming to Poland 🇵🇱! We are hosting @EffectTS_ meetup in Warsaw in September! It's going to be beginner friendly, pinky promise! Get your ticket at: luma.com/29fn6spj
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Effect Office Hours 🔥 every Wednesday at 10:00 AM ET / 16:00 CET on our YouTube channel.
Visit our Effect Community Events calendar and subscribe for updates on upcoming Effect events.
Community Highlights
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🪄
Why is the AI so good at @EffectTS_ ?
Why is the AI so good at Three.js?
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The state library that made me drop Zustand by Lucas Barake.
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effect-domain - a domain action graph for Effect applications, letting you define resources, computed fields, actions, subscriptions, and runtime schemas once with Effect Schema and serve them over REST, RPC, GraphQL, or sync engines. By mac-monet.
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New course added: Retrieval-Augmented Generation - learn to build a chat-with-your-PDF app with Effect, covering the full pipeline from PDF text extraction through vector storage to AI-powered answer generation. By Hemanta Kumar Sundaray.
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repo-dive - dive into a git repo’s history with per-commit snapshots, an indexed metrics catalog, and an interactive dashboard, with MCP support for AI agents. By Alexey Kachkaev.
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.
John A. De Goes, the creator of ZIO, as well as CEO of Ziverge and Golem Cloud, joins Johannes Schickling and Michael Arnaldi to discuss how AI is reshaping software engineering, what developers should still learn, and why Effect’s primitives are especially valuable for coding agents.
Effect Team Content Update
- Maple.dev | Effect Office Hours 41 🔥
- Resumable/durable streams for AI agents
- Modeling URI string protocols | Community Code Review
Effect Job Opportunities
Looking for a role where you can work with Effect? We now have a dedicated Effect jobs page featuring open roles from companies that use Effect. We’ll keep it updated as new opportunities come in.
New this week: Superwall is hiring a Global Remote Support Engineer (US time zones preferred).
Explore Effect job opportunities →
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.
Effect Merch is here! We’re excited to announce the launch of our Effect merch page! Grab your favorite swag & show your love for Effect in style! 🧢 effect.website/merch
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