This Week in Effect - 131

Effect v4 has officially moved to Release Candidate status, marking the final stretch before stable release, with the API surface presumed stable and focus shifted to correctness, reliability, and documentation. The Effect team also released the Effect AI SDK version 0.27.0 and announced durable workflows in TypeScript with @effect/workflow, currently in alpha, alongside Effect Days 2026.

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 https://www.effect.website/blog/releases/effect/40-rc 🚀 Effect AI SDK https://github.com/Effect-TS/effect/releases/tag/%40effect%2Fai%400.27.0 Release.- Durable workflows in TypeScript with - currently in alpha. @effect/workflow Effect Days 2026 ✨ https://www.effect.website/effect-days . Technology Effect v4 updates: RC Announcement. This week marks a milestone: Effect v4 has officially moved to Release Candidate https://www.effect.website/blog/releases/effect/40-rc 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/… https://www.effect.website/blog/releases/effect/40-rc The team continued its deep codebase audit, with the focus now squarely on correctness and reliability. - 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. - Cluster & durable execution : Fixed a cluster shutdown hang from abandoned requests, fixed defecting execution-plan observers replacing outcomes and leaving events unpaired, fixed TxPubSub subscriber release interrupting after hub shutdown, fixed SQL findById resolvers invoking NonEmpty callbacks 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. - Platform & HTTP : Fixed Bun and Deno fileWebResponse ignoring range options, fixed closing an older Bun server not properly tearing down, fixed client-server-client FormData round-trip, fixed rcRef leaking resources acquired before acquisition failure, fixed scopedRef.set orphaning 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 the WorkerError channel. - Fiber & runtime : Fixed fiber.joinAll erasing input fiber error types, fixed NodeTerminal readline staying alive between prompts. - SQL & persistence : Migrated NodeRedis from ioredis to redis node-redis , added SQL , HttpApi testing, and CLI schema coverage to AI docs. - Documentation & examples : Updated HttpApi examples to use handleAll , added AI docs coverage for SQL, HttpApi testing, and CLI schemas. You can follow the full changelog in the effect repository https://github.com/Effect-TS/effect/commits/main . To catch up on more updates, check out Effect v4 Beta updates https://effect.website/blog/tags/effect-v4-beta-recaps/ . Other technical changes from the past week. Effect CLI Effect Adoption Partner Save your seat for the first Effect Training Workshop https://www.eventbrite.com/e/ziverge-effect-ts-workshop-tickets-1993621741295?aff=oddtdtcreator by John De Goes We're ramping up for the @EffectTS https://twitter.com/EffectTS Workshop 🚀 Saved your seat? eventbrite.com/e/ziverge-effe… https://www.eventbrite.com/e/ziverge-effect-ts-workshop-tickets-1993621741295 See you there Thank you @MichaelArnaldi https://twitter.com/MichaelArnaldi for sitting down with us and having such a fantastic conversation 🙏 More to come @jdegoes https://twitter.com/jdegoes @effectfultech https://twitter.com/EffectfulTech Community Events - 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 https://www.effect.website/effect-days - The first Effect Warsaw https://luma.com/29fn6spj meetup is scheduled on September 15 Effect is coming to Poland 🇵🇱 We are hosting @EffectTS https://twitter.com/EffectTS meetup in Warsaw in September It's going to be beginner friendly, pinky promise Get your ticket at: luma.com/29fn6spj https://luma.com/29fn6spj - Effect Office Hours 🔥 every Wednesday at 10:00 AM ET / 16:00 CET on our YouTube channel https://www.youtube.com/@effect-ts . Visit our Effect Community Events calendar https://luma.com/effect-community and subscribe for updates on upcoming Effect events. Community Highlights - 🪄 Why is the AI so good at @EffectTS https://twitter.com/EffectTS ? - The state library that made me drop Zustand by Lucas Barake. Play https://youtube.com/watch?v=397MsJf8HGg - effect-domain https://github.com/mac-monet/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. - New course added: Retrieval-Augmented Generation https://www.effective.software/courses/rag - 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. - repo-dive https://github.com/kachkaev/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 https://www.youtube.com/@effect-ts , X Twitter https://x.com/EffectTS /status/2085682364315783506 , and audio platforms like Spotify https://open.spotify.com/episode/12L2neeIte6LUYQpzTh9n6 and Apple Podcast https://podcasts.apple.com/us/podcast/software-engineering-in-the-age-of-ai-10/id1781879869?i=1000780438320 . John A. De Goes, the creator of ZIO https://zio.dev/ , as well as CEO of Ziverge https://www.ziverge.com/ and Golem Cloud https://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. Play https://youtube.com/watch?v=irmz5X3c7Do Effect Team Content Update - Maple.dev | Effect Office Hours 41 🔥 Play https://youtube.com/watch?v=YWxxSC9qL4o - Resumable/durable streams for AI agents Play https://youtube.com/watch?v=4CrbT4zHctg - Modeling URI string protocols | Community Code Review Play https://youtube.com/watch?v=GmqnyKZpM98 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 → https://www.effect.website/effect-jobs 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 https://effect.website/merch offers a selection of Effect-branded items designed for the community. All orders are processed and fully managed through Printful https://www.printful.com/ . 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 https://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