This Week in Effect - 137

Effect, the TypeScript library for building AI-era applications, shipped a runtime performance pass in issue 137 of its "This Week in Effect" newsletter, eliminating wasted work across Schema compilation, the core run loop, Queue, Stream, and Scope. The release also fixed concurrency bugs including Queue takers and offers parking forever after a yield, a lost wakeup during taker registration, and Layer.MemoMap hanging or leaking a shared layer when a requester is interrupted, and added APIs such as Config.flatMap, Schema.StringForLiteralAutocomplete, and isPubSub, isTxChunk, and isPlatformError type guards. On the AI provider side, Effect added support for raw JSON Schema dynamic tool calls, fixed Anthropic gateway 4xx error mapping, and retried OpenAI WebSocket turns after a previous_response_not_found error.

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: New Module of the Week https://effect.website/blog/module-of-the-week/rcmap post by Maxwell Brown https://x.com/maxwellbrown , featuring RcMap . Better late than never - this week's Module of the Week is all about RcMap, @EffectTS https://twitter.com/EffectTS 's reference counted map module. See you nerds at Office Hours tomorrow effect.website/blog/module-of… https://effect.website/blog/module-of-the-week/rcmap This week brought a major runtime performance pass, with dozens of fixes eliminating wasted work across Schema compilation, the core run loop, Queue, Stream, and Scope, alongside several new APIs and continued RC hardening. - Runtime performance pass : Stopped the Effect run loop from building a success Exit between continuations, stopped Queue / TxPriorityQueue from doing unnecessary re-sorting and traversal work, stopped MutableList from retaining a slot for every element that ever passed through a never-emptying list, stopped forked Scope s from registering a finalizer just to leave their parent, and fixed Stream.forever / Stream.repeat slowing down and leaking memory on every repetition. - Schema compilation performance : Compiled recursive Schema equivalence once instead of once per value level, stopped Schema compilation re-analyzing every sub-schema for each enclosing schema, stopped rebuilding parser wrappers on every SchemaParser.asserts call, stopped compiled Schema structs retaining an unused parse traversal, and stopped a recursive Schema formatter holding one compiled body per level. - Concurrency correctness fixes : Fixed Queue takers and offers parking forever after a yield, fixed a lost wakeup during taker registration, fixed cleanup registration interruption gaps, fixed spans that never end when a traced region is interrupted as it starts, fixed Layer.MemoMap hanging or leaking a shared layer when a requester is interrupted, and made awaitAllChildren interruptible. - New APIs : Added Config.flatMap , added Schema.StringForLiteralAutocomplete , added family-aware NetAddress type helpers, added isPubSub , isTxChunk , and isPlatformError type guards, and added dual forms to several existing APIs. - Module reorganization : Moved Arbitrary to the top-level module, moved several unstable Effect modules to top-level paths, split encoding formats into dedicated modules, and renamed the HTTP API module path. - Cluster & workflow : Fixed workflow execution ID collisions from ambiguous hash inputs, and bounded local entity registration waits. - AI providers : Added support for raw JSON Schema dynamic tool calls, fixed Anthropic gateway 4xx error mapping, retried OpenAI WebSocket turns after a previous response not found error, and preserved streamed text and tool arguments for nullable delta role and tool call IDs. - Bundle size : Reduced BigDecimal bundle size, and built Mime lookup tables lazily on first use instead of eagerly. - Documentation : Clarified JSON Schema decoding with the canonical codec, and refreshed PlatformError migration guidance. 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 Updates https://www.effect.website/blog?category=effect-v4-updates , starting from the recently published Effect v4 RC: August 2026 Updates https://www.effect.website/blog/effect-v4-rc-august-recap . Other technical updates from the past week. - Fix Kysely result plugins with Effect SQL clients https://github.com/Effect-TS/effect/pull/8262 Bug Fix - Fix sql-pg pool cleanup after failed readiness probe https://github.com/Effect-TS/effect/pull/8480 Bug Fix - Effect NYC Meetup was a blast Thanks to all the attendees, Zach Sherman, and Hyper for hosting us The NYC @EffectTS https://twitter.com/EffectTS community was out in force tonight Huge shout out to @zshrm https://twitter.com/zshrm and Hyper for hosting us in their amazing office Had an awesome time with the rest of the Springbird team Thanks for hosting an awesome event The NYC @EffectTS community was out in force tonight Huge shout out to @zshrm and Hyper for hosting us in their amazing office - We have one more Meetup in the US next week. Join us at Effect San Francisco https://luma.com/all-things-effect on Sep 30 at CodeRabbit. - Only a few 2-day passes left for Effect Days 2026 https://effect.website/effect-days ? The conference is scheduled for December 9–11 in Livorno, Italy.I’ll be speaking here about @warpdotco https://twitter.com/warpdotco ’s effect journeyEffect 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 - 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. We’re thrilled to announce Ziverge as the first Effect Adoption Partner Here are 3 things we're thrilled to announce, as part of our partnership with @EffectfulTech https://twitter.com/EffectfulTech , creators of @EffectTS https://twitter.com/EffectTS 🔥 ➡️ Ziverge will be sponsoring Effect Days ➡️ We have produced an Effect SDK for @GolemCloud https://twitter.com/GolemCloud ➡️ We've launched an @EffectTS https://twitter.com/EffectTS Training Workshop Sign up for - Okay, say no more, Matthew🤝 I sort of feel like @astrodotbuild https://twitter.com/astrodotbuild should do something to integrate with @EffectTS https://twitter.com/EffectTS some how. I have no actual ideas here so don't ask me, it just feels directionally the right thing to do. I was in on @EffectTS https://twitter.com/EffectTS two and a half years ago, receipts: x.com/matthewcp/stat… https://x.com/matthewcp/status/1783199977969193132 Very excited. I remember a number of years ago there were a number of attempts to do similar things in regular JavaScript that didn't catch on. I think TypeScript has made it much more viable. I think it's one of the most important libraries being developed today. - Can’t wait for the episode to come out we just recorded a @NextTokenShow https://twitter.com/NextTokenShow episode where @RhysSullivan https://twitter.com/RhysSullivan dives into how he’s using this exact stack It’s so good in Executor v2, it's actually taking advantage of effect's error system now all of the error states will have clear error messages, along with that, for the ones that are fixable via your agent i.e apps using the wrong auth they will include a prompt to use - Anyone? anyone else wanna join me in pressuring @benswerd https://twitter.com/benswerd to make an @EffectTS https://twitter.com/EffectTS SDK for @freestyle dev https://twitter.com/freestyle dev - Welcome, Fernando i started using effect this week...and i think i'm really enjoying it - Coach https://www.masterclass.com/coach by MasterClass - a real-time professional coaching app from MasterClass, built with Effect in both the Electron app and the backend. - saas-starter https://github.com/vantionlabs/saas-starter - a production-ready multi-tenant B2B SaaS template built on Effect 4, React 19, TanStack Start, Postgres with row-level security, Redis, and Stripe, shipping with auth, billing, and tenant isolation already implemented. By Vantion Labs. - Sweetener https://sweetener-ts.github.io/ - hygienic, declarative macros for TypeScript. Try the Effect do-notation macro https://sweetener-ts.github.io/ /play/effect-do in the playground. 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 Office Hours 47 🔥 Play https://youtube.com/watch?v=chLdsLqRs1E - Effect-mq: Background jobs for Effect w/ Adam Rankin, Warp CTO. Play https://youtube.com/watch?v=rmChtqHB9jY - PersistedQueue | Module of the Week 1 by Maxwell Brown. Play https://youtube.com/watch?v=Fzmdn4wWGpU 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. 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. 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 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 Previous Module of the Week - RcMap https://effect.website/blog/module-of-the-week/rcmap