Hi Effecters!
Welcome back to This Week in Effect, your weekly roundup of news from the Effect community and ecosystem.
Recent major announcements:
- Effect v4 Stable Release ๐
- Effect Days 2026 โจ
Technology
Effect 4.1 has been released! New crypto modules, HttpApi improvements, and lots of other great additions and fixes. Read more here: effect.website/blog/releases/โฆ Enjoy! @EffectTS_
- Mattiaโs work on Effect LSP led to significant performance improvements and proxy commands support!
Gotta go fast
Effect LSP's now ship with support for "proxy" commands, allows you to run most of the effect-enhanced tooling without having to patch your local node_modules installation
Effect v4 updates.
Effect 4.1 is out. This recap covers what landed after 4.1, including the fixes shipped in 4.1.1 (October 30) and 4.1.2.
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Additions: Added JSON5 and JSONC parsers, fixed-width integer schemas for
SchemaBinary, anonRejectionoption forCircuitBreaker.executeand probe context forCircuitBreakerclassifiers, and MCP discovery limits with configurable toolkits. Non-strict Anthropic tools can now use recursive parameters, SQL transaction control statements and connection waits are now traced, andGlob.matchgot faster. -
Cluster & workflow: Defect restart backoff is now isolated per entity and reset after recovery, and cluster sends from
WithTransactionhandlers are notified after commit. FixedClusterWorkflowEngineblocking shard release on pending resume interrupts, parent workflows not resuming when a suspended child is interrupted, and persisted success replies surviving a rolled back request transaction. -
MCP & RPC: Fixed
McpServerdeclared tool failures that are not JSON, toolkit results whose encoded value is not JSON, middleware running in the wrong place when combined, and MCP2026-07-28listings failing for resources, templates and prompts registered as plain objects. On the RPC side, discarded calls no longer hang on transport errors,RpcClientno longer acknowledges dropped stream chunks on interruption, and one crashed pool worker no longer fails calls on healthy workers. -
HTTP, SQL & platform: Fixed
withCookiesRefnot sending cookies when the URL is completed after it,HttpApiSchema.StreamSsedata now being encoded with its JSON codec, and generated OpenAPI clients with unescaped spec names.PgClientnow rolls back transactions whose prepared statements went missing, remote libSQL clients allow concurrent statements, andNodeRedisacquisition is interruptible and finalizes pending connections correctly, with theredispeer minimum raised to 5.1.0. -
Core & runtime fixes: The audit continued with fixes for
Effect.requestretaining completed request context (the batch pool was removed), span references now released when fibers exit,Pool.gethanging in a finalizer of the poolโs own scope,AtomRegistry.subscribenever notifying for an unread derived atom, andIterable.unfold,takeWhileandfilterMapWhilestaying exhausted after completion. Also fixedSchedule.fixed,Schedule.windowedandSchedule.cronzero delays,DateTimeoffsets when rounding inside a repeated hour, rate limiter zero limits and expired keys, Unicode normalization in domain names, andPath.formatmissing extension dots.
You can follow the full changelog in the effect repository.
Other technical updates from the past week.
Effect Core
- Add Match.whenFilter for Filter-backed extracting cases (Feature, next-minor)
- Follow OTEL_TRACES_SAMPLER in the OTLP tracer (Bug Fix, next-minor)
- Map declared toolkit failures to MCP input_required results (Feature, next-minor)
- Support TOML 1.1 syntax in Toml.parse (Bug Fix, next-minor)
- Add SqlClient.batch and send PostgreSQL batches in one Sync (Feature, next-minor)
- Build HttpRouter.toHttpEffect apps with a fresh router (Bug Fix, next-minor)
- Return Result from Yaml.parse instead of throwing (Bug Fix, next-minor)
- Document per-signal opt-in for OTLP layerFromConfig (Improvement, next-minor)
Effect AI
- Fix(ai-anthropic): read message batch results instead of failing on 200 (Bug Fix, next-minor)
Effect SQL
- Add SqlClient.batch and send PostgreSQL batches in one Sync (Feature, next-minor)
Community Highlights
- ๐งก
I have been all in for almost a year.
- A Halloween game made with Effect?! ๐ป
Built a zombie game for Halloween! Free to play, no ads, multiplayer, and works offline! Enjoy ๐
- Just in case you missed it: Maxwellโs series Module of the Week is a banger.
Quick hack to actually understand distributed systems and the actor model Just read the this week in effect cluster series blog by @maxwellbrown Theyโre actually pretty enjoyable and fun to read as well Every engineer in our team has read it all by now
- Yes!
Write your TypeScript backends in @EffectTS_ or live long enough to realize you should have.
- CAFE-style Vercel Domains by Devin Jameson.
I made Vercel Domains, CAFE style. A fun excuse to hack with @Cloudflare, @alchemy_run, @foldkit, and @EffectTS_ (and put the new Blocks and Layers API through its paces). As @RhysSullivan pointed out, this is a deceptively complex UI: - URL synchronization - Debounced
fun fact, the most difficult frontend work i've ever done was the vercel domains search input naively it's a simple problem, but there's so much under the hood that goes into it
- Domain-driven design for Effect in Alchemy.
I finally like effect now. Pump it into my veins
New: domain-driven design for Effect, in alchemy.run/domain. Translate business requirements directly into working software and integrate into your alchemy infrastructure.
- 2026 Year of Effect intensifies.
This + alchemy domain ๐ฅ 2026 year of effect @alchemy_run @EffectTS_
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ability - an authorization library with Schema-defined types and denials reported as Effect errors. By nmnmcc.
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inkline-town - a browser-based town-building simulation drawn in pale isometric line art. By SandroMaglione.
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effect-sql-pg-boss - bring the pg-boss Postgres job queue to Effect. By wmaurer.
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skill-guard - a trust gate that scans agent skill files, records approval of their exact content, and blocks unapproved or changed skills from loading in Claude Code, Codex, OpenCode, and Pi. By NoksLabs.
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microfw - a small TypeScript framework implementing the SAM (StateโActionโModel) pattern on Effect v4. By Trebh.
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Effect Kit - open-source packages (Redis, Email, and Storage coming soon) that expose your infrastructure as Effect services with swappable Layers and typed errors.
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effect-atom-tanstack-router - connect TanStack Router SSR hydration to Effect Atom for React and Solid. By carloitaben.
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herdr-web - a browser view of your herdr terminals, spaces, tabs, and panes. By DanielFGray.
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check - a strict TypeScript linter for Bun projects that steers code toward Effect. By sshkeda.
Effect Job Opportunities
New this week: Gen & Freckle are hiring Effect engineers.
Disclaimer: Please note that these job postings are shared for informational purposes, and we encourage applicants to verify details directly with the hiring companies.
Community Events
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Effect Days 2026 tickets are officially sold out! โจ
Effect Days 2026 is officially sold out! Thank you to everyone joining us, our speakers, and sponsors for making this possible. See you in December! ๐ฎ๐น effect.website/effect-days
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A big thank you to all our amazing sponsors for supporting Effect. ๐ค
We bet on Effect early on and its been one of our best infrastructure decisions as Warp has scaled Therefore, approving our sponsorship was one of my easiest finance decisions yet! Catch @rankintweets our CTO headlining Effect Days in December
Huge thanks to all our sponsors for helping us bring the Effect community together in Italy this December. ๐ค We're so happy to have you on board! @zivergetech @EffectfulTech @warpdotco @executorsh @academind_real @Cloudflare @novelcrafter effect.website/effect-days#spโฆ
So proud to be sponsoring this
Huge thanks to all our sponsors for helping us bring the Effect community together in Italy this December. ๐ค We're so happy to have you on board! @zivergetech @EffectfulTech @warpdotco @executorsh @academind_real @Cloudflare @novelcrafter effect.website/effect-days#spโฆ
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Weโve started revealing our speaker lineup!
.@kitlangton, currently a 9,000x developer @opencode, is joining us at Effect Days 2026 as both MC and speaker! If you've ever watched Kit talk about Effect, you know we're in for a good time. See you in Livorno, December 9โ11! ๐ฎ๐น
Excited to announce @rankintweets, CTO of @warpdotco, as a speaker at Effect Days 2026! ๐ฎ๐น Warp is also joining us as a Main Sponsor, helping make this year's event possible.
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If youโre in SF and want to talk about Effect in healthcare
We are hosting a Series A launch party on November 6th! Free food, drinks, merch, and can come talk with us about using @EffectTS_ at hospitals! luma.com/0y09r6nn
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Effect Miami is scheduled for Nov 9.
๐ฅ ๐๐ผ๐ต๐ป ๐๐ฒ ๐๐ผ๐ฒ๐. ๐๐ฎ๐ฟ๐ฟ๐ ๐ฆ๐ผ๐น๐ผ๐๐ฎ๐. ๐๐ฒ๐๐ถ๐ป ๐๐ฎ๐บ๐ฒ๐๐ผ๐ป. ๐ข๐ป๐ฒ ๐๐๐ฎ๐ด๐ฒ ๐ถ๐ป ๐ ๐ถ๐ฎ๐บ๐ถ. Proud to announce the full lineup for ๐๐ณ๐ณ๐ฒ๐ฐ๐ ๐ ๐ถ๐ฎ๐บ๐ถ #๐ฏ! ๐ค @jdegoes ยท @ZivergeTech โHarnessing AI Models with Effect TSโ ๐ค @harrysolovay ยท
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Effect Warsaw #2 is coming up on November 17!
Effect Warsaw #2 is coming next month! ๐ Sam is going to talk about full stack effect. More talks, ๐ and ๐ป coming too! luma.com/k5o7m2pg
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Effect Office Hours ๐ฅ 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.
Effect Team Content Update
- Effect Office Hours 52 ๐ฅ
- Reducing external dependencies
Cause & Effect Podcast
Donโt 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 Effectโs primitives are especially valuable for coding agents.
Effect Adoption Partner
Weโre 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, creators of @EffectTS_ ๐ฅ โก๏ธ Ziverge will be sponsoring Effect Days โก๏ธ We have produced an Effect SDK for @GolemCloud โก๏ธ We've launched an @EffectTS_ Training Workshop Sign up for
New to Effect?
Effect is a TypeScript library for building reliable applications, with built-in concurrency, cancellation, and safe resource management. Explore the documentation and installation guide below to get started.
Effect Community Team