"I think I just fell in love with the dependency injection. I had not seen that elegant of a solution in other languages" – Elliot Dauber (Effect Days 2025)
This Week in Effect - 2025-05-09
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 create 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:
- New Effect Days 2025 talks every week on YouTube!
- The Effect community on Discord reached 4180+ members!
- Effect featured in the Thoughtworks Technology Radar.
Here are all the technical changes from this week.
- Fix Layer.discard jsdoc (Documentation Update)
- SONSchema: respect annotations on declarations (Bug Fix)
- Improve Effect.filter* types to exclude candidates in fallback functions (Improvement, next-minor)
- Add Either.transposeMapOption (Feature, next-minor)
- Fix Mailbox.fromStream ((Bug Fix))
- Schema: TaggedError no longer crashes when the message field is explicitly defined (Bug Fix)
- Expose isTimeoutException (Feature, Bug Fix, next-minor)
- Fix sqlite SqlMessageStorage.repliesFor (Bug Fix)
- Ensure clientOnly mode without storage falls back to network messaging (Bug Fix)
- Sending persisted messages without MessageStorage is now a defect (Improvement)
- Fix causeResponse to always return internalServerError for defects (Bug Fix)
- Fix StreamAdapter error forwarding (Bug Fix)
- Allow overriding http span names (Feature)
- Update sql-drizzle (Improvement, next-minor)
This week, we published Elliot Dauber’s Building LLM Systems with Effect at Markprompt talk, where he shares how they use Effect to build a type-safe, composable agent framework for complex customer support use cases at Markprompt. Elliot introduces the concepts of actions, subagents, and workflows, showing how to combine deterministic and non-deterministic behaviors in LLM-powered applications.
In his post-conference interview, Elliot shared further insights on his experience with Effect.
We also published Edouard Penin’s Testing the easy and hard stuff with Effect talk, where he demonstrates effective testing strategies using Effect, aimed at making real-world testing scenarios with Effect easier and more reliable.
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Lucas Barake published a new video about RPC for Workers in TypeScript.
Play -
Rhys Sullivan shared how Effect is used to write tests at Vercel.
Here's how we use Effect to write our tests at Vercel
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Inalegwu Ikwue released Vision, an Electron-based desktop app for reading comic books that leverages Effect to improve performance.
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A reminder that the 5th edition of the Effect Paris Meetup is coming on May 20th, hosted by Spiko and sponsored by Evryg. The meetup will be in French.
The next @EffectTS_ Paris meetup (#5) I'm co-organizing is happening on May 20th! Once again, this edition will be hosted by @Spiko_finance in their brand-new office, and sponsored by @EvrygDotCom Paris folks, be sure to register for the event! meetup.com/fr-FR/effect-p…
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Dillon Mulroy livestreamed four episodes of his series Building a tool to sync Splitwise and YNAB with EffectTS 🚀 on his Twitch channel.
- Mattia Manzati was live on Twitch and X(Twitter) with a new episode of Building an Effect Warehouse App.
Welcome to our live show! x.com/i/broadcasts/1…
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. This podcast highlights stories from software engineers and companies using Effect in production. Each episode explores their journey of adopting Effect, including the learning process, challenges faced, and benefits of integrating Effect into their tech stack.
We published our second episode with Michael Fester from Markprompt about scaling AI-powered customer support with Effect, building reliable and high-performance infrastructure, and enhancing developer productivity in a fast-evolving AI landscape. Give it a listen and let us know what you think on our social media or Discord!
In December 2024, we unveiled the Effect Merch Store with a selection of Effect-branded items designed for the community. All orders are processed 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
More and more companies are adopting Effect in their projects. Here’s a list of companies looking for software engineers with Effect experience:
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Expand.ai: Founding Engineer
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Platonic Systems: Remote Effect Engineers
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Inato: Senior Product Engineer
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Medbill.ai: Founding Software Engineers (full-stack and backend)
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Oneiro Solutions: Software Engineer - Core Team. Join Effect Discord and DM leighman for further info.
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Microsub: TS Developer
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Samsung Food: Full Stack Developer
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Precurion looking for a remote‑first Founding Engineer with Effect experience. The job posting is available in the
#job-boardchannel on our Discord. -
Vitalize is hiring a full-stack engineer with Effect experience: Senior Full-Stack Engineer
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Stealth team looking for a software engineer with Effect experience. The job posting is available in the
#job-boardchannel on our Discord. -
Stephan Le Dorze is looking for a French-speaking freelancer to join him in a small team in a startup - see his LinkedIn post for more details.
Disclaimer: Please note that these job postings are shared for informational purposes, and we encourage applicants to verify details directly with the hiring companies.
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