{"slug": "this-week-in-effect-139", "title": "This Week in Effect - 139", "summary": "Effect 4.0.1 and 4.0.2 shipped on October 5 and October 8, 2025, respectively, as the TypeScript library's first patch releases since Effect 4.0, according to Sebastian's post on the project's first week. Roughly 30 contributors landed about 150 commits on `main` in that week, with 4.0.2 adding missing `@stability` tags to modules intended to ship as unstable and the pipeline now enforcing stability levels on every module and importable export. The releases also aligned HTTP, SQL and AI spans with OpenTelemetry semantic conventions, added a `DatagramSocket` (UDP) module and PowerShell `--completions` support, and fixed Anthropic streamed tool JSON errors while caching per-tool response schemas for better AI performance.", "body_md": "Hi Effecters!\n\nWelcome back to This Week in Effect, your weekly update of the latest developments in the Effect community and ecosystem.\n\nEffect 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.\n\nTo get started, below you’ll find links to our documentation and our guide for installing Effect. Enjoy!\n\n**Recent major updates:**\n\n## \n\nNew [Module of the Week](https://effect.website/blog/module-of-the-week/cluster-messaging) post by [Maxwell Brown](https://x.com/maxwellbrown), diving into **Cluster messaging**.\n\nEffect Cluster, Part 2 - Module of the Week #4\nWith no coordinator in charge, how does a message find its entity?\nThis week, we define our first entity and follow one message from webhook to punchline 👨\nQuestions? Office Hours tomorrow, link in 🧵\n[effect.website/blog/module-of…](https://effect.website/blog/module-of-the-week/cluster-messaging/)\n\n### \n\nIt has been a week since Effect 4.0 shipped, and the pace has not slowed. According to [Sebastian’s post on the first week](https://effect.website/blog/effect-4-first-week), almost 30 contributors landed around 150 commits on `main`, and two patch releases went out: 4.0.1 on October 5 and 4.0.2 on October 8. Here are the most notable changes.\n\n- \n**Stability tags** : Every module and importable export now declares its`@stability` level explicitly, enforced by automated checks in the pipeline. 4.0.2 also adds the tags that were missing from some modules intended to ship as unstable. Nothing changes in your code: no behavior, signatures or types are affected. The Effect language service builds on these tags to warn you when you use unstable or experimental APIs. Sebastian’s post has the full story.\n- \n**OpenTelemetry alignment** : Aligned HTTP, SQL and AI spans with the OpenTelemetry semantic conventions, and brought the OTLP exporter, resource and logger in line with the OpenTelemetry spec. Also preserved active OpenTelemetry parents for Effect spans, left interrupted spans unset, and fixed B3 sampling and zero W3C IDs in HTTP trace context.\n- \n**Additions** : Added a`DatagramSocket` (UDP) module, PowerShell support for`--completions` , a`delay` option on`PersistedQueue.offer` , a deterministic`TestCrypto` layer, a`noFollow` open option and positional reads for`FileSystem` , compact JSON and inspect output for`SchemaError` , and more atom registry APIs.\n- \n**Cluster & workflow** : Fixed orphaned workflow activity recovery after a crash, fixed entity recovery when replayed requests defect during handler rebuild, and avoided workflow replay for self-completed checkpoints.`WithTransaction` replies are now delivered once the transaction outcome is known, with failure replies persisted after rollback. Cluster SQL storage can now run without runtime DDL, and`HashRing.getShards` no longer depends on node history.\n- \n**HTTP, MCP & OpenAPI** : Preserved query strings during router slash normalization, fixed`HttpApi` form and GET payloads rejecting single-value arrays, fixed`HttpStaticServer`` If-Range` validation, and fixed OpenAPI client response inference. On the MCP side, interrupted reverse requests now send cancellation notifications, cancelled HTTP request POSTs get an empty event stream, and stateful extension capabilities are preserved.\n- \n**Streams, SQL & AI** : Fixed`Stream.slidingSize` dropping elements from the final partial window,`Stream.throttle` exceeding its configured rate, and several`tapSink` edge cases. Fixed typed SQL transaction`COMMIT` error recovery and MSSQL pool recovery. Fixed Anthropic streamed tool JSON errors, and cached per-tool response schemas for better AI performance.\n- \n**Continued audit** : The correctness audit carried on after the release, with targeted fixes across STM transactions,`PubSub` ,`Queue` ,`Pool` ,`Channel` ,`ScopedCache` ,`Layer` ,`ManagedRuntime` and Schema union parsing, covering edge cases around interruption, shutdown, retries and resource cleanup.\n- \n**Config, Schema & docs** : Kept`=` inside values when decoding key-value config strings, canonicalized imported JSON Schema pattern sources, and fixed zoned`DateTime` when`Intl` omits fractional seconds. Migration guidance now notes the v4 decoding change in`NumberFromString` and points`parseJson` users to`fromJsonString(Schema.Unknown)` .\n\nYou can follow the full changelog in the [effect repository](https://github.com/Effect-TS/effect/commits/main).\n\nTo 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: September 2026 Updates](https://effect.website/blog/effect-v4-rc-september-recap).\n\n## \n\n- \n[Effect Paris 🇫🇷](https://www.meetup.com/effect-paris/events/316600366/) meetup is scheduled for Tuesday, Oct 13!Back to [@EffectTS_](https://twitter.com/EffectTS_) community work in Paris next Tuesday with the 7th edition! The edition will probably be the first one ever recorded in Paris thanks to Inato folks 🔥🎥\nRendez-vous 7pm at[@EvrygDotCom](https://twitter.com/EvrygDotCom) , 4 great speakers, 4 great talks ahead!\nRegistration link in comment 👇\n- \n[Effect Warsaw #2](https://luma.com/k5o7m2pg) is coming on November 17!Effect Warsaw #2 is coming next month! 👉 Sam is going to talk about full stack effect. More talks, 🍕 and 🍻 coming too! [luma.com/k5o7m2pg](https://luma.com/k5o7m2pg)\n- \nVery 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’m so happy to share that I’ve received the loveliest invitation to give a talk on [@EffectTS_](https://twitter.com/EffectTS_) day!\nMy lawyers assured me that once my picture is on their page, revoking the invitation is actually illegal.\nSee you there, and please only ask questions I know the answers to,\n- \nAny Effecter in Boston? [@EffectTS_](https://twitter.com/EffectTS_) Boston meetup?!!?!\nWould love to make it happen.\nIf you’re in Greater Boston and would come (or know of companies in Boston using Effect I can reach out to), reply or DM me so I can get a sense of whether there’s enough interest.\n- \nEffect Office Hours 🔥 every Wednesday at 10:00 AM ET / 16:00 CET on our [YouTube channel](https://www.youtube.com/@effect-ts) .\n\nVisit our [Effect Community Events calendar](https://luma.com/effect-community) and subscribe for updates on upcoming Effect events.\n\n## \n\nWe’re thrilled to announce Ziverge as the first Effect Adoption Partner!\n\nHere 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_)  🔥 \n➡️ Ziverge will be sponsoring Effect Days\n➡️ We have produced an Effect SDK for [@GolemCloud](https://twitter.com/GolemCloud)\n➡️ We've launched an [@EffectTS_](https://twitter.com/EffectTS_) Training Workshop\nSign up for \n\n## \n\n- **Effect 4.0 Just Got a Lot Harder to Ignore** by Better Stack.\n\n[Play](https://youtube.com/watch?v=OsL9EJWz9UY)\n\n- …or the new [`@xstate/effect` package](https://stately.ai/docs/xstate/v6/effect/quick-start)\n\n[Replying to @vkryukov](https://twitter.com/vkryukov/status/2107920576048431503)\n\nwell you can also think of it as token efficiency. for example if your agents can’t verify their work, chances are there will be a lot of bugs and rework that needs to happen later, which also requires more tokens (and unhappy customers) there’s also many ways to improve ttr\n\n- Alchemy 🤍 Effect\n\nNew alchemy is on Effect 4.0 stable and has too many awesome changes to fit into a single tweet.\nMy favorite this time round is that [@neondatabase](https://twitter.com/neondatabase) is no longer just a database company. It might be time to update their twitter handle 😅 \n\nalchemy@2.0.0-beta.80 brings a ton of new stuff, including broad GCP coverage, Neon becomes more than a Database, pluggable secret providers, Prisma ORM, better scheduling primitives for Durable Objects and much more. alchemy.run/blog/2026-09-2…\n\n[@alchemy_run](https://twitter.com/alchemy_run) v2 + [@EffectTS_](https://twitter.com/EffectTS_) v4 is an incredible combo for infra-as-code\nbiggest shocker: new frameworks and tools can be sooo much better than existing SotA/SoP that agents perform better with something not in pretraining than with \"industry standards\"\nwell freaking done\n\nWe all know that the @foldkit, @alchemy_run, @EffectTS_, and @Cloudflare stack is GOATed but what name should we give it? Reply with your own suggestions\n\n- Effect agent frameworks:\n\nwe dont do a good job of talking about it but [@0xblacklight](https://twitter.com/0xblacklight) built a dope effectTS agent harness that\n1) stores state as a portable append only log\n2) runs on durable objects out of the box\n3) has cool retro opentui UI with 10 themes\n\nthree Effect agent frameworks worth checking out: - Fold by @0xblacklight - Yielded Agent by @danieljvdm - Tardigrade by @arjunkmrm particularly interesting to see they all support cloudflare durable objects as host and worth asking an agent to talk you through their\n\n- 👀\n\n[Replying to @theo](https://twitter.com/theo/status/2107781364607226227)\n\nDid it. Effect plugin included too, so no more patch packaging :) [x.com/theo/status/21…](https://x.com/theo/status/2107789940482621795)\n\nAnnouncing tsc-rs (aka ts-rust), my complete rewrite of the Typescript compiler, type checker, and LSP, all in Rust. This is a project I've had agents working on for 5 months now. I burned ~$400k of Codex tokens and got nowhere. Burned ~$20k of Opus and got there in 2 weeks. I\n\n- Congrats, Tanner and the Vitalize team!\n\nWe raised a 31M Series A at [@vitalize_care](https://twitter.com/vitalize_care)! We're tackling a critical problem with staffing in healthcare! \nIf you want to work with [@EffectTS_](https://twitter.com/EffectTS_) and clusters at scale, [@bunjavascript](https://twitter.com/bunjavascript), [@tan_stack](https://twitter.com/tan_stack) router/query, and [@PlanetScale](https://twitter.com/PlanetScale) Postgres, DM me! SF hybrid.\n\n- 💯\n\n[Replying to @thefubhy](https://twitter.com/thefubhy/status/2107356300023615881)\n\nInstead of counter measure, we created better tools for the maintainers to triage, recycle and crunch through submissions. Productivity is through the roof, engagement with the community/contributors too and [@EffectTS_](https://twitter.com/EffectTS_)  is ultimately better thanks to it.\nTL;DR: Improve your\n\n- Effect is obviously the solution 😎\n\nEffect is obviously the solution and i know literally no one likes writing `yield *` but it is 2026 and you don’t have to write it yourself\n\nrust never was the defacto language for agents and will not be. i love rust - it’s my primary language - but i work on runtimes and platforms application code belongs in the default language - JavaScript (or its extension TS)\n\n- Effect mentioned at `36:18` .\n\n[Play](https://youtube.com/watch?v=HuJB97hUPWk)\n\n- \n[effect-uai](https://effect-uai.betalyra.com/) is now on Effect 4.0.\n- \n[**Changes to STM in Effect 4**](https://dev.to/khraks_mamtsov/changes-to-stm-in-effect-4-33c3) blog post by Max Khramtsov.\n- \n[**Structure an Effect codebase by domain**](https://ratstack.sh/lore/structure-effect-by-domain) - a guide on organizing Effect codebases by domain. By RatStack.\n- \n[effect-harness](https://github.com/julia-script/effect-harness) - durable AI conversations built with Effect. By Julia Ortiz.\n- \n[effect-atom-svelte](https://github.com/jarrednorrisdev/effect-atom-svelte) - Svelte 5 bindings for Effect Atom. By Jarred Norris.\n- \n[ensforge](https://ensforge.com/migrations/overview) - an ENS SDK that has just released 0.6.0, updated to Effect 4.0. By The Namespace.\n- \n[opfs-vfs](https://github.com/opfs-vfs/opfs-vfs) - a virtual filesystem for the Origin Private File System (OPFS).\n- \n[openchart](https://github.com/longsurf-ai/openchart) - an open-source TradingView alternative with your own AI, free and unlimited. By longsurf.ai.\n- \n[effectlings](https://github.com/stardazed/effectlings) - small exercises that teach Effect v4, one idea at a time. By stardazed.\n\n## \n\nDon’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).\n\nJohn 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.\n\n[Play](https://youtube.com/watch?v=irmz5X3c7Do)\n\n## \n\n- Effect Office Hours 49 🔥\n\n[Play](https://youtube.com/watch?v=dlbrbz3KW40)\n\n- Local Telemetry, Grafana LGTM, Motel, and Effect v4 Tracing\n\n[Play](https://youtube.com/watch?v=R7kjeiQXQOE)\n\n- Effect Cluster, Part 1 | Module of the Week #3\n\n[Play](https://youtube.com/watch?v=TB145FAQnDM)\n\n- Effect Cluster, Part 2 | Module of the Week #4\n\n[Play](https://youtube.com/watch?v=9QDcO50YriA)\n\n## \n\nLooking 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.\n\n[Explore Effect job opportunities →](https://www.effect.website/effect-jobs)\n\n*Disclaimer: Please note that these job postings are shared for informational purposes, and we encourage applicants to verify details directly with the hiring companies.*\n\n## \n\nThe [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/).\n\nEffect Merch is here! \nWe’re excited to announce the launch of our Effect merch page! Grab your favorite swag & show your love for Effect in style! 🧢\n[effect.website/merch](https://effect.website/merch)\n\n## \n\nThat’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.\n\n*Effect Community Team*\n\n[Previous Effect 4.0: The First Week](https://effect.website/blog/effect-4-first-week)", "url": "https://wpnews.pro/news/this-week-in-effect-139", "canonical_source": "https://effect.website/blog/this-week-in-effect/139/", "published_at": "2026-10-09 00:00:00+00:00", "updated_at": "2026-10-09 16:22:40.066664+00:00", "lang": "en", "topics": ["developer-tools", "ai-tools", "artificial-intelligence", "agent-protocols"], "entities": ["Effect", "Sebastian", "Maxwell Brown", "OpenTelemetry", "Anthropic", "DatagramSocket", "Effect Cluster", "MCP"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/this-week-in-effect-139", "markdown": "https://wpnews.pro/news/this-week-in-effect-139.md", "text": "https://wpnews.pro/news/this-week-in-effect-139.txt", "jsonld": "https://wpnews.pro/news/this-week-in-effect-139.jsonld"}}