Big Kotlin/JS testing milestone in 2.4.20: We’re starting the migration away from Karma (deprecated ~3 years ago) with a new browser-test DSL + Playwright-based implementation. Huge respect to Karma for serving the ecosystem for so long. kotlinlang.org/docs/whatsne...

What's new in Kotlin 2.4.20-Beta2 | Kotlin

Read the Kotlin Early Access Preview release notes and try the latest experimental Kotlin features before they are officially released.

kotlinlang.org

For Kotlin’s 15th anniversary, I consulted the highest authority on Kotlin/JS roadmap planning: a tarot spread with respectable engineers.

Servo now passes 100% of WPT tests for the WebCrypto API, all 73,292 subtests, covering 25 cryptographic algorithms 🎉 A complete, spec-correct cryptography implementation in an independent Rust-powered browser engine is a big milestone!

“React without the historical constraints” - I like this. Came for SSR + hydration, stayed for the model: * atomic commits * execution journal with time-travel replay * batteries included I’ll try it and share notes later. kinetica.heapy.io github.com/Heapy/kinetica

👀 JS Composites proposal update "After benchmarking and general reflection, the proposal is now pursuing an interning based approach." - @acutmore We didn't get Records & Tuples but we may still get interned data structures in JS! Really exciting update if this lands in JS

Rob Palmer@robpalmer.bsky.social · last yr.

ECMAScript excitement 😉 Congrats to @ashley-c.bsky.social on advancing the Composites proposal to Stage 1 at TC39 today 🎉 This is the evolution of Stage 2 Record & Tuple which has now been withdrawn. A key difference is that Composites are objects, not primitives. github.com/tc39/proposa...

A fantastical contribution from Sébastien Doeraene (Scala.js creator) just gave a very real speedup to 64-bit number arithmetic (non-BigInt path). github.com/JetBrains/ko... I’m seeing ~2–3x per-op improvements on average, with peaks around 5x+ (and even 7.3x in more complex benchmarks). Thread 👇

[K/JS] Improve performance of boxed Longs (signed and unsigned). by sjrd · Pull Request #6450 · JetBrains/kotlin

We take all the algorithms from Scala.js. Most of them were published in the following paper: S. Doeraene and T. Schlatter, "64-bit Integer Division for the JavaScript Platform," 33rd IE...

github.com

TypeScript compiler in Go. Maybe a TypeScript compiler in KMP too? A friend just shared this cool project: github.com/xemantic/xem... Curious to see how far a Kotlin Multiplatform implementation can go.

GitHub - xemantic/xemantic-typescript-compiler: A TypeScript to JavaScript compiler written in multiplatform Kotlin (experiment)

A TypeScript to JavaScript compiler written in multiplatform Kotlin (experiment) - xemantic/xemantic-typescript-compiler

github.com

📌 New to Kotlin Multiplatform? The Basics of Kotlin Multiplatform pathway from Android Developers walks you through adding KMP to a project and using platform-specific APIs, and shows how shared code fits into Android and iOS apps. Start here 👇 https://kotl.in/6nyqaz


Really enjoyed the talk by @sergiocarrilho.bsky.social. Strong storytelling, real-device demos, and a very pragmatic story about choosing a tech stack in a big company. I especially liked the focus on problem-solving rather than advocating for a technology www.youtube.com/watch?v=VVf6...

Sony’s KMP Journey: Scaling BLE & Hardware with Kotlin Multiplatform | Sergio Carrilho

Recording brought to you by American Express. https://americanexpress.io/kotlin-jobs “You have 9 months to build iOS and Android apps from scratch for our next premium headphones. How you do it is…

youtube.com

Kotlin folks, I need your gut feeling on this one. If `when` guards were allowed with comma-separated branches, what should this mean? A) guard applies only to Success B) guard applies to both Failed and Success This can actually impact the language design.

Continuing yesterday's topic on `copy()` visibility: In multiplatform, `public` isn't always public. To make Kotlin code visible to TypeScript/Swift, you need additional setup. And that distinction just collided with data classes. 👇 Docs: kotlinlang.org/docs/native-...

Interoperability with Swift using Swift export | Kotlin

Kotlin's interoperability with Swift through Swift export is currently in Alpha. Swift export allows you to export Kotlin sources directly and call Kotlin code from Swift idiomatically, eliminating…

kotlinlang.org

A "tiny" Kotlin design question that turned into an 8-year discussion, new default + a multi-release deprecation plan: If a data class constructor is private, should its generated `copy()` still be public?

I'm currently working on exporting `Flow` to TypeScript. The idea is to expose an async-iteration adapter, similar to Swift Export’s `asAsyncSequence()` PR: github.com/Kotlin/kotli... SwiftExport: kotlinlang.org/docs/native-...

I’ve been enjoying these neat API design tricks from @ivcanet.bsky.social. Just handy little patterns to keep in your back pocket when building your own Kotlin libraries: - Non-exhaustive enums: ivan.canet.dev/blog/2026/06... - Mandatory varargs: ivan.canet.dev/blog/2026/03...

This is legal TypeScript: function Foo {} namespace Foo {} interface Foo {} // or type Foo = … // All in one file. Thread on how it solved a Kotlin ↔ TypeScript interop problem 👇


In the next version of Kotlin/JS, the boundary between Kotlin `suspend` and TypeScript `async` gets much thinner. No Promise adapters. No ceremony.


TIL a tiny Kotlin/JVM thing while aligning behavior between JS and JVM compilers: ::topLevelFun is Function1, as expected. But it’s also KFunction0, KFunction1, and KFunction2 according to is. FunctionN knows arity, KFunctionN just vibes 🙂 pl.kotl.in/nF4b2Je2w

A friend today basically told me: “You’re doing interesting stuff around Kotlin, TypeScript, compilers, Wasm… and somehow sharing none of it.” Fair. Expect more about: - Kotlin lang/compiler - TypeScript interop - JS & Wasm targets - compiler/engineering rabbit holes

ECMAScript Excitement 🎉 This week, at its 114th meeting, TC39 advanced these proposals: 4️⃣ Atomics.pause 4️⃣ Joint iteration 3️⃣ Error stack accessor 3️⃣ Intl: Keep Trailing Zeros 3️⃣ Iterator Chunking 3️⃣ Iterator Includes 3️⃣ Iterator Join 3️⃣ RegExp Buffer Boundaries 2️⃣ Amount 2️⃣ Intl Sequence Units and... 👇

Note-takers are the unsung heroes of TC39. Without them, no progress could be made. It is right to give them thanks and praise. Here's to those who helped at this week's meeting! 🥳👏🙌 👇

Welcome the Kotlin Toolchain! #KotlinConf

Kobweb demo with @bitspittle.bsky.social !

Source maps are more exciting than ever 😉 🔶 Recently standardized! (one year ago) 🔶 An active @tc39.es Task Group 🔶 New features soon: Scopes & Range Maps Read all about it 📜 bloomberg.github.io/js-blog/post...

On Apple M3, a Linux KDE plasma desktop under Fedora Asahi Remix is now WORKING! Super excited to share this update and happy to answer any questions! Co-credits to noopwafel and Shiz. :)