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Sebastian Sellmair

@sellmair.dev
548 followers 58 following 148 posts

Software Engineer @ JetBrains Working on all things Kotlin. KMP | Intellij | Compose

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Sebastian Sellmair @sellmair.dev · 17/07/2026
Something big might happen to the Kotlin Multiplatform Ecosystem 👀 We were never too happy about how Kotlin publishes and resolves KMP libraries. It takes up significantly more space than it has to, produces a ton of artifacts and Maven modules, and is just... complex!
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Sebastian Sellmair @sellmair.dev · 17/01/2026
The Kotlin ecosystem might not choose a strict 'SemVer' notation (and it's gonna be fine!) blog.sellmair.io/the-kotlin-e...
blog.sellmair.io
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Kotlin by JetBrains @kotlinlang.org · 14/01/2026
Compose Hot Reload is now stable and bundled with Compose Multiplatform since v.1.10.0! 🎉 This deep dive by @sellmair.dev and Azat Abdullin walks through the engineering behind Compose Hot Reload and how it works under the hood. For the curious among you 👀 kotl.in/hotreload100
kotl.in
The Journey to Compose Hot Reload 1.0.0 | The Kotlin Blog
Compose Hot Reload has been promoted to stable. The blog post provides a high-level overview of how Compose Hot Reload works under the hood.
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Sebastian Sellmair @sellmair.dev · 16/01/2026
I am working on a proposal on making Kotlin's ecosystem versioning more consistent (at least for JetBrains projects at first). It sparked this nice blog post from @mbonnin.net . I'll respond on blog.sellmair.io soon 🔜 mbonnin.net/2026-01-16-s...
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Sebastian Sellmair @sellmair.dev · 18/12/2025
Compose Hot Reload 1.1.0-alpha03 just released, and it's pretty hot. 🔥 github.com/JetBrains/co... - New, more advanced re-initialisation for statistics ↪️ - Up to 10x reload speeds by default 🏃🏽‍♀️ - Significantly reduced runtime memory usage 💾
github.com
Release v1.1.0-alpha03 · JetBrains/compose-hot-reload
Release summary We introduced a new re-initialisation mode for static variables. Enable it by setting compose.reload.staticsReinitializeMode=AllDirty and share your feedback! We sped up incrementa...
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Márton Braun @zsmb.co · 08/12/2025
So, today I found out about a secret, unsafe, internal property that makes Hot Reload waaaay faster. Like lightning fast. Even in a real project, not just with Hello World. We're currently discussing if y'all are ready for this yet - we'll probably add it to guidance later.
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Márton Braun @zsmb.co · 27/11/2025
We're doing an AMA on /r/Kotlin on December 11th! Prepare your questions, mark your calendars, and join us there in 2 weeks! www.reddit.com/r/Kotlin/
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Sebastian Sellmair @sellmair.dev · 24/11/2025
"It should be easily doable to build a stateful hot reload" - silly me, almost one year ago. After one year of hard work and many people involved, we can finally commit to the user experience and call it done (as in 1.0.0) 🔥 github.com/JetBrains/co... 🧵 What's next?
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Ivan “CLOVIS” Canet @ivcanet.bsky.social · 19/11/2025
Ahhhh so that's why it's called the Gradle Wrapper?
Package with a ‘Gradle’ adhesive
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Sebastian Sellmair @sellmair.dev · 19/11/2025
Say hello to Compose Hot Reload 1.1 🔥 Please give it a try and provide feedback: github.com/JetBrains/co... ☕️ JBR 25 support ⚡️ Recompilation Speed optimizations 😎 New visuals, New DevTools UX 📦 Faster, more lightweight protocol under the hood
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Sebastian Sellmair @sellmair.dev · 06/10/2025
We released Compose Hot Reload 1.0.0-rc01 🎆 What started as a happy accident was promised to be pushed towards stability as quickly as possible, allowing you to rely on a stable user experience. github.com/JetBrains/co...
github.com
Release v1.0.0-rc01 · JetBrains/compose-hot-reload
Release summary 🔥🎆 The project is promoted to the 'RC' stage. We are still working on convenient tooling in IntelliJ and Android Studio and will continue experimenting there. The 'core technology' ...
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Sebastian Sellmair @sellmair.dev · 29/09/2025
I said it once, I'll say it again: You might think you're doing your project a favor by always upgrading to the latest AGP version. What you do instead is break the project for everyone who has not downloaded the latest IDE. This is pain
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Andrei Shikov @shikasd.bsky.social · 19/09/2025
Casey Muratori pretty much sums up how I feel about LLMs for coding: "The AI will always be useless for me. I physically can't get what I want from programming when AI is involved, because what it is doing is robbing me of the experience that I wanted to have and the knowledge that I wanted to get"
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Sebastian Sellmair @sellmair.dev · 17/09/2025
Say hello to hot reloading compose resources, supported from CMP 1.10.0-alpha01 🔥 Initially requested by @zsmb.co and @rakhman.info Thanks to Nikita Lipsky 😇
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Sebastian Sellmair @sellmair.dev · 12/09/2025
Can kotlinx.coroutines outperform the GPU 🤯? Watch me getting humbled while trying to find out... www.youtube.com/watch?v=JCOS...
youtube.com
kotlinx.coroutines outperforming the GPU? 🤯
YouTube video by Sebastian Sellmair
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Sebastian Sellmair @sellmair.dev · 03/09/2025
Oh, I did not expect to have so much fun building the IDE tooling/integration for Compose Hot Reload 😍 See the small floating toolbar when a session is present, even allowing you to reset your UI state!
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Sebastian Sellmair @sellmair.dev · 30/08/2025
Had fun with Skia/Skiko lately! Pretty sure some of you folks might enjoy working with it as well 😍 www.youtube.com/watch?v=bsaq...
youtube.com
High-Performance Skiko Image Processing
YouTube video by Sebastian Sellmair
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Kotlin by JetBrains @kotlinlang.org · 02/07/2025
🔥 In his KotlinConf’25 talk, “Implementing Compose Hot Reload”, @sellmair.dev explains how to use Compose Hot Reload today – and how JetBrains tech made it all possible. ✨ Plus: challenges, lessons, and a few surprises. 📹 Watch on YouTube: kotl.in/conf-compose...
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Sebastian Sellmair @sellmair.dev · 04/07/2025
🌴 Compose Hot Reload has finally reached Beta! github.com/JetBrains/co... I started the project by accident, and it's been so much fun to work on. Time for a small break 🌴, and we'll target the first stable release soon. 🫡
github.com
Release v1.0.0-beta03 · JetBrains/compose-hot-reload
DevTools Support for 'detached mode': See compose.reload.devToolsDetached property Shutdown Procedure: More aggressively shutdown build processes Gradle Ensure Recompiler uses the same 'JAVA_HOM...
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Sebastian Sellmair @sellmair.dev · 19/06/2025
The KotlinConf talks are available online 🎉 Check-out how Compose Hot Reload is implemented: youtu.be/UebhKUdO2sQ?...
youtu.be
Implementing Compose Hot Reload | Sebastian Sellmair
YouTube video by Kotlin by JetBrains
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Sebastian Sellmair @sellmair.dev · 03/06/2025
I joined JetBrains 5 years ago, and I still love the team. What a great experience, thank you all! ❤️
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Sebastian Aigner 📡 @sebi.io · 25/05/2025
i love kotlin
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Sebastian Sellmair @sellmair.dev · 24/05/2025
If you liked Compose Hot Reload at this year's #KotlinConf then you might also enjoy this podcast with personal stories and behind the scenes of hot (and why) it was built: thebakery.dev/98/
thebakery.dev
#98 - Compose Hot Reload with Sebastian Sellmair
Hot Reloading your composable functions with Sebastian Sellmair
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Sebastian Sellmair @sellmair.dev · 20/05/2025
See you at KotlinConf 🤪🎇
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Rick Clephas @rickclephas.dev · 15/05/2025
KMP-NativeCoroutines is now using a K2 compiler plugin to generate Kotlin code. Allowing for a better IDE experience. Please report any issues on Github. github.com/rickclephas/...
github.com
Release v1.0.0-ALPHA-43 · rickclephas/KMP-NativeCoroutines
Kotlin Enabled K2 mode by default. Please report any issues. Disable K2 mode to temporarily use KSP: nativeCoroutines { k2Mode = false } Updated Kotlin to 2.1.21 IDE plugin Fixed compatibi...
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Sebastian Sellmair @sellmair.dev · 15/05/2025
Compose Hot Reload alpha10 just dropped 🔥 github.com/JetBrains/co... - Dark Mode - CLI improvements - Better Process Management Please provide feedback! Beta should be around the corner!
github.com
Release v1.0.0-alpha10 · JetBrains/compose-hot-reload
Changes This build switches Hot Reload from using 'continuous builds' to the 'explicit reload' model. Previously, a daemon would have picked this up, recompiled the code, and sent a 'reload' reques...
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Louis CAD @louiscad.bsky.social · 03/05/2025
@sellmair.dev Your Compose Hot Reload thing is a pure banger! 🤯😍😍🤯 Tweaking animations & everything else is such a breeze now. Thanks to the way shorter feedback loop, I can tell I'll do things I'd have never done without it. Thank you!! ❤️❤️ github.com/JetBrains/co...
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Sebastian Sellmair @sellmair.dev · 24/04/2025
🎉 Looking forward to feedback for Compose Hot Reload alpha06, which finally supports 'jar-based reloads' and async launch modes. github.com/JetBrains/co...
github.com
Release v1.0.0-alpha06 · JetBrains/compose-hot-reload
Migration Notes The default 'runtime-api' dependency was removed. Wrapping code into DevelopmentEntryPoint {} is not necessary anymore. Updating the version requires removing the call (or adding t...
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Sebastian Sellmair @sellmair.dev · 14/04/2025
Compose Hot Reload alpah05 is available. 🎉 github.com/JetBrains/co... If the feedback is good enough, we will start targeting beta soon 🤞
github.com
Release v1.0.0-alpha05 · JetBrains/compose-hot-reload
Plugin id("org.jetbrains.compose.hot-reload") version "1.0.0-alpha05" Important Notes 🎉 Wrapping your code with DevelopmentEntryPoint is no longer required. It is advised to remove the call. The de...
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Sebastian Sellmair @sellmair.dev · 12/04/2025
Feel free to hate me, but I might actually like yaml. Used it to define internal & advanced properties for Compose Hot Reload (which will generate code at build time). github.com/JetBrains/co... Defining a schema is simple, IDE support is great. I am likely using it more in the future. 👌
github.com
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Sebastian Sellmair @sellmair.dev · 11/04/2025
Call for Feedback: github.com/JetBrains/co... Compose Hot Reload, targeting beta hopefully soon.
github.com
Release v1.0.0-alpha05-91 · JetBrains/compose-hot-reload
Call for Feedback This dev build has two significant changes that testing shall emphasize: DevelopmentEntryPoint {} is no longer required: The Compose Window {} will act as an entry point automati...
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Sebastian Sellmair @sellmair.dev · 10/04/2025
Things getting serious #compose #hotreload
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Mark Murphy @commonsware.com · 08/04/2025
I pushed the button on jetc.dev Newsletter Issue #260! Wrapping! Wrapping! More wrapping! Optimizing composables! @sellmair.dev on optimizing Hot Reload! @paligot.com and JSON Forms! LiveKit! jetc.dev/issues/260 #JetpackCompose #AndroidDev
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Sebastian Sellmair @sellmair.dev · 03/04/2025
Actually, I would also like to share a fun story about this Compose Hot Reload Release (alpha04)! github.com/JetBrains/co... The Toolbox team was working on integrating Hot Reload into their project and discovered that the runtime-analysis failed on some Composables.
github.com
Release v1.0.0-alpha04 · JetBrains/compose-hot-reload
Plugin id("org.jetbrains.compose.hot-reload") version "1.0.0-alpha04" Changes Fixed issue #122 where analyzing compose code failed due to missing handling of BIPUSH and SIPUSH opcodes (@Avvessalom...
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Sebastian Sellmair @sellmair.dev · 03/04/2025
Try out Compose Hot Reload alpha04! It contains some nice fixes for Windows and the Runtime Tracking. github.com/JetBrains/co...
github.com
Release v1.0.0-alpha04 · JetBrains/compose-hot-reload
Plugin id("org.jetbrains.compose.hot-reload") version "1.0.0-alpha04" Changes Fixed issue #122 where analyzing compose code failed due to missing handling of BIPUSH and SIPUSH opcodes (@Avvessalom...
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Sebastian Sellmair @sellmair.dev · 01/04/2025
I just had one of the coolest calls in quite some time with @bnorm.dev. We wanted to talk about a potential issue, but then drifted into him explaining his project, github.com/bnorm/storyboard, to me. I wish he had shown me this before I started preparing for my next talk. 🤯🔥
github.com
GitHub - bnorm/storyboard: Library for building presentations using Compose Multiplatform.
Library for building presentations using Compose Multiplatform. - bnorm/storyboard
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Sebastian Sellmair @sellmair.dev · 21/03/2025
⚡️ From 8 minutes down to 0.5ms: Compose Hot Reload 1.0.0-alpha03 was released with a re-implementation of its core 'dirty resolution algorithm': blog.sellmair.io/being-quick-... Enjoy 🍻 github.com/JetBrains/co...
blog.sellmair.io
Being Quick: Resolve what's dirty.
Compose Hot Reload: 1.0.0-alpha03
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iury souza @iurysouza.dev · 19/03/2025
www.youtube.com/watch?v=jwev... Kotlin 🤝 MCP @sebi.io nailed it on this one! I rly want to try this out! github.com/SebastianAig...
youtube.com
Building MCP with Kotlin: Claude Desktop Controls My Smart Home Lights!
YouTube video by Kotlin by JetBrains
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Sebastian Sellmair @sellmair.dev · 13/03/2025
Oooh, there might be something cool in the pipeline 😳 While Compose is slowly getting hot 🔥, it seems that the Kotlin compiler might get cool ❄️😎 @rakhman.info 😬
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Mark Murphy @commonsware.com · 11/03/2025
I sent out jetc.dev Newsletter Issue #256! Compose beta! Compose Multiplatform alpha! @sellmair.dev on hot reload! @c5inco.bsky.social on mesh gradients! @jorgecastillo.dev on strong skipping! Permissions! And... what happens if our desktop goes dark!? jetc.dev/issues/256 #JetpackCompose #AndroidDev
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Sebastian Sellmair @sellmair.dev · 05/03/2025
Maybe the time for European technologies is now? Kotlin ftw.
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Sebastian Sellmair @sellmair.dev · 03/03/2025
🎉 🎇 First 'alpha01' artifacts for Compose Hot Reload are available on Maven Central! Enjoy! 🥳 github.com/JetBrains/co...
github.com
Release v1.0.0-alpha01 · JetBrains/compose-hot-reload
🎉 This is the first deployment to the 'maven central' repository. Note: This publication follows the 'Stability of Kotlin components' rules defined here: https://kotlinlang.org/docs/components-stab...
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Sebastian Sellmair @sellmair.dev · 27/02/2025
github.com/JetBrains/compose-hot-reload/releases/tag/v1.0.0-dev-65: Compose Hot Reload now supports even more complex environments. Happy to announce: Hot Reloading UI now works when building and working on the IntelliJ IDE.
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Sebastian Sellmair @sellmair.dev · 18/02/2025
youtube.com/shorts/xgtHm...
youtube.com
Hot Reload for Compose Multiplatform is a game changer for iterating on your UIs!
YouTube video by Kotlin by JetBrains
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Sebastian Sellmair @sellmair.dev · 13/02/2025
Everyone, it is with great pleasure to inform you that the project 'Compose Hot Reload' is now bootstrapped and one can develop 'Compose Hot Reload' by 'Hot Reloading' the project 🥳
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Sebastian Sellmair @sellmair.dev · 11/02/2025
See you all at Kotlin Conf 🎆🎇
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Sebastian Sellmair @sellmair.dev · 07/02/2025
Advanced technique on improving the DX for debugging of complex projects. Sharing my new favorite System Property with you folks: blog.sellmair.io/dx-deep-debu...
blog.sellmair.io
DX; Deep Debugging and my new favorite System Property
I think nobody here would disagree with me, saying that 'good Developer Experience (DX) is key to successful projects and teams'. Nice tests, reliable IDE integration and smooth CI are obvious. Sometimes, however, things get dirty: We do have complic...
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Sebastian Sellmair @sellmair.dev · 07/02/2025
I am incredibly flattered 🙇. Thank you, Dmitry. This means a lot to me!
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Sebastian Sellmair @sellmair.dev · 06/02/2025
People who never drove a car cannot build a good car. Trivially simple, almost always ignored when building software.
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Sebastian Sellmair @sellmair.dev · 06/02/2025
Maven Central *really* needs some alternatives/competitors. I admire the service for the community, but the UX they provide for developers is a puzzle to me.
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