iiinova — where your digital self keeps evolving

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?

3230

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

0315

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 😇

1155

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!

0100

Sebastian Sellmair @sellmair.dev · 20/05/2025

See you at KotlinConf 🤪🎇

140

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.

0160

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 🥳

2356

Sebastian Sellmair @sellmair.dev · 29/01/2025

Building Hot Reload for Compose is challenging. One of the bigger challenges is testing. I did not use JUnit but built a custom test framework for building Hot Reload Tests. I especially like that test methods can just be top-level functions ☺️

0111

Sebastian Sellmair @sellmair.dev · 28/01/2025

Mocking?! Who the hell needs mocking if you can just recompile the code withing your tests directly... 🤯😎

Screenshot of code & corresponding 'HotReloadTest'

1204

Sebastian Sellmair @sellmair.dev · 10/01/2025

Therefore, statics are 're-initialized' significantly less often and in a much more reasonable order! The topological sort even resolves circles by breaking the fewest possible dependencies between classes.

000

Sebastian Sellmair @sellmair.dev · 18/12/2024

And here is the final goodie: There is a tooling window placed next to your application. In this example, the tooling window is used to 'clean the composition', leading to all remembered states to be reset.

0100

Sebastian Sellmair @sellmair.dev · 18/12/2024

I know that we all once got burned, wondering why our code did not work, only to find out that our code was not even running at all. See how the hot-reload renders a red bar next to your application if something went wrong. Also, see how it recovers once reloaded again.

190

Sebastian Sellmair @sellmair.dev · 18/12/2024

I am really proud of this one, but you'll need to look close to see what is going on here: The remembered value will get invalidated when bytecode, used to produce this value, is changed. If the static 'calculateMagic' is changed, the using composable is invalidated.

130

Sebastian Sellmair @sellmair.dev · 18/12/2024

I know what you're thinking. Surely it breaks if you try to add properties to an existing class, right? Again, a huge recommendation for reading the previous paper about DCEVM

130

Sebastian Sellmair @sellmair.dev · 18/12/2024

You want even more? Fine: Let's add new classes. No Problem.

150

Sebastian Sellmair @sellmair.dev · 18/12/2024

More tricks? You can remove functions or even refactor and do some ABI incompatible changes. Look how the function here is renamed, but the reload still works fine.

240

Sebastian Sellmair @sellmair.dev · 18/12/2024

You ready for lifting typical 'Hot Reload' restrictions? Look Ma, I am adding a new function, and it reloads! This is a unique feature of the JetBrains Runtime. Read this paper if you're interested on how this works: sciencedirect.com/science/arti...

380

Sebastian Sellmair @sellmair.dev · 18/12/2024

Let's look into more serious demos. Hot Reload without a retained state would just be a Preview. This demo will add a state and a Button interacting with this state. Hot Reloading the 'onClick' to suddenly decrement the counter is possible.

160

Sebastian Sellmair @sellmair.dev · 18/12/2024

We can continue simple. Obviously, arbitrary changes to compose code are allowed. Here is an example switching a layout from Row to Column and back.

160

Sebastian Sellmair @sellmair.dev · 18/12/2024

Let's start simple: Obviously you can just swap out some literals. Notice the floating button and status indicator next to the app.

140

Sebastian Sellmair @sellmair.dev · 19/11/2024

🔥 🎇 Demo showing that Compose Hot Reload (Firework) only invalidates remembered state if you change code affecting the slot table (e.g. changing code inside 'remember {}')

2273