---
title: "Kotlin Toolchain 0.12: Multiplatform Library Publishing, Wasm Apps, and More"
description: "Kotlin Toolchain 0.12.0 extends its multiplatform build and publishing capabilities with multiplatform library publication, preview support for Wasm applications, command-line Compose Hot Reload, and broader IDE and terminal improvements. Libraries use the existing publishing configuration and produce a common API, per-platform artifacts, sources, module metadata, plus commonized and platform-specific cinterop bindings; Compose Multiplatform resources are not yet included. wasm-js/app modules can be built into ready-to-use web applications, run with kotlin run, customized through resources, and supplied transitive npm dependencies from Kotlin Multiplatform libraries. The release also reduces default Maven Central files, supports Compose Hot Reload through an MCP server, and recommends project-root-relative // dependencies while retaining the older syntax. It raises minimum compilation requirements to JDK 17 and Kotlin 2.2.20, updates bundled versions including Kotlin 2.4.10 and JDK 25, and recommends IntelliJ IDEA 2026.2.1 or newer for the latest features."
---

# Kotlin Toolchain 0.12: Multiplatform Library Publishing, Wasm Apps, and More

[Jetbrains](https://yomu.fyi/company/jetbrains) · Joffrey Bion · Sep 3, 2026

**Type:** Announcement

## Summary

Kotlin Toolchain 0.12.0 extends its multiplatform build and publishing capabilities with multiplatform library publication, preview support for Wasm applications, command-line Compose Hot Reload, and broader IDE and terminal improvements. Libraries use the existing publishing configuration and produce a common API, per-platform artifacts, sources, module metadata, plus commonized and platform-specific cinterop bindings; Compose Multiplatform resources are not yet included. wasm-js/app modules can be built into ready-to-use web applications, run with kotlin run, customized through resources, and supplied transitive npm dependencies from Kotlin Multiplatform libraries. The release also reduces default Maven Central files, supports Compose Hot Reload through an MCP server, and recommends project-root-relative // dependencies while retaining the older syntax. It raises minimum compilation requirements to JDK 17 and Kotlin 2.2.20, updates bundled versions including Kotlin 2.4.10 and JDK 25, and recommends IntelliJ IDEA 2026.2.1 or newer for the latest features.

## Context

Kotlin Toolchain 0.11 introduced library publishing only for JVM libraries. Version 0.12 extends publication to multiplatform libraries, adds Wasm application support and other workflow improvements, and changes default publication behavior in response to upcoming Maven Central quotas.

## Approach / What changed

The release adds configuration-driven publication for common and platform-specific library artifacts, sources, metadata, and cinterop bindings; builds wasm-js/app modules as web applications; and expands command-line, IDE, diagnostics, dependency-path, and Compose Hot Reload capabilities. It also raises minimum JDK and Kotlin versions and updates default toolchain and framework versions.

## Takeaways

- Multiplatform publication includes the common API, one artifact per platform, sources, module metadata, and both commonized and per-platform cinterop bindings. Compose Multiplatform resources are not included yet.
- wasm-js/app modules can be built into ready-to-use web applications, run with kotlin run, customized through index.html and other resources, and supplied transitive npm dependencies from Kotlin Multiplatform libraries.
- Compilation now requires JDK 17 or newer and Kotlin 2.2.20 or newer; settings.jvm.release can still target a lower runtime, and the default versions include Kotlin 2.4.10 and JDK 25.

**Tags:** [Kotlin Multiplatform](https://yomu.fyi/topic/kotlin-multiplatform), [MCP](https://yomu.fyi/topic/mcp), [WebAssembly](https://yomu.fyi/topic/webassembly)

- Source: [Jetbrains](https://blog.jetbrains.com/kotlin/2026/09/kotlin-toolchain-0-12-multiplatform-library-publishing-wasm-apps-and-more)
- Source URL: https://blog.jetbrains.com/kotlin/2026/09/kotlin-toolchain-0-12-multiplatform-library-publishing-wasm-apps-and-more
- Ingested by Yomu: 2026-09-03T12:00:53.924Z

[Read original post](https://blog.jetbrains.com/kotlin/2026/09/kotlin-toolchain-0-12-multiplatform-library-publishing-wasm-apps-and-more)