Kotlin Multiplatform

The Kotlin Toolchain 0.13 adds a kotlin new interactive project creation command, automated iOS simulator and Xcode setup, aligned Android SDK provisioning between CLI and IDE, Swift Package Manager dependency support, and Kotlin/Native compiler caching for faster rebuilds across builds and projects. The Kotlin team now officially recommends the Toolchain for most new Kotlin Multiplatform projects, requiring IntelliJ IDEA 2026.2.3 or Android Studio Rabbit 1/2026.2.1 or newer along with the latest Toolchain plugin to access these features.

Matters for: Teams starting new Kotlin Multiplatform apps that target both iOS and Android, especially those integrating Swift Package Manager dependencies or using AI coding agents for project setup.

Kotlin 2.5.0-Beta1 introduces experimental companion blocks and companion extensions, letting you define expected companion block members that are actualized by a Java class with static members, and add companion-style functions to classes you don't control. To use this, you must recompile the project and any dependents after migrating from companion objects (removing the object keyword), and any library exposing companion extensions produces pre-release binaries that cannot be consumed as dependencies until the feature stabilizes.

Matters for: Engineers using Kotlin Multiplatform who need to actualize expected declarations against existing Java static members or interop with Java classes they don't control.

Kotlin Toolchain 0.12 now lets you publish Kotlin Multiplatform libraries (not just JVM) with a single configuration, producing per-platform artifacts, sources, common API, and commonized cinterop bindings consumable from Gradle; it also adds preview support for building wasm-js/app modules into deployable web applications and Compose Hot Reload from the command line. It also reduces default published checksum files to meet upcoming Sonatype Maven Central quotas, so projects needing sha256/sha512 checksums must explicitly set settings.publishing.checksums.

Matters for: Teams maintaining shared Kotlin Multiplatform libraries with C interop that need to publish to Maven Central under new Sonatype quota limits.

You can now connect AI coding agents to a running app via an MCP server in Compose Hot Reload to trigger reloads, take screenshots, inspect the semantic tree, simulate input, and read logs, and web apps automatically download matching Noto font subsets for unresolved characters instead of requiring bundled fonts; desktop apps also gain an experimental v2 WindowState/DialogState API for finer control over window positioning, sizing, and screen placement.

Matters for: Teams building Kotlin Multiplatform desktop and web apps that need AI-assisted debugging in Compose Hot Reload, multilingual text rendering without bundling fonts, or precise window and dialog placement across multiple screens.