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Kotlin Runtime Web Assembly

Kotlin Runtime Web Assembly is a Kotlin-first WebAssembly runtime and component toolchain for running plugins without JSON-only plugin boundaries.

The main artifacts are Kotlin Multiplatform libraries. Portable modules target JVM, Android, iOS ARM, and Kotlin/Wasm browser builds. JVM, Android, and iOS execution require a linked Wasmtime backend; wasmJs uses the host browser or Node WebAssembly engine. JVM artifacts are compiled for Java 25.

Project Status

This project is experimental and under active development. Every push to main publishes immutable 0.3.0-dev.<12-character-commit> artifacts for evaluation and integration work. Production use should wait for reviewed releases and pinned versions. Public APIs in experimental modules may change while the Kotlin Multiplatform and Component Model surfaces settle.

Special thanks to dylibso/chicory for the solid foundations this project builds on.

What To Use

  • runtime: portable WebAssembly runtime APIs backed by platform execution.
  • wasm: common parser model and Okio-based byte input.
  • wasi: WASI Preview 1 host support.
  • component-model: WIT parsing, Kotlin WIT bindings, canonical ABI, WASI Preview ⅔ host wiring, and the lightweight component runtime.
  • component-model-tooling: optional JVM WIT normalization and Component Model packaging/unbundling backed by the embedded wasm-tools executable.
  • wasi-preview3: Kotlin-first WASI Preview 3 facade with coroutine-friendly futures, streams, clocks, random, networking, and preopened filesystem APIs.
  • tools/cli: command-line entrypoint for local experiments.

Start Here

Add the development Maven repository, then depend on the modules you need:

val runtimeVersion = "0.3.0-dev.<12-character-commit>"

dependencies {
    implementation(platform("uk.shusek.krwa:bom:$runtimeVersion"))
    implementation("uk.shusek.krwa:runtime")
    implementation("uk.shusek.krwa:wasi")
    implementation("uk.shusek.krwa:component-model")
    implementation("uk.shusek.krwa:wasi-preview3")
}

The installation guide shows the repository configuration and Kotlin Multiplatform setup. The runtime basics page covers parsing, instantiation, exports, and memory.

Operational Topics

  • Security: trust boundaries, host imports, and resource limits.
  • CPU limits: timeouts, Wasmtime fuel/resource limits, and host-side accounting.
  • Tools: WAT parsing, validation, and local integration helpers.
  • Logging: the lightweight logger facade and JVM backend.

Generated API documentation is published separately under API Reference.