boomslang

Python, but Java.

Boomslang runs CPython 3.14 from a WASI build. The default artifact embeds that runtime in Java through Chicory, so Python runs inside the JVM without JNI, subprocesses, or a system Python install — sandboxed, with the stdlib plus NumPy, Pandas, Matplotlib, Pillow, Pydantic, ijson, and Jinja2 included. The same runtime is also packaged as a Python wheel (boomslang-py/, executed with wasmtime) and embeddable from Rust or any WASM runtime via a language-neutral ABI.

Documentation: https://github.hubspot.com/boomslang/

Quickstart (Java)

<dependency>
  <groupId>com.hubspot</groupId>
  <artifactId>boomslang</artifactId>
  <version>0.1.1</version>
</dependency>

Path pythonRoot = Files.createTempDirectory("boomslang-python");
PythonExecutorFactory factory = PythonExecutorFactory
  .builder()
  .withStdlibPath(pythonRoot)
  .addExtension(HostBridge.builder().buildExtension())
  .build();

PythonResult result = factory.runOnWasmThread(() -> {
  PythonInstance instance = factory.createInstance(pythonRoot);
  return instance.execute("print('hello from Python')");
});

System.out.println(result.stdout());

Quickstart (Python)

Sandboxed Python from Python — wheels are attached to GitHub releases:

from boomslang import Sandbox

with Sandbox() as sandbox:
    result = sandbox.execute("print('hello from the sandbox')")
    print(result.stdout)

See the Quickstart for a walkthrough, the User Guide for timeouts, host functions, async, the Python host, and custom runtimes, and Installation for the slim no-python-runtime variant. The Python package is documented in boomslang-py/README.md.

Building this repo

The full pipeline (CPython → WASM in containers, Rust guest, Java AOT) is driven by Mill, with a just shim for common loops:

nix develop            # Java 21, Maven, just, mdBook, WASI toolchain
just fetch-main-wasm   # prebuilt runtime resources from GitHub Releases (skips the ~1hr container build)
just build             # Maven package with AOT
just test              # integration tests
just python-test       # boomslang-py package tests (staged resources + venv + pytest)

Building everything from source: ./mill artifacts.installAll && ./mill build. Details, the artifact DAG, container-engine selection (Docker / Apple container), and the Rust change loop are in the contributor docs.

Repo map

• core/ — Java runtime API and bundled Python resources
• boomslang-py/ — Python host package (Sandbox API, wheel bundling the WASM runtime)
• python-host/, python-host-core/ — Rust code compiled into the WASM guest
• extensions/ — built-in host extensions
• boomslang-hostgen/ — extension code generator (Rust DSL + CLI)
• examples/ — custom Python build and Rust/Wasmtime host examples
• cpython/ — CPython, native library, and container build pipeline
• tests/, benchmarks/ — integration tests and JMH benchmarks

License

Apache 2.0