Glossary

Boomslang sits at the intersection of three ecosystems (JVM, WebAssembly, CPython), and some names mean different things in each. This page is the tiebreaker.

Term	Meaning
host	The outside process embedding `boomslang.wasm` and implementing its imports — the Java/Chicory runtime in the default setup, or Rust/Wasmtime in `examples/rust-host/`.
guest	Everything inside `boomslang.wasm`: the Rust glue code and the CPython interpreter it wraps.
host function	A function implemented by the host and imported by the guest — e.g. the Java handlers registered through `HostBridge`. This is Chicory/WASM terminology.
`python-host/`	Rust code compiled into the guest. The name is historical: this crate “hosts” CPython (via PyO3) inside the WASM module. It is not the WASM host.
`python-host-core/`	The reusable core of the guest, published as the crate `boomslang-host-core`. Custom Python builds compose this with their own extension crates.
extension	A set of typed host functions declared with the `boomslang-hostgen` DSL in a crate’s `build.rs`. The guest half is generated Rust; the host half is a generated Java or Rust adapter.
`boomslang` (import module)	The WASM import namespace the guest expects its host functions under (e.g. `boomslang.call`, `boomslang.log`).
`boomslang_host` (Python module)	The Python-side bridge module available to guest code: `boomslang_host.call(...)`, `boomslang_host.log(...)`, `boomslang_host.asyncio`.
golden snapshot	The pre-initialized guest memory image produced by Wizer at build time. New `PythonInstance`s are copy-on-write views of it, which is why instance creation is milliseconds instead of a full CPython start.
prewarm	Importing a Python module during Wizer initialization so it is frozen into the golden snapshot. Prewarmed modules are served from the snapshot’s `sys.modules` at runtime.
AOT	Chicory’s ahead-of-time translation of the WASM module to JVM bytecode (`com.hubspot.boomslang.compiled.*`), avoiding interpretation overhead.
stdlib path	The host directory where the factory extracts packaged Python resources; instance roots are mounted from it.
overlay	Source-controlled files under `core/src/main/resources/python-overlay/` copied over the generated Python tree at extraction time.