Bessemer

Bessemer (bsmr) builds native TypeScript and Rust projects with a shared, content-addressed cache. It reads package.json, pnpm-lock.yaml, Cargo.toml, and Cargo.lock. Conventional projects do not need build files or Starlark.

Note

Bessemer is a preview. TypeScript with pnpm is the primary integration. Rust with Cargo is experimental. A stable binary release is not available yet.

Interface

The beginner interface has three commands:

bsmr init                 # Create .bsmr in the current project.
bsmr build <path>         # Build one native package and its dependencies.
bsmr clean                # Delete generated files and local build state.

Use package paths in normal work:

bsmr build apps/api
bsmr build packages/rust/dfa

bsmr -h shows this small surface. bsmr --help shows the complete command line, including target labels, graph queries, custom rules, and operational tools.

TypeScript and pnpm

A buildable package needs package.json, tsconfig.json, and tsdown.config.ts. The workspace root needs pnpm-workspace.yaml and a frozen pnpm-lock.yaml.

bsmr init
bsmr build apps/api

Bessemer installs the exact pinned pnpm workspace once. It then schedules and caches package builds independently.

Rust and Cargo

A workspace needs Cargo.toml, Cargo.lock, and an exact Rust toolchain. Use an exact stable version such as 1.94.1 or a dated nightly such as nightly-2026-04-11.

bsmr init
bsmr build packages/rust/dfa

Bessemer caches the complete Cargo output and can restore deleted outputs without running Cargo again. The Cargo adapter is local-only until Rust toolchains and registry inputs are fully content addressed.

Documentation

Read the quick start or the full documentation.

Build the documentation locally:

python -m pip install -r docs/requirements.txt
python -m mkdocs serve -f mkdocs.yml

Development

cargo build --locked --bin bsmr
python3 test.py --ci --git --bsmr=target/debug/bsmr
pnpm install --frozen-lockfile --ignore-scripts
pnpm run ci check

Provenance and license

Bessemer began as a Buck2 fork and now has its own product interface, native ecosystem adapters, cache policy, release process, and roadmap. See NOTICE and UPSTREAM_CHANGELOG.md for upstream provenance.

Except where an inherited notice states otherwise, Bessemer is licensed under the Apache License 2.0.