# Development
These pages are for modifying molpack rather than just using it.
molpack is a Rust packing engine with three public surfaces:
- `molcrafts-molpack` Rust library (`lib` name: `molpack`)
- `molpack` CLI binary (`cli` feature)
- `molcrafts-molpack` Python wheel under `python/`
## Read first
- [Architecture](../architecture.md) maps modules, data flow, optimizer loops,
and the objective-evaluation hot path.
- [Extending](../extending.md) walks through custom `AtomRestraint`,
`Region`, `Handler`, and `Relaxer` implementations.
## Validation commands
```bash
cargo test -p molcrafts-molpack --lib --tests
cargo test -p molcrafts-molpack --release --test examples_batch -- --ignored
cd python
maturin develop --release
pytest
cargo fmt
cargo clippy -- -D warnings
```
The ignored `examples_batch` test runs the canonical Packmol-equivalent
workloads and is intentionally slower than the fast unit/integration tier.