Chai-1 is a molecular structure prediction tool that takes FASTA sequences (proteins, DNA, RNA, ligands, glycans) and predicts 3D structures using a diffusion model. It is packaged as a Python library with a CLI (`chai-lab fold`) and a Python API (`chai_lab.chai1.run_inference`). The pipeline ingests sequences, optionally generates MSAs via ColabFold server, loads templates from RCSB, computes ESM embeddings, applies user-defined restraints (contacts, pockets, covalent bonds), tokenizes all atoms, generates a rich set of features, collates them into batches, and runs a TorchScript diffusion model to produce multiple structure samples. Outputs are ranked by confidence metrics (pTM, ipTM, pLDDT, clash score) and saved as CIF files. The codebase is well-structured with clean abstractions (feature generators, data contexts, collation), strong typing (jaxtyping, beartype), and CI quality gates. It is a hybrid of a production-grade inference tool and research code, with some copied components (rigid transformations from AlphaFold, ColabFold MSA server) and a monolithic inference entry point. The repository is actively maintained with recent commits, PyPI releases, and comprehensive examples.