Reference

Public API

item	what it is
Term	the arrow-calculus term algebra every scheme is written in
Model / ModelCtx	the trait an engine implements, and the context it is handed
LanguageView	object-safe read-only view over a language definition (ADR-0081)
AstRef / AstNode	arena handle + placeholder node — cycle-free by construction
interpret	interpret a Term against a Model
EvalError / LangError	failure kinds surfaced by interpretation

Crate

crate	role
hnl-engine	foundation types

Build and test

cargo build     # sibling [patch] tables resolve deps from ../<repo>
cargo test      # no test suite here — covered by consumers

Dependencies are git deps on branch = "main"; locally the [patch] tables point at sibling checkouts (regenerated by host/scripts/dev-link.sh).