kernel

The arrow-calculus substrate of the Handl platform (ADR-0040): the Language data schema, the tagged Value representation, the extension ABI, and the handl-lib-* floor-lib packages. The Term/Model foundation types live in handl-lang/engine (hnl-engine); the Plugin/Host/Operation/Behavior/ RuleAcceptor/Contribution host primitives live in handl-lang/host.

• crates/handl-language — the Language data schema and the staged lex/parse/eval dispatch signatures (ADR-0044 "language as data").
• crates/handl-value — the tagged Value representation shared by the eval engines.
• crates/handl-ext — the shared ABI for hnl dynamic extensions (ADR-0149).
• crates/defining-handl — the self-hosting infrastructure (ADR-0044 Phase 8).
• crates/{bytes,cmp,combinators,error,mood,obj,ops,prim,prim-handl,type} — the handl-lib-* substrate packages.

Engines, emitters, kits, plugins, and hosts are not kernel — they live in handl-lang/host and the target repos. The kernel deps on handl-lang/engine (hnl-engine, git dep on main), so downstream repos can pin the substrate without pulling the host repo.

It was extracted from the handl-lang/host workspace per the ADR-0128 repo-split pattern: git subtree split preserves each crate's history, grafted under crates/. Consumers take the crates as git deps on handl-lang/kernel (branch = "main", float-on-main); for local development a sibling ../kernel checkout is wired through the consumer's [patch] table (scripts/dev-link.sh in host regenerates it).

Documentation

Published site (Diátaxis): https://handl-lang.github.io/docs/kernel/

• Reference — public API surface
• How-to — task recipes
• Explanation — design and rationale

Decision records live on the project branch under project/adrs/.