# Phase 20.9 — Structure (Lang Line)

Decision
- Introduce `lang/` at the repository root to host the C ABI kernel and related artifacts (no Rust here).
- Keep Rust engine/crates under `crates/` and `src/` untouched. The `lang` line is a separate box.

Layout
- `lang/` — top-level
  - `c-abi/` — headers and libc-backed shim for canaries
    - `README.md` — responsibilities and contracts
  - `README.md` — scope and principles

Rationale
- Clear separation of concerns: script-driven ABI vs. Rust runtime internals.
- Makes it easy to package/link the C shim with external harnesses without dragging Rust sources.

Notes
- Migration is incremental: existing headers/shims remain in `include/` and `c/abi/` until references are updated.
- CI/docs should point to `lang/c-abi` once stabilized; older paths deprecated after a grace period.