Architecture decision records (ADRs)

This directory holds ADRs at the repository root, alongside the specification tree (phase-0/, phase-1/, …). That layout is committed in Phase 0 Section 5 (Implementation Infrastructure); see phase-0/05-implementation-infrastructure.md (repo layout and the decisions/ bullet in the notes).

Conventions

• One ADR per major, durable commitment (not every PR).
• Use the usual structure: Context, Decision, Consequences.
• Filenames: short kebab-case.md (for example bootstrap-stance.md, abi-stability.md).

Recorded decisions

• toolchain-pins.md — LLVM/MLIR, Z3/ocaml-z3, Lean/mathlib pinning policy (Phase 0 §05 §11).
• phase-0-reference-implementation-status.md — what the OCaml compiler implements today vs Phase 0 §02 (structural shapes, partial op/cast/reduce lowering); companion to phase-0/REVIEW-CHECKLIST.md §4.

Planned / cited elsewhere

Forward tracks and Phase 1 name additional ADRs as they appear. Examples: bootstrap stance, ABI stability policy, Arrow as canonical tabular format.