Constitution

Towards unbreakable code — the supreme design law of System F Software

Articles • Use it • Update • Amendment

CONSTITUTION.md is the design law that governs every repository under System F Software: a pure functional core behind a thin imperative shell, types before logic, the Testing Trophy, and removal over addition. It is stack-neutral — it states principles, never tools or languages, so it binds any codebase regardless of stack.

This repository is the single source of truth. systemfsoftware.com/constitution renders this file, and consumer repositories vendor it via git subtree + symlink — so the constitution is authored in exactly one place and an edit here propagates everywhere, never a copy that silently drifts.

Articles

Article	Principle
I — The Pure Core	Decisions are pure; types come first; errors are variants; null is not a state; one path.
II — The Boundary	Functional core / imperative shell; effects are values; decode never cast; dependencies point inward.
III — Verification	The Testing Trophy; properties over examples; mutation is the measure.
IV — Organization	Organized by what it does; names scream the domain; fits in the head.
V — Conduct	Depth over expedience; challenge before you commit; subtract before you add.
VI — Amendment	How the document changes.

Use it in a repository

Vendor the constitution as a squashed, signed subtree, then symlink it to your repo root:

# 1. Fetch into a named ref (a transient FETCH_HEAD is the failure mode to avoid)
git fetch https://github.com/systemfsoftware/constitution.git main:refs/remotes/vendor/constitution

# 2. Vendor it as a squashed, signed subtree
git subtree add --prefix=vendor/constitution refs/remotes/vendor/constitution --squash -S \
  -m "chore: vendor shared constitution"

# 3. Symlink it to the repo root
ln -s vendor/constitution/CONSTITUTION.md CONSTITUTION.md

Reference it from your agent harness (CLAUDE.md / AGENTS.md) as @CONSTITUTION.md — the symlink resolves it.

Update a consumer

git fetch https://github.com/systemfsoftware/constitution.git main:refs/remotes/vendor/constitution
git subtree pull --prefix=vendor/constitution refs/remotes/vendor/constitution --squash -S \
  -m "chore: update constitution"

Note

The symlink never changes — it always points at vendor/constitution/, so a pull just refreshes the content underneath.

Amendment

The constitution is amendable by design (Article VI). An amendment carries a written rationale, a version bump, a date, and a matching update to the consuming AGENTS.md.