lamina-evolutionary-ruleslisted

# Evolutionary Rules Products change. Design rules and invariants so they can evolve without silent breakage — prefer reversible choices until the cost of waiting exceeds the cost of committing. ## Decision frameworks - **Reversible decision**: Can be undone without corrupting domain state (toggle feature flag, add optional field). - When to use: Uncertain requirements, early iterations. - How: Document in `implement.md` as low-risk; verify after each change. - **Irreversible decision**: Hard to undo (merge two entity types, remove invariant). - When to use: Only when delay cost is high and trade-offs are explicit. - How: Record in `decisions.md`; full scenario coverage before ship. - **Invariant regression check**: New feature must not violate existing `domain` rules — re-run verify after external build. - When to use: Every `/lamina-verify` after changes touching shared entities. - **Defer commitment**: Wait until you need the rule — but do not defer documenting invariants you already know. ## Checklists 1. Tag design decisions reversible vs irreversible in run or `decisions.md`. 2. When adding workflows, re-check all existing invariants for the touched entities. 3. After external implementation, run verify — not one-time at handoff. 4. Prefer additive rule changes over breaking changes to actor permissions. ## Anti-patterns - **Big-bang rule change**: New payment rule breaks all issued tickets without migration scenario. - **Forgotten invariants**: Feat