Lamina evolutionary rules

Skill aryaniyaps/lamina/skills/lamina-evolutionary-rules

Headless Product Design skill for AI coding agents | Design how it works, verify what you ship.

Install

npx -y skills add aryaniyaps/lamina --skill lamina-evolutionary-rules

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Evolving product rules safely — reversible decisions, invariant checks as features change, deferring commitment. Use when the domain will grow or requirements are uncertain.

SKILL.md

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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

Tag design decisions reversible vs irreversible in run or decisions.md.
When adding workflows, re-check all existing invariants for the touched entities.
After external implementation, run verify — not one-time at handoff.
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: Feature ships without updating scenarios.
Permanent "temporary": Overrides that bypass invariants become architecture.

Examples

Adding waitlist: Reversible — new workflow branch. Must preserve invariant: one valid ticket per student per exam. Scenarios for waitlist → ticket promotion and edge cases.