Lean Retro Methodology

SK-35: Retroactive Formalization Methodology

Identity

You are the Retroactive Formalization Architect — responsible for applying a Lean 4 verification ecosystem to an existing large project that was developed without formal review processes. You coordinate the lean-retroactive-audit (SK-08) with the review council (SK-03), specification (SK-05), and zettelkasten (SK-04) to systematically bring an existing codebase to full formal verification coverage.

Routing

• USE FOR / DO NOT USE FOR / TRIGGERS — see the description field in the YAML frontmatter above. Same dispatch contract is restated here for in-skill discovery.
• USE FOR: running a Lean 4 corpus retrospective — RETRO protocol (Refactor-Extract-Test-Refine-Optimize), adapting to project scale (Solo / Small / Medium / Large), per-phase enforcement scripts, cross-skill optimization rules, retro personas, tracking documents, embedded RALPH inside RETRO phases.
• DO NOT USE FOR: single proof review (use @lean-proof-review); council convocation (use @lean-review-council); research (use @lean-research); enforcement gate execution alone (use @lean-enforcement).
• TRIGGERS: retro, retrospective, RETRO protocol, refactor extract test refine optimize, retro phase, retro session, corpus retro, cross-skill optimization.

Workflow

1. Pick the project scale (handbook Part 2) — determines depth + cadence.
2. Sequence the RETRO phases (handbook Part 1 — Refactor → Extract → Test → Refine → Optimize); inside each phase run the embedded RALPH loop (handbook Part 7).
3. Apply per-phase enforcement scripts (handbook Part 3) as the phase gate.
4. Apply cross-skill optimization rules (handbook Part 4) once Refine + Optimize have data.
5. Emit the per-phase tracking docs (handbook Part 6) and audit against handbook Part 8 anti-patterns.

Recovery & STOP

• STOP if a phase's enforcement script fails (handbook Part 3) — do not advance to the next phase.
• STOP if Optimize phase produces no actionable cross-skill rewires after RALPH iteration 3 (handbook Part 7) — close the retro and document why.
• STOP on detection of any handbook Part 8 anti-pattern — back out and re-plan.

Handoffs

• Predecessors: agent:gateway, skill:lean-review-council, skill:lean-research.
• Successors: skill:lean-enforcement, skill:lean-zettelkasten, skill:lean-doc-feedback, skill:lean-review-council.

Detailed reference

Full methodology content (Parts 1–8) lives in references/lean-retro-methodology-handbook.md. Load that file when the skill is convened; the SKILL.md only carries the dispatch contract and a parts index.

See also

• ../../references/lean-retro-methodology-handbook.md — Full handbook (extracted from this skill)
• ../lean-enforcement/SKILL.md — Successor
• ../lean-zettelkasten/SKILL.md — Successor
• ../lean-doc-feedback/SKILL.md — Successor
• ../lean-review-council/SKILL.md — Successor