| name | assess-legacy-estate |
| description | Assess a legacy system and choose a modernization strategy with the 6 R's (retain/rehost/replatform/refactor/rearchitect/replace). Reach for this when the question is 'rewrite or refactor?' or 'is this worth modernizing?'. |
Skill: Assess the legacy estate
Decide whether and how to modernize before any code changes.
Step 1 — Inventory the capability
List what the system does, its dependencies, runtime, data stores, and the team that owns it. Cite the pain it causes (incident load, lead time, change-failure rate) — don't assert it (§2 #7).
Step 2 — Name the driver
The specific reason to change this now: scaling limit, change-failure rate, security/end-of-life, hiring drag, cost, or strategic pivot. No driver → retain.
Step 3 — Pick the R (per capability)
Traverse the 6-R's tree in ../../knowledge/legacy-modernization-decision-trees.md. Most estates are a portfolio of R's, decided capability by capability — not one verdict for the whole system.
Step 4 — Make the carrying-cost case
Quantify the cost of not modernizing vs the cost/risk of doing it. Recommend only when the trade is favorable. Date and source every external figure.
Step 5 — Sequence value-first
Order the work so increments ship early, the riskiest unknowns de-risk first, and rollback stays cheap. Capture it in the modernization-assessment template.
