legacy-specifier

name	legacy-specifier
description	Extrai especificações de um sistema legado (código existente) quando não há documentação adequada.
triggers	["legacy","reverse engineer","extract spec","existing code"]

Legacy Specifier

Purpose

Reverse-engineer specifications from an existing system:

• Identify behaviors from code, routes, UI, tests
• Extract APIs and contracts
• Infer business rules ONLY when strongly evidenced
• Mark uncertainties explicitly

This skill prioritizes accuracy over completeness.

When to Use

• User asks to extract specs from repo/code
• Plan Lead routes "existing codebase" input to this skill

Inputs

• Repository code, existing docs (if any)
• API schemas (OpenAPI), test suites, UI flows (routes/pages)

Outputs

• spec/00-context/system-context.md (update)
• spec/20-design/api-contracts.md
• spec/30-features//{spec.md, acceptance.md, test-plan.md}
• spec/99-meta/open-questions.md

Rules (non-negotiable)

1. Never guess business intent. If unclear → UNKNOWN + Open Question.
2. Prefer evidence sources in this order: tests > docs > code paths > UI > comments.
3. Separate: Observed behavior (fact) vs Intended behavior (hypothesis, mark as such).
4. Track "contract surface" carefully: public APIs, payloads, status codes; UI visible behaviors; integrations.

Process

Step 0 — System Map

Produce a map: Components (services, frontend, jobs), Entry points (routes, commands), Data stores, Integrations.

Step 1 — Contract Extraction

For each entry point: Inputs, Outputs, Errors, Auth requirements (if observed), Side effects.

Step 2 — Behavior Extraction

Identify: Happy path, Validation, Authorization, Idempotency/retries (if present), Pagination/sorting rules, Data boundaries.

Step 3 — Feature Grouping

Group endpoints + UI flows into feature candidates. Assign FEATURE-001, FEATURE-002…

Step 4 — Spec Drafting

For each feature: Write spec.md (observed behavior), acceptance.md (provisional if needed), test-plan.md (existing tests + missing ones).

Step 5 — Unknowns + Risks

List open questions: Intent unclear, Inconsistent behavior across services, Missing tests for critical paths.

Feature Spec Template (legacy)

FEATURE-XXX — . Status: LEGACY-DERIVED. Confidence: HIGH | MEDIUM | LOW. Evidence (files/tests/docs). Observed Behavior. Inputs/Outputs. Business Rules (Observed). Edge Cases. Known Gaps/Uncertainties. Acceptance (Provisional if needed) with GWT scenarios.