write-brownfield-guardrail

name	write-brownfield-guardrail
description	Write a Brownfield Guardrail when current code and target direction differ in a way that could mislead the AI — capturing what to use, what not to copy, and when to ask. Use when creating, updating, or applying one (in bootstrap, guidance updates, or brownfield review). A Guardrail records a divergence; it never originates an architecture decision.

Inputs

• trigger — a misleading divergence between current code and target direction that could lead the AI astray. Absent a divergence, there is nothing to write.
• template fields — the Guardrail fields the writer fills: Topic, Status, Source, Current state, Target direction, Rule for new work, Rule for existing code, Do not copy, Ask when.

Procedure

1. Gate. If current code and target direction are aligned, stop and emit nothing. Otherwise continue.
2. Select exactly one Status from the four reachable options:
   • current is approved → Use current
   • target is adopted (new work follows it even if code differs) → Use target
   • target exists but is out of scope (don't move there unless scoped) → Target not ready
   • no decision exists yet → Ask first
3. If the Guardrail requires a decision that doesn't exist yet, set Status Ask first, fill Ask when with the deciding owner, and recommend formalizing the decision. Do not decide it within the Guardrail — a Guardrail records a divergence; it never originates an architecture decision.

Output

Return the filled Guardrail template — the single artifact this skill produces:

## Brownfield Guardrail: <Topic>
Status: <Use current | Use target | Target not ready | Ask first>
Source: <SAD / ADR / spec / decision>
Current state: <what exists today>
Target direction: <what new work should use, if known>
Rule for new work: <what to do for new work>
Rule for existing code: <what to keep or must not change>
Do not copy: <misleading legacy pattern>
Ask when: <conditions needing clarification>