Put an explicit reuse-before-write ladder in your instructions file.

Steal Ponytail's seven rungs: does this need to exist → already in the codebase → stdlib → native platform feature → installed dependency → one line → minimal working solution. Then add a command that audits the current diff against that ladder. The claimed 54% code reduction is a vendor number, but the mechanism costs you ten lines of instructions and reduces review load regardless of whether you hit their figure.