D030 - The guard routes a location and never rewrites an identity

Status: decided Date: 2026-09-26

guard::check refuses a destination the target will not scan (IssueKind::InertPath) and offers the same title under /data/homebrew. Any other destination is accepted whatever the title's prefix, and suggested_id is always the id that came in.

Why: the prefix rule was reasoned, not measured, and rewriting an id sent one title on top of an unrelated installed one. A title under the homebrew folder with its own id is where it belongs.

Rejected:

• A list of supported prefixes: unmeasured, and it refused correct destinations.
• Rewriting the id to a supported prefix: a silent overwrite of another title.