Blast radius
Code a change could break but does not touch. Marking it explicitly tells a reviewer where to look for second-order damage without reading the whole diff.
Reviewers are good at judging the lines in front of them and bad at guessing what else calls them. Blast radius is the author admitting where the danger is, in writing, before anyone gets paged.
It is also the most honest thing in a spec, because it is where the author says "this might be wrong and I have not tested it". A blast-radius note reading "the other upload path now meters — intended, but untested" is worth more to a reviewer than three paragraphs of confident approach.
Agents are poor at this by default. A model will describe what it changed with great fluency and go quiet on the second-order effects, because those are not in the diff it just produced. Asking specifically for blast radius is one of the few prompts that reliably surfaces risk a generated plan otherwise hides.
- Code ref
A GitHub permalink attached to a spec — repo, path, line range, commit — with a note saying why those lines matter. Rendered as source inline beside the document.
- Drift
When two things that should agree quietly stop agreeing — the doc and the code, the counter and reality, staging and production.