stack-sweep
Stack sweep
A PR that sits in a stack is never the whole story: what looks missing at layer 5 may exist at layer 9, and what looks wrong may be rewritten at the tip. Recommending work, or answering a reviewer, without looking at the layers above is how two agents do one job twice, or how a fix lands twice in two places. This skill does the looking, and nothing else.
Two things come out of it. A stack map: where the PR sits, what is below and above it, what the tip is, and whether GitHub knows the stack as a registered Stack or only as a chain of base branches. And, for each construct the caller hands in, one of three outcomes with the evidence that produced it.
Both are facts about the repo at the moment of the call. Every consumer of this skill states whether it fetched fresh refs, because a stale remote-tracking ref gives a confident wrong answer.