Blast Radius

What it does

• Hunts for what a change breaks somewhere else, not just inside the diff. Listing callers isn't the job — the job is the breakage grep won't show.
• Identifies "the one fact the change is safe because of" and proves it with a script or test that calls the real code, pasting the actual output.
• Grades confidence on a 5-step ladder: you said so → you pointed at a file:line → you walked the failure path → you ran it → you reproduced it in the running app. Anything below step 4 must be labeled unproven.
• Looks where grep stops: API JSON shapes, DB columns, wire formats, another language reading the same bytes, feature flags, code three hops downstream, pinned library versions and local patches.
• Returns a fixed report: what changed / the safety fact (proven or unproven) / real risks with file:line, likelihood and cost / what was cleared / the cheapest pre-merge test.

Who it's for

• Developers reviewing a small diff they don't quite trust
• Teams refactoring legacy code or widening an API's public surface
• Tech leads who want to verify a brief's assertion ("X already handles Y") before designing against it
• Anyone who refuses to trust a convincing-sounding AI impact analysis at face value

Examples

1. A brief says "make endpoint X public" → the skill runs a consumer census first, treating the assertion as a hypothesis and letting the census drive the design.
2. A one-line cache-eviction change → it isolates the fact "this call only drops already-dead entries", writes a small script that imports the shipped library and calls that exact function, runs it, and pastes the result as proof.
3. A wide rename or signature change → it runs in arena mode, asking several models the same question and merging answers, since different models catch different real bugs.

Read the instructions in this file and follow them to help me:
https://raw.githubusercontent.com/michael-denyer/pstack-claude/HEAD/plugins/pstack/skills/blast-radius/SKILL.md

What I want: (describe your task here)

Install the skill I found on Claude Skill Mart.
Copy the plugins/pstack/skills/blast-radius folder from the GitHub repo michael-denyer/pstack-claude into my ~/.claude/skills/blast-radius/.
When it's done, tell me in one line what this skill can do.