# Blast Radius

> Investigate what a change could break beyond its diff and prove the important safety claims.

- Skill: `yeshwanthyk/blast-radius` (Agent Skill)
- Install (CLI): `npx skillmds@latest add yeshwanthyk/blast-radius`
- Raw SKILL.md: https://api.skillmd.com/api/skills/yeshwanthyk/blast-radius/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: Yeshwanthyk (https://skillmd.com/u/yeshwanthyk)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/yeshwanthyk/blast-radius

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# Blast radius

Find the breakage a diff or grep result can miss. Trace the changed behavior through runtime, data, lifecycle, and integration seams, then focus proof on the one or two facts the safety conclusion depends on.

## Investigate

1. Read the diff and changed/deleted symbols. Note behavior that is implicit in types, serialization, timing, flags, generated output, or downstream consumers.
2. Identify the small set of safety facts that make the change safe or unsafe. Look beyond callers: inspect dependency source/version, lifecycle ordering, wire and storage formats, other languages, feature flags, and multi-hop consumers when relevant.
3. Classify risks by real likelihood and consequence. Separate confirmed risks, checked-and-cleared paths, and unresolved facts. Cite concrete paths/symbols and avoid invented callers.

## Prove

Give each safety fact an evidence rung: source citation, failure reasoning, executable call to the real code, or running-app reproduction. Prefer a small script or focused test over a long argument. Step 4 (the real-code execution) is strong proof but not always cheap; mark facts that stop earlier as unproven. Use [`how`](../how/SKILL.md) or [`why`](../why/SKILL.md) when current mechanics or history changes the risk assessment. Run [`arena`](../arena/SKILL.md) only for a genuinely wide change where competing reviews add value.

## Report

- **What changed**, including non-obvious behavior.
- **Safety facts**, each with its evidence rung and proof.
- **Risks**, only when a concrete break path exists, with likelihood, impact, location, and check.
- **Cleared and unproven**, so limits are visible.
- **Before merge**, the cheapest check that would catch the material bug.

Use plain language and redact private data. Do not expand into an unrelated review.

## Completion

The review is complete when changed and beyond-grep paths are traced, material risks are classified, key safety facts have executable proof or an explicit unproven status, and the report names the relevant next check.