Blast radius
Find what a change breaks somewhere else, before it ships. Companion
to how and why. Listing callers is not the job. The job is the
breakage grep will not show you.
Authorized Scope
Apply this engine only within the user's requested task and existing explicit
authorization. Loading or delegating to it grants no additional authority.
Preserve report-only restrictions and the caller's target, host, provider, and
cost limits. Existing approval satisfies a gate only for the same actions and
scope; obtain approval before expanding them. Forward these limits to delegates.
Contract
Inputs:
- A diff, PR, or proposed change that looks small
Outputs:
- What it does, the one safety fact (proven or marked unproven),
confirmed risks, cleared checks, and the cheapest merge-time test
Creates/Modifies:
- An optional proof script under the current repo
.tmp/
External Side Effects:
- Runs local proof scripts or tests. No production writes.
Confirmation Required:
- None for the analysis. Proof scripts stay local unless the caller
commits them.
Delegates To:
why step 2 for PR and commit anchorsarena for a wide change that needs several independent reads
How sure are you
For each safety fact, get as far down this list as is cheap, and say
where it stopped.
- You said so. Worthless on its own.
- You pointed at the line.
- You walked the bad case and it does not reach.
- You ran it. A script or test that calls the real code.
- You reproduced it in the running app.
Any safety fact you cannot get to step 4, say so out loud.
Steps
- Read the change, including the part the diff does not spell out.
- Find the one fact it is safe because of.
- Look where grep stops: library source, pinned versions, timing,
wire formats, feature flags, three hops downstream.
- Be honest about each risk. Cite a real
file:line. A search that
finds nothing is still an answer.
- Prove the one fact. Run real code. Paste what happened.
- For a big or wide change, run it as an
arena.
What to hand back
- What it does. Including the part that is not obvious.
- The one fact it is safe because of. State it, say which step
you got it to, and show the proof.
- Risks. Only the real ones.
- Cleared. What you checked and why it is fine.
- Before you merge. The cheapest test or repro that catches the
real bug.
Blast Radius procedure
Read blast-radius procedure when running this workflow.
Apply the authorized scope and mode of this entry point to every step.
Resolve other skills through this distribution’s active catalog; resolve
resources relative to the installed skill directory.
1---
2name: blast-radius
3description: Find what a small-looking change could break somewhere else, and prove the one fact it is safe because of by running real code. Use for blast radius of X, what could this break, or reviewing a small diff you do not trust.
4license: MIT
5metadata:
6 portable_source: "https://github.com/ericlitman/open-pstack"
7 portable_commit: "56bfd14418fa733e34d98f714f357d28788470e3"
8 version: "1.2.0"
9 tags: "impact, safety, review, verification"
10 author: Ship Shit Dev
11 source: https://github.com/cursor/plugins/blob/main/pstack/skills/blast-radius/SKILL.md
12 upstream_repo: cursor/plugins
13 upstream_ref: main
14 upstream_commit: bdf7aa355337
15 last_synced: "2026-09-05"
16 license: MIT
17when_to_use: "blast radius, what could this break, is this small diff safe"
18---
19
20# Blast radius
21
22Find what a change breaks somewhere else, before it ships. Companion
23to `how` and `why`. Listing callers is not the job. The job is the
24breakage grep will not show you.
25
26## Authorized Scope
27
28Apply this engine only within the user's requested task and existing explicit
29authorization. Loading or delegating to it grants no additional authority.
30Preserve report-only restrictions and the caller's target, host, provider, and
31cost limits. Existing approval satisfies a gate only for the same actions and
32scope; obtain approval before expanding them. Forward these limits to delegates.
33
34## Contract
35
36Inputs:
37
38- A diff, PR, or proposed change that looks small
39
40Outputs:
41
42- What it does, the one safety fact (proven or marked unproven),
43 confirmed risks, cleared checks, and the cheapest merge-time test
44
45Creates/Modifies:
46
47- An optional proof script under the current repo `.tmp/`
48
49External Side Effects:
50
51- Runs local proof scripts or tests. No production writes.
52
53Confirmation Required:
54
55- None for the analysis. Proof scripts stay local unless the caller
56 commits them.
57
58Delegates To:
59
60- `why` step 2 for PR and commit anchors
61- `arena` for a wide change that needs several independent reads
62
63## How sure are you
64
65For each safety fact, get as far down this list as is cheap, and say
66where it stopped.
67
681. You said so. Worthless on its own.
692. You pointed at the line.
703. You walked the bad case and it does not reach.
714. You ran it. A script or test that calls the real code.
725. You reproduced it in the running app.
73
74Any safety fact you cannot get to step 4, say so out loud.
75
76## Steps
77
781. Read the change, including the part the diff does not spell out.
792. Find the one fact it is safe because of.
803. Look where grep stops: library source, pinned versions, timing,
81 wire formats, feature flags, three hops downstream.
824. Be honest about each risk. Cite a real `file:line`. A search that
83 finds nothing is still an answer.
845. Prove the one fact. Run real code. Paste what happened.
856. For a big or wide change, run it as an `arena`.
86
87## What to hand back
88
89- **What it does.** Including the part that is not obvious.
90- **The one fact it is safe because of.** State it, say which step
91 you got it to, and show the proof.
92- **Risks.** Only the real ones.
93- **Cleared.** What you checked and why it is fine.
94- **Before you merge.** The cheapest test or repro that catches the
95 real bug.
96
97## Blast Radius procedure
98
99Read [blast-radius procedure](references/blast-radius-procedure.md) when running this workflow.
100Apply the authorized scope and mode of this entry point to every step.
101Resolve other skills through this distribution’s active catalog; resolve
102resources relative to the installed skill directory.
shipshitdev