blast-radius

A Claude Code plugin that shows what your branch can break, while Claude is still working on it.

After each Claude turn, and whenever you run /blast-radius, it looks at what your branch removed or changed, and finds the code that will no longer work. It looks inside the repo and in your other repos that pull it in as a gem or npm package. Changes that can't break anything stay out of the pane.

	Means
🔴	Will break: a removed class, constant or method is still used, a call no longer fits its method's new arguments, a deleted JS file is still imported, or a Sidekiq worker's queued jobs will fail.
🟡	May break: an instance method changed, and code calls a method with that name. Ruby can't say for sure which class a call goes to.
🟢	Nothing in the branch breaks other code.

It also reads changes to package_todo.yml, so a new Packwerk rule break shows up before review, not after.

Install

1. Install the plugin:

   /plugin install blast-radius --marketplace ltarar/blast-radius
   

2. Tell it where your repos live. Run /plugin configure blast-radius@blast-radius and set Repos folder (only needed if repos aren't in ~/Repositories).

3. Open the pane:

   /blast-radius
   

Requirements

• Claude Code 2.1.294 or later
• git on your PATH
• Your repos cloned side by side in one folder

Commands

Command	What it does
/blast-radius	Opens the pane for the repos in focus
/blast-radius <repo>...	Adds repos to focus
/blast-radius all	Shows every repo with changes
/blast-radius clear	Clears focus back to the current repo

A repo joins focus by itself when Claude edits a file in it. The status line carries a one-line summary.

How it works

blast-radius compares the branch with its merge base on origin/HEAD, including uncommitted and new files.

In Ruby, it reads the classes, modules, constants and public methods that the changed files define, before and after. It then searches for code that still uses anything that disappeared, and checks each call against a method's new arguments, so a new optional argument stays quiet. Changes inside a method body, a new parent class, and moves that keep a name are left out, since callers still work.

In JS and TS, it finds deleted files that something still imports.

To find other repos that use this one, it reads the gemspec or package.json name and checks every repo's Gemfile.lock and package.json for it.

It can't see calls through send, described_class or other dynamic code. Your specs still cover those.

Everything runs locally with git and the files on disk. Nothing is sent anywhere.