Skill · CLAUDE.md rule

Map the Blast Radius Before You Edit

A forcing function that makes the agent trace who depends on a symbol before it changes it.

TypeCLAUDE.md rule

Rename a function, tweak what it returns, change one default — it feels like a one-line edit. The agent makes it, the file looks clean, the test it runs passes. What it never saw is the eleven other places that called that function expecting the old shape. Those don't fail loudly; they fail later, somewhere you weren't looking, one at a time.

A shared symbol has no local edits. Every change to it is a change to everything that depends on it — and the agent, working inside one file, sees only the file in front of it. The rule forces it to look outward before it touches anything load-bearing:

✕ Without the rule

Edits the function in place — the file looks clean

▼

The one test in this file still passes

▼

Eleven callers break later — one at a time, in production

✓ With the rule

Lists every caller of the symbol first

▼

States what breaks if the shape changes

▼

You approve the load-bearing ones before the edit

Drop it into your CLAUDE.md. On an isolated, private function it costs nothing — there are no callers to list, so the rule gets out of the way. Where it earns its keep is exactly where damage hides: the shared helper, the config key, the public signature that fifty things quietly assume. Find-and-replace is the most dangerous tool in that situation, because it rewrites text without understanding the call graph — so the rule makes the agent trace before it touches.

Paste into CLAUDE.md

## Before editing shared code
Before changing a function, type, signature, or config value that other code depends on:
1. List every caller or dependent of the symbol you are about to change.
2. State the blast radius: what breaks if the change is wrong, and how far it reaches.
3. If it touches a widely-used symbol or a public interface, say so and wait for my go-ahead before editing.
Never change a shared signature with blind find-and-replace — trace the callers first, then edit.

Prefer your agent install it?

Add this rule to my CLAUDE.md, verbatim:

## Before editing shared code
Before changing a function, type, signature, or config value that other code depends on:
1. List every caller or dependent of the symbol you are about to change.
2. State the blast radius: what breaks if the change is wrong, and how far it reaches.
3. If it touches a widely-used symbol or a public interface, say so and wait for my go-ahead before editing.
Never change a shared signature with blind find-and-replace — trace the callers first, then edit.

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Tags#workflow #claude.md #skill

Other skills

01Verify Before You Call It Done 02Plan First, Then Code 04If It's Deterministic, Don't Make It Guess 05Diagnose From the Symptom, Not the Guess 06Make It Argue Against Its Own Plan 07Hand Off to Your Next Session 08A Review That Doesn't Rubber-Stamp 09Run to the gate, then stop — not step-by-step 10A CLAUDE.md skeleton — turn a description into operating law 11The weekly review prompt — five minutes that turn experience into skill 12Split the work into focused slices, each with clean context 13Is this even worth an agent — ask before you open the chat 14Probe with a small task before you trust it in a new domain

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✕ Without the rule

✓ With the rule

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