bp-refactor

bp-refactor is a skill for Claude Code from kulmam92/cc-best-practices-marketplace. It costs 49 tokens per session (426 once invoked), scanned A, original, MIT.

A step-by-step method for changing old code while first recording tests for how it currently behaves. Characterization tests capture existing behavior, including bugs, before changes begin.

In plain words
What is it for?
Use it to split large refactors into reviewable pieces, verify each piece, and discard a failed piece instead of layering fixes onto it.
Why use it?
It reduces the risk of breaking undocumented behavior during refactoring, migration, API restructuring, or cleanup.

Skill for Claude Code

Written for Claude Code: argument-hint in frontmatter. Also seen: mentions CLAUDE.md.

Part of the cc-best-practices plugin — 6 skills, 1 hook shipped together

Good fit Use it to split large refactors into reviewable pieces, verify each piece, and discard a failed piece instead of layering fixes onto it.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/kulmam92/cc-best-practices-marketplace/bp-refactor
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add kulmam92/cc-best-practices-marketplace --skill bp-refactor
Clone the repo
git clone --depth 1 https://github.com/kulmam92/cc-best-practices-marketplace

Made for: Claude Code.

Or install cc-best-practices, the plugin that ships this one along with the rest of its 6 skills, 1 hook.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for bp-refactor

README.md
[![agentmods](https://agentmods.dev/badge/skills/kulmam92/cc-best-practices-marketplace/bp-refactor/github.svg)](https://agentmods.dev/skills/kulmam92/cc-best-practices-marketplace/bp-refactor)
Your own site
<a href="https://agentmods.dev/skills/kulmam92/cc-best-practices-marketplace/bp-refactor"><img src="https://agentmods.dev/badge/skills/kulmam92/cc-best-practices-marketplace/bp-refactor/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for bp-refactor

Your own site · 80×15
<a href="https://agentmods.dev/skills/kulmam92/cc-best-practices-marketplace/bp-refactor"><img src="https://agentmods.dev/badge/skills/kulmam92/cc-best-practices-marketplace/bp-refactor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 426 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00049 $0.00426
Opus 5 $0.00024 $0.00213
Sonnet 5 $0.00010 $0.00085
Haiku 4.5 $0.00005 $0.00043

Measured 11d ago against content hash 61c915e58346, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

bp-refactor scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/cc-best-practices/skills/bp-refactor/SKILL.md · 40 lines

What it actually says

Safe Refactoring Protocol

Never refactor without locking down existing behavior first. This follows Boris Cherny's 4-step legacy refactoring protocol.

Steps

  1. Write characterization tests FIRST -- Before touching any logic, write tests that lock down the current behavior. Even if the current behavior is buggy, test it as-is. For large refactors (50k+ LOC), Boris recommends spending the first 4 days purely on characterization tests.

  2. Check CLAUDE.md for load-bearing walls -- Verify that the area to be refactored is not protected. If it is, stop and discuss with the developer.

  3. Plan atomic chunks -- Split the refactor into independently landable pieces:

    • Interfaces and types first
    • Helper functions second
    • Implementation changes last
    • Each chunk should be independently reviewable and revertable
  4. Execute one chunk at a time -- Implement each chunk and run /bp-verify after each one. Never combine multiple chunks into a single change.

  5. If a chunk fails -- Revert the chunk entirely and rescope. Do NOT patch on top of a failed refactoring step. Go back to the plan and try a different approach.

Anti-Patterns

  • DO NOT refactor and change behavior simultaneously -- separate them
  • DO NOT skip characterization tests -- they are the safety net
  • DO NOT submit one giant diff -- break it into atomic, landable chunks
  • DO NOT patch around failures -- revert and rescope

Quality Checks

  • Characterization tests pass before AND after each chunk
  • No chunk exceeds 200 lines of changes
  • Existing behavior is preserved (unless intentionally changed in a separate PR)
  • Load-bearing walls are respected
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 40 lines · 49 tokens per session scan A 61c915e58346

Subscribe to this mod's changes

bp-refactor is a skill published in the GitHub repository kulmam92/cc-best-practices-marketplace (2 stars, last pushed 5mo ago), licensed MIT. It adds 49 tokens to every session and 426 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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