drywall

# DRYwall

A Claude Code plugin for detecting and eliminating code duplication using [jscpd](https://jscpd.dev/).

DRY = Don't Repeat Yourself

This was motivated by the observation that coding agents, including Claude Code, have a bias towards producing new code over reusing existing code or extracting common code. The resulting creeping code duplication weighs down AI-native codebases. This is a tool to make ongoing deduplication quick and easy from within Claude Code.

Because DRYwall detects code duplication using a deterministic toolchain (the awesome jscpd), this plugin is significantly more effective and cheaper in tokens than just telling an agent to find and refactor duplication.

## Installation & Quickstart

Prerequisite: [Node.js](https://nodejs.org/) must be installed on your system (with `node` and `npx` binaries available to Claude Code).

Open Claude Code and add the marketplace, then install the plugin:

```
/plugin marketplace add nikhaldi/drywall
/plugin install drywall@drywall
```

To start refactoring duplicated code with manual supervision, run the scan skill within Claude Code:

```
/drywall:scan
```

If you just want Claude Code to take care of everything, prompt it with something like this after installing the plugin (it will launch a dedicated subagent):

```
Deduplicate code in this codebase
```

## Configuration

Create a `.drywallrc.json` in your project root to set defaults. Values correspond to [jscpd CLI options](https://jscpd.dev/getting-started/configuration#cli-options), except for the DRYwall-specific ones listed below:

```json
{
  "minTokens": 50,
  "minLines": 5,
  "ignore": ["**/node_modules/**", "**/dist/**", "**/*.generated.*"],
  "respectGitignore": true,
  "jscpdVersion": "4.0.8"
}
```

The configuration options specific to DRYwall are:

- **`respectGitignore`** — `true` by default. Passes `--gitignore` to jscpd so that files excluded by `.gitignore` are automatically skipped. Set to `false` to disable.
- **`jscpdVersion`** — Pin the jscpd version used via `npx`. Defaults to `4.0.8` if not set.
- **`maxDuplicates`** — Maximum number of duplicate pairs to return, ranked by impact. Defaults to `20`. (This needs to be restricted to avoid blowing past context limits right away in large codebases.)
- **`maxFragmentLength`** — Maximum character length of each code fragment before truncation. Defaults to `500`.

### Ignored code blocks

If you want to exclude some code from all of DRYwall's refactoring, you can use `jscpd:ignore-start` and `jscpd:ignore-end` [markers](https://github.com/kucherenko/jscpd/blob/master/apps/jscpd/README.md#ignored-blocks) in the code. JavaScript example:

```
/* jscpd:ignore-start */
import lodash from 'lodash';
import React from 'react';
import {User} from './models';
import {UserService} from './services';
/* jscpd:ignore-end */
```

## Components

### Skill: `/drywall:scan`

Scans the current codebase for duplication and shows a ranked report of suggested deduplication refactorings. This is the simplest way to tackle some refactorings with manual control.

Invoke within a Claude Code session with:

```
/drywall:scan
/drywall:scan --min-tokens=100 --min-lines=10
```

Arguments are passed through as is to [jscpd](https://jscpd.dev/getting-started/configuration#cli-options). These arguments are additive (or override) defaults configured in `.drywallrc.json` (see Configuration above).

### Agent: `dedup-refactor`

An autonomous agent that detects duplication and refactors it end-to-end — extracting shared utilities, updating call sites, and verifying the changes. Claude delegates to this agent for large deduplication tasks.

### MCP Tool: `detect_code_duplication`

Automatically invoked by Claude Code when your task involves refactoring or deduplication. Runs [jscpd](https://jscpd.dev/) under the hood and returns structured results.

Parameters:

- `path` — directory to scan (default: `.`)
- `options` — object of [jscpd options](https://jscpd.dev/getting-started/configuration#cli-options) passed as CLI flags (e.g., `{"minTokens": 30, "minLines": 5, "ignore": ["**/test/**"]}`)

## License

This project is licensed under the [MIT License](./LICENSE.txt).