RepoDecay

Detect technical debt caused by AI coding tools before your codebase becomes unmaintainable.

A CLI tool that measures how AI assistants are silently degrading your repository quality — one scan at a time.

npx repodecay scan

Cursor, Copilot, Claude Code — great at writing code. Terrible at not creating technical debt. RepoDecay is the first tool built specifically to detect and quantify the damage AI-generated code leaves behind.

Repository Decay Score

One percentage. Zero to 100. How much has your AI assistant degraded your codebase?

| Score | Label | Meaning | |-------|-------|---------| | 0–20% | Pristine | No detectable AI damage | | 21–40% | Light Sprinkle | Minor issues, watch trends | | 41–60% | Drizzle | AI creating visible debt | | 61–80% | Pouring | Significant AI-caused damage | | 81–100% | Monsoon | Codebase degrading faster than it improves |

Quick Start

# Run a scan
npx repodecay scan

# Scan a specific directory
npx repodecay scan --path ./src

# JSON output (pipe to jq, CI scripts)
npx repodecay scan --output json

# Track trends over time
npx repodecay scan --baseline
npx repodecay compare

Install

npm install -g repodecay

How It Works

RepoDecay runs 5 static analysis passes designed to catch patterns common in AI-generated code:

1. Duplication — Hashes function bodies to find identical blocks (AI loves copy-paste)
2. Dead Code — Resolves export/import references to find unused code (AI generates bloat)
3. Complexity — Cyclomatic complexity per function (AI writes convoluted code)
4. File Size — Flags oversized files >300 lines (AI generates mega-files)
5. Architecture — Detects any types, mutable let, nested callbacks — hallmarks of AI slop

Results stored in .repodecay/history.json. Trend tracking built in.

Why RepoDecay Exists

Existing tools treat all code the same. SonarQube, CodeRabbit, Semgrep — they scan code without asking where it came from.

RepoDecay is different: it measures damage specifically from AI coding tools. Not a generic linter. A damage report for what your AI assistant did when you weren't looking.

Backed by data:

• CMU study: Cursor repos show +41% complexity, +30% more static warnings
• GitClear: 211M LOC analyzed — copy-paste up 12.3%, refactoring collapsed
• CodeRabbit: AI PRs contain 1.7× more issues, 3× more readability problems

Configuration

Create .repodecayrc in your repo root:

{
  "extensions": [".ts", ".tsx", ".js", ".jsx"],
  "maxFileLines": 300,
  "maxComplexity": 10,
  "cloneRateThreshold": 5,
  "excludeDirs": ["node_modules", "dist", ".git", "build", ".next"]
}

License

MIT