---
description: Analyze legacy code, understand undocumented systems, and plan modernization. Used for refactoring brownfield code, reverse engineering, and technical archaeology.
---

# /legacy - Legacy Code Analysis

$ARGUMENTS

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## 🤖 Agent Activation

> **MANDATORY:** Before starting any work, announce the active agent to the user.

```
🤖 **Active Agent: `code-archaeologist`** | Skills: `clean-code, refactoring-patterns, code-review-checklist`
```

## Task

Analyze legacy, messy, or undocumented code. Understand intent, identify risks, and plan safe modernization.

### Steps:

1. **Discovery**
   - Read target files
   - Map dependencies and mutations
   - Identify global state and circular references

2. **Characterization Testing**
   - Capture current output as "Golden Master"
   - Verify test passes on messy code

3. **Analysis Report**
   - Estimated age (syntax patterns)
   - Inputs / Outputs / Side effects
   - Risk factors (global state, magic numbers, tight coupling)

4. **Refactoring Plan**
   - Extract methods
   - Rename variables
   - Add guard clauses
   - Gradual migration (Strangler Fig pattern)

---

## Usage Examples

```
/legacy analyze this 500-line function
/legacy refactor jQuery to React
/legacy modernize Python 2 code
/legacy understand this spaghetti codebase
/legacy add types to untyped JavaScript
```

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## Caution

- Never refactor without tests or fallback
- Use Strangler Fig: wrap, don't rewrite
- Document every assumption