Code Editing Agent

A minimal AI coding agent built with Claude. ~200 lines of Python running in a loop with LLM tokens.

Inspired by Geoffrey Huntley's workshop.

Setup

1. Create a virtual environment and install dependencies:

python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate
pip install anthropic

2. Install ripgrep (for code search):

brew install ripgrep      # macOS
apt install ripgrep       # Ubuntu/Debian

3. Set your API key:

export ANTHROPIC_API_KEY=your-api-key-here

Usage

python main.py

Then chat with Claude:

You: what files are in this directory?
You: search the code for "ToolDefinition"
You: read agent.py and explain how the loop works
You: create a fizzbuzz.py that prints fizzbuzz from 1 to 100
You: run python fizzbuzz.py
You: fix the bug in fizzbuzz.py

Use Ctrl+C to quit.

Tools

Tool	Description
list_files	List files and directories at a given path
read_file	Read the contents of a file
edit_file	Edit a file by replacing text, or create new files
bash	Execute shell commands (dangerous commands blocked)
code_search	Search code with ripgrep

Tool Details

edit_file — Uses string replacement. Pass old_str="" to create a new file.

bash — Blocks dangerous patterns: rm -rf, sudo, > /dev, mkfs, dd if=, :{(). Times out after 30 seconds.

code_search — Requires ripgrep (rg). Returns matching lines with file paths and line numbers.

Project Structure

├── main.py      # Entry point, sets up and runs the agent
├── agent.py     # Agent loop and tool execution
└── tools.py     # Tool definitions

How It Works

┌─────────────────────────────────────────────────────┐
│                    Agent Loop                       │
├─────────────────────────────────────────────────────┤
│  1. Get user input                                  │
│  2. Send conversation to Claude                     │
│  3. If Claude returns text → print it               │
│  4. If Claude returns tool_use → execute tool       │
│  5. Add tool result to conversation                 │
│  6. Go to step 2 (until no more tool calls)         │
│  7. Go to step 1                                    │
└─────────────────────────────────────────────────────┘