Anthropic API Proxy

A simple local proxy for inspecting Anthropic API requests and responses. Sits between your client and the Anthropic API, logging all traffic as JSON files with a web UI for browsing.

Quick Start

# Terminal 1 - Start the API proxy
uv run simple_proxy.py

# Terminal 2 - Start the web viewer
uv run viewer.py

Then point your Anthropic client's base URL to http://localhost:5001.

How It Works

The proxy forwards all requests to https://api.anthropic.com, passing through headers (including your API key) unchanged. Both requests and responses are saved as JSON files in ./logs/.

The web viewer at http://localhost:5002 lets you browse and inspect logged API calls — messages, tool use, token counts, etc.

Endpoints

Service	URL	Description
Proxy	http://localhost:5001	Point your client here
Viewer	http://localhost:5002	Web UI for browsing logs
Health	http://localhost:5001/health	Health check

Client Configuration Examples

Any client that lets you set a custom base URL will work:

# Python SDK
client = anthropic.Anthropic(base_url="http://localhost:5001")

# Claude Code
ANTHROPIC_BASE_URL=http://localhost:5001 claude

Log Format

Logs are saved to ./logs/ as pairs of JSON files:

• {timestamp}_request.json — full request body
• {timestamp}_response.json — full response (streaming responses are reconstructed)