Capturly

Record, replay, and debug any HTTP API — with built-in AI traffic intelligence

Capturly is an HTTP proxy that captures, replays, and inspects API traffic. It works with any REST/GraphQL endpoint but goes deeper on AI protocols — automatically detecting OpenAI and AGUI (Agent GUI) traffic, extracting system prompts, combining streaming chunks, and surfacing tool calls.

Quick Start

# Install
pip install capturly

# Point at OpenAI and watch traffic
capturly --mode log --backend https://api.openai.com --combine-chunks

# Open dashboard at http://localhost:9090
# See your system prompts, tool definitions, and complete conversations

Use Cases

Debug AI Applications

See exactly what your app sends to OpenAI:

capturly --mode log --backend https://api.openai.com --combine-chunks
# Configure your app to use http://localhost:9999 instead of api.openai.com

The dashboard extracts:

• System prompts (including multi-part array content)
• Tool definitions and tool calls
• Token usage
• Complete conversation history (streaming chunks combined)
• AGUI agent runs: messages, tool calls, reasoning, and state

Create Deterministic Test Fixtures

Record real API responses, replay them in tests:

# Record once
capturly --mode record --backend https://api.stripe.com
curl http://localhost:9999/v1/charges

# Replay forever (no network, instant, deterministic)
capturly --mode replay
pytest tests/

Performance Testing

Stress test your service with cached responses:

# Replay with zero delay (simulate fast API)
capturly --mode replay --delay 0

# Or simulate slow upstream
capturly --mode replay --delay 2000

Development Speedup

Cache common endpoints, record new ones automatically:

capturly --mode hybrid --backend https://api.example.com
# First request: hits backend, caches response
# Subsequent requests: instant replay from cache

Dashboard

The built-in web dashboard (default: http://localhost:9090) shows a newest-first traffic list with filters and tag chips (AI, AGUI, SSE, Tools, Tool Results), plus per-request detail views that surface system prompts, new inputs vs. conversation history, tool calls, token usage, and AGUI agent runs. See the Dashboard Guide.

Modes

Configuration

CLI arguments:

capturly --mode log --backend https://api.openai.com --port 8080

Environment variables:

export CAPTURLY_RECORDINGS_DIR=./recordings
capturly --mode record --backend https://api.example.com

Installation

pip install capturly

Requirements: Python 3.9+

Documentation

• Getting Started — 5-minute tutorial
• Mode Reference — Detailed behavior of each mode
• Dashboard Guide — Traffic list, filters, detail views, API
• Configuration — All options, all sources

Contributing

Contributions welcome! See CONTRIBUTING.md for guidelines.

License

MIT License - see LICENSE file.