# agent-cassette

[![ci](https://github.com/kanchingyg/agent-cassette/actions/workflows/ci.yml/badge.svg)](https://github.com/kanchingyg/agent-cassette/actions/workflows/ci.yml)
[![npm](https://img.shields.io/npm/v/agent-cassette)](https://www.npmjs.com/package/agent-cassette)
[![JSR](https://jsr.io/badges/@kanchingyg/agent-cassette)](https://jsr.io/@kanchingyg/agent-cassette)
[![Bun](https://img.shields.io/badge/runtime-Node_%7C_Bun-f9f1e1)](https://github.com/kanchingyg/agent-cassette)
[![license](https://img.shields.io/github/license/kanchingyg/agent-cassette)](https://github.com/kanchingyg/agent-cassette/blob/HEAD/LICENSE)

Deterministic VCR cassette recorder and offline replay proxy for LLM HTTP/SSE streams and MCP stdio runs. Replay multi-turn agent tests in ~0ms in CI without GPUs or live API keys.

## Install

[Bun](https://bun.sh) / [npm](https://www.npmjs.com/package/agent-cassette):

```bash
bunx agent-cassette record -- npm test
npx agent-cassette record -- npm test

# or install in your project / globally
bun add -d agent-cassette
npm i -D agent-cassette
```

[JSR](https://jsr.io/@kanchingyg/agent-cassette):

```bash
bunx jsr add @kanchingyg/agent-cassette
npx jsr add @kanchingyg/agent-cassette
```

## Quick start

```bash
# Record live LLM HTTP/SSE and MCP interactions into a deterministic cassette
npx agent-cassette record -- npm test
bunx agent-cassette record -- bun test

# Replay offline in CI in ~0ms with zero network calls or API keys
npx agent-cassette replay -- npm test

# Run as an MCP server over stdio
npx agent-cassette --mcp
```

## Features

- **HTTP & SSE stream recording**: Captures chunked token streams from OpenAI, Anthropic, Ollama, and OpenAI-compatible endpoints and replays them deterministically.
- **Prompt & tool-call hashing**: Normalizes volatile headers and timestamps while matching prompt and tool-call signatures.
- **Automatic secret scrubbing**: Strips `Authorization`, `x-api-key`, and bearer tokens before writing cassette files to disk.
- **SSRF & path containment**: Blocks private-network target redirection and enforces workspace path containment on cassette reads/writes.

## MCP setup

```json
{
  "mcpServers": {
    "agent-cassette": {
      "command": "npx",
      "args": ["-y", "agent-cassette", "--mcp"]
    }
  }
}
```

## License

[MIT](./LICENSE)