GitHub - mtford90/httap: Inspect, intercept & mock HTTP traffic from your terminal or AI agent

httap is a powerful HTTP proxy for your terminal. Intercept, inspect & rewrite HTTP traffic — from your shell or your AI agent.

Feature Highlights

• Project-scoped — each project gets its own .httap/ directory with isolated daemon, database, CA cert and interceptors. No cross-project bleed.
• Multiple surfaces — powerful CLI for scripting, a lazygit-style TUI for browsing traffic, an MCP server for AI agents, and a Node.js API for programmatic access.
• Interceptors — mock, modify or observe traffic by writing TypeScript. Your AI agent can write these for you, so you can express complex scenarios in natural language.

Quick Start

npm install -g @mtford/httap

# Configure environment e.g. HTTP_PROXY
eval "$(httap on)"

# Send a request
curl https://api.example.com/users

# Open UI
httap tui

# Add MCP server to your AI tool
claude mcp add httap -- httap mcp

Demo

Want to try httap without pointing it at a real project? examples/demo/ has a self-contained mock API, a traffic generator, and two example interceptors — see examples/demo/README.md for the three-command flow (pnpm demo does it in one). The walkthrough above was recorded from it.

Browser Interception

Launch any browser pre-configured to route through httap — no manual proxy setup, no certificate warnings:

# Auto-detect and launch your default browser
httap browser

# Open a specific URL
httap browser https://example.com

# Choose a specific browser
httap browser --browser firefox
httap browser --browser brave

Each browser session gets its own isolated profile and is automatically attributed in the TUI (e.g. source: chrome). Close the browser or press Ctrl+C to stop — the temp profile is cleaned up automatically.

Supported browsers:

Project Scoping

httap doesn't use a global system proxy. Each project gets its own .httap/ directory in the project root (detected by .git or an existing .httap/):

your-project/
├── .httap/
│   ├── interceptors/   # TypeScript interceptor files
│   ├── config.json     # Optional project config
│   ├── proxy.port      # Proxy TCP port
│   ├── control.sock    # IPC socket
│   ├── requests.db     # Captured traffic
│   ├── ca.pem          # CA certificate
│   └── daemon.pid      # Process ID
└── src/...

Separate daemon, database, certificates etc. You can run httap in multiple projects at the same time without them interfering with each other.

For non-project contexts or custom setups, use --config to point directly at a data directory (no .httap appended):

httap --config /tmp/my-httap-data on

See CLI Reference for the full resolution order (--config > --dir > auto-detect).

MCP Integration

httap has a built-in MCP server that gives AI agents full access to your captured traffic and interceptor system.

Setup

Claude Code:

claude mcp add httap -- httap mcp

Codex:

codex mcp add httap -- httap mcp

Cursor — add to .cursor/mcp.json:

{
  "mcpServers": {
    "httap": {
      "command": "httap",
      "args": ["mcp"]
    }
  }
}

Other MCP clients (Windsurf, etc.) — add to your client's MCP config:

{
  "mcpServers": {
    "httap": {
      "command": "httap",
      "args": ["mcp"]
    }
  }
}

The proxy must be running (eval "$(httap on)") — the MCP server connects to the same daemon as the TUI.

Available Tools

See full MCP documentation for filtering, output formats, and examples.

Interceptors

TypeScript files in .httap/interceptors/ that intercept HTTP traffic as it passes through the proxy. They can return mock responses, modify upstream responses, or just observe.

import type { Interceptor } from "@mtford/httap/interceptors";

export default {
  name: "mock-users",
  match: (req) => req.path === "/api/users",
  handler: async () => ({
    status: 200,
    headers: { "content-type": "application/json" },
    body: JSON.stringify([{ id: 1, name: "Alice" }]),
  }),
} satisfies Interceptor;

See full interceptors documentation for modify, observe, querying past traffic, handler context, and how they work.

How It Works

┌─────────────────────────────────────────────────────────────┐
│  Your Shell                                                 │
│  ┌─────────────────────────────────────────────────────┐   │
│  │  curl, wget, node, python...                        │   │
│  │          │                                          │   │
│  │          ▼                                          │   │
│  │  HTTP_PROXY=localhost:54321                         │   │
│  └─────────────────────────────────────────────────────┘   │
│                          │                                  │
└──────────────────────────┼──────────────────────────────────┘
                           ▼
┌─────────────────────────────────────────────────────────────┐
│  httap daemon                                                │
│  ┌─────────────┐    ┌─────────────┐    ┌─────────────┐     │
│  │ MITM Proxy  │───▶│   SQLite    │◀───│ Control API │     │
│  │  (mockttp)  │    │  requests   │    │ (unix sock) │     │
│  └─────────────┘    └─────────────┘    └─────────────┘     │
└─────────────────────────────────────────────────────────────┘
                           ▲
                           │
┌──────────────────────────┼──────────────────────────────────┐
│  httap tui                │                                  │
│  ┌───────────────────────┴─────────────────────────────┐   │
│  │ ● POST /api/users   │ POST https://api.example.com  │   │
│  │   GET  /health      │ Status: 200 │ Duration: 45ms  │   │
│  │   POST /login       │                               │   │
│  │                     │ Request Headers:              │   │
│  │                     │   Content-Type: application/  │   │
│  └─────────────────────┴───────────────────────────────┘   │
└─────────────────────────────────────────────────────────────┘

eval "$(httap on)" starts a daemon, sets HTTP_PROXY/HTTPS_PROXY in your shell, and captures everything that flows through. eval "$(httap off)" unsets them. The TUI connects to the daemon via Unix socket.

Environment Variables

eval "$(httap on)" sets these in your shell (eval "$(httap off)" unsets them):

Additionally, httap on sets PYTHONPATH, RUBYOPT, and PHP_INI_SCAN_DIR to load runtime-specific override scripts that ensure edge-case HTTP clients trust the proxy CA.

Configuration

Create .httap/config.json to override defaults:

{
  "maxStoredRequests": 5000,
  "maxBodySize": 10485760,
  "maxLogSize": 10485760,
  "pollInterval": 2000
}

See full configuration documentation for details on each setting.

Supported HTTP Clients

Anything that respects HTTP_PROXY works. httap sets the right CA cert env vars for each runtime automatically.

Works automatically (env vars only):

Works with httap overrides (injection scripts):

Not currently supported (needs system-level config):

TUI

j/k to navigate, Tab to switch panels, / to filter, e to export, Enter to inspect bodies, q to quit. Mouse support included.

The TUI is drawn by OpenTUI. Set HTTAP_TUI=ink to fall back to the previous Ink interface, which will be removed in the next minor release — see TUI runtime.

See full TUI documentation for all keybindings and export features.

Documentation

• CLI Reference — all commands, flags, and examples
• Interceptors — mock, modify, observe, query traffic, handler context
• MCP Integration — tools, filtering, output formats, examples
• TUI — keybindings, export features
• Configuration — .httap/config.json options

Development

git clone https://github.com/mtford90/httap.git
cd httap
npm install

npm run build        # Compile TypeScript
npm test             # Run all tests
npm run typecheck    # Type checking only
npm run lint         # ESLint
npm run dev          # Watch mode

Troubleshooting

Certificate errors

httap sets common CA environment variables automatically, but some tools need manual configuration:

Daemon won't start

Check if something else is using the socket:

httap status
httap daemon stop
eval "$(httap on)"

Requests not appearing

Your HTTP client needs to respect proxy environment variables.

There are workarounds implemented for node - e.g. fetch override. Other libraries in different environments may need a similar treatment.

Acknowledgements

httap is built on top of MockTTP by Tim Perry, the same MITM proxy engine that powers HTTP Toolkit.

Licence

MIT