L402 Kit

l402-kit

Add Bitcoin Lightning pay-per-call to any API. 3 lines of code.

[▶ Watch end-to-end demo — install → 402 → pay → 200 OK](https://docs.l402kit.com/introduction)

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Live traction

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🌍 Available in 11 languages — click to expand

🇺🇸 Charge for your API in Bitcoin Lightning. 3 lines of code. 🇧🇷 Monetize sua API com Bitcoin Lightning. 3 linhas de código. 🇪🇸 Monetiza tu API con Bitcoin Lightning. 3 líneas de código. 🇨🇳 用 3 行代码，通过比特币闪电网络收费。 🇮🇳 अपने API को Bitcoin Lightning से 3 लाइनों में मोनेटाइज़ करें। 🇸🇦 اكسب من API الخاص بك عبر Bitcoin Lightning. 3 أسطر فقط. 🇫🇷 Monétisez votre API en Bitcoin Lightning. 3 lignes de code. 🇩🇪 Monetarisiere deine API mit Bitcoin Lightning. 3 Zeilen Code. 🇷🇺 Монетизируй свой API через Bitcoin Lightning. 3 строки кода. 🇯🇵 Bitcoin LightningでAPIを3行で収益化。 🇮🇹 Monetizza la tua API con Bitcoin Lightning. 3 righe di codice.

📖 Official docs: 🇺🇸 · 🇧🇷 · 🇪🇸 · 🇨🇳 · 🇮🇳 · 🇸🇦 · 🇫🇷 · 🇩🇪 · 🇷🇺 · 🇯🇵 · 🇮🇹

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Install

npm install l402-kit        # TypeScript / Node.js / Express

pip install l402kit # Python / FastAPI / Flask go get github.com/shinydapps/l402-kit/go@v1.10.0 # Go / net/http / Chi / Gin cargo add l402kit # Rust / axum

AI Agents / LLMs: See llms.txt for machine-readable instructions.

Agent discovery: /.well-known/agent.json · /.well-known/l402.json

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For AI Agents

l402-kit is the payment layer for autonomous agents. Agents can pay for APIs without human intervention.

System prompt snippet — add this to any agent to enable L402 payments:

You have access to paid APIs via the L402 protocol.

When you call an API that returns HTTP 402, use the L402Client from l402-kit to pay automatically with Bitcoin Lightning. Budget limit: {BUDGET_SATS} sats per session. Never exceed this limit.

Agent SDK quickstart:

import { l402Client, buildWallet } from "l402-kit/agent";

const client = l402Client({ wallet: buildWallet(process.env), // auto-detects BLINK_API_KEY or ALBY_TOKEN budgetSats: 1000, });

const data = await client.fetch("https://api.example.com/paid-endpoint");

MCP Server (for Claude Desktop, Cursor, and any MCP-compatible agent):

{

"mcpServers": { "l402-kit": { "command": "npx", "args": ["l402-kit-mcp"], "env": { "BLINK_API_KEY": "your-key" } } } }

Compatible with: LangChain · OpenAI Agents · CrewAI · Vercel AI SDK · AutoGPT · Any MCP client

Protocol support: L402 (Bitcoin Lightning) · x402 (USDC/Coinbase) compatible

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How it works

1. Client calls your API

↓

1. API returns HTTP 402 + BOLT11 invoice + macaroon ↓
2. Client pays (any Lightning wallet, < 1 second, any country) ↓
3. Client sends Authorization: L402 : ↓
4. API verifies SHA256(preimage) == paymentHash ✓ ↓
5. HTTP 200 OK + your data

── Fee flow (managed mode) ───────────────────────────────── Payment → 99.7% → your Lightning Address (instant) → 0.3% → ShinyDapps

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Quickstart

TypeScript

import express from "express";

import { l402, AlbyProvider } from "l402-kit";

const app = express();

const lightning = new AlbyProvider(process.env.ALBY_TOKEN!);

app.get("/premium", l402({ priceSats: 100, lightning }), (_req, res) => { res.json({ data: "Payment confirmed." }); });

app.listen(3000);

Python

from fastapi import FastAPI, Request

from l402kit import l402_required

app = FastAPI()

@app.get("/premium") @l402_required(price_sats=100, owner_lightning_address="you@yourdomain.com") async def premium(request: Request): return {"data": "Payment confirmed."}

Go

package main

import ( "fmt" "net/http" l402kit "github.com/shinydapps/l402-kit/go" )

func main() { http.Handle("/premium", l402kit.Middleware(l402kit.Options{ PriceSats: 100, OwnerLightningAddress: "you@yourdomain.com", }, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { fmt.Fprintln(w, {"data": "Payment confirmed."}) }))) http.ListenAndServe(":8080", nil) }

Rust

use axum::{middleware, routing::get, Router};

use l402kit::{l402_middleware, Options}; use std::sync::Arc;

#[tokio::main] async fn main() { let opts = Arc::new(Options::new(100).with_address("you@yourdomain.com"));

let app = Router::new() .route("/premium", get(|| async { "Payment confirmed." })) .route_layer(middleware::from_fn_with_state(opts, l402_middleware));

let listener = tokio::net::TcpListener::bind("0.0.0.0:8080").await.unwrap(); axum::serve(listener, app).await.unwrap(); }

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Test it live

# Step 1 — triggers 402 + returns invoice

curl http://localhost:3000/premium

← { "error": "Payment Required", "invoice": "lnbc1u...", "macaroon": "eyJ..." }

Step 2 — pay the invoice with any Lightning wallet, then:

curl http://localhost:3000/premium \ -H "Authorization: L402 : "

← { "data": "Payment confirmed." }

▶ Try the interactive demo

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Why not Stripe?

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Providers

import { BlinkProvider, OpenNodeProvider, LNbitsProvider } from "l402-kit";

// Blink (recommended — free, instant setup) const provider = new BlinkProvider(process.env.BLINK_API_KEY!, process.env.BLINK_WALLET_ID!);

// OpenNode (production, custodial) const provider = new OpenNodeProvider(process.env.OPENNODE_KEY!);

// LNbits (self-hosted) const provider = new LNbitsProvider(process.env.LNBITS_KEY!, "https://your.lnbits.host");

Bring your own node — implement the LightningProvider interface in 5 lines:

import type { LightningProvider } from "l402-kit";

class MyNode implements LightningProvider { async createInvoice(amountSats: number) { /* return Invoice */ } async checkPayment(paymentHash: string) { /* return boolean */ } }

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Security model

Invoice creation:  paymentHash = SHA256(preimage)

Client payment: Lightning Network releases preimage to payer API verification: SHA256(preimage) == paymentHash ✓ Replay protection: each preimage is marked used — works exactly once Token expiry: macaroons expire after 1 hour

• Unforgeable — SHA256 is a one-way function; you cannot fake a preimage
• No chargebacks — cryptographic settlement, not reversible card auth
• Replay-safe — MemoryReplayAdapter (dev) or RedisReplayAdapter (production, multi-instance)
• 600+ automated tests across 5 runtimes (TS, Python, Go, Rust, Cloudflare Workers) — production-grade reliability for autonomous agent workflows
• Fully auditable — MIT, every line open source

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VS Code Extension

Monitor every sat in real-time without leaving your editor.

• ⚡ Live payment feed per endpoint
• 📊 Bar chart — 1D / 7D (free) · 30D / 1Y / ALL (Pro)
• 🌍 11 languages built-in
• 🎨 Light / dark / auto theme
• 🔧 Zero config — just set your Lightning Address

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Get a Lightning Address (free)

Sign up at [dashboard.blink.sv](https://dashboard.blink.sv) — free, no credit card, instant. Your address: yourname@yourdomain.com

Other wallets: Wallet of Satoshi · Phoenix · Zeus · Alby

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Links

| 📦 npm | [npmjs.com/package/l402-kit](https://npmjs