White Paper — Extended Edition

The complete technical specification of l402-kit. 100 sats. Served by l402-kit itself.

White Paper — Extended Edition

Version 1.1 — May 2026 · ~25 pages

Payment is the credential.

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This is the complete technical specification of l402-kit — the founding principles in full, design decisions with tradeoffs, expanded threat model, architectural properties, L402 vs x402 comparison, and versioning commitments.

The document is served by l402-kit itself. Paying 100 sats is an end-to-end test of the protocol in production.

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What’s inside

Section	Contents
Preface	Author’s note — why this was built
§1 Founding Principles	All 7 principles in full (80–120 words each)
§2 The Problem	HTTP was built for humans — 25 years of dormancy
§3 Protocol in 5 Minutes	Four-step sequence, token format, three properties
§4 Architecture	Two modes, replay protection layers, agent discovery
§5 Design Decisions	Why 4 languages, why Blink, why MIT, what’s excluded
§6 Threat Model	Full table: 11 threats, mitigations, responsibilities
§7 Architectural Properties	Invariants: constant-time, horizontal scale, memory
§8 Use Cases	Pay-per-call, AI agents, content gating
§8.1 Autonomous Agent Economy	The complete loop: earn → accumulate → spend → reputation — zero human capital
§9 L402 vs x402	Honest comparison table — including where x402 is better
§10 Economic Model	0.3% fee, Pro, Founder — with reasoning
§11 Versioning	Patch/minor/major commitments, wire format stability
Appendix A	Glossary — 7 terms
Appendix B	References — 6 sources
Appendix C	Document changelog — v1.0 → v1.1
Appendix D	Design notes: Macaroons vs JWT, Blink, 0.3%, stateless

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Pay and read

# Step 1 — Request the document (get invoice)
curl -i https://l402kit.com/whitepaper-extended

# HTTP/1.1 402 Payment Required
# WWW-Authenticate: L402 macaroon="<macaroon>", invoice="lnbc..."
# {"priceSats":100,"invoice":"lnbc...","macaroon":"<macaroon>"}

# Step 2 — Pay the invoice with any Lightning wallet
# Get the preimage from your wallet after payment

# Step 3 — Access the document
curl -H "Authorization: L402 <macaroon>:<preimage>" \
     -H "Accept: text/html" \
     https://l402kit.com/whitepaper-extended \
     -o whitepaper-extended.html

# Open whitepaper-extended.html in your browser → File → Print → Save as PDF

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One-liner with l402-kit client

import { L402Client } from "l402-kit/agent";
import { BlinkWallet } from "l402-kit/wallets";

const client = new L402Client({
  wallet: new BlinkWallet(process.env.BLINK_API_KEY!),
  budget: { maxSats: 200 },
});

const html = await client.fetch("https://l402kit.com/whitepaper-extended", {
  headers: { Accept: "text/html" },
});
// Paid automatically. html is the complete document.

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Price

100 sats (approximately the cost of an SMS, in any country).

The public version — abstract, architecture, quickstart, and seven principles in brief — is free at docs.l402kit.com/whitepaper.

This endpoint is served by l402-kit itself using the ManagedProvider. When you pay, the split runs automatically: 99.7 sats to ShinyDapps, 0.3 sats as protocol fee. The entire flow — invoice creation, payment, verification, document delivery — runs without human intervention.