# Loop XXI

Loop XXI is a privately held company. Public education work is the journal: macroeconomics, monetary systems and Bitcoin. Articles cite sources and record the Bitcoin block height at publication; a block height is a publication reference, not a claim that the article is stored on-chain.

Loop Gateway is an active machine-purchasable AI API. Agents buy prepaid inference with Bitcoin Lightning.

- Home: https://loopxxi.com/
- Journal: https://loopxxi.com/journal
- About the company: https://loopxxi.com/company
- Journal index: https://loopxxi.com/journal/index.json
- Journal RSS: https://loopxxi.com/journal/feed.xml
- Machine catalog: https://loopxxi.com/products.json
- Company product index: https://loopxxi.com/businesses
- Gateway API: https://api.loopxxi.com/v1
- Gateway docs: https://api.loopxxi.com/llms.txt
- Human purchase page (Lightning top-up, no account): https://gateway.loopxxi.com/buy
- Quickstart (top up, pay, check balance, chat): https://loopxxi.com/businesses#quickstart
- OpenAPI 3.1 (topup, balance, chat completions, models): https://loopxxi.com/openapi/gateway.json
- Free discovery example (three public GETs, no payment): https://loopxxi.com/tools/gateway-discovery
- Payment discovery: https://api.loopxxi.com/.well-known/agent-payments.json
- Pricing: https://api.loopxxi.com/v1/pricing
- Human Lightning tip (optional, not API credit): https://loopxxi.com/tip
- Lightning address: pay@loopxxi.com
- Support: business@loopxxi.com
- X: https://x.com/Loop_XXI
- Nostr: https://primal.net/p/51096f5ab3f86aa11fd661e241f7bd8e0f25e3a0e446b8f2a71a6b818d5461d0

## Agent purchase (Gateway)

Preferred path, same prepaid pattern as NWC / Alby Hub: POST /v1/topup with amount_sats → pay BOLT11 → use loop_ bearer.

Example: POST https://api.loopxxi.com/v1/topup with {"amount_sats":5000}. Pay the Lightning invoice from a wallet you control. Confirm credit with GET https://api.loopxxi.com/v1/balance and Authorization: Bearer <token> (HTTP 401 unknown_prepaid_token until the invoice settles). Then POST /v1/chat/completions with the same header. Keep the token private.

Gateway topup is prepaid sats credit for OpenAI-compatible inference (BoltHub buyCredit analogy). Credit pays for API usage; it is not custody of customer funds.

Per-call L402 is advertised as available: unauthenticated POST /v1/chat/completions returns HTTP 402 L402. Paying that challenge with stock clients (lnget, BoltHub L402Client) is not yet tested. Preferred first purchase is still prepaid Lightning top-up (POST /v1/topup, min 5000 sats) or the human purchase page https://gateway.loopxxi.com/buy. Read payment.min_sats and payment_discovery.l402.min_amount_sats before paying a one-off invoice.

Other human offers on this site remain paused. Preserved legacy downloads are historical assets, not evidence of an active offer.

Writing is educational commentary, not personalized investment advice or an investment offer. Do not infer company holdings, customers, revenue or investor returns from the content.

## Human Lightning tip (not Gateway credit)

Humans can send optional sats to pay@loopxxi.com or https://loopxxi.com/tip. That path is a tip. It does not add Gateway credit and it is not a paid AI purchase.

Agents buy prepaid inference with POST /v1/topup. Do not treat a tip invoice as API credit.

Experimental Loop Scope (not a paid offer; not in the sitemap; noindex): an Agent Specification Auditor spike for coding agents. POST JSON to https://loopxxi.com/api/loop-scope (brief, optional plan / acceptance_criteria / constraints / agent_id). Heuristic audit only; payment is not open. OpenAPI: https://loopxxi.com/downloads/loop-scope-auditor.openapi.json. Human landing: https://loopxxi.com/tools/loop-scope.

## Public directory
- All current public destinations: https://loopxxi.com/links
- Includes product pages, tools, published writing, API references, social channels and company information. Preview labels do not imply paid availability.