# The lodestone

Every design decision in Relaystation is judged against one use case:

> An AI agent makes one HTTPS call with a payload and a payment, gets back a result, and never created an account.

We call that the lodestone. It is the case that points the way; if a feature would make it harder, the answer is no.

## Why it matters

The agent economy does not look like the SaaS economy. An agent has no inbox to confirm, no phone to verify, no browser to click through a checkout. It has a process, a config, and a private key. Anything that demands interactive identity verification is a wall the agent cannot climb.

Most infrastructure was not built for that. A monthly plan does not fit a script that runs once. An OAuth signup does not fit a program with no human attached. Pay-per-call with a wallet does.

## What the lodestone buys you

The wallet is the identity. You do not register; you sign. The signature on the payment authorization proves who you are, and the same wallet address ties together everything you do later — every file you convert, every document you send for signature, every baton you create, every charge on your ledger. Come back a month later with the same key and your history is intact.

It also means you pay only for what you use. One call, one charge, no relationship.

## The shape of a lodestone call

One `POST` to any product endpoint — a PDF op, a media convert, an LLM task, a baton create — carries three things: the payload (whatever that op accepts), a signed payment header (a USDC or EURC authorization), and an `Idempotency-Key` (so a [retry is safe](/docs/idempotency)). The response carries the result and a `PAYMENT-RESPONSE` [receipt](/docs/receipts). No prior call, no session, no account.

That is the whole contract — and it holds across the platform: files over 4 MB ride the free [scratch tier](/docs/receiving-outputs) with the same wallet identity, and nothing on this path ever requires an account or a storage product. Developers who prefer a balance and an API key can have that too — see [Authentication modes](/docs/authentication) — but the lodestone is the path everything else is measured against.

## How sub-cent calls settle (the sawtooth)

On-chain settlement costs gas — more than a sub-cent call is worth — so Relaystation doesn't settle every penny-scale call on its own transaction. Instead:

- Every x402 call carries a signed authorization for a **settlement chunk of $0.01** (the 402 challenge advertises this as `maxAmountRequired`).
- A call priced **at or above $0.01** settles on-chain individually, on its own authorization.
- A call priced **below $0.01** draws down from an already-settled chunk **off-chain** — no new on-chain transaction, no gas, no nonce consumed. When that chunk's residual is exhausted, the **next call settles a fresh $0.01 chunk on-chain**, and subsequent sub-cent calls draw from it.

You authorize $0.01 with each call, but you are **charged exactly the sum of your actual call prices** — never $0.01 per call. On-chain settlement is batched at the chunk; your charges are exact. We call the pattern the **sawtooth**: settle a chunk, draw it down, settle the next. On common sub-cent ops, a single penny covers around 50 calls before the next chunk settles. Each chunk and draw-down is a [ledger](/docs/receipts) row you can audit.