On this page
- x402 answers an unpaid HTTP request with 402 Payment Required and lets the caller, often an agent, pay in stablecoins and retry; x402.org showed 75.41 million transactions in the 30 days before 15 October 2026.
- Solana's Subscriptions program, live on mainnet since its 2 June 2026 announcement, includes Allowances: a capped, optionally expiring spend a user grants to another party, such as an agent.
- Fianto supports neither. Its agent skill teaches coding agents to build Fianto checkout; it is not a payment rail for agents.
Which stablecoin payment rails can an AI agent use today?
Two rails let software pay in stablecoins without a person approving each payment: x402 for per-request payments over HTTP, and on-chain allowances that cap what an agent may spend. A third effort, the Agentic Commerce Protocol, defines how agents and merchants talk at checkout rather than how money moves. Fianto publishes this post; it sells USDC checkout and subscriptions on Solana, and has built none of the three.
| Mechanism | What it does | Who documents it | Status on 15 Oct 2026 |
|---|---|---|---|
| x402 | The server replies 402 Payment Required with a price; the client pays in stablecoins and repeats the request | x402.org and Coinbase CDP docs | Live; "more than 100 million x402 payments across Base and Solana" through Coinbase's service |
| Allowances (Solana) | A user pre-authorises a spend up to a cap, with an optional expiry; the authorised party draws on it until the cap or the date is reached | Solana's announcement | Live on mainnet, announced 2 June 2026 |
| Agentic Commerce Protocol | A shared format for agents and merchants to run a checkout | Stripe's announcement | Released by Stripe and OpenAI on 29 September 2025, per Stripe's newsroom post of 30 September |
Each row cites the page that describes it, read on 15 October 2026. Projects in this area change month to month, so check the date before you rely on any figure here.
How does x402 let an agent pay per request?
x402 lets an agent pay for an API call inside the call itself: the server answers the first request with a price, the agent signs a stablecoin payment, and the second request carries it. x402.org calls it "an open, neutral standard for internet-native payments" and says it "supports all EVM-compatible chains, Solana, and more". Coinbase's x402 overview puts the appeal for software in one sentence: "There is no checkout page, card form, or signup flow."
The usage is measurable. On 15 October 2026 x402.org showed 75.41 million transactions and $24.24 million in volume over the previous 30 days, or about 32 cents a transaction on average.
The costs, the facilitator that verifies and settles payments, and a worked comparison against a monthly plan at 30,000 requests are in x402 vs API subscriptions. The short version: per-request payment fits callers with no account who may never return, which is exactly what an agent often is.
What are Solana Allowances, and why do they matter for agents?
Solana Allowances let a person give another party, such as an AI agent, a spending budget in tokens that the program refuses to exceed. They are one of three models in the Subscriptions program announced on solana.com on 2 June 2026, beside recurring delegations and subscription plans. The announcement's own description:
This is the building block for AI agents that need to act autonomously within a budget — the user sets the limit, the agent operates within it, and the authorization expires naturally.
The safety comes from the cap. The announcement puts it this way: "The authorized party draws on that allowance freely until the limit is hit or the window closes." It also says that pay.sh, which it describes as Solana's pay-as-you-go layer for APIs, where a user or an AI agent can find an endpoint and pay for it in stablecoins, now supports subscriptions through the same program.
Fianto uses the same program for something else: subscription plans, where the customer approves a cap per billing period and Fianto collects each renewal. It does not create Allowances. How a delegation differs from a plan, and what each lets the other party take, is in Solana Subscriptions and Allowances, for merchants and Solana token delegation explained.
Can an AI agent pay through Fianto?
No Fianto feature is built for an agent buyer. Fianto has no x402 endpoint, no allowance support, no metered or per-request billing and no API that pays. Its checkout is a hosted web page that a person opens and approves in a wallet that supports Wallet Standard transaction signing, and every price is at least 0.01 USDC.
What Fianto does have that matters near agents is on the selling side, the onchain commerce of people paying from their own wallets. If you sell access to an AI product to people, they can pay by subscription, monthly or yearly, and your server grants or revokes access from signed webhooks; accepting USDC for an AI app covers that setup, and the Solana subscriptions page explains the cap the customer approves.
Sell your AI product on a monthly USDC plan the customer approves once.
USDC billing for SaaS and APIsWhat is the Fianto agent skill, if not a payment rail?
The Fianto agent skill is a set of instructions for AI coding agents, such as Claude Code, Cursor or Codex, that teaches them to write a correct Fianto integration in your codebase. You install it with one command:
npx skills add fianto-xyz/skills
Version 0.3.0 covers checkout sessions, subscriptions, webhooks, shop and payment-link sales and the official @fianto/* SDK packages. It writes code; it does not spend money. Its own instructions say "An agent cannot create accounts or applications" and tell the agent to ask you for an explicit yes before cancelling a real subscription or moving any USDC. Install steps and what it asks first are in adding USDC checkout with an AI coding agent, and the developer docs are the reference it is built from.
What should a merchant do about agent payments today?
A merchant should decide from who buys today, not from who might buy later. Three cases, by buyer:
- Your buyers are people on a plan. A monthly or yearly subscription in USDC or by card serves them; nothing about agents changes that.
- You sell single API calls to callers with no account. Read the x402 specification and a facilitator's pricing; that is the rail built for this case, and Fianto is not.
- You want customers to give software a budget. Allowances on Solana are the documented mechanism; you would integrate the Subscriptions program yourself or through a provider that supports it.
If you want your own coding agent to set up a USDC checkout or subscription for people, the Fianto skill and SDKs do that today.