Agent An autonomous AI program that acts on behalf of a user or system. In the context of Recur, an agent is the party that holds a wallet and makes payments for services.

Allowance An on-chain authorization permitting a service (the grantee) to spend up to a capped total from an agent’s wallet (the granter). Unlike subscriptions, allowances have no fixed billing interval — the grantee draws down as needed. See Allowances.

Billing cycle The recurring interval at which a subscription is charged. Defined by the Plan’s interval field: monthly, weekly, daily, or per-request.

Collection The act of the service provider pulling funds from a subscriber’s wallet at the end of a billing cycle. Collection is authorized by the Subscription Authority and executed by the Solana Subscriptions and Allowances Program.

Facilitator The off-chain component that verifies payment headers and submits transactions to Solana. During beta, operated by Recur as a centralized service. Post-beta, a permissionless network of staked operator nodes. See Facilitator Network.

Grantee In an Allowance, the service or wallet authorized to spend funds from the granter.

Granter In an Allowance, the agent wallet that authorizes the spend cap.

MPP (Machine Payments Protocol) An open, IETF-tracked standard for machine-to-machine payments over HTTP, published by Stripe and Tempo in March 2026. Recur is designed to be compatible with MPP-speaking agents. See MPP Compatibility.

Payment gate The middleware component (recur.paymentGate()) that intercepts unauthenticated requests to a service API and returns a 402 Payment Required response with payment terms.

Payment proof A signed object returned by the Facilitator after a successful on-chain payment. Included in the X-PAYMENT request header on retried requests. The service verifies the proof before serving the resource.

Payment session A short-lived token that authorizes a burst of requests against a pre-committed balance, with periodic batch settlement. Designed for high-frequency agents. Coming in general availability. See Payment Sessions.

Plan An on-chain pricing record published by a service provider to the Recur Plan Registry. Defines the price, billing interval, token, and optional trial period for a service. Immutable after creation. See Plans.

Plan Registry The on-chain catalog on Solana mainnet where service providers publish Plans. Publicly readable by any Solana client.

Provider A service or API that accepts payments from agents via Recur. Providers create plans, add the payment gate to their API, and collect from subscribers.

Recur SDK (@recur/sdk) The TypeScript library that abstracts all protocol and on-chain interactions for both agents (RecurAgent) and providers (RecurProvider).

SPL token A fungible token on Solana following the SPL (Solana Program Library) token standard. USDC and USDT on Solana are SPL tokens. Recur uses SPL tokens for all payments.

Subscription An on-chain account linking an agent wallet to a Plan, with an authorized billing delegation. Enables automatic recurring billing without per-transaction signatures from the agent. See Subscriptions.

Subscription Authority The delegation granted by an agent at subscription time, allowing the service provider to pull up to the authorized amount per billing cycle. Enforced by the Solana Subscriptions and Allowances Program.

Trial period An optional free period at the start of a subscription, defined in the Plan. No funds are collected during a trial. The first billing cycle begins when the trial ends.

USDC USD Coin — a regulated US dollar stablecoin issued by Circle. The primary payment token in Recur during beta. Address on Solana mainnet: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v. 6 decimal places.

Webhook An HTTP POST sent by Recur to a configured endpoint when a payment lifecycle event occurs (subscription renewed, payment failed, allowance depleted, etc.). See Webhooks.

x402 An HTTP-native payment protocol that defines how servers signal a payment requirement and how clients attach payment proofs. Originated by Coinbase in May 2025, now governed by the x402 Foundation. Recur is a first-class x402 implementation on Solana. See x402 Compatibility.