Glossary

A handful of terms in these docs are worth pinning down up front. Some come from card-payments vocabulary. The rest are specific to billing on a stablecoin chain.

API key kinds

Secret key. Full permissions, server-side only. Prefixed sk_test_ or sk_live_.

Publishable key. Read access plus the ability to create a payment session. Safe to ship in a browser. Prefixed pk_test_ or pk_live_.

Charge attempt ID

A 32-byte deterministic identifier passed to the contract's batchCharge so retries are safe. Computed as keccak256(subscriptionId, periodEndAt). The contract's usedAttempts mapping rejects duplicates.

Confirmations

The number of blocks the indexer waits behind the chain head before projecting an event. Default 5. Higher = more reorg-safe, lower = faster updates.

EIP-2612

The "permit" standard. The payer signs a structured message that grants a contract an ERC-20 allowance. USDC and EURC both implement it natively. Strimz uses it for the single-signature subscription enrolment call (permitAndCreateSubscription). The meta-tx flow page walks through the full sequence.

EIP-3009

The "transfer with authorization" standard. The payer signs a structured message authorising a specific recipient to pull a specific amount of a specific token. USDC and EURC implement it natively. Strimz uses it for the single-signature one-shot payment call (payWithAuthorization). See the meta-tx flow page for the wire-level detail.

EIP-712 typed-data

The format a wallet uses to display a structured message instead of a raw transaction or an opaque personal_sign blob. EIP-3009 and EIP-2612 are both built on top of it, which is how the wallet renders human-readable fields like from, to, value, and deadline rather than a hex string.

ERC-7201

The "namespaced storage" pattern. It lets a contract park its state at a deterministic slot so adding fields later can't collide with the previous layout. Strimz's upgradeable contracts use it, which makes forge upgrade provably safe.

Idempotency key

A string the client picks per write that the API uses to dedupe retries. Sent in the Idempotency-Key header on every POST. The second call with the same key returns the first call's response verbatim and does not create a duplicate resource. The SDK adds one for you on every request.

Indexer cursor

The bookmark that tracks "what block has the indexer projected up to". One row per (network, contractAddress) in the IndexerCursor table. Truncating it = re-process from genesis.

KMS-backed signer

The pattern Strimz uses to sign relayer transactions on Arc. The signing key is held by a Key Management System (software-backed in development, hardware-backed in production) and never appears in an environment variable or on disk. The relayer asks the KMS for a signature; the KMS returns one. The relay section of the API reference covers the operator-side configuration.

Live mode and test mode

Two fully separate environments. Different on-chain deployments, different databases, different API keys. A resource created in one mode cannot be read or modified from the other.

Meta-tx

Short for "meta-transaction." The customer signs a structured message off-chain. A third party (Strimz's relayer) wraps that signature into a transaction and broadcasts it. The customer pays no gas. The relayer pays gas but cannot move funds on its own; the contract verifies the customer's signature on every call. payWithAuthorization and permitAndCreateSubscription are both meta-tx entrypoints.

Mode

A column on most resources (Subscription.mode, Transaction.mode, etc.) recording whether it was created in test or live mode.

On-chain merchant ID

A uint96 assigned by StrimzRegistry when a merchant first registers their payout wallet on-chain. Stored in Merchant.onchainMerchantId and exposed on session/plan payloads as chainMerchantId. The contracts use it (not the off-chain cuid) as the canonical merchant identifier.

Permit nonce

A per-owner monotonic counter that EIP-2612 tokens maintain. The current value goes into the signed permit; every successful permit increments it on-chain. A stale nonce reverts. Read it just before signing via tokens.permitNonce(token, owner).

Pull-based subscription

The customer signs once, granting the contract a multi-period allowance. The merchant's scheduler then "pulls" payment each period. The opposite is push-based, where the customer initiates each charge themselves.

Ref

A bytes32 identifier passed to StrimzPayments.pay() and payWithAuthorization(). The indexer uses it to join an on-chain payment back to its PaymentSession.id.

Relayer

The Strimz process that broadcasts payer-signed authorisations to the chain. It holds a KMS-backed signing key it uses only to pay gas. The contracts authorise the payer's signature, not the relayer's, so a relayer-key compromise costs Strimz some gas and nothing else. It cannot be used to move customer funds.

Sub-tenancy

The parentMerchantId field on StrimzRegistry. Lets a merchant register under another merchant for hierarchical billing arrangements: resellers, agency-of-record relationships, multi-brand orgs. Charges still settle to the child merchant's own payoutAddress. The parent field is metadata the reseller can reconcile against.

UUPS

Universal Upgradeable Proxy Standard (EIP-1822). Used by Strimz's policy contracts: Registry, FeeCollector, TokenWhitelist, AgentRegistry, AgentEscrow. StrimzPayments and StrimzSubscriptions are not UUPS. They are deliberately immutable. On-chain architecture covers why the line falls where it does.

Webhook delivery

One attempt to POST a specific event to a specific endpoint. Persisted in the WebhookDelivery table, so you can see every attempt's response code and body in your dashboard.

Webhook signing secret

The HMAC key Strimz uses to sign outbound webhook deliveries. Generated when you create the endpoint and returned to you exactly once. Stored on the Strimz side as an AES-256-GCM ciphertext in Postgres so a database dump leaks nothing useful. The scheduler decrypts it into a Redis cache on startup; that cache is what the delivery worker reads on the hot path.