Specification · Architecture

System Architecture & Protocol Invariants

Circulator is a production-grade cross-chain payment clearinghouse. It couples an ERC-7683 origin settlement engine with emerging autonomous agent protocols (MPP and OWS) to deliver trust-minimized, multi-rail stablecoin settlement.

Core Layer Division

Layer 1: Wire & Negotiation (MPP)

Standardizes HTTP 402 challenge negotiation and payment receipt headers between clients and servers. Rail-agnostic and decoupled from cryptographic key storage.

Layer 2: Keystore & Spend Governance (OWS)

Local-first encrypted keystore (~/.ows/wallets/) enforcing client-side autonomous spend limits (per-transaction caps, daily rolling budgets) before issuing cryptographic signatures.

Layer 3: Cross-Chain Settlement Core (Circulator)

ERC-7683 standard implementation (IOriginSettler) with Permit2 witness verification and multi-rail adapters (Circle CCTP V2, Across V3, LayerZero OFT).

Layer 4: State Indexing & Notification (Settlement Watcher)

PostgreSQL-backed event follower and settlement poller, enabling merchants and payers to query settlement status via REST without direct blockchain RPC interaction.

Architectural Guarantees

•Stateless Merchant Operation: Paylinks and payment challenges are cryptographically self-describing; merchants do not need accounts, custody, or stateful sessions to issue quotes.
•Zero Private Key Exposure: Autonomous agents never expose raw private keys to runtime memory or application code; all signing is mediated via OWS policy guardrails.
•Idempotency & Replay Protection: Every order commits to a unique 32-byte order hash and strictly monotonic voucher nonces, preventing replay attacks.