r402-http

HTTP transport for the x402 payment protocol, part of the r402 workspace.

Highlights

Server Paygate middleware — axum-style layer enforcing payments with three settlement modes (sequential, concurrent, background) and pluggable hooks for KYT / API keys / observability.
Client X402Middleware — reqwest_middleware adapter that handles 402 challenges, signs payments, and retries the protected request.
Remote FacilitatorClient — talks to a remote facilitator's /verify, /settle, and /supported endpoints with a 30-second default timeout, exponential-backoff retry on 429/5xx, and a 10-minute cache for /supported shared across clones.
CORS-aware — automatically appends Access-Control-Expose-Headers for the Payment-Required and Payment-Response headers.
Structured 4xx parsing — facilitator clients deserialise structured VerifyResponse::Invalid / SettleResponse::Failure bodies regardless of HTTP status code, preserving spec §9 error reasons end-to-end.

Feature	Surface
`client`	`reqwest_middleware`-based buyer middleware.
`server`	axum paygate / facilitator HTTP servers.
`facilitator`	`FacilitatorClient` for talking to a remote
	facilitator.
`telemetry`	OpenTelemetry tracing instrumentation.
`full`	All of the above.

Dual-licensed under MIT and Apache-2.0.