Module server 

Available on crate feature server only.

Axum middleware for enforcing x402 payments on protected routes (V2-only).

This middleware validates incoming payment headers using a configured x402 facilitator, and settles valid payments either before or after request execution (configurable).

Returns a 402 Payment Required response if the request lacks a valid payment.

See X402Middleware for full configuration options. For low-level interaction with the facilitator, see facilitator::FacilitatorClient.

Settlement Timing

By default, settlement occurs after the request is processed. You can change this behavior:

• X402Middleware::settle_before_execution - Settle payment before request execution. This prevents issues where failed settlements need retry or authorization expires.
• X402Middleware::settle_after_execution - Settle payment after request execution (default). This allows processing the request before committing the payment on-chain.

Configuration Notes

• X402Middleware::with_price_tag sets the assets and amounts accepted for payment (static pricing).
• X402Middleware::with_dynamic_price sets a callback for dynamic pricing based on request context.
• X402Middleware::with_base_url sets the base URL for computing full resource URLs. If not set, defaults to http://localhost/ (avoid in production).
• X402Middleware::with_supported_cache_ttl configures the TTL for caching facilitator capabilities.
• X402LayerBuilder::with_description is optional but helps the payer understand what is being paid for.
• X402LayerBuilder::with_mime_type sets the MIME type of the protected resource (default: application/json).
• X402LayerBuilder::with_resource explicitly sets the full URI of the protected resource.

Re-exports

pub use layer::X402LayerBuilder;

pub use layer::X402Middleware;

pub use pricing::DynamicPriceTags;

pub use pricing::PriceTagSource;

pub use pricing::StaticPriceTags;

Modules

facilitator

A r402::facilitator::Facilitator implementation that interacts with a remote x402 Facilitator over HTTP.

layer

Axum middleware for enforcing x402 payments on protected routes.

paygate

Core payment gate logic for enforcing x402 payments (V2-only).

pricing

Price tag sources for the x402 payment gate.

Enums

PaygateError

Paygate error type that wraps verification and settlement errors.

VerificationError

Common verification errors shared between protocol versions.