# r402-core
Core types, traits, and wire formats for the x402 payment protocol.
This crate is blockchain-agnostic. It defines the shared data model used by
client, server, and facilitator implementations across every chain. Chain
specific behavior lives in sibling crates — see [`crates/README.md`](../README.md).
## Modules
- [`wire`] — On-the-wire JSON types (offer, facilitator RPC, codecs) and settlement overrides
- [`facilitator`] — `Facilitator` trait, `DynFacilitator` erasure, verify/settle hooks
- [`scheme`] — Payment scheme registry and builder traits
- [`extensions`] — Extension framework for x402 protocol extensions
- [`client`] — `PaymentClient` orchestration
- [`resource_server`] — Transport-agnostic verify → execute → settle
- [`chain`] — CAIP-2 chain identifiers, address, provider abstractions
- [`amount`] — Human-readable currency amount parsing (`"$0.01"` etc.)
- [`error`] — Layered errors and machine-readable [`ErrorReason`] wire codes
## Feature Flags
| `telemetry` | | Enable `tracing` instrumentation |
| `cache` | | Enable `moka`-backed TTL caches |
| `ext-bazaar` | | Enable the bazaar resource discovery ext. |
| `ext-payment-id` | | Enable the payment-identifier idempotency. |
| `ext-eip2612` | | Enable EIP-2612 gas-sponsoring extra. |
| `ext-erc20-approval` | | Enable ERC-20 approval gas-sponsoring extra. |
| `metrics` | | Enable the `metrics` facade counters. |
| `all-extensions` | | Enable every built-in extension |
| `full` | | Enable every feature |
## License
Licensed under either of MIT or Apache-2.0, at your option.