ksef_client

https://github.com/tibortc/ksef_client

A Ruby client for KSeF 2.0, Poland's mandatory national e-invoicing system. Covers the REST transport layer (KSeF-token authentication, payload encryption, interactive sessions, invoice submission, status polling and UPO retrieval) and ships a standalone FA(3) invoice builder with XSD-backed validation. The builder has no HTTP dependency and can be used on its own.