The difference is that Buf's LSP is fully spec-complete since it's built on the same tooling that powers the buf CLI. I've seen several attempts at Protobuf LSPs over the years, but none that actually conform to the Protobuf specification, including the one you linked. That project is built on `emicklei/proto`, which readily accepts broken Protobuf and always has. The author says so in the README: "Current parser implementation is not completely validating .proto definitions." Maybe Buf should update the headline to "Protobuf finally has LSP support that works."