I've just started using xpc_connection_set_peer_code_signing_requirement() and can happily report that it meets all of my needs in terms of validating who my XPC connection is really connected to. However there seems to have been a slight oversight in that the new error XPC_ERROR_PEER_CODE_SIGNING_REQUIREMENT has either not been made public, or is not available to Swift code for some reason. For example: if event === XPC_ERROR_CONNECTION_INVALID { // OK } else if event === XPC_ERROR_TERMINATION_IMMINENT { // OK } else if event === XPC_ERROR_CONNECTION_INTERRUPTED { // OK } else if event === XPC_ERROR_PEER_CODE_SIGNING_REQUIREMENT { // Error: Cannot find in scope }