The errors thrown are hardcoded: https://github.com/dotansimha/graphql-yoga/blob/50f7cd7943fe92fdbe7020927e6c8d7c1a070565/packages/plugins/persisted-operations/src/index.ts#L63 https://github.com/dotansimha/graphql-yoga/blob/50f7cd7943fe92fdbe7020927e6c8d7c1a070565/packages/plugins/persisted-operations/src/index.ts#L71 https://github.com/dotansimha/graphql-yoga/blob/50f7cd7943fe92fdbe7020927e6c8d7c1a070565/packages/plugins/persisted-operations/src/index.ts#L76 There is currently no way to customize this part of the protocol - e.g. use a custom status code or different error format or even extensions.