X_CLIENT_RECORD_ENVELOPE_INVALID
Means
a response marked as a records envelope has the wrong shape
Typical cause
a response carried x-ultimate-records: 1, and its body is not { data, records?, removed? }: no own data, records not record type → record key → row, or removed not record type → list of keys. The cause names the position and never echoes the body
Fix
build the body with encodeRecordEnvelope() from @ultimat3/core in the handler that set the header, or stop setting the header