Findings: This is entirely the clients issue. The encoding is most likely wrong: If the client doesn't send it in this format on the GQL layer (https://github.com/prisma/prisma-engines/pull/1354/files#diff-75b6d96ece3b54882a54bb29dbe12f1c0c3230024573d1b619ac83fae3c62247R1) then it fails with the above error. The reason is that the GQL parser we use craps out if the escaping isn't on point, causing list values to be parsed extremely weirdly.