Member is not part of the ARTF message
The envelope carries a member the ARTF proto does not define. Protobuf JSON rejects unknown fields by default.
What it means
A member appears that is not in the RTBRequest or RTBResponse definition. The most common instance is a camelCased spelling, bidRequest for bid_request, which the reference server marshals with proto names and so does not produce.
Why it matters
protojson.Unmarshal rejects unknown fields unless the caller opts into DiscardUnknown, so this fails the call rather than being ignored. When it is ignored, the effect is worse: the auction the agent reasons about is not the auction the orchestrator sent.
How to fix it
Use proto field names and drop anything the message does not define. Extensions belong in the ext member the proto reserves for them.
Example that trips it
{ "id": "ep-1", "tmax": 120, "lifecycle": "LIFECYCLE_PUBLISHER_BID_REQUEST", "bidRequest": { "id": "a-1" } }bidRequest is the protojson camelCase spelling; the field is bid_request.
Check your payload
Paste a bid request or response into the tester to see whether this code fires against it, or gate on the id in CI with the CLI: the id is stable, wording is not.
Back to the full diagnostic code reference.