openrtb.response.request_id_mismatch
What it means
BidResponse.id must echo the id of the bid request it answers; here it carries something else. The echo is how exchanges correlate a response to the auction that solicited it.
Why it matters
A response the exchange cannot correlate is a response it cannot use: at best it is dropped, at worst it is attributed to the wrong auction and pollutes reporting on both sides. This is usually a bidder generating a fresh id instead of copying the request's.
How to fix it
Copy BidRequest.id into BidResponse.id verbatim. Your own response identifier, if you need one, belongs in bidid or your ext.
Example that trips it
{ "id": "resp-8841", "seatbid": [] }Answering request "req-1" under a self-generated id.
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.