openrtb.bid.dealid_unknown
What it means
The bid references a dealid that is not among the deals the referenced Imp's pmp object offered. Because deals negotiated out of band (not carried in the request) legitimately exist, this is a warning rather than an error.
Why it matters
If the deal was supposed to be in the request, one side has a stale deal sync: the buyer bids a deal the seller no longer offers, the bid loses deal treatment, and both sides see the deal underdeliver without an obvious cause.
How to fix it
Echo a Deal.id from the imp's pmp.deals when answering an in-request deal. If you transact out-of-band deals, confirm with the exchange that they accept dealids not present in the request; otherwise treat this warning as a sync failure to chase.
Example that trips it
{ "seatbid": [{ "bid": [{ "id": "1", "impid": "1", "price": 8.0, "dealid": "PG-2025-old" }] }] }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.