ARTF Explained: How a Live Bid Request Gets Patched Before the Auction

On October 14, 2026, Prebid revealed a new auction model that inverts the traditional process. Ad servers now bid into Prebid Server rather than the other way around. The IAB Tech Lab introduced ARTF v1.0, a framework that introduces containerized agents to propose changes to the bid request before any bidding occurs. These agents work alongside the existing auction process, adding an extra layer of modification.

ARTF is not a substitute for OpenRTB but rather an extension point built on top of it. The host retains control of the auction, while agents propose deltas to the object in transit. The host decides whether to accept or reject each mutation independently. ARTF operates as an RTBRequest, containing essential information such as the lifecycle stage, a unique request ID, and the OpenRTB payload.

Agents can propose various intentions, such as activating deals, adjusting deal floors, or adding metrics. They specify how to perform the operation, the path within the request, and the value to apply. Each mutation is a self-contained unit, and the host can accept or reject them as it sees fit. The final merged OpenRTB object may contain fields that are not valid for the exchange's specific version, and the agent is unaware of these issues.

Implementations that allow models to emit ARTF envelopes and mutation lists must validate these structures against the wire contract. Tools like rtblint can perform these checks, ensuring that the modifications are correct and compatible with the OpenRTB version in use. Production ARTF implementation means paying attention to the patch bugs that can arise during this process.