Published: 17 September 2026

TL;DR: An exchange runs auctions: the SSP manages deal setup, price is determined by the highest bid, and the publisher holds no shared deal record. An agentic marketplace runs bilateral negotiations: the sell-side agent evaluates proposals against the publisher's mandate, the agreed CPM is respected rather than competed around, and both parties hold a DealSheet written before delivery. The difference matters most for premium inventory categories and for publishers who need reliable reconciliation evidence.

Publishers operate in both models today. Most premium display, video, and contextual inventory runs through an exchange of some form, whether open auction, preferred deal, or programmatic guaranteed. Agentic marketplace deals are newer and less universal, but growing quickly.

Understanding the structural difference between the two models helps publishers decide which categories of inventory to route through each, and what operational changes agentic marketplace deals require.

How an Exchange Works

An exchange is an auction-based infrastructure layer. The publisher connects their inventory through an SSP, which manages floor prices, deal configurations, and auction participation. When an impression becomes available, the exchange runs an auction among eligible buyers. The buyer with the highest bid wins. The price is the auction outcome.

The publisher's control in this model is limited to the floor price and the buyer category restrictions they set in the SSP. They cannot direct the price above the auction outcome. If the auction produces a price above the floor, the publisher receives the higher price. If the market is thin and bids cluster near the floor, the publisher receives close to the floor.

The deal record in an exchange is post-auction. The SSP records the transaction after the impression fires. The publisher has an impression log and an SSP revenue report. They do not have a pre-delivery record of what was agreed, because nothing was agreed before the auction ran. The auction determines the outcome; it does not produce a bilateral agreement.

Reconciliation in an exchange relies on comparing SSP logs against ad server logs. Discrepancies are common and are resolved through the SSP's reporting tools and, when those fail, through bilateral negotiation with the buyer.

How an Agentic Marketplace Works

An agentic marketplace is a bilateral negotiation infrastructure. The publisher connects their inventory through a sell-side agent operating under a mandate the publisher approved. When a buy-side agent sends a proposal, the sell-side agent evaluates it against the mandate parameters. If the proposal meets the CPM floor and the other mandate conditions, the sell-side agent can accept it autonomously. If it falls short, the sell-side agent rejects or counters.

The price in this model is the negotiated CPM. The publisher sets a floor in the mandate; the agreed CPM is at or above that floor by the terms of the deal. There is no auction dynamic that could push the clearing price to the floor. The CPM floor is respected because the sell-side agent will not accept below it.

The deal record in an agentic marketplace is pre-delivery. The marketplace writes a DealSheet at the moment of agreement: agreed CPM, inventory scope, audience conditions, delivery commitment, and agent identities. Both the buy-side and sell-side agents hold a copy. The publisher has the agreed terms before a single impression is served.

Reconciliation in an agentic marketplace begins with the DealSheet. Both parties have the agreed terms. The comparison is between the DealSheet and delivery data. Discrepancies are identifiable against a shared reference rather than through competing logs.

What Changes for Publisher Operations

Moving inventory from exchange to agentic marketplace requires operational preparation.

Mandate construction is the first change. The publisher must build a sell-side mandate before deploying a sell-side agent. This involves making explicit decisions about CPM floors, inventory categories, deal types, audience data permissions, and buyer restrictions that were previously handled case by case or through SSP floor settings.

Deal record infrastructure is the second change. The publisher needs systems that can receive and store a DealSheet at the time of agreement. This is a new data type in the publisher's operational stack.

Reconciliation process update is the third change. Reconciliation against a DealSheet is different from reconciliation against SSP logs. The publisher's finance and operations teams need to understand the DealSheet format and how to use it as the primary reconciliation reference.

Which Inventory Categories Each Model Suits

Exchanges are well suited to impression-level demand that does not require pre-commitment. Open audience targeting, remnant inventory, and demand categories where the buyer's preference is broad are natural fits for auction-based pricing.

Agentic marketplace deals are better suited to premium inventory where the publisher wants guaranteed CPM floors, defined audience conditions, and a bilateral deal record. Video inventory with audience data, premium contextual placements, and high-value publisher properties benefit from the pre-delivery agreement structure.

Most publishers will continue to use both models. The strategic question is which categories to move toward bilateral deal structure and what mandate parameters to set. Starting with one or two premium inventory categories, building the mandate carefully, and reviewing DealSheet quality over the first campaigns is the most straightforward path from exchange dependence to bilateral deal capability.