TL;DR: Supply path optimisation has historically been a manually managed discipline, requiring analysis of which SSPs and DSPs add genuine capability versus routing fees. Agent-to-agent advertising introduces a structural alternative: a buy-side agent and a sell-side agent can negotiate directly, bypassing the DSP-SSP intermediary pair for deals where connection, not capability, was the only thing being added. The shared deal record that both agents write to at the point of agreement replaces the clearing function that exchanges currently provide. Intermediaries that provide infrastructure, data, or accountability will retain margin; those whose primary function was routing a connection between parties who can now establish it directly face the clearest structural displacement.
The programmatic supply chain has a margin problem that predates agentic advertising by a decade. Between the advertiser's budget and the publisher's inventory sits a chain of intermediaries, each charging a fee as a percentage of spend passing through. Supply path optimisation emerged as the industry's discipline for addressing this: identify which SSPs and DSPs provide genuinely distinct access to publishers and which are reselling inventory already available through another route, then remove the redundant hops. For most of that decade, the discipline required human analysis, ongoing publisher relationship management, and periodic audits. Agentic advertising changes the structural conditions the problem grew from.
What did the ISBA study find about intermediary costs?
The ISBA programmatic supply chain transparency study, conducted with PwC and published in 2020, tracked 267 million impressions across 15 major UK advertisers. The study found that publishers received 51 pence for every pound of advertiser spend, meaning 49 pence was retained across the intermediary chain. Of that retained sum, 15 pence in every pound could not be attributed to any identifiable entity in the supply chain. It did not reach publishers. It did not reach the buyer's verified partners. The ISBA and PwC researchers labelled this the "unknown delta": money that passed through the supply chain and could not be accounted for.
Supply path optimisation was built to address the known portion: the fees buyers could identify and choose to eliminate by routing through shorter, more transparent paths. The 15p unknown delta was harder to address because its origin was unclear. Agentic infrastructure addresses a different version of the same structural problem.
How does agent-to-agent negotiation change the supply path?
In a conventional programmatic transaction, a buy-side system connects to an SSP through a DSP, or routes a bid request through an exchange that handles the match between buyer and seller. Each connection layer charges a fee. The DSP-SSP combination for a single impression can involve two organisations, both taking margin, even when both are subsidiaries of the same holding group.
Agent-to-agent advertising introduces a structural alternative. A buy-side agent, operating on an authorised mandate from a brand or agency, can negotiate directly with a sell-side agent representing a publisher. Both agents agree deal terms: the CPM, the audience parameters, the brand-safety criteria, the delivery commitments. Both write the agreed terms to a shared deal record. The shared record is the authoritative source for both sides.
This bypasses the clearing function that exchanges and SSPs currently provide: matching buyers to sellers, holding the canonical version of deal terms, and managing the financial reconciliation between them. When agents establish the match and write jointly to a shared record at the point of negotiation, that clearing function exists in the record, not in an intermediary platform.
Brian O'Kelley, co-founder of the Ad Context Protocol (AdCP), stated in an ADOTAT investigation published in August 2026 that a shared, machine-readable deal record is a prerequisite for cross-company agent-to-agent buying to function. The protocol he is developing assumes that the deal record is accessible to both parties and authoritative for both, without either requiring a third-party exchange to hold the canonical version.
Does this mean the DSP and SSP disappear?
Not as a near-term outcome, and possibly not at all for their substantive capabilities. The supply path displacement argument applies most directly to one function: routing a connection between a buyer and a seller. When agents can establish that connection directly and hold the record without a clearing intermediary, the connection-only value of the DSP-SSP pair reduces.
What does not reduce is the value that DSPs and SSPs provide beyond the connection itself. A DSP that provides audience data assets, attribution infrastructure, or measurement integration offers capabilities that an agent mandate can depend on but not replicate through direct publisher negotiation. An SSP that provides publisher yield management, privacy-compliant consent infrastructure, or viewability tooling provides services the publisher's agent cannot build itself. Both categories of intermediary retain margin proportionate to the capabilities they actually contribute.
The ISBA study's unknown delta represents intermediary cost for which buyers received no identifiable benefit. Agentic infrastructure does not reduce the spend that goes to identifiable services with genuine capability. It reduces the cost of the connection itself, which was historically bundled with those services in a way that made it difficult to price separately.
What infrastructure does a shortened supply path require?
A directly negotiated agent deal requires configuration that most programmatic buyers have not built. The buy-side agent needs a mandate that specifies what it may offer, at what terms, and within what constraints. The publisher's sell-side agent needs the equivalent. Both need a shared record to write to at the point of agreement, with that record accessible to both parties' measurement and finance reconciliation systems.
The IAB Tech Lab's agentic advertising working group specifications require that material commitments above defined approval thresholds trigger human review before commitment is finalised. This is not a limitation of the agent architecture; it is a deliberate governance design to maintain human oversight at the decision points that carry material financial consequences.
Volume context matters here. Andrew Mole of pubX told ADOTAT in August 2026 that live agentic media spend sits at approximately $3,000 a day from one named operator. At that volume, structural supply chain effects are minimal. The infrastructure being designed and standardised now will govern how much larger volumes flow once agentic buying scales. The organisations building mandate frameworks and supply path governance today will apply them to materially larger numbers.
*This article references the ISBA programmatic supply chain transparency study, conducted with PwC and published in 2020; the IAB Tech Lab's published agentic advertising working group specifications; statements by Brian O'Kelley of AdCP, published in an ADOTAT investigation in August 2026; and volume data from Andrew Mole of pubX, published in the same investigation.*