There’s a quiet structural war underway in programmatic, and this week it came into focus. On one side, the agency holding companies are using AI agents to buy media directly — squeezing out the ad-tech middlemen and the cut they take. On the other, the sell-side platforms are racing to ship agentic operating systems that make themselves indispensable to exactly those agents. Publishers sit in the middle, and the outcome determines how much margin survives the trip from buyer to seller.
01The buy side: agents that cut out the middle
Omnicom has been explicit about it. On its Q1 earnings call, the holdco said it has already executed live buys for several clients through an agent-to-agent (A2A) framework — software negotiating directly with publishers. As Digiday reported, the objective isn’t necessarily to eliminate DSPs and SSPs entirely, but to diminish the role they play and, with it, the cut they take. One Omnicom exec called reducing that dependency “an objective,” flatly.
WPP is making the same bet from a different angle. WPP Open, its “agentic marketing platform,” has crossed 75,000+ active internal users and is being positioned as the operating system for the entire holdco’s media and creative output. The framing across WPP, Omnicom, Havas, and Dentsu has shifted from “we use AI” to “we are an AI operating system.” The holdcos have stopped talking about agents and started shipping them.
02The sell side: become the OS the agents can’t route around
The SSPs aren’t waiting to be disintermediated. PubMatic’s AgenticOS — launched in January as “the operating system for agent-to-agent advertising” — is, by PubMatic’s account, accelerating globally in Q2 as agentic campaigns move from test to live. It runs on NVIDIA-accelerated infrastructure, embeds in PubMatic’s global pipes, and is paired with an Agentic AI Acceleration Program to push advertisers and publishers from pilot to production “within weeks.” Real campaigns are already running: PubMatic and agency Butler/Till launched an AdCP-enabled agentic campaign across CTV. Magnite, for its part, is leaning on the same protocol momentum and its CTV/retail strength.
The logic is symmetrical. The buy side wants agents that route around the sell-side toll. The sell side wants to be the rails those agents run on. Whoever becomes the indispensable layer keeps the margin.
03Why this matters
This is a fight about who captures the value between a budget and an impression — and historically, publishers have been the ones who lost margin to every new intermediary. Agentic A2A could go either way:
| Upside | If agents negotiate directly with publishers over transparent protocols (see this week's AAMP/AdCP piece), the layers of opaque intermediaries — and their fees — thin out. More of the dollar reaches the seller. |
|---|---|
| Downside | If the new "operating systems" simply replace the old toll-takers with new ones, publishers trade a known tax for an unknown one — and a more concentrated one. |
The deciding factor is whether publishers are legible and represented in the agentic stack. Agents route spend to inventory that’s cleanly described, well-governed, and outcome-instrumented. Everything else gets skipped without a human ever looking.
Disintermediation is the oldest promise in programmatic and the one most often broken — the middle layer gets rebuilt under a new name every few years.
04What publishers should do this quarter
05What marketers should do
06The bottom line
Disintermediation is the oldest promise in programmatic and the one most often broken — the middle layer gets rebuilt under a new name every few years. Agentic A2A is the latest attempt, and this time the protocols are open enough that it might actually thin the stack. Publishers who get legible and demand transparent terms now can ride the upside. Those who wait will find a new operating system has been built around them, with a new tariff attached.