For a decade, the ad tech pitch from the supply side was simple: bring inventory, let the demand-side platform decide who buys it. That division of labor is breaking down. Across CTV and open web supply, sell-side platforms are pulling the actual buying decision, not just the auction, onto their own infrastructure, and Magnite’s second-quarter earnings show why the shift is accelerating now rather than later.
The Auction Was Never the Valuable Part
Magnite reported second-quarter revenue of $192.8 million, up 11% year over year, with CTV contribution ex-TAC climbing 36% to $97.1 million, beating the company’s own guidance range. CEO Michael Barrett used the earnings call to frame those numbers as evidence of a structural move rather than a cyclical one. “We are uniquely positioned between supply and demand, and with our agentic offerings we believe we will benefit from serving as vital infrastructure for the future of digital advertising,” Barrett told investors.
The mechanism behind that claim is SpringServe, Magnite’s ad server for streaming and CTV, which the company has spent the past year turning from a passive delivery system into an active one. SpringServe now handles inventory packaging and audience routing itself, using AI models to decide which impression serves which campaign at which price, work that used to sit exclusively on the demand side inside a DSP’s bidding logic.
Orchestration, Not Just Optimization
In June, Magnite layered a second piece on top: Magnite Orchestration, infrastructure built specifically so autonomous buying agents can communicate and coordinate with the supply side directly, rather than routing every decision through a human trader or a DSP’s own agent layer. Barrett was careful to draw a line around what this is not: “We are introducing products that are DSP-like,” he said, “but in no way, shape or form are trying to replace the DSP.” The distinction matters less to advertisers than the practical effect: more of the decision about which impression is worth what now happens on infrastructure Magnite owns.
That infrastructure is increasingly stitched to commerce data the DSP side can’t easily replicate. Magnite has built integrations with Fanatics, CVS Media Exchange, Best Buy, PayPal Ads and Walmart Connect, pairing first-party retail signals directly with its own inventory before a bid ever reaches an exchange. Publishers, in other words, are no longer just selling impressions. They’re selling impressions pre-packaged with the audience data needed to price them well, a job that used to belong entirely to the buy side.
The Rest of the Supply Side Is Making the Same Bet
Magnite is not moving alone. PubMatic’s agentic push with Optable follows the identical logic: give publishers the tooling to act on their own first-party data instead of handing it upstream. And the pressure is coming from both directions at once, since DSPs are simultaneously rebuilding themselves around AI agents that promise to do a media planner’s job in a chat window. Every layer of the stack is trying to own the decision at the same moment, and the supply side has one advantage the buy side does not: it sits closest to the first-party data an agent actually needs to be accurate.
None of this means the DSP disappears. Magnite’s own CTV contribution ex-TAC, while up sharply, is still a fraction of what flows through the demand side industry-wide, and Barrett’s insistence that Magnite isn’t “trying to replace the DSP” is as much a hedge against antagonizing his platform’s biggest customers as it is a technical description. What’s changing is where the profitable, differentiated work happens. Auction mechanics are increasingly commoditized; deciding which impression, at which price, for which audience, backed by proprietary data, is where the margin is moving.
The Trade-Off Buyers Should Weigh
There is a real cost to this consolidation, and it is worth naming rather than assuming away. When a supply-side platform owns both the inventory and the decisioning logic that prices it, the transparency buyers have spent years demanding from DSPs does not automatically carry over. A platform that packages its own audience data with its own inventory and prices both in one motion has less incentive to show its work than an independent auction did. Marketers who welcomed SSP-side AI for the efficiency gain should also expect to push harder for auditability, because the black box did not disappear, it just moved one layer closer to the publisher.
What It Means for the Marketing Leader
For a brand or agency buying CTV and programmatic inventory, this shift changes what to ask a supply-side partner. It’s no longer enough to ask which publishers a platform represents. The better question is whose first-party data and decisioning logic sits behind the inventory before it ever reaches a bid request, because that logic increasingly determines price and performance before the DSP gets involved. Marketers who treat SSPs as a passive pipe are going to find pricing and targeting decisions being made upstream of their own media plan, by systems they never evaluated.
It also raises a measurement question worth asking now rather than after a quarter of murky reporting: if a supply-side platform’s own AI is choosing which impression serves a campaign, buyers need transparency into that logic, not just the price it produces. That scrutiny is exactly the kind CTV measurement has been building toward, as show-level CTV reporting becomes the baseline expectation rather than a differentiator.
How to Evaluate a Supply-Side Partner Now
Ask three things before the next upfront or programmatic RFP: what first-party data sources feed the platform’s decisioning models, what visibility you get into why a given impression was priced or routed the way it was, and whether the platform’s agentic tools are additive to your DSP’s own AI stack or duplicative of it. Supply-side platforms that can’t answer the first question clearly are still selling inventory the old way, whatever the marketing deck says. The ones that can are the ones worth building a direct relationship with, because the decision that used to happen exclusively in your DSP is, increasingly, already made by the time your bid request arrives.
Source: Magnite Investor Relations
