Programmatic Transparency in 2026: Why Agencies Are Fighting The Trade Desk (And Both Sides Have Questions to Answer)

The Publicis and The Trade Desk dispute has been framed as a transparency scandal, but I think it is more interesting than that. What this dispute actually reveals is a slow-building structural breakdown in how value flows through the programmatic ecosystem, and why agencies, platforms, and even some publishers all have something to answer for.

So let me give you the version the trade press is mostly missing.

How the Agency USP Got Quietly Dismantled

Not long ago, an agency’s core value was built on relationships. They knew the publishers, they could get your brand in front of the right audience because they had access and influence that advertisers simply could not replicate on their own. The deal was straightforward: hand over a budget, trust the agency’s network, and hopefully see the return.

Then platforms like Meta, Google, and The Trade Desk arrived and democratised access to audiences at scale. The expertise shifted from “who you know” to “how well can you work the platform.” Critically, those platforms also started showing advertisers exactly how much of their spend was reaching actual media versus being absorbed in fees along the way. That transparency slowly eroded the opacity that agencies had always, if quietly, relied upon.

Brands have continued bringing capabilities in-house, putting mounting pressure on agencies to prove their value.[2] A Typeface survey found that 60% of US senior marketing leaders said they spend less on agencies in 2025 as a direct result of AI.[2] The squeeze is real, and it is accelerating.

Fee Compression: The Root Cause Nobody Wants to Say Out Loud

Here is the part most coverage skips entirely. Agencies have chronically undercut each other on fees for years. The race to the bottom on retainers and management fees left holding companies with margins too thin to survive on service revenue alone. Low-margin project-based engagements replaced once lucrative retainer fees, two decades of marketing insourcing commoditised creative execution, and consistent procurement pressure ultimately forced agencies to monetise media, technology, and data instead.[8]

That explains, directly, why principal media and supply path arrangements came back. If you cannot charge enough on the service side, you find the money somewhere else.

How the Money Gets Recovered (The Part Advertisers Rarely See)

Principal-based media buying is where an agency pre-purchases inventory in bulk, typically at a discount, then resells it to the advertiser at a markup. The stated rationale is client savings. Forrester projects that in 2026, principal media will account for nearly 33% of total agency billings.[8] The scale of this is significant, and the advertiser awareness of it often is not.

But there is a second, less-discussed mechanic that happens directly inside platforms like The Trade Desk. Agencies can hardcode business rules into the DSP that direct spend toward specific supply partners, regardless of whether those paths are the most efficient route to an impression. The Trade Desk’s own systems can flag that a cheaper or higher-quality path exists. The agency’s rule stays anyway. In most cases, there is a commercial arrangement between the agency and that supply partner driving the decision.

The numbers behind this kind of opacity are damning. According to the ANA’s Q1 2025 Programmatic Transparency Benchmark, only 41% of programmatic ad spend resulted in quality impressions, meaning nearly 60% of spend was lost to non-quality inventory, with over one-third of open-programmatic spend representing an estimated $21.6 billion in unrealised media value globally.[8] Industry analysis estimates that 40% of budgets disappear into undisclosed fees, with a single impression often passing through four to ten vendors. On a $10 million campaign, only $4.7 million may actually reach real media placements.[1]

The Publisher Conflict Nobody Is Talking About

Here is one that rarely makes it into trade press, and it should. Some major publishers, including broadcasters like NBCU, are willing to sell inventory to agencies through principal buying arrangements. They are happy to receive agency money in that context. But when that same agency manages an advertiser’s campaign budget, those same publishers refuse to allow their inventory to be purchased on the advertiser’s behalf. They will not be on both sides of the transaction with the same partner.

That contradiction tells you almost everything you need to know about how the incentives in this market are actually structured.

Was the Omnicom Audit Really Independent?

One detail largely absent from the coverage: the Omnicom audit of The Trade Desk did not happen in isolation. Three of the big six holding companies have now either exited or audited TTD since Publicis made its bold public announcement. My read is that Omnicom’s move was at least partly reactive. Once Publicis staked out that ground publicly, others had little choice but to follow or risk looking like they were endorsing the very practices being called out. That is not a criticism of Omnicom specifically. It is an honest observation about how competitive positioning drives decisions in this industry, often as much as genuine governance concerns do.

The Pot Calling the Kettle Black

The most uncomfortable part of this story, for Publicis at least, is this: the practices they are auditing The Trade Desk for facilitating are the same ecosystem in which Publicis operates, and from which it profits. Publicis’s own CFO acknowledged that principal media accounts for slightly more than half of its third-party service costs. GroupM reportedly crossed $1 billion in principal media revenue.

Publicis is asking hard questions about programmatic transparency while simultaneously being one of the largest practitioners of the opacity they are criticising. That does not make the transparency questions about The Trade Desk invalid. But it does mean the framing of Publicis as the transparency champion deserves its own scrutiny. The Trade Desk, for its part, has not helped itself with a communications approach through this dispute that has been more combative than constructive.

Where This Is Actually Heading

The advertising agency landscape is undergoing its most significant restructuring in decades.[2] My view is that the long-term trajectory for large agencies, particularly with major clients, is a shift toward an advisory and oversight role. Strategy, governance, accountability, and measurement: things that genuinely require human judgment. The transactional execution of programmatic buying will, over time, be further commoditised.

The agencies that lean into that evolution openly and build their value proposition around client alignment rather than margin extraction will come out of this period with the strongest relationships. In 2026, the programmatic industry will push toward simplification and trust, with a stronger drive for transparent supply paths and real value for both publishers and advertisers.[3] That shift is coming whether agencies drive it or have it imposed on them.

Further Reading:

• Forrester: Predictions 2026 — Marketing Agencies Resign Their Agency
• ANA Q1 2025 Programmatic Transparency Benchmark — HUMAN Security Analysis
• eMarketer: FAQ on Ad Agencies — Consolidation, AI, and What’s Changing in 2026
• AI Digital: How Programmatic Platforms Absorb Budget Through Supply Chain Inefficiency