Unmasking Hidden Hops: What schain 1.1 Means for Media Buyers

By Chris Coupland, Platform Operations Director, Basis

When you walk into a grocery store to buy produce, you usually look at the label. You want to know if the apples are organic, what country they were grown in and whether they meet your standards. Depending on your values, you evaluate several factors and make an informed choice based on clear origin data.

The same principles apply in programmatic advertising, but agency buyers and DSP users rarely get that level of transparency. Billions of bid requests flow through the ecosystem every day, passing through hidden technology providers that buyers can’t observe. These undeclared intermediaries introduce friction, enforce unexpected creative policies and siphon efficiency out of the media spend.

The IAB Tech Lab’s proposed SupplyChain v1.1 specification aims to pull these invisible layers into the light. Media buyers and hands-on DSP operators need to understand what schain 1.0 was built to do, what 1.1 adds to it, and what buyers need to do for it to work.

Money Flow Was Only Ever Half the Picture

To understand why schain 1.1 is necessary, start with what schain 1.0 was built to do. It maps payment flow: a node is declared if that entity pays another company in the chain, so a buyer can trace where the money goes. That was the whole job, and it worked.

It was also only ever half the picture. Plenty of companies handle a bid request without touching the money, and those companies never appeared in 1.0. An entity that handled requests while letting others pay was not required to show itself, and the buyer never saw it.

Consider an exchange that has two paths to a publisher, one direct and another through a large header-bidding vendor that collects payment, acting much like a traditional SSP. Under schain 1.0, the header-bidder appeared in the supply chain object as an intermediary because it collected the money and paid the publisher behind it. That visibility was what made it actionable. A buyer could see the same publisher inventory arriving through multiple paths, once straight from the exchange and once wrapped in an extra hop, and block the wrapped copy while keeping the direct one. Plenty of buyers did exactly that.

Now the intermediary stops collecting the auction money and lets the exchange pay the publisher directly, charging a separate fee for its own services outside the auction. Nothing about the request path changes. It still receives the request, still shapes it, still hands it to the same exchange. But because it no longer handles the payment, it falls outside what the specification asks about. Its node disappears, and the wrapped copy now looks identical to the direct one. The buyer cannot tell the two apart, so the block it used to run stops working. SupplyChain 1.0 is still telling the truth here. It is just telling a smaller truth than buyers assume they are reading. Intermediaries that can hide this way stack the odds in their favor.

Worse, nobody can size the problem. The evidence of the hop was the node, and now the node is gone.

Why Hidden Hops Hurt Buyers Beyond Extra Fees

It is easy to assume that unmapped supply chain nodes are purely a financial problem, a hidden adtech tax. But for agency media planners and DSPs, the operational friction can be far more damaging.

First, there are silent bid losses, where undeclared intermediaries enforce their own creative and content policies. An unnamed vendor may be rejecting your bids, and you have no way to fix it because you don’t know it is there. You are left pulling your hair out wondering why win rates dropped, unaware that an unlisted node has been blocking your creative. You cannot appeal a decision made by a company you cannot name.

Second is bandwidth and deduplication waste. Without clear path disclosures, DSPs could receive the same impression from many indirect routes. This creates infrastructure bloat, forcing buying platforms to evaluate redundant inventory rather than focusing processing power on optimal paths. In a first-price auction, you are less exposed to bidding yourself up than you once were, but multiple paths still put your own budget in competition with itself for a single slot.

What 1.1 Adds

SupplyChain v1.1 supplies the missing half, extending disclosure from payment flow to custody of the bid request. If a tech vendor handles or modifies the bid request, such as server-side ad insertion tools, header-bidding wrappers or pre-bid servers, it must be declared regardless of whether it handles money. The specification does this without adding new fields to the nodes themselves. Each node already carries a flag for handling payment, and a vendor that took custody of your request but no cut of the auction is simply marked hp=0, where hp stands for handling payment.

This is a welcome step. Two things about it shape how buyers should use it.

There is still some “custody” ambiguity, where the entire specification hinges on who takes custody of a request. Yet even among top adtech engineers, there is a lack of consensus on what custody technically means. Until the industry agrees on a baseline, implementation will remain subjective, which is exactly what a public comment period is for.

The second is verification, which matters more for how buyers use this data than for whether they trust it. SupplyChain 1.0’s payment mapping is checkable because it forms a triangle with ads.txt and sellers.json, two public files anyone can validate a declared payment node against. SupplyChain v1.1 does not extend that triangle to non-payment nodes. No ads.txt entry is required for them, a sellers.json entry is only recommended, and the flag that marks one is set by the vendor in its own file. That is a deliberate choice, and it points at how to use the data: for now, treat these nodes as enrichment, not as a filter.

That is also the answer to the concern holding back publisher and SSP disclosure. If buyers are not filtering on custody nodes, declaring them honestly cannot diminish demand for a seller. A longer chain is not a penalty — it is a fuller description of a path a seller was already selling. The greater risk sits with staying opaque, because the paths buyers cannot describe are the paths they eventually stop trusting.

What Buyers and DSP Users Should Do Now

There is no need to wait for market-wide adoption to get value from schain 1.1.

Update bidding logic for disclosed chains. As schain 1.1 rolls out, supply chains will appear longer, but a longer declared chain does not mean a worse path. It means that previously hidden hops are now visible. DSPs must count payment-handling hops when reasoning about fees and treat custody nodes as information, rather than penalizing transparent publishers for listing them. Ask how your platform tells a 1.1 chain from a 1.0 one.

Then demand supply path clarity from partners. Ask your DSP account leads how they plan to ingest and act on schain 1.1 data.

More transparency in the programmatic supply chain is worth having. SupplyChain 1.1 gives buyers more to read before it gives anyone more to enforce, which is the right order. It won’t fix programmatic opacity overnight. But if buyers start asking the right questions today and the sell side answers them, we can start separating clean, direct supply from padded, invisible paths.

Author Bio:

Chris Coupland is Platform Operations Director at Basis, where he specializes in programmatic architecture, Supply Path Optimization (SPO) and adtech specifications. Coupland also contributes to IAB Tech Lab’s OpenRTB working group.