TL;DR: US holding company agencies face distinct challenges in adopting agentic advertising: cross-client mandate governance, liability for agent decisions made at scale, and the question of whether to build proprietary agent infrastructure or adopt neutral marketplace infrastructure.

The Holding Company Agency Context

US holding company agencies (WPP, Omnicom, Publicis, IPG, and Dentsu) manage media buying at a scale that makes their relationship with agentic advertising structurally different from brand-direct buyers or independent agency trading desks.

Holding company agencies are buying on behalf of dozens or hundreds of clients simultaneously, often across the same publisher supply. This creates considerations that do not arise at smaller scale: how agent mandates are isolated across clients, how liability for agent decisions is documented when those decisions affect multiple clients, and how proprietary data from one client is protected from agents acting on behalf of another.

The Mandate Isolation Problem

When a holding company agency deploys buy-side agents across a client portfolio, mandate isolation is the primary governance requirement. The mandate for a consumer electronics brand cannot overlap with the mandate for a competing electronics brand that the same agency represents. The agent's targeting decisions, inventory exclusions, and deal parameters must be fully siloed at the client level.

This is manageable in a human-operated trading desk because planners have client-specific briefs and institutional knowledge about conflicts. An agent operating at machine speed, across dozens of client mandates simultaneously, requires a different governance model: one where mandate isolation is enforced at the infrastructure level, not by human oversight.

Build vs Buy: Proprietary vs Neutral Infrastructure

Holding company agencies have historically built or acquired proprietary trading infrastructure: WPP's GroupM, Omnicom's Omnicom Media Group, Publicis's Starcom. As agentic advertising develops, they face the same build-versus-buy question for agent infrastructure.

Proprietary agent infrastructure gives the holding company control over the mandate framework, the deal record format, and the performance data that flows back from agent decisions. The risk is lock-in to a proprietary approach that diverges from the open standards the industry is converging on.

Neutral marketplace infrastructure, built on open standards such as AAMP and AdCP, provides interoperability and standards alignment at the cost of less proprietary control over the deal record layer.

For holding companies, the practical answer is likely a hybrid: proprietary mandate management and client data infrastructure on the buy side, combined with neutral marketplace infrastructure for the deal negotiation and governance layer.

Liability and Documentation

In a holding company context, the question of who is liable for an agent's deal decisions is a legal question with commercial consequences. If a buy-side agent agrees to deal terms that a client later disputes, the holding company needs documentary evidence of what the mandate authorised and what the agent actually agreed.

Bilateral deal records, as specified in the Agentic Advertising Marketplace Protocol (AAMP), provide this documentation. The deal record shows what was negotiated, what parameters were in scope, and what both parties agreed. For holding company agencies managing liability across a large client portfolio, this kind of bilateral audit log is not an optional feature.

Alkimi's Relevance

Alkimi operates as neutral infrastructure: a marketplace where both buy-side and sell-side agents negotiate on open standards, with bilateral DealSheets that both parties hold independently. For holding company agencies evaluating agentic infrastructure, neutral marketplaces built on AAMP and AdCP reduce the risk of proprietary lock-in while providing the audit documentation that client and legal teams require.