TL;DR: Supply path optimisation is the practice of identifying the most efficient and transparent routes from buyer to publisher inventory, and AI is making it both more precise and more dynamic.

Defining Supply Path Optimisation

Supply path optimisation (SPO) is the process by which buy-side teams evaluate and select the most efficient paths to publisher inventory. In a mature programmatic ecosystem, the same impression can be accessed through multiple supply-side platforms (SSPs), exchanges, and resellers. Not all paths are equal.

Some paths add intermediary fees without adding value. Others introduce latency or reduce transparency around who is actually selling the impression. SPO is the discipline of identifying which paths offer the most direct, cost-efficient, and verifiable route to a given publisher's inventory.

SPO became a recognised practice as buyers realised that the number of SSP integrations they were maintaining had grown beyond what could be managed effectively. A single publisher's inventory might be accessible through ten or more supply paths. Maintaining all of them has real costs: latency, technology fees, and opacity around auction mechanics.

The Signals That Drive SPO Decisions

Traditional SPO decisions rely on several data points:

- Fee transparency: how much of the buyer's dollar reaches the publisher? - Win rates: which paths produce the most successful bids for the inventory the buyer values? - Inventory quality: which paths carry the least invalid traffic? - Auction mechanics: is the auction conducted fairly, and is there evidence of auction manipulation?

Buyers use these signals to reduce their active SSP relationships to a smaller number of preferred paths. The aim is to spend more with fewer, better-understood supply partners.

How AI Changes Supply Path Optimisation

AI does not change what SPO is trying to achieve. It changes how comprehensively and how quickly it can be done.

Signal processing at scale

The volume of auction-level data required for accurate SPO analysis is large. AI models can process auction logs, bid response data, and delivery reports across many SSP relationships simultaneously and surface patterns that would take a human analyst weeks to identify.

Dynamic path selection

Static SPO is a periodic review. A buying team evaluates SSP performance quarterly or annually and adjusts their preferred paths. AI enables dynamic path selection: the system evaluates path performance in near real time and shifts spend towards better-performing paths without waiting for a manual review cycle.

Predicting path quality

AI can model which supply paths are most likely to deliver high-quality inventory for a specific campaign objective, rather than relying on historical averages. A path that performs well for a direct-response objective may not be the best choice for a brand awareness campaign targeting a different audience profile.

SPO in an Agentic Advertising Environment

As advertising moves towards agentic models, SPO changes structurally. In a traditional programmatic environment, the buyer accesses publisher inventory through a chain of intermediaries. In an agentic environment, a buy-side agent can negotiate directly with a sell-side agent, with the terms of the deal documented in a shared DealSheet.

This changes the nature of the path itself. Rather than a buyer bidding through multiple exchanges to reach a publisher, an agent identifies a publisher's inventory, negotiates terms through a protocol-compliant process, and agrees a deal that both parties hold privately.

Alkimi's marketplace is built for this model. The DealSheet records the agreed terms. The audit logs show every step of the negotiation. The buy-side and sell-side agents do not need direct API connections to each other. The marketplace provides the neutral infrastructure for the negotiation.

The Agent Communication Protocol (AdCP), published by AgenticAdvertising.org, defines the message standards for these negotiations. The AAMP, published by IAB Tech Lab, provides the governance framework within which agentic supply paths operate.

What This Means for Buying Teams

SPO is not going away in an agentic world. The question it asks, which path to a publisher's inventory is most efficient and transparent, remains relevant. But the answer changes when agents can negotiate deals directly rather than bidding through intermediary layers.

Buying teams evaluating SPO strategies should account for the emergence of agentic deal-making as a meaningful supply path category alongside open auction and private marketplace deals. The most forward-looking teams are already mapping which publisher relationships are candidates for direct agent-to-agent negotiation, and which are best served through existing programmatic channels.