Why this protocol is now called OSP

On 15 September 2026 the Agent Commerce Protocol became the Open Storefront

Protocol. The specification did not change, the version did not change, and no

endpoint moved. Only the name did. This post is why, because a rename with no

stated reason reads as a rebrand and this one was not.

The collision

The old acronym was ACP. That acronym now belongs to something else.

From agenticcommerce.dev, fetched 16 September 2026: "Stripe and OpenAI

developed the Agentic Commerce Protocol to define a common language for how

agents and businesses transact." It is published under Apache 2.0, supports

REST and MCP compatible integrations, and names ChatGPT as the first AI platform

implementation.

OpenAI's own developer documentation, at developers.openai.com/commerce, fetched

the same day, documents two integration paths against it: merchants implement

the Agentic Checkout Spec, and payment service providers implement the Delegated

Payment Spec. Product feeds go in by API or by SFTP.

That is a real specification, actively documented, with a payments company and a

model provider behind it. Two protocols in the same problem space sharing one

three letter acronym is not a branding inconvenience. It is a category of bug: a

developer reads "ACP" in a search result, lands on the wrong specification, and

writes code against it.

What we did not do

Nothing was renamed inside the protocol. The endpoints did not move. The

specification is still v3.0 and the wire revision a caller receives in

X-OSP-Version is still 2026-03-01, unchanged by the rename.

Responses carry both X-OSP-Version and X-ACP-Version, with the same value,

and both are documented. A compatibility header that gets quietly dropped six

months later is a rename that breaks clients on a delay, which is the thing this

was supposed to avoid.

The discovery manifest does the same: it carries osp_version and acp_version

side by side, both 3.0.

The name we chose, and what it gives up

"Open Storefront Protocol" is narrower than "Agent Commerce Protocol" and that

is deliberate. It names the thing the protocol actually does: a merchant

publishes a storefront, in a shape an agent can read. It does not claim the

whole of agent commerce, which is a larger area with several specifications in

it and no settled answer.

The cost is that the new name is less evocative. The benefit is that it is

harder to confuse with anything else, which was the entire problem.

The dated posts stay dated

The v2.0 announcement on this blog was published under the old name. It has been

updated to use the current one, with a note at the top saying so, because a post

that switches names halfway leaves a reader unable to tell whether they are

reading about one protocol or two. The dates, versions and technical content are

untouched. The changelog carries the rename as its own

entry.

If you integrated before the rename

Nothing to do. Same paths, same headers, same version. If you are reading a page

that says ACP and you are not sure which one it means, check the version string:

this protocol's specification version is 3.0 and its wire revision is a date.