UCP version is a known release

What we check

We read ucp.version from your profile. The UCP schema requires a date in YYYY-MM-DD format. We also check that it is a published UCP release. On 2026-10-30, ucp.dev/versions.json listed four: 2026-08-25 (the current one), 2026-04-08, 2026-01-23 and 2026-01-11. Any older releases you list under supported_versions appear in the result.

Why it matters

The version tells an agent which rules your profile and services follow. Without one, an agent cannot tell which release to speak, and the schema treats the profile as invalid. A version that is not a published release leaves the agent guessing which rules apply.

How we check

This check uses the profile the scan already read, so it makes no extra request. PASS: the version is a well-formed date and a published release. WARN (score 50): the date is well formed but is not a release we know, such as a draft, a future date or a typo. FAIL: the version is missing, or is not a real calendar date (for example 2026-13-01). SKIPPED: there is no profile, we could not read it, or it is not JSON.

How to fix it

1. Set ucp.version in /.well-known/ucp to the UCP release you implement. The current release is 2026-08-25.
2. List any older releases you still serve under ucp.supported_versions, each pointing to the URL of that profile.

What good looks like

{
  "ucp": {
    "version": "2026-08-25",
    "supported_versions": {
      "2026-04-08": "https://shop.example/.well-known/ucp/2026-04-08"
    },
    ...
  }
}

Sources

• UCP releases (versions.json)
• UCP 2026-08-25 specification: overview
• UCP 2026-08-25 base schema (ucp.json)

Read more

• UCP explained

  The Universal Commerce Protocol: the profile a store publishes at /.well-known/ucp, the capabilities it declares there, and the checkout flow from a new basket to a placed order.