Lighthouse 13.5: llms.txt becomes one of the discovery points

Lighthouse 13.5.0 came out on September 18, 2026. The llms.txt check neither disappeared nor grew stronger: it moved into a common group of agent discovery checks.

What changed

The llms.txt line used to stand alone in the Agentic Browsing category. Now it sits in one group with other points through which an agent learns what a site can offer.

The meaning of the move: the file is treated not as a goal in itself, but as one of the ways of discovery.

What stayed the same

• Only the response of /llms.txt is checked. The content is not judged.
• Status 404 gives “not applicable”, not an error.
• The category is experimental and has no overall score.
• The performance, accessibility and SEO scores do not depend on the file.

History of the check

Date	Version	What happened
May 1, 2026	13.2.0	the check was added to the code
May 7, 2026	13.3.0	turned on by default
July 20, 2026	13.4.1	available through the PageSpeed Insights API
September 18, 2026	13.5.0	grouped with other discovery checks

How to read it

In four and a half months the check went from a novelty to a line in a group. The Chrome team neither removed it nor made it mandatory. The makeup of an experimental category changes from release to release, and plans should not be built on its current shape.

What a site owner should do

If the file exists and is real, nothing needs to be done. If new lines appeared next to llms.txt in the report, read them as hints, not errors. What the check proves and what it does not: Lighthouse and llms.txt.