Chrome's Lighthouse added an Agentic Browsing audit that fails llms.txt files whose links are not written in Markdown syntax. One SEO went from a failing score to perfect by reformatting links in five minutes. It is a tooling quirk, not an SEO penalty.
A five-minute formatting fix that flips a score from fail to perfect is the kind of quick win most sites never bother to claim.
Chrome's Lighthouse tool has a new Agentic Browsing category, and it is already catching people out. SEO consultant Slobodan Manic ran the audit on his llms.txt file and it failed with the error "File does not appear to contain any links," even though the file was full of working links. The catch was formatting. Lighthouse wants the links written in Markdown syntax, the bracket-and-parenthesis format, not as plain text.
The fix was almost comically small. Manic rewrote each line in Markdown link syntax, roughly five characters changed per link, and kept the file served as plain text. His Agentic Browsing score jumped from 0.67 to a perfect 1.0 with no other changes. The audit also checks separately for an H1 header and a minimum length of 50 characters. Worth knowing if you have an llms.txt file and want it to pass.
Why it matters
Before anyone panics, context. Google has said llms.txt is not required for AI search visibility, and a failing Lighthouse score here is a tooling-compatibility signal, not a ranking penalty. Your organic performance does not tank because this audit fails. It is telling you whether AI agents can cleanly read a file you may have set up for them.
For Australian businesses experimenting with llms.txt as AI crawlers grow more important, the lesson is practical. If you are going to publish the file, publish it in a format the tools actually parse. A file that exists but fails the check is doing half a job.
The jump in Agentic Browsing score from reformatting llms.txt links into Markdown, with no other change
What to do about it
If you have an llms.txt file, write every link in Markdown syntax. Plain-text URLs and dashes will fail the audit even when the links work.
Add an H1 header and keep the file over the 50-character minimum. Both are separate checks in the same audit.
Run Lighthouse's Agentic Browsing audit to see where you stand. It takes minutes and the fixes are usually trivial.
Keep it in perspective. This is about agent readability, not search rankings, so do not let a failing score send you chasing an SEO problem that is not there.
The quick wins in AI readiness are cheap and dull. Claim them anyway, because your competitors will not bother.