I noticed some "Page includes" snippet extensions showing up in site search - unable to replicate on regular SERPs so far.

Looks like the snippet extensions in bubble format relate directly to headings (example one) but the plain text versions are created whole cloth by AI (example two - none of these words appear in any heading, 'Treatment' only appears one time in text, and 'Disease comparison' isn't on the page at all).

Apparently Google first started testing these in Feb. '25, then started up again in June '25 (ht Brodie Clark). Good to be aware of in case a client notices clickable text below their search snippet, especially if any of them contain "unofficial" wording.

Currently, there's no way to control how/when these appear. But if I were trying to influence them, I'd make sure there were plenty of helpful, succinct headings structuring the page content.