Agent Ready HTML

Fern adds llms.txt filters and wider agent 404s

In short

Fern added lang=php and excludeChangelog=true to llms.txt and per-page markdown URLs, and raised the similar-page suggestions in agent 404 responses from three to five. Fern serves llms.txt at the root and for every navigation node: sections, products, versions, tabs, API references and changelogs.

Published 18 September 2026

Dated 18 September 2026. Source type: primary source. Read the source, read 4 November 2026.

What it changes for a reader

  • The llms.txt reference covers the proposal, the versions and the evidence on whether agents use the file. Open it.
  • The guide to serving markdown on request shows the rule and the headers. Open it.
  • The guide to real status codes shows how to make a missing page answer 404. Open it.

On this site

Sources

  1. Fern changelog https://buildwithfern.com/learn/docs/changelog, read 4 November 2026

Last reviewed 4 November 2026