A file named INDEX.md stops jekyll-readme-index from publishing the README

Fact

jekyll-readme-index, one of the plugins GitHub Pages enables by default, promotes README.md to a directory's index only when that directory has no index already. The test matches built URLs against index\.(html?|xhtml|xml)$ case-insensitively, so a repository whose table of contents is INDEX.md — built to /INDEX.html — counts as already having one.

The README is then left as a static file, served as raw Markdown, and the site root returns 404. readme_index: {with_frontmatter: true} does not help: the same guard runs before it.

Why it matters

Nothing reports the problem. The build succeeds, every other page works, and only / is missing — which looks like a propagation delay rather than a configuration result, so the obvious response is to wait rather than to look.

How to apply

Do not rely on the plugin. Give one page the root explicitly:

---
layout: default
permalink: /
---

Name that file anything but index.md when the repository already has an INDEX.md: on a case-insensitive filesystem (macOS by default) the two are the same file, so creating one overwrites the other. home.md with the permalink above is safe. Exclude README.md from the build if it should not also be served as raw Markdown.