404 Error for Translated Versioned Index Document

[LuggaLugga]

Have you read the Contributing Guidelines on issues?

• [x] I have read the Contributing Guidelines on issues.

Prerequisites

• [x] I'm using the latest version of Docusaurus.
• [x] I have tried the npm run clear or yarn clear command.
• [x] I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• [x] I have tried creating a repro with https://new.docusaurus.io.
• [ ] I have read the console error message carefully (if applicable).

Description

For the explanation, it's sufficient to assume that there's only one document, index.mdx, located under /docs. I have versioned this document for versions 1.0.0 and 2.0.0. Version 2.0.0 represents the current version. Additionally, /docs also represents the next version. My documentation is also internationalized into de, alongside the default en.

With this setup, the document should be accessible in English at /1.0.0, /, and /next, and in German at /de/1.0.0, /de, and /de/next. All these paths correctly serve the corresponding document after running npm run build and npm run serve, except for /de/1.0.0, which returns a 404 error.

While searching for the cause of this issue, I noticed the following:

• If I add another versioned and internationalized document intro.mdx to /docs, it is correctly served under /de/1.0.0/intro after running npm run build and npm run serve.

• When I run npm run start -- --locale de, the document is correctly served on every path.

• If I rename the version 1.0.0 to abc, the document is correctly served on all paths after npm run build and npm run serve.

• If I add another versioned and internationalized document index.mdx in /docs/tutorial, this one is also not accessible under /de/1.0.0/tutorial after npm run build and npm run serve.

Reproducible demo

https://github.com/LuggaLugga/docusaurus-bug-demo

Steps to reproduce

1. Build the demo with npm run build
2. Run the demo with npm run serve
3. Navigate to http://localhost:3000/de/1.0.0

Expected behavior

I expect the document from i18n/de/docusaurus-plugin-content-docs/version-1.0.0/index.mdx to be rendered.

Actual behavior

The document from i18n/de/docusaurus-plugin-content-docs/version-1.0.0/index.mdx is not accessible according to the 404 error code.

Your environment

• Public source code: https://github.com/LuggaLugga/docusaurus-bug-demo
• Public site URL: none
• Docusaurus version used: 3.7.0
• Environment name and version (e.g. Chrome 89, Node.js 16.4): Safari 18.04, Node 22.14.0
• Operating system and version (e.g. Ubuntu 20.04.2 LTS): macOS Sequoia 15.4

Self-service

• [ ] I'd be willing to fix this bug myself.

[slorber]

This is not a docusaurus build bug: the expected static file is here: build/de/1.0.0/index.html

This looks like a bug in docusaurus serve, probably coming from our dependency https://github.com/vercel/serve-handler: the /de/1.0.0/ and /de/1.0.0/index.html pathnames always redirect to /de/1.0.0 for some reason.

I can also reproduce by running npx serve build, so it's likely not a Docusaurus bug and should probably be reported to the underlying package that has the bug with a minimal repro.

Using an alternate server works: npx http-server build will serve your page

If you deploy your site on a CDN, it should work fine.