feat(dev-server): Add .md/.mdx to defaultOptions.exclude

[kenn]

Summary

• exclude .md/.mdx files from dev-server request handling so they pass through Vite
• prevent MDX routes from being treated as HTTP requests by the server adapter

Motivation

Using @mdx-js/rollup with @hono/vite-dev-server causes .mdx files to be intercepted by the dev server and treated as HTTP routes (e.g. No route matches URL "/app/routes/privacy.mdx").

This happens because the default exclude list does not include Markdown/MDX files.

Adding .mdx? avoids the interception and lets Vite handle transforms as intended.

Current Workaround

Users must override the entire exclude list to add MDX support (for a React Router v7 app):

export default defineConfig({
  plugins: [
    serverAdapter({
      entry: 'server/index.ts',
      exclude: [/^\/app\//, /^\/@/, /^\/node_modules\//], // add this line
    })
    mdx(), // must come before reactRouter
    reactRouter(),
    ...

This is error-prone because:

1. The default array isn’t merged (uses ??, not a spread/concat).
2. Users may miss important patterns
3. The workaround isn't documented

Alternatively, we could add a safe way to extend the default excludes, but that would be a lot more work. Supporting .md/.mdx covers a large share of common use cases.

[changeset-bot]

🦋 Changeset detected

Latest commit: 1a0233a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@hono/vite-dev-server	Minor

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[yusukebe]

Hi @kenn

Thank you for the PR. I think this is good. One thing. Can you add a changeset file by running yarn changeset at the top of the project? This is a slight change, but introducing a new feature, so a minor change is okay.

[kenn]

Thanks @yusukebe, done!

[yusukebe]

Thank you @kenn ! I'll merge.