Root path "/" is missing prerendered HTML file and is excluded from sitemap.xml when using SPA mode #8741

Which project does this relate to?

Start

Describe the bug

These issues occur when using SPA mode:

• Root path "/" is missing prerendered HTML file:
  • The build tool shows: [prerender] - / but dist/client/index.html is missing.
  • For comparison, for [prerender] - /about there is a dist/client/about/index.html file.
• Root path "/" is excluded from sitemap.xml:
  • The build tool creates dist/client/sitemap.xml but the <url /> for / is missing.
  • The dist/client/pages.json file claims that the path is excluded from the sitemap.

Complete minimal reproducer

https://github.com/jonathanpotts/start-spa-prerender-root-repro

Steps to Reproduce the Bug

1. Create a new TanStack Start project by running: npx @tanstack/cli@latest create --non-interactive --no-intent project-name
2. Edit vite.config.ts and add the following configuration for the tanstackStart plugin:

 {
  spa: {
    enabled: true,
    prerender: {
      enabled: true,
    },
  },
  prerender: {
    enabled: true,
  },
  sitemap: {
    host: 'https://localhost:3000',
  },
}

3. Run npm run build
4. Observe that dist/client/index.html is missing and the <url /> for / is missing from dist/client/sitemap.xml

Expected behavior

After running npm run build:

• There is a dist/client/index.html file which contains the static prerender for the / route
• There is a <url /> entry for / in dist/client/sitemap.xml

Screenshots or Videos

No response

Platform

• Start Version: 1.169.3
• OS: Windows
• Browser: N/A
• Browser Version: N/A
• Bundler: vite
• Bundler Version: 8.3.4

Additional context

No response