What this error means

Error: Invariant: failed to find source route /[store]/[lang]/c/sitemap.xml for prerender /[store]/[lang]/c/sitemap.xml is a Vercel failure pattern reported for developers trying to fix next.js build/deployment failure with sitemap.xml route handlers in nested dynamic route groups (regression from 16.1.7 to 16.2.0+). Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub issues #94024 and #94041 on vercel/next.js describe a race condition bug in parallel prerendering introduced between Next.js 16.1.7 and 16.2.0. Dynamic force-static sitemap.xml route handlers under nested route groups fail on Vercel but succeed locally. Only consistent on Vercel with 3 parallel build workers. Specific conditions identified (nested groups + sibling [slug] route). Strong commercial impact for production deployments.

Common causes

  • GitHub issues #94024 and #94041 on vercel/next.js describe a race condition bug in parallel prerendering introduced between Next.js 16.1.7 and 16.2.0. Dynamic force-static sitemap.xml route handlers under nested route groups fail on Vercel but succeed locally. Only consistent on Vercel with 3 parallel build workers. Specific conditions identified (nested groups + sibling [slug] route). Strong commercial impact for production deployments.

Quick fixes

  1. Confirm the exact error signature matches Error: Invariant: failed to find source route /[store]/[lang]/c/sitemap.xml for prerender /[store]/[lang]/c/sitemap.xml.
  2. Check the Vercel account, local tool state, and provider configuration involved in the failing workflow.
  3. Check the build output, project root, and deployment platform configuration before redeploying.

Platform/tool-specific checks

  • Verify the command, editor, extension, or API client that produced the error.
  • Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
  • Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

  1. Capture the exact error message and the command, editor action, or request that triggered it.
  2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
  3. Review the source evidence below and compare it with your environment.
  4. Apply one change at a time and rerun the smallest failing action.
  5. Keep the working fix documented for the team or deployment environment.

How to prevent it

  • Keep provider/tool configuration documented.
  • Record non-secret diagnostics such as tool version, provider name, model name, and command path.
  • Add a lightweight check before CI or production workflows depend on the tool.