Fixing Next.js 15 Dynamic Sitemap Routes: When [id].xml Does Not Match

🤖 Ghostwritten by Claude · Curated by Tom Hundley

This article was written by Claude and curated for publication by Tom Hundley.

By Tom Hundley, Elegant Software Solutions — debugged in collaboration with Claude Code (Opus 4.5)

The Bug That Broke Our Sitemaps

We had a problem: our dynamic blog sitemap at /sitemap-blog-1.xml was returning 404. Google could not fetch it. Our blog posts were not getting indexed.

The route existed. The code was correct. But Next.js 15 refused to match it.

The Setup

We built a paginated sitemap system for our blog. With 50+ posts, we needed dynamic sitemaps that could scale:

src/app/sitemap-blog-[id].xml/route.ts

This should generate:

/sitemap-blog-1.xml
/sitemap-blog-2.xml
etc.

The main sitemap.xml index referenced these URLs. Standard stuff.

But every request to /sitemap-blog-1.xml returned 404.

Debugging with Claude Code

The investigation started with a simple health check using Google Search Console API:

# The symptom
curl -sI https://www.elegantsoftwaresolutions.com/sitemap-blog-1.xml
# HTTP/2 404
# x-matched-path: /_not-found

That x-matched-path: /_not-found header was the clue. Next.js was not matching our route at all.

We verified:

The route file existed
The code was valid TypeScript
It appeared in .next/app-path-routes-manifest.json
But requests never hit the handler

Root Cause: Dynamic Segments + File Extensions Do Not Mix

Next.js 15 App Router has a limitation (or bug) where dynamic segments [param] inside folder names containing file extensions do not get captured properly.

The folder structure:

src/app/sitemap-blog-[id].xml/route.ts
         ^ dynamic segment
                       ^ file extension

Next.js generates a regex pattern to match routes. When you combine [id] with .xml in the same folder name, the regex breaks. The dynamic parameter is never extracted.

This is a known edge case that is not documented.

The Fix: Restructure + Rewrite

Step 1: Clean Folder Structure

Move from a folder name with extension:

# Before (broken)
src/app/sitemap-blog-[id].xml/route.ts

# After (works)
src/app/sitemap-blog/[id]/route.ts

The clean structure sitemap-blog/[id] works because there is no file extension confusing the router.

Step 2: URL Rewrite for SEO

We still want the SEO-friendly .xml URLs. Add a rewrite in next.config.ts:

async rewrites() {
  return [
    {
      // Map /sitemap-blog-1.xml to /sitemap-blog/1
      source: /sitemap-blog-:id.xml,
      destination: /sitemap-blog/:id,
    },
  ];
}

This intercepts the .xml request and routes it internally to the clean path.

Verification

Before the fix:

curl -sI https://example.com/sitemap-blog-1.xml
# HTTP/2 404
# x-matched-path: /_not-found

After the fix:

curl -sI https://example.com/sitemap-blog-1.xml
# HTTP/2 200
# content-type: application/xml; charset=utf-8

Google Search Console successfully fetched the sitemap within minutes of deployment.

Key Takeaways

Avoid dynamic segments in folder names with extensions — Next.js 15 App Router does not handle this well
Use rewrites to preserve URL structure — You can have SEO-friendly URLs while using clean internal routing
Check the x-matched-path header — It tells you exactly what Next.js matched (or did not)
Test sitemaps before relying on them — A 404 sitemap silently breaks your SEO
AI-assisted debugging works — Claude Code traced this issue through logs, headers, and route manifests faster than manual debugging

The Pattern

If you need dynamic routes with file extensions in Next.js 15:

// next.config.ts
async rewrites() {
  return [
    {
      source: /your-route-:param.xml,
      destination: /your-route/:param,
    },
  ];
}

// Folder structure
src/app/your-route/[param]/route.ts

This pattern maintains external URL compatibility while working around the routing limitation.

Closing Thought

This bug cost us indexing time. But finding it with AI assistance took minutes instead of hours. The combination of systematic debugging and Claude Code ability to trace through manifests, headers, and code simultaneously made this a 30-minute fix instead of a half-day investigation.

That is the vibe coding advantage: AI does not just write code — it debugs alongside you.

This bug fix was discovered and implemented during a site health check using Google Search Console MCP tools and Claude Code. The fix was deployed to Vercel and verified in production on December 14, 2025.