Client-side fetch HTTP methods match handler exports

A client calls fetch('/api/posts', { method: 'DELETE' }) but the route handler at app/api/posts/route.ts only exports GET and POST. Next.js and every other App Router framework respond with HTTP 405 Method Not Allowed — the server is reachable, the path resolves, but the method is refused. This is a reference-integrity failure that neither the bundler nor tsc can catch because HTTP methods are stringly-typed, and the error only surfaces when the user clicks the delete button.

Add the missing method export to the route handler so the server accepts the request shape the client sends. Open the route file and export a named function per method:

// app/api/posts/route.ts
export async function GET() { /* ... */ }
export async function POST() { /* ... */ }
export async function DELETE() { /* ... */ }

Or change the client to use a method the handler already exports.

• ID: ai-slop-hallucinations.route-references.client-fetch-methods-match

• Severity: high

• What to look for: For every relative fetch URL that successfully resolves to a route file (per the previous check), extract the HTTP method used: fetch(url, { method: "POST" }), axios.post(url), axios.delete(url), ky.put(url), etc. If no method is specified, default to GET. Then read the resolved route file and check whether it exports a function named for that method (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS). Count all method-method comparisons made, total matched, total mismatched.

• Pass criteria: 100% of fetch calls use a method that is exported by the resolved route handler. Report: "X method comparisons checked, Y matched, 0 mismatched."

• Fail criteria: At least 1 fetch call uses a method that the resolved route handler does not export (e.g., fetch('/api/users', { method: 'DELETE' }) but app/api/users/route.ts only exports GET and POST).

• Skip (N/A) when: Project has no API routes detected, OR no relative fetch URLs were found in the previous check.

• Detail on fail: "2 method mismatches: fetch('/api/posts', { method: 'DELETE' }) in src/components/PostCard.tsx — route handler exports GET, POST only. fetch('/api/auth/login', { method: 'GET' }) — route handler exports POST only."

• Remediation: A method mismatch returns HTTP 405 (Method Not Allowed) in production. AI tools sometimes generate a route handler that exports the wrong methods, or a client that calls the wrong method. Add the missing method to the route handler:

  // app/api/posts/route.ts
  export async function GET() { /* ... */ }
  export async function POST() { /* ... */ }
  export async function DELETE() { /* add this */ }
  

  Or fix the client to use the correct method.