HTTP Status 506 - Variant Also Negotiates

GET /document HTTP/1.1
Host: www.example.com
Accept: application/pdf, text/html
Negotiate: trans

HTTP/1.1 506 Variant Also Negotiates
Content-Type: application/json

{
  "error": "variant_negotiation_error",
  "message": "Server configuration error in content negotiation",
  "details": "Circular reference detected in variant selection",
  "resource": "/document",
  "issue": "Variant /document.pdf is configured to negotiate, creating infinite loop",
  "contact": "Contact system administrator"
}

GET /api/data HTTP/1.1
Host: api.example.com
Accept: application/json, application/xml
Negotiate: 1.0

HTTP/1.1 506 Variant Also Negotiates
Content-Type: text/plain

Error: Transparent Content Negotiation configuration error.

The requested resource is configured with circular variant references:
  - /api/data -> negotiates between /api/data.json and /api/data.xml
  - /api/data.json -> also configured to negotiate

This creates an infinite negotiation loop.
Server administrator must fix variant configuration.

GET /content/article HTTP/1.1
Host: cdn.example.com
Accept-Language: en, de
Accept: text/html, application/xhtml+xml
Negotiate: trans

HTTP/1.1 506 Variant Also Negotiates
Content-Type: application/json

{
  "status": 506,
  "error": "negotiation_loop",
  "message": "Cannot determine best variant due to configuration error",
  "resource": "/content/article",
  "variants_affected": [
    "/content/article.en.html",
    "/content/article.de.html"
  ],
  "problem": "One or more variants are themselves configured for negotiation",
  "action": "Server misconfiguration - contact support"
}