One thing that does not get enough attention in LLM backend security discussions is how vendor diversity creates new attack surfaces. Most production systems now route across multiple inference providers depending on cost, latency and availability. Each of those providers has different authentication patterns, rate limiting behaviors and response formats. A secure by design approach has to account for the fact that the backend is not a single endpoint anymore but a dynamic mix of 50+ potential vendors depending on what is cheapest and fastest at any given moment. We track that vendor landscape weekly at a7om.com and the fragmentation is real.