One of the most important architectural decisions in AI development today: should you lock into one provider's API, or build with an OpenAI-compatible layer that lets you swap models instantly? In 2026, the answer is clear: build OpenAI-compatible from day one. What Is OpenAI Compatibility? OpenAI released the Chat Completions API format — a standardized way to send messages and receive AI responses. Many providers now offer endpoints that accept the exact same format: json POST /v1/chat/completions { "model": "gpt-4", "messages": [ {"role": "user", "content": "Hello!"} ] } If your code works with this format, it works with any OpenAI-compatible provider — without changing a line of code. Why OpenAI Compatibility Matters Avoid Vendor Lock-in If you hardcode gpt-4 everywhere, switching to Claude or Gemini requires rewriting your entire integration. OpenAI-compatible endpoints let you swap providers in one config change. Cost Optimization Different providers price differently.…