When an AI product grows beyond the first prototype, the model question usually becomes more complicated. You may want GPT for general reasoning, Claude for long-context analysis, Gemini for multimodal workflows, DeepSeek for cost-sensitive reasoning, and Qwen or another Chinese LLM for Chinese-language product testing. The hard part is not only choosing a model. The hard part is testing several models without turning your codebase into a collection of provider-specific SDKs, API keys, request formats, and billing flows. This post shows a simple pattern: use one OpenAI-compatible API gateway, keep the request shape stable, and compare multiple global and Chinese LLMs from the same application code.…