OpenAI-Compatible Gateway Control Plane Checklist

A lot of teams start their LLM stack with one model string in application code. That is fine for prototypes. It becomes painful once multiple products, customers, background jobs, and fallback paths all share the same AI budget. At that point, an OpenAI-compatible gateway should not just be a convenience proxy. It should become a control plane: the place where routing, quotas, cost attribution, keys, and failover are managed consistently. Here is the checklist I use when evaluating whether a gateway setup is production-ready. 1. Keep the SDK surface stable Your application should not need to know every provider-specific header, endpoint, or auth detail. A simple OpenAI-compatible client shape keeps provider changes out of the main code path: from openai import OpenAI import os client = OpenAI ( api_key = os . environ [ " AI_GATEWAY_API_KEY " ], base_url = os . environ . get ( " AI_GATEWAY_BASE_URL " ), ) The app should usually call a logical model or route. Provider-specific decisions should live in gateway configuration where they can be reviewed and changed safely. 2. Route by feature, not by vibes A global default model is easy to start with, but it hides important differences between workloads. A better routing table looks like this: Feature Default tier Fallback tier Budget sensitivity Classification low-cost fast model second low-cost model high Support summary low/mid model mid model high Customer chat mid/frontier model safe fallback medium Coding/analysis strongest reliable model reasoning model low/medium Background enrichment batch/cheap model skip/defer very high The goal is not always to use the cheapest model. The goal is to use the cheapest model that reliably clears the quality bar for that feature. 3. Enforce limits at the gateway boundary Do not rely only on scattered application code for cost control. A shared gateway should enforce: per-API-key quotas per-project or per-customer spend caps per-feature token limits provider and model allow-lists e