Six LLM providers behind one interface

DBWhisper generates SQL through a chain of six providers — OpenAI → OpenRouter → DeepSeek → Groq → Anthropic → Gemini. The first one with credentials wins; Gemini's free tier is the floor.

The point isn't redundancy for its own sake. It's that no single vendor is a hard dependency, and the whole thing still runs at zero LLM spend. A rate-limit or an outage at one provider degrades to the next, not to a 500. On a $0 stack that's not a nice-to-have — it's the only way the product stays up.

The interface is the invariant: generation asks for "SQL for this schema and question," and which model answers is a config detail, not an architecture decision. The full chain is in the DBWhisper case study.