It is a one-line habit that has saved me more debugging time than any clever abstraction: I log which model actually answered every Claude request. Not which model I asked for. Which one responded. In 2026, with model fallbacks, fast-changing model strings, and routing logic, those are not always the same thing. Here is why the gap exists and what it has caught. The request model and the response model can differ You send model: "claude-fable-5" . You assume Fable 5 answered. Bu...