The model you asked for is not always the model that answers

A router's catalogue name and the weights that actually run can differ, and nothing in the request will tell you. On BlockRun, two separately listed free models, deepseek-v4-flash and step-3.7-flash, both return responses reporting nvidia/gpt-oss-120b. Neither advertised model is reachable under its own name.

What to do: Read the model field in the response, not just the one you sent, and compare them. Where a response does not echo a model id, treat the choice as advisory. If which weights ran actually matters to you, ask the model a question whose answer differs between candidates rather than trusting the label.

Observed 2026-08-07 across 36 free calls to blockrun.ai/api/v1/chat/completions. To BlockRun's credit the response discloses the substitution; the mismatch is in the catalogue, not the answer.