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Findings: live-API measurements across MiniMax M3/M2.7/M2.5, qwen and deepseek, plus a survey of how nine unified gateways model per-model parameter divergence. Key facts: reasoning_effort is MiniMax's real switch, M2.x reasoning is mandatory and cannot be disabled, and the relay's local token-count fallback silently drops reasoning_tokens. Design: keep the parameter shape at provider level, push capability down to model level, split "unknown" / "unsupported" / "no opinion" into three distinct values, and fail at assembly time when a model cannot honour enable_thinking=False.