DeepSeek Chat (R1-based) and GPT-5 nano don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. DeepSeek Chat (R1-based) shipped 199 days before GPT-5 nano, so benchmark comparisons should account for the intervening progress.

DeepSeek Chat (R1-based) is open weight, while GPT-5 nano is proprietary.

Direct benchmark comparisons are unavailable — DeepSeek Chat (R1-based) and GPT-5 nano don't publish scores on any of the same benchmarks.