gpt-oss-20b and Grok 4 Fast don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. gpt-oss-20b shipped 27 days before Grok 4 Fast, so benchmark comparisons should account for the intervening progress.

gpt-oss-20b is open weight, while Grok 4 Fast is proprietary.

Direct benchmark comparisons are unavailable — gpt-oss-20b and Grok 4 Fast don't publish scores on any of the same benchmarks.