Model comparison
GPT-OSS 120B vs Grok 4 Fast (Reasoning)
Head-to-head evidence from 11 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-OSS 120B #116 (Supported); Grok 4 Fast (Reasoning) #76 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-OSS 120B and Grok 4 Fast (Reasoning) share 11 comparable benchmark results. 0 of 8 categories are comparable. 15 results are unique to GPT-OSS 120B; 2 to Grok 4 Fast (Reasoning).
Updated July 23, 2026- Shared results
- 11
- GPT-OSS 120B only
- 15
- Grok 4 Fast (Reasoning) only
- 2
- Comparable categories
- 0 / 8
Benchmark data for GPT-OSS 120B and Grok 4 Fast (Reasoning) is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 11 shared benchmark results across 5 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Grok 4 Fast (Reasoning) has the larger context window at 2M, compared with 128K for GPT-OSS 120B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-OSS 120B | Grok 4 Fast (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-OSS 120B$0 input / $0 output | Grok 4 Fast (Reasoning)Not available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-OSS 120B262 tok/s | Grok 4 Fast (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-OSS 120B0.79 s | Grok 4 Fast (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-OSS 120B128K | Grok 4 Fast (Reasoning)2M | Grok 4 Fast (Reasoning) lists the larger context window. |
Benchmark Deep Dive
Agentic8 benchmarks
| Benchmark | GPT-OSS 120B | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA Agentic IndexSource | 13.2% | — | Not comparable |
| APEX-Agents-AASource | 3.1% | — | Not comparable |
| τ²-bench resultsSource | 65.8% | 65.8% | Tie |
| GDPval-AASource | 15.0% | — | Not comparable |
| GDPval-AASource | 799 | — | Not comparable |
| Gert LabsSource | 29.61% | — | Not comparable |
| AA EnterpriseOps-GymSource | 25.5% | — | Not comparable |
| AA ITBenchSource | 5.6% | — | Not comparable |
Coding5 benchmarks
Reasoning2 benchmarks
Knowledge8 benchmarks
| Benchmark | GPT-OSS 120B | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 23.8% | 27.4% | Grok 4 Fast (Reasoning) leads |
| AA-GPQA DiamondSource | 78.2% | 84.7% | Grok 4 Fast (Reasoning) leads |
| AA-HLESource | 18.5% | 17.0% | GPT-OSS 120B leads |
| AA-Omniscience IndexSource | -50.0% | -28.4% | Grok 4 Fast (Reasoning) leads |
| AA-Omniscience AccuracySource | 21.5% | 22.6% | Grok 4 Fast (Reasoning) leads |
| AA-Omniscience Hallucination RateSource | 91.2% | 66.0% | Grok 4 Fast (Reasoning) leads |
| AA Openness IndexSource | 38.9% | — | Not comparable |
| AA MMLU-ProSource | 80.8% | — | Not comparable |
Math1 benchmarks
| Benchmark | GPT-OSS 120B | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA AIME 2025Source | 93.4% | — | Not comparable |
Multilingual1 benchmarks
| Benchmark | GPT-OSS 120B | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA Global-MMLU-LiteSource | 82.8% | — | Not comparable |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-OSS 120B | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | 69.0% | 50.5% | GPT-OSS 120B leads |
Frequently Asked Questions (3)
Can I compare GPT-OSS 120B and Grok 4 Fast (Reasoning) on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for GPT-OSS 120B and Grok 4 Fast (Reasoning) today?
GPT-OSS 120B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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