Model comparison
GPT-5 nano vs Grok 4 Fast (Reasoning)
Head-to-head evidence from 0 shared benchmark results across 0 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5 nano #139 (Estimated); Grok 4 Fast (Reasoning) #76 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5 nano and Grok 4 Fast (Reasoning) share 0 comparable benchmark results. 0 of 8 categories are comparable. 0 results are unique to GPT-5 nano; 13 to Grok 4 Fast (Reasoning).
Updated July 23, 2026- Shared results
- 0
- GPT-5 nano only
- 0
- Grok 4 Fast (Reasoning) only
- 13
- Comparable categories
- 0 / 8
Benchmark data for GPT-5 nano and Grok 4 Fast (Reasoning) is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 0 shared benchmark results across 0 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 does not have sourced benchmark coverage for GPT-5 nano yet. This comparison is currently limited to metadata such as context window, reasoning mode, and pricing where available.
Grok 4 Fast (Reasoning) has the larger context window at 2M, compared with 400K for GPT-5 nano.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5 nano | Grok 4 Fast (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5 nano$0.05 input / $0.4 output | Grok 4 Fast (Reasoning)Not available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5 nano137 tok/s | Grok 4 Fast (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5 nano83.30 s | Grok 4 Fast (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5 nano400K | Grok 4 Fast (Reasoning)2M | Grok 4 Fast (Reasoning) lists the larger context window. |
Benchmark Deep Dive
Agentic1 benchmarks
| Benchmark | GPT-5 nano | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| τ²-bench resultsSource | — | 65.8% | Not comparable |
Coding2 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | GPT-5 nano | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | — | 27.4% | Not comparable |
| AA-GPQA DiamondSource | — | 84.7% | Not comparable |
| AA-HLESource | — | 17.0% | Not comparable |
| AA-Omniscience IndexSource | — | -28.4% | Not comparable |
| AA-Omniscience AccuracySource | — | 22.6% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 66.0% | Not comparable |
Multimodal1 benchmarks
| Benchmark | GPT-5 nano | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA-MMMU-ProSource | — | 61.8% | Not comparable |
Inst. Following1 benchmarks
| Benchmark | GPT-5 nano | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 50.5% | Not comparable |
Frequently Asked Questions (3)
Can I compare GPT-5 nano 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-5 nano and Grok 4 Fast (Reasoning) today?
GPT-5 nano: $0.05 input / $0.40 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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