Model comparison
GPT-5.1-Codex vs Grok 4.1 Fast (Reasoning)
Head-to-head evidence from 13 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.1-Codex #99 (Estimated); Grok 4.1 Fast (Reasoning) #48 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1-Codex and Grok 4.1 Fast (Reasoning) share 13 comparable benchmark results. 0 of 8 categories are comparable. 3 results are unique to GPT-5.1-Codex; 0 to Grok 4.1 Fast (Reasoning).
Updated July 23, 2026- Shared results
- 13
- GPT-5.1-Codex only
- 3
- Grok 4.1 Fast (Reasoning) only
- 0
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex and Grok 4.1 Fast (Reasoning) is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 13 shared benchmark results across 6 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 4.1 Fast (Reasoning) has the larger context window at 2M, compared with 400K for GPT-5.1-Codex.
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-5.1-Codex | Grok 4.1 Fast (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-CodexNot available | Grok 4.1 Fast (Reasoning)Not available | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5.1-CodexNot available | Grok 4.1 Fast (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-CodexNot available | Grok 4.1 Fast (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex400K | Grok 4.1 Fast (Reasoning)2M | Grok 4.1 Fast (Reasoning) lists the larger context window. |
Benchmark Deep Dive
Agentic3 benchmarks
Coding2 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | GPT-5.1-Codex | Grok 4.1 Fast (Reasoning) | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | 30.6% | GPT-5.1-Codex leads |
| AA-GPQA DiamondSource | 86.0% | 85.3% | GPT-5.1-Codex leads |
| AA-HLESource | 23.4% | 17.6% | GPT-5.1-Codex leads |
| AA-Omniscience IndexSource | -6.0% | -28.7% | GPT-5.1-Codex leads |
| AA-Omniscience AccuracySource | 39.2% | 25.3% | GPT-5.1-Codex leads |
| AA-Omniscience Hallucination RateSource | 74.4% | 72.4% | Grok 4.1 Fast (Reasoning) leads |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.1-Codex | Grok 4.1 Fast (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | 70.0% | 52.7% | GPT-5.1-Codex leads |
Frequently Asked Questions (2)
Can I compare GPT-5.1-Codex and Grok 4.1 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.
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