Model comparison
GPT-5.1-Codex-Max vs Grok Code Fast 1
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-5.1-Codex-Max #90 (Estimated); Grok Code Fast 1 #180 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1-Codex-Max and Grok Code Fast 1 share 11 comparable benchmark results. 0 of 8 categories are comparable. 2 results are unique to GPT-5.1-Codex-Max; 1 to Grok Code Fast 1.
Updated July 20, 2026- Shared results
- 11
- GPT-5.1-Codex-Max only
- 2
- Grok Code Fast 1 only
- 1
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex-Max and Grok Code Fast 1 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.
GPT-5.1-Codex-Max is priced at $1.25 input / $10.00 output per 1M tokens, versus $0.20 input / $1.50 output per 1M tokens for Grok Code Fast 1. GPT-5.1-Codex-Max has the larger context window at 400K, compared with 256K for Grok Code Fast 1.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.1-Codex-Max | Δ | Grok Code Fast 1 |
|---|---|---|---|
| Coding | GPT-5.1-Codex-MaxNot measured | MarginNo overlap | Grok Code Fast 170.8 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.1-Codex-Max | Grok Code Fast 1 | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-Codex-Max$1.25 input / $10 output | Grok Code Fast 1$0.2 input / $1.5 output | Grok Code Fast 1 has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.1-Codex-MaxNot available | Grok Code Fast 1172 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-Codex-MaxNot available | Grok Code Fast 12.81 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex-Max400K | Grok Code Fast 1256K | GPT-5.1-Codex-Max lists the larger context window. |
Benchmark Deep Dive
Agentic1 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Grok Code Fast 1 | Result |
|---|---|---|---|
| τ²-bench resultsSource | 83% | 75.7% | GPT-5.1-Codex-Max leads |
Coding3 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Grok Code Fast 1 | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | 21.6% | GPT-5.1-Codex-Max leads |
| AA-GPQA DiamondSource | 86.0% | 72.7% | GPT-5.1-Codex-Max leads |
| AA-HLESource | 23.4% | 7.5% | GPT-5.1-Codex-Max leads |
| AA-Omniscience IndexSource | -6.0% | -36.0% | GPT-5.1-Codex-Max leads |
| AA-Omniscience AccuracySource | 39.2% | 23.8% | GPT-5.1-Codex-Max leads |
| AA-Omniscience Hallucination RateSource | 74.4% | 78.5% | GPT-5.1-Codex-Max leads |
Multimodal1 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Grok Code Fast 1 | Result |
|---|---|---|---|
| AA-MMMU-ProSource | 72.5% | — | Not comparable |
Inst. Following1 benchmarks
| Benchmark | GPT-5.1-Codex-Max | Grok Code Fast 1 | Result |
|---|---|---|---|
| AA-IFBenchSource | 70.0% | 41.4% | GPT-5.1-Codex-Max leads |
Frequently Asked Questions (3)
Can I compare GPT-5.1-Codex-Max and Grok Code Fast 1 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-5.1-Codex-Max and Grok Code Fast 1 today?
GPT-5.1-Codex-Max: $1.25 input / $10.00 output per 1M tokens Grok Code Fast 1: $0.20 input / $1.50 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
Related Comparisons
Explore More
Choose a model with this week’s evidence
Join 2,000+ readers for ranking moves, pricing changes, and the claims that still need proof.
One email each week. Unsubscribe anytime.