Model comparison
GPT-5.1-Codex vs Grok 4.20
Head-to-head evidence from 3 shared benchmark results across 3 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.1-Codex #99 (Estimated); Grok 4.20 #88 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1-Codex and Grok 4.20 share 3 comparable benchmark results. 0 of 8 categories are comparable. 13 results are unique to GPT-5.1-Codex; 15 to Grok 4.20.
Updated July 23, 2026- Shared results
- 3
- GPT-5.1-Codex only
- 13
- Grok 4.20 only
- 15
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex and Grok 4.20 is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 3 shared benchmark results across 3 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 4.20 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.
| Category | GPT-5.1-Codex | Δ | Grok 4.20 |
|---|---|---|---|
| Agentic | GPT-5.1-CodexNot measured | MarginNo overlap | Grok 4.2047.1 |
| Coding | GPT-5.1-CodexNot measured | MarginNo overlap | Grok 4.2067.1 |
| Reasoning | GPT-5.1-CodexNot measured | MarginNo overlap | Grok 4.2053.3 |
| Multimodal | GPT-5.1-CodexNot measured | MarginNo overlap | Grok 4.2070.1 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.1-Codex | Grok 4.20 | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-CodexNot available | Grok 4.20$2 input / $6 output | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5.1-CodexNot available | Grok 4.20233 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-CodexNot available | Grok 4.2010.33 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex400K | Grok 4.202M | Grok 4.20 lists the larger context window. |
Benchmark Deep Dive
Agentic5 benchmarks
Coding5 benchmarks
Reasoning3 benchmarks
Knowledge10 benchmarks
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | — | Not comparable |
| AA-GPQA DiamondSource | 86.0% | — | Not comparable |
| AA-HLESource | 23.4% | — | Not comparable |
| AA-Omniscience IndexSource | -6.0% | — | Not comparable |
| AA-Omniscience AccuracySource | 39.2% | — | Not comparable |
| AA-Omniscience Hallucination RateSource | 74.4% | — | Not comparable |
| GPQA-DSource | — | 88.5% | Not comparable |
| HLE w/o toolsSource | — | 31.6% | Not comparable |
| HealthBench HardSource | — | 20.3% | Not comparable |
| MedXpertQA (Text)Source | — | 50.2% | Not comparable |
Multimodal7 benchmarks
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Result |
|---|---|---|---|
| AA-MMMU-ProSource | 72.5% | — | Not comparable |
| Design Arena WebsiteSource | 1191 | 1257 | Grok 4.20 leads |
| MMMU-ProSource | — | 75.2% | Not comparable |
| CharXivSource | — | 60.9% | Not comparable |
| ERQASource | — | 54.1% | Not comparable |
| SimpleVQASource | — | 57.4% | Not comparable |
| MedXpertQA (MM)Source | — | 65.8% | Not comparable |
Inst. Following1 benchmarks
| Benchmark | GPT-5.1-Codex | Grok 4.20 | Result |
|---|---|---|---|
| AA-IFBenchSource | 70.0% | — | Not comparable |
Frequently Asked Questions (3)
Can I compare GPT-5.1-Codex and Grok 4.20 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 and Grok 4.20 today?
Grok 4.20: $2.00 input / $6.00 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.