Model comparison
GPT-5.1-Codex vs GPT-5.4 nano
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); GPT-5.4 nano #25 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1-Codex and GPT-5.4 nano share 13 comparable benchmark results. 0 of 8 categories are comparable. 3 results are unique to GPT-5.1-Codex; 16 to GPT-5.4 nano.
Updated July 23, 2026- Shared results
- 13
- GPT-5.1-Codex only
- 3
- GPT-5.4 nano only
- 16
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex and GPT-5.4 nano 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.
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 | GPT-5.4 nano |
|---|---|---|---|
| Agentic | GPT-5.1-CodexNot measured | MarginNo overlap | GPT-5.4 nano42.9 |
| Knowledge | GPT-5.1-CodexNot measured | MarginNo overlap | GPT-5.4 nano43.8 |
| Math | GPT-5.1-CodexNot measured | MarginNo overlap | GPT-5.4 nano21.0 |
| Multimodal | GPT-5.1-CodexNot measured | MarginNo overlap | GPT-5.4 nano66.1 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.1-Codex | GPT-5.4 nano | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-CodexNot available | GPT-5.4 nano$0.2 input / $1.25 output | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5.1-CodexNot available | GPT-5.4 nano191 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-CodexNot available | GPT-5.4 nano3.64 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex400K | GPT-5.4 nano400K | Listed context windows are equal. |
Benchmark Deep Dive
Agentic11 benchmarks
| Benchmark | GPT-5.1-Codex | GPT-5.4 nano | Result |
|---|---|---|---|
| τ²-bench resultsSource | 83% | 76% | GPT-5.1-Codex leads |
| Gert LabsSource | 49.68% | — | Not comparable |
| JobBenchSource | 26.2% | — | Not comparable |
| Terminal-Bench 2.0Source | — | 46.3% | Not comparable |
| OSWorld-VerifiedSource | — | 39% | Not comparable |
| MCP AtlasSource | — | 56.1% | Not comparable |
| ToolathlonSource | — | 35.5% | Not comparable |
| AA Agentic IndexSource | — | 27.5% | Not comparable |
| APEX-Agents-AASource | — | 24.9% | Not comparable |
| GDPval-AASource | — | 30.0% | Not comparable |
| GDPval-AASource | — | 1100 | Not comparable |
Coding3 benchmarks
Reasoning2 benchmarks
Knowledge9 benchmarks
| Benchmark | GPT-5.1-Codex | GPT-5.4 nano | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | 38.2% | GPT-5.4 nano leads |
| AA-GPQA DiamondSource | 86.0% | 81.7% | GPT-5.1-Codex leads |
| AA-HLESource | 23.4% | 26.5% | GPT-5.4 nano leads |
| AA-Omniscience IndexSource | -6.0% | -29.5% | GPT-5.1-Codex leads |
| AA-Omniscience AccuracySource | 39.2% | 25.4% | GPT-5.1-Codex leads |
| AA-Omniscience Hallucination RateSource | 74.4% | 73.6% | GPT-5.4 nano leads |
| GPQASource | — | 82.8% | Not comparable |
| HLESource | — | 37.7% | Not comparable |
| HLE w/o toolsSource | — | 24.3% | Not comparable |
Math2 benchmarks
Multimodal4 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.1-Codex | GPT-5.4 nano | Result |
|---|---|---|---|
| AA-IFBenchSource | 70.0% | 75.9% | GPT-5.4 nano leads |
Frequently Asked Questions (3)
Can I compare GPT-5.1-Codex and GPT-5.4 nano 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 GPT-5.4 nano today?
GPT-5.4 nano: $0.20 input / $1.25 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.