Model comparison
GPT-5-Codex vs Llama 3.1-405B
GPT-5-Codex is the stronger model overall, scoring 37.9 to 30.7 on the Noometry Index.
Last verified . 2 shared benchmarks.
MetaSummary
- They share 2 benchmarks with published results for both. GPT-5-Codex scores higher in 3 categories and Llama 3.1-405B in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5-Codex leads 30.9 to 16.8.
- The biggest single-benchmark swing is WeirdML: 54.5% for GPT-5-Codex and 21.4% for Llama 3.1-405B.
- Llama 3.1-405B has downloadable open weights; the other is API-only.
Side by side
| GPT-5-Codex | Llama 3.1-405B | |
|---|---|---|
| Provider | OpenAI | Meta |
| Noometry Index | 37.9 | 30.7 |
| Released | 2025-09-15 | 2024-07-23 |
| Weights | Proprietary | Open |
| Context window | 400K | — |
| Max output | 128K | — |
| Input $ / M tokens | $1.25 | — |
| Output $ / M tokens | $10 | — |
| Results tracked | 3 | 42 |
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Category by category
Coding GPT-5-Codex leads
GPT-5-Codex: 42.4 (#103), Llama 3.1-405B: 33.1 (#262)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| WeirdML | 54.5% | 21.4% |
| LMArena Coding | — | 1291 |
Agentic & Tool Use GPT-5-Codex leads
GPT-5-Codex: 31.0 (#72), Llama 3.1-405B: 21.0 (#140)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| Terminal-Bench | 44.3% | — |
| TheAgentCompany | — | 7.4% |
| Cybench | — | 7.5% |
Reasoning GPT-5-Codex leads
GPT-5-Codex: 30.9 (#83), Llama 3.1-405B: 16.8 (#300)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| Kagi LLM Benchmark | 70.3% | 45% |
| SimpleBench | — | 23% |
| LMArena Hard Prompts | — | 1269 |
| DTBench | — | 61.4% |
| BIG-Bench Hard | — | 82.9% |
| Epoch Capabilities Index | — | 128.75 |
| ForecastBench | — | 59.9 |
| HellaSwag | — | 89.2% |
| PIQA | — | 85.9% |
| WinoGrande | — | 89.2% |
Math Not comparable
GPT-5-Codex: —, Llama 3.1-405B: 18.4 (#290)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| OTIS Mock AIME 2024-2025 | — | 9.7% |
| Omni-MATH | — | 24.9% |
| LMArena Math | — | 1281 |
| MATH Level 5 | — | 49.8% |
Knowledge Not comparable
GPT-5-Codex: —, Llama 3.1-405B: 30.4 (#227)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| GPQA Diamond | — | 50.9% |
| MMLU-Pro | — | 72.3% |
| Confabulations | — | 17.6% |
| GPQA (HELM) | — | 52.2% |
| LMArena Expert | — | 1243 |
| ARC (AI2) Challenge | — | 95.3% |
| MMLU | — | 84.5% |
| TriviaQA | — | 82.7% |
Multilingual Not comparable
GPT-5-Codex: —, Llama 3.1-405B: 40.7 (#214)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| LMArena Non-English | — | 1248 |
| LMArena Chinese | — | 1242 |
| LMArena French | — | 1279 |
| LMArena German | — | 1252 |
| LMArena Japanese | — | 1208 |
| LMArena Korean | — | 1184 |
| LMArena Russian | — | 1265 |
| LMArena Spanish | — | 1260 |
Instruction Following Not comparable
GPT-5-Codex: —, Llama 3.1-405B: 65.9 (#214)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| IFEval | — | 81.1% |
| LMArena Instruction Following | — | 1259 |
Long Context Not comparable
GPT-5-Codex: —, Llama 3.1-405B: 38.4 (#197)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| LMArena Longer Query | — | 1266 |
Writing & Preference Not comparable
GPT-5-Codex: —, Llama 3.1-405B: 38.9 (#251)
| Benchmark | GPT-5-Codex | Llama 3.1-405B |
|---|---|---|
| LMArena Text | — | 1284 |
| LMArena Creative Writing | — | 1262 |
| EQ-Bench Creative Writing | — | 870 |
| WildBench | — | 78.3% |
| LMArena Multi-Turn | — | 1297 |
Frequently asked questions
Is GPT-5-Codex better than Llama 3.1-405B?
GPT-5-Codex is the stronger model overall, scoring 37.9 to 30.7 on the Noometry Index.
Is GPT-5-Codex or Llama 3.1-405B better for coding?
GPT-5-Codex scores higher on coding benchmarks: 42.4 versus 33.1 in the Noometry coding category.
How many benchmarks do GPT-5-Codex and Llama 3.1-405B share?
2 benchmarks have published results for both models. GPT-5-Codex has 3 scored results on Noometry and Llama 3.1-405B has 42.