Model comparison
GPT-6 Luna vs Grok 4 Fast
GPT-6 Luna is the stronger model overall, scoring 45.1 to 39.0 on the Noometry Index.
Last verified . 14 shared benchmarks.
Summary
- They share 14 benchmarks with published results for both. GPT-6 Luna scores higher in 4 categories and Grok 4 Fast in 4 categories; 6 gaps are clear of the uncertainty.
- The widest gap is in coding, where GPT-6 Luna leads 54.7 to 32.3.
Side by side
| GPT-6 Luna | Grok 4 Fast | |
|---|---|---|
| Provider | OpenAI | xAI |
| Noometry Index | 45.1 | 39.0 |
| Released | 2026-09-22 | 2025-09-19 |
| Weights | Proprietary | Proprietary |
| Context window | 1.05M | — |
| Max output | 128K | — |
| Input $ / M tokens | $0.10 | — |
| Output $ / M tokens | $0.50 | — |
| Results tracked | 18 | 30 |
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Category by category
Coding GPT-6 Luna leads
GPT-6 Luna: 54.7 (#24), Grok 4 Fast: 32.3 (#264)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena WebDev | 1583 | 1160 |
| LMArena Coding | 1448 | 1429 |
| DeepSWE | 66.6% | — |
| FrontierCode | 42.4% | — |
| WeirdML | — | 42.9% |
Agentic & Tool Use Not comparable
GPT-6 Luna: —, Grok 4 Fast: 29.3 (#80)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| τ²-bench Banking | — | 15.7% |
| Cybench | — | 30% |
| LMArena Search | — | 1171 |
Reasoning GPT-6 Luna leads
GPT-6 Luna: 31.7 (#68), Grok 4 Fast: 22.5 (#179)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena Hard Prompts | 1415 | 1413 |
| ARC-AGI-2 | — | 5.3% |
| Kagi LLM Benchmark | — | 66.1% |
| NYT Connections (extended) | 68.7% | — |
| ARC-AGI-1 | — | 48.5% |
| DTBench | — | 82.7% |
| Epoch Capabilities Index | — | 144.21 |
| ForecastBench | — | 60.5 |
Math Too close to call
GPT-6 Luna: 35.6 (#140), Grok 4 Fast: 36.1 (#126)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena Math | 1396 | 1419 |
Knowledge GPT-6 Luna leads
GPT-6 Luna: 40.1 (#110), Grok 4 Fast: 31.5 (#211)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena Expert | 1458 | 1411 |
| Vectara Hallucination Rate | — | 19.7% |
Multimodal Not comparable
GPT-6 Luna: 42.0 (#27), Grok 4 Fast: —
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| Furniture Assembly | 44.2% | — |
Multilingual Too close to call
GPT-6 Luna: 51.0 (#111), Grok 4 Fast: 51.5 (#106)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena Non-English | 1390 | 1397 |
| LMArena Chinese | 1425 | 1458 |
| LMArena Russian | 1392 | 1387 |
| LMArena Spanish | 1416 | 1414 |
| LMArena French | — | 1433 |
| LMArena German | — | 1383 |
| LMArena Japanese | — | 1358 |
| LMArena Korean | — | 1359 |
Instruction Following GPT-6 Luna leads
GPT-6 Luna: 74.7 (#85), Grok 4 Fast: 73.4 (#116)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena Instruction Following | 1414 | 1388 |
Long Context Grok 4 Fast leads
GPT-6 Luna: 43.3 (#95), Grok 4 Fast: 63.2 (#3)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena Longer Query | 1417 | 1415 |
| Fiction.LiveBench | — | 94.4% |
Writing & Preference Grok 4 Fast leads
GPT-6 Luna: 58.4 (#115), Grok 4 Fast: 60.2 (#96)
| Benchmark | GPT-6 Luna | Grok 4 Fast |
|---|---|---|
| LMArena Text | 1392 | 1407 |
| LMArena Creative Writing | 1357 | 1388 |
| LMArena Multi-Turn | 1400 | 1414 |
Frequently asked questions
Is GPT-6 Luna better than Grok 4 Fast?
GPT-6 Luna is the stronger model overall, scoring 45.1 to 39.0 on the Noometry Index.
Is GPT-6 Luna or Grok 4 Fast better for coding?
GPT-6 Luna scores higher on coding benchmarks: 54.7 versus 32.3 in the Noometry coding category.
How many benchmarks do GPT-6 Luna and Grok 4 Fast share?
14 benchmarks have published results for both models. GPT-6 Luna has 18 scored results on Noometry and Grok 4 Fast has 30.