Model comparison
Claude Opus 4.8 vs GPT-5.6 Luna
Claude Opus 4.8 is the stronger model overall, scoring 60.7 to 54.6 on the Noometry Index. GPT-5.6 Luna costs 22× less per token, which makes it the better buy when Claude Opus 4.8's lead doesn't matter for your workload.
Last verified . 50 shared benchmarks.
Summary
- They share 50 benchmarks with published results for both. Claude Opus 4.8 scores higher in 10 categories and GPT-5.6 Luna in 0 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Opus 4.8 leads 64.7 to 47.6.
- The biggest single-benchmark swing is Kagi LLM Benchmark: 88.8% for Claude Opus 4.8 and 49.1% for GPT-5.6 Luna.
- GPT-5.6 Luna is cheaper at $0.20 / $1.20 per million input/output tokens, against $5 / $25 for Claude Opus 4.8.
- GPT-5.6 Luna accepts more context: 1.05M tokens versus 1M.
Side by side
| Claude Opus 4.8 | GPT-5.6 Luna | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 60.7 | 54.6 |
| Released | 2026-05-28 | 2026-07-09 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $5 | $0.20 |
| Output $ / M tokens | $25 | $1.20 |
| Results tracked | 65 | 52 |
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Category by category
Coding Claude Opus 4.8 leads
Claude Opus 4.8: 59.9 (#12), GPT-5.6 Luna: 54.5 (#28)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| DeepSWE | 59% | 67.2% |
| FrontierCode | 46.5% | 39.8% |
| LMArena WebDev | 1556 | 1519 |
| SciCode | 53.5% | 53.6% |
| WeirdML | 82.9% | 60.9% |
| LMArena Coding | 1490 | 1466 |
| ALE-Bench | 1,564 | 1,667 |
| CursorBench | — | 35.9% |
| GSO | 47.1% | — |
Agentic & Tool Use Claude Opus 4.8 leads
Claude Opus 4.8: 47.6 (#11), GPT-5.6 Luna: 34.4 (#45)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| APEX-Agents | 48.9% | 43% |
| GDP.pdf | 24% | 22.7% |
| Vending-Bench 2 | 5,787 | 4,095 |
| OSWorld 2.0 | 20.6% | — |
| Remote Labor Index | 8.3% | — |
| τ²-bench Banking | 39.7% | — |
| DeepResearch Bench | 50.2% | — |
| PostTrainBench | 33.8% | — |
| BALROG | — | 45.6% |
| GBAEval | 70.9% | — |
| LMArena Search | 1204 | — |
Reasoning Claude Opus 4.8 leads
Claude Opus 4.8: 64.7 (#16), GPT-5.6 Luna: 47.6 (#43)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| ARC-AGI-2 | 72.1% | 59.5% |
| SimpleBench | 64.8% | 46.8% |
| Kagi LLM Benchmark | 88.8% | 49.1% |
| NYT Connections (extended) | 91.1% | 69.4% |
| ARC-AGI-1 | 92.5% | 88% |
| CritPt | 20.9% | 20.6% |
| Chess Puzzles | 34% | 40% |
| LMArena Hard Prompts | 1482 | 1451 |
| Mystery Game Puzzles | 36% | 21% |
| DTBench | 94.9% | 89.1% |
| LMCA | 57.5% | 48.5% |
| Surface Evolver Bench | 87.5% | 61.9% |
| Epoch Capabilities Index | 158.21 | 156.39 |
| EnigmaEval | 23.5% | — |
| EBR-Bench | 28.6% | — |
| Bench to the Future 3 | 0.14 | — |
| ForecastBench | 59.9 | — |
Math Too close to call
Claude Opus 4.8: 78.4 (#13), GPT-5.6 Luna: 77.7 (#14)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| FrontierMath (Tiers 1-3) | 80% | 82.1% |
| FrontierMath Tier 4 | 56.1% | 61% |
| OTIS Mock AIME 2024-2025 | 98.3% | 98.3% |
| ProofBench | 69% | 60% |
| LMArena Math | 1487 | 1458 |
| MathArena Final-Answer Competitions | 91.8% | — |
| FrontierMath (Feb 2025 set) | 47.2% | — |
| FrontierMath Tier 4 (v1) | 31.3% | — |
Knowledge Claude Opus 4.8 leads
Claude Opus 4.8: 61.3 (#29), GPT-5.6 Luna: 58.5 (#34)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| GPQA Diamond | 91% | 91.6% |
| SimpleQA Verified | 53% | 41% |
| LMArena Expert | 1502 | 1478 |
Multimodal Too close to call
Claude Opus 4.8: 42.9 (#26), GPT-5.6 Luna: 42.7 (#28)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| LMArena Vision | 1294 | 1258 |
| Blueprint-Bench 2 | 14.5% | 22.6% |
| Furniture Assembly | 42.5% | 42.5% |
| LMArena Document | 1475 | 1457 |
Multilingual Claude Opus 4.8 leads
Claude Opus 4.8: 55.2 (#33), GPT-5.6 Luna: 52.8 (#78)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| LMArena Non-English | 1450 | 1417 |
| LMArena Chinese | 1507 | 1470 |
| LMArena French | 1481 | 1456 |
| LMArena German | 1472 | 1454 |
| LMArena Japanese | 1440 | 1411 |
| LMArena Korean | 1432 | 1415 |
| LMArena Russian | 1474 | 1428 |
| LMArena Spanish | 1466 | 1448 |
Instruction Following Claude Opus 4.8 leads
Claude Opus 4.8: 77.4 (#24), GPT-5.6 Luna: 75.6 (#57)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| LMArena Instruction Following | 1476 | 1437 |
Long Context Claude Opus 4.8 leads
Claude Opus 4.8: 45.4 (#35), GPT-5.6 Luna: 43.9 (#82)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| LMArena Longer Query | 1483 | 1436 |
Writing & Preference Claude Opus 4.8 leads
Claude Opus 4.8: 72.0 (#16), GPT-5.6 Luna: 68.0 (#29)
| Benchmark | Claude Opus 4.8 | GPT-5.6 Luna |
|---|---|---|
| LMArena Text | 1461 | 1431 |
| LMArena Creative Writing | 1454 | 1396 |
| EQ-Bench Creative Writing | 1840 | 1829 |
| EQ-Bench 4 | 1281 | 1156 |
| LMArena Multi-Turn | 1476 | 1434 |
Frequently asked questions
Is Claude Opus 4.8 better than GPT-5.6 Luna?
Claude Opus 4.8 is the stronger model overall, scoring 60.7 to 54.6 on the Noometry Index. GPT-5.6 Luna costs 22× less per token, which makes it the better buy when Claude Opus 4.8's lead doesn't matter for your workload.
Which is cheaper, Claude Opus 4.8 or GPT-5.6 Luna?
GPT-5.6 Luna is cheaper. It lists at $0.20 per million input tokens and $1.20 per million output tokens; Claude Opus 4.8 lists at $5 and $25.
Is Claude Opus 4.8 or GPT-5.6 Luna better for coding?
Claude Opus 4.8 scores higher on coding benchmarks: 59.9 versus 54.5 in the Noometry coding category.
Which has the bigger context window?
GPT-5.6 Luna does, with 1.05M tokens against 1M.
How many benchmarks do Claude Opus 4.8 and GPT-5.6 Luna share?
50 benchmarks have published results for both models. Claude Opus 4.8 has 65 scored results on Noometry and GPT-5.6 Luna has 52.