Model comparison
GPT-5.6 Luna vs Step 5 Preview
GPT-5.6 Luna is the stronger model overall, scoring 54.7 to 43.8 on the Noometry Index.
Last verified . 3 shared benchmarks.
StepFunSummary
- They share 3 benchmarks with published results for both. GPT-5.6 Luna scores higher in 2 categories and Step 5 Preview in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.6 Luna leads 47.5 to 38.0.
- The biggest single-benchmark swing is SciCode: 53.6% for GPT-5.6 Luna and 58.9% for Step 5 Preview.
- GPT-5.6 Luna is cheaper at $0.20 / $1.20 per million input/output tokens, against $1 / $2.70 for Step 5 Preview.
- GPT-5.6 Luna accepts more context: 1.05M tokens versus 1.02M.
Side by side
| GPT-5.6 Luna | Step 5 Preview | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 54.7 | 43.8 |
| Released | 2026-07-09 | 2026-09-16 |
| Weights | Proprietary | Proprietary |
| Context window | 1.05M | 1.02M |
| Max output | 128K | 66K |
| Input $ / M tokens | $0.20 | $1 |
| Output $ / M tokens | $1.20 | $2.70 |
| Results tracked | 51 | 3 |
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Category by category
Coding GPT-5.6 Luna leads
GPT-5.6 Luna: 53.9 (#25), Step 5 Preview: 50.6 (#40)
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| LMArena WebDev | 1517 | 1569 |
| SciCode | 53.6% | 58.9% |
| DeepSWE | 67.2% | — |
| FrontierCode | 39.8% | — |
| CursorBench | 35.9% | — |
| WeirdML | 60.9% | — |
| LMArena Coding | 1466 | — |
| ALE-Bench | 1,667 | — |
Agentic & Tool Use Not comparable
GPT-5.6 Luna: 35.3 (#37), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| BALROG | 45.6% | — |
| GDP.pdf | 22.7% | — |
| Vending-Bench 2 | 4,095 | — |
Reasoning GPT-5.6 Luna leads
GPT-5.6 Luna: 47.5 (#38), Step 5 Preview: 38.0 (#58)
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| CritPt | 20.6% | 20.9% |
| ARC-AGI-2 | 59.5% | — |
| SimpleBench | 46.8% | — |
| Kagi LLM Benchmark | 49.1% | — |
| NYT Connections (extended) | 69.4% | — |
| ARC-AGI-1 | 88% | — |
| Chess Puzzles | 40% | — |
| LMArena Hard Prompts | 1452 | — |
| Mystery Game Puzzles | 21% | — |
| DTBench | 89.1% | — |
| LMCA | 48.5% | — |
| Surface Evolver Bench | 61.9% | — |
| Epoch Capabilities Index | 156.32 | — |
Math Not comparable
GPT-5.6 Luna: 77.5 (#12), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| FrontierMath (Tiers 1-3) | 82.1% | — |
| FrontierMath Tier 4 | 61% | — |
| OTIS Mock AIME 2024-2025 | 98.3% | — |
| ProofBench | 60% | — |
| LMArena Math | 1455 | — |
Knowledge Not comparable
GPT-5.6 Luna: 58.6 (#31), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| GPQA Diamond | 91.6% | — |
| SimpleQA Verified | 41% | — |
| LMArena Expert | 1479 | — |
Multimodal Not comparable
GPT-5.6 Luna: 43.0 (#22), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| LMArena Vision | 1259 | — |
| Blueprint-Bench 2 | 22.6% | — |
| Furniture Assembly | 42.5% | — |
| LMArena Document | 1457 | — |
Multilingual Not comparable
GPT-5.6 Luna: 53.0 (#73), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| LMArena Non-English | 1418 | — |
| LMArena Chinese | 1469 | — |
| LMArena French | 1457 | — |
| LMArena German | 1459 | — |
| LMArena Japanese | 1416 | — |
| LMArena Korean | 1414 | — |
| LMArena Russian | 1428 | — |
| LMArena Spanish | 1445 | — |
Instruction Following Not comparable
GPT-5.6 Luna: 76.0 (#48), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| LMArena Instruction Following | 1440 | — |
Long Context Not comparable
GPT-5.6 Luna: 43.9 (#78), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| LMArena Longer Query | 1437 | — |
Writing & Preference Not comparable
GPT-5.6 Luna: 68.3 (#27), Step 5 Preview: —
| Benchmark | GPT-5.6 Luna | Step 5 Preview |
|---|---|---|
| LMArena Text | 1432 | — |
| LMArena Creative Writing | 1397 | — |
| EQ-Bench Creative Writing | 1829 | — |
| EQ-Bench 4 | 1156 | — |
| LMArena Multi-Turn | 1433 | — |
Frequently asked questions
Is GPT-5.6 Luna better than Step 5 Preview?
GPT-5.6 Luna is the stronger model overall, scoring 54.7 to 43.8 on the Noometry Index.
Which is cheaper, GPT-5.6 Luna or Step 5 Preview?
GPT-5.6 Luna is cheaper. It lists at $0.20 per million input tokens and $1.20 per million output tokens; Step 5 Preview lists at $1 and $2.70.
Is GPT-5.6 Luna or Step 5 Preview better for coding?
GPT-5.6 Luna scores higher on coding benchmarks: 53.9 versus 50.6 in the Noometry coding category.
Which has the bigger context window?
GPT-5.6 Luna does, with 1.05M tokens against 1.02M.
How many benchmarks do GPT-5.6 Luna and Step 5 Preview share?
3 benchmarks have published results for both models. GPT-5.6 Luna has 51 scored results on Noometry and Step 5 Preview has 3.