Model comparison
Mercury 2 vs Step 5 Preview
Step 5 Preview is the stronger model overall, scoring 47.9 to 39.1 on the Noometry Index. Mercury 2 costs 3.8× less per token, which makes it the better buy when Step 5 Preview's lead doesn't matter for your workload.
Last verified . 14 shared benchmarks.
StepFunSummary
- They share 14 benchmarks with published results for both. Mercury 2 scores higher in 0 categories and Step 5 Preview in 7 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in coding, where Step 5 Preview leads 51.8 to 33.5.
- The biggest single-benchmark swing is SciCode: 38.7% for Mercury 2 and 58.9% for Step 5 Preview.
- Mercury 2 is cheaper at $0.25 / $0.75 per million input/output tokens, against $1 / $2.70 for Step 5 Preview.
- Step 5 Preview accepts more context: 1.02M tokens versus 128K.
Side by side
| Mercury 2 | Step 5 Preview | |
|---|---|---|
| Provider | Inception | StepFun |
| Noometry Index | 39.1 | 47.9 |
| Released | 2026-02-20 | 2026-09-16 |
| Weights | Proprietary | Proprietary |
| Context window | 128K | 1.02M |
| Max output | 50K | 66K |
| Input $ / M tokens | $0.25 | $1 |
| Output $ / M tokens | $0.75 | $2.70 |
| Results tracked | 17 | 18 |
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Category by category
Coding Step 5 Preview leads
Mercury 2: 33.5 (#255), Step 5 Preview: 51.8 (#36)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| LMArena WebDev | 1171 | 1564 |
| SciCode | 38.7% | 58.9% |
| LMArena Coding | 1391 | 1480 |
| WeirdML | 43.2% | — |
| ALE-Bench | 785.58 | — |
Reasoning Step 5 Preview leads
Mercury 2: 23.8 (#170), Step 5 Preview: 40.0 (#57)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| CritPt | 0.8% | 20.9% |
| LMArena Hard Prompts | 1362 | 1465 |
Math Not comparable
Mercury 2: —, Step 5 Preview: 46.1 (#72)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| ProofBench | — | 42% |
| LMArena Math | — | 1470 |
Knowledge Step 5 Preview leads
Mercury 2: 36.2 (#172), Step 5 Preview: 41.2 (#112)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| LMArena Expert | 1358 | 1470 |
| Vectara Hallucination Rate | 12.3% | — |
Multimodal Not comparable
Mercury 2: —, Step 5 Preview: 41.0 (#41)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| LMArena Vision | — | 1267 |
Multilingual Step 5 Preview leads
Mercury 2: 46.6 (#157), Step 5 Preview: 53.8 (#54)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| LMArena Non-English | 1331 | 1432 |
| LMArena Chinese | 1417 | 1519 |
| LMArena Russian | 1304 | 1436 |
| LMArena Spanish | — | 1439 |
Instruction Following Step 5 Preview leads
Mercury 2: 70.2 (#165), Step 5 Preview: 76.0 (#50)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| LMArena Instruction Following | 1329 | 1444 |
Long Context Step 5 Preview leads
Mercury 2: 40.5 (#154), Step 5 Preview: 44.5 (#64)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| LMArena Longer Query | 1330 | 1455 |
Writing & Preference Step 5 Preview leads
Mercury 2: 53.8 (#155), Step 5 Preview: 62.8 (#71)
| Benchmark | Mercury 2 | Step 5 Preview |
|---|---|---|
| LMArena Text | 1355 | 1442 |
| LMArena Creative Writing | 1289 | 1410 |
| LMArena Multi-Turn | 1358 | 1447 |
Frequently asked questions
Is Mercury 2 better than Step 5 Preview?
Step 5 Preview is the stronger model overall, scoring 47.9 to 39.1 on the Noometry Index. Mercury 2 costs 3.8× less per token, which makes it the better buy when Step 5 Preview's lead doesn't matter for your workload.
Which is cheaper, Mercury 2 or Step 5 Preview?
Mercury 2 is cheaper. It lists at $0.25 per million input tokens and $0.75 per million output tokens; Step 5 Preview lists at $1 and $2.70.
Is Mercury 2 or Step 5 Preview better for coding?
Step 5 Preview scores higher on coding benchmarks: 51.8 versus 33.5 in the Noometry coding category.
Which has the bigger context window?
Step 5 Preview does, with 1.02M tokens against 128K.
How many benchmarks do Mercury 2 and Step 5 Preview share?
14 benchmarks have published results for both models. Mercury 2 has 17 scored results on Noometry and Step 5 Preview has 18.