Model comparison
Mercury 2 vs Step 3.5 Flash
Step 3.5 Flash is the stronger model overall, scoring 42.3 to 39.1 on the Noometry Index.
Last verified . 11 shared benchmarks.
StepFunSummary
- They share 11 benchmarks with published results for both. Mercury 2 scores higher in 1 category and Step 3.5 Flash in 6 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in coding, where Step 3.5 Flash leads 42.4 to 33.5.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $0.25 / $0.75 for Mercury 2.
- Step 3.5 Flash accepts more context: 256K tokens versus 128K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.
Side by side
| Mercury 2 | Step 3.5 Flash | |
|---|---|---|
| Provider | Inception | StepFun |
| Noometry Index | 39.1 | 42.3 |
| Released | 2026-02-20 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 128K | 256K |
| Max output | 50K | 256K |
| Input $ / M tokens | $0.25 | $0.10 |
| Output $ / M tokens | $0.75 | $0.30 |
| Results tracked | 17 | 19 |
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Category by category
Coding Step 3.5 Flash leads
Mercury 2: 33.5 (#255), Step 3.5 Flash: 42.4 (#105)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1391 | 1436 |
| LMArena WebDev | 1171 | — |
| SciCode | 38.7% | — |
| WeirdML | 43.2% | — |
| ALE-Bench | 785.58 | — |
Reasoning Mercury 2 leads
Mercury 2: 23.8 (#170), Step 3.5 Flash: 22.2 (#202)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1362 | 1411 |
| NYT Connections (extended) | — | 28.4% |
| CritPt | 0.8% | — |
Math Not comparable
Mercury 2: —, Step 3.5 Flash: 42.6 (#84)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| MathArena Final-Answer Competitions | — | 66.8% |
| LMArena Math | — | 1408 |
Knowledge Step 3.5 Flash leads
Mercury 2: 36.2 (#172), Step 3.5 Flash: 39.6 (#132)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1358 | 1421 |
| Vectara Hallucination Rate | 12.3% | — |
Multilingual Step 3.5 Flash leads
Mercury 2: 46.6 (#157), Step 3.5 Flash: 50.5 (#119)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1331 | 1385 |
| LMArena Chinese | 1417 | 1447 |
| LMArena Russian | 1304 | 1385 |
| LMArena French | — | 1421 |
| LMArena German | — | 1405 |
| LMArena Japanese | — | 1354 |
| LMArena Korean | — | 1352 |
| LMArena Spanish | — | 1419 |
Instruction Following Step 3.5 Flash leads
Mercury 2: 70.2 (#165), Step 3.5 Flash: 73.1 (#124)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1329 | 1385 |
Long Context Step 3.5 Flash leads
Mercury 2: 40.5 (#154), Step 3.5 Flash: 42.8 (#117)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1330 | 1402 |
Writing & Preference Step 3.5 Flash leads
Mercury 2: 53.8 (#155), Step 3.5 Flash: 58.8 (#113)
| Benchmark | Mercury 2 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1355 | 1403 |
| LMArena Creative Writing | 1289 | 1357 |
| LMArena Multi-Turn | 1358 | 1405 |
Frequently asked questions
Is Mercury 2 better than Step 3.5 Flash?
Step 3.5 Flash is the stronger model overall, scoring 42.3 to 39.1 on the Noometry Index.
Which is cheaper, Mercury 2 or Step 3.5 Flash?
Step 3.5 Flash is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; Mercury 2 lists at $0.25 and $0.75.
Is Mercury 2 or Step 3.5 Flash better for coding?
Step 3.5 Flash scores higher on coding benchmarks: 42.4 versus 33.5 in the Noometry coding category.
Which has the bigger context window?
Step 3.5 Flash does, with 256K tokens against 128K.
How many benchmarks do Mercury 2 and Step 3.5 Flash share?
11 benchmarks have published results for both models. Mercury 2 has 17 scored results on Noometry and Step 3.5 Flash has 19.