Model comparison
DeepSeek-V3.1-Terminus vs Step 3.5 Flash
DeepSeek-V3.1-Terminus and Step 3.5 Flash score almost the same on the Noometry Index (43.1 vs 42.3), so choose on price, context window or the category you care about most.
Last verified . 10 shared benchmarks.
DeepSeek
StepFunSummary
- They share 10 benchmarks with published results for both. DeepSeek-V3.1-Terminus scores higher in 5 categories and Step 3.5 Flash in 2 categories; 4 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where DeepSeek-V3.1-Terminus leads 26.4 to 22.2.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $0.27 / $1 for DeepSeek-V3.1-Terminus.
- Step 3.5 Flash accepts more context: 256K tokens versus 164K.
Side by side
| DeepSeek-V3.1-Terminus | Step 3.5 Flash | |
|---|---|---|
| Provider | DeepSeek | StepFun |
| Noometry Index | 43.1 | 42.3 |
| Released | 2025-09-22 | 2026-01-29 |
| Weights | Open | Open |
| Context window | 164K | 256K |
| Max output | 147K | 256K |
| Input $ / M tokens | $0.27 | $0.10 |
| Output $ / M tokens | $1 | $0.30 |
| Results tracked | 16 | 19 |
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Category by category
Coding Too close to call
DeepSeek-V3.1-Terminus: 42.0 (#113), Step 3.5 Flash: 42.4 (#105)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1426 | 1436 |
| SciCode | 40.6% | — |
| ALE-Bench | 745.17 | — |
Reasoning DeepSeek-V3.1-Terminus leads
DeepSeek-V3.1-Terminus: 26.4 (#133), Step 3.5 Flash: 22.2 (#202)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1426 | 1411 |
| Kagi LLM Benchmark | 57.4% | — |
| NYT Connections (extended) | — | 28.4% |
| CritPt | 1.7% | — |
| DTBench | 81.3% | — |
| LMCA | 28.6% | — |
Math Step 3.5 Flash leads
DeepSeek-V3.1-Terminus: 38.5 (#137), Step 3.5 Flash: 42.6 (#84)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1402 | 1408 |
| MathArena Final-Answer Competitions | — | 66.8% |
Knowledge Not comparable
DeepSeek-V3.1-Terminus: —, Step 3.5 Flash: 39.6 (#132)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | — | 1421 |
Multilingual DeepSeek-V3.1-Terminus leads
DeepSeek-V3.1-Terminus: 52.1 (#92), Step 3.5 Flash: 50.5 (#119)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1407 | 1385 |
| LMArena Russian | 1436 | 1385 |
| LMArena Chinese | — | 1447 |
| LMArena French | — | 1421 |
| LMArena German | — | 1405 |
| LMArena Japanese | — | 1354 |
| LMArena Korean | — | 1352 |
| LMArena Spanish | — | 1419 |
Instruction Following Too close to call
DeepSeek-V3.1-Terminus: 74.0 (#106), Step 3.5 Flash: 73.1 (#124)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1404 | 1385 |
Long Context Too close to call
DeepSeek-V3.1-Terminus: 43.4 (#97), Step 3.5 Flash: 42.8 (#117)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1421 | 1402 |
Writing & Preference DeepSeek-V3.1-Terminus leads
DeepSeek-V3.1-Terminus: 61.0 (#92), Step 3.5 Flash: 58.8 (#113)
| Benchmark | DeepSeek-V3.1-Terminus | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1419 | 1403 |
| LMArena Creative Writing | 1403 | 1357 |
| LMArena Multi-Turn | 1411 | 1405 |
Frequently asked questions
Is DeepSeek-V3.1-Terminus better than Step 3.5 Flash?
DeepSeek-V3.1-Terminus and Step 3.5 Flash score almost the same on the Noometry Index (43.1 vs 42.3), so choose on price, context window or the category you care about most.
Which is cheaper, DeepSeek-V3.1-Terminus 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; DeepSeek-V3.1-Terminus lists at $0.27 and $1.
Is DeepSeek-V3.1-Terminus or Step 3.5 Flash better for coding?
They score almost the same on coding (42.0 vs 42.4); test both on your own repository before choosing.
Which has the bigger context window?
Step 3.5 Flash does, with 256K tokens against 164K.
How many benchmarks do DeepSeek-V3.1-Terminus and Step 3.5 Flash share?
10 benchmarks have published results for both models. DeepSeek-V3.1-Terminus has 16 scored results on Noometry and Step 3.5 Flash has 19.