Step 3.5 Flash vs DeepSeek V3.1

Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.

Step 3.5 Flash is clearly ahead on the aggregate, 66 to 35. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Step 3.5 Flash's sharpest advantage is in mathematics, where it averages 84.5 against 44.2. The single biggest benchmark swing on the page is MuSR, 82 to 29.

Step 3.5 Flash gives you the larger context window at 256K, compared with 128K for DeepSeek V3.1.

Quick Verdict

Pick Step 3.5 Flash if you want the stronger benchmark profile. DeepSeek V3.1 only becomes the better choice if its workflow or ecosystem matters more than the raw scoreboard.

Agentic

Step 3.5 Flash

Step 3.5 Flash

60.2

DeepSeek V3.1

32.9

62
Terminal-Bench 2.0
29
66
BrowseComp
39
54
OSWorld-Verified
33

Coding

Step 3.5 Flash

Step 3.5 Flash

47.1

DeepSeek V3.1

14.8

77
HumanEval
25
48
SWE-bench Verified
13
45
LiveCodeBench
15
49
SWE-bench Pro
15

Multimodal & Grounded

Step 3.5 Flash

Step 3.5 Flash

66.7

DeepSeek V3.1

39.5

64
MMMU-Pro
35
70
OfficeQA Pro
45

Reasoning

Step 3.5 Flash

Step 3.5 Flash

78.3

DeepSeek V3.1

40.7

82
SimpleQA
31
82
MuSR
29
83
BBH
61
74
LongBench v2
46
73
MRCRv2
48

Knowledge

Step 3.5 Flash

Step 3.5 Flash

60.8

DeepSeek V3.1

30.5

84
MMLU
33
83
GPQA
32
81
SuperGPQA
30
79
OpenBookQA
28
76
MMLU-Pro
53
12
HLE
2
71
FrontierScience
37

Instruction Following

Step 3.5 Flash

Step 3.5 Flash

87

DeepSeek V3.1

67

87
IFEval
67

Multilingual

Step 3.5 Flash

Step 3.5 Flash

82.8

DeepSeek V3.1

60.8

86
MGSM
64
81
MMLU-ProX
59

Mathematics

Step 3.5 Flash

Step 3.5 Flash

84.5

DeepSeek V3.1

44.2

85
AIME 2023
33
87
AIME 2024
35
86
AIME 2025
34
81
HMMT Feb 2023
29
83
HMMT Feb 2024
31
82
HMMT Feb 2025
30
84
BRUMO 2025
32
85
MATH-500
59

Frequently Asked Questions

Which is better, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash is ahead overall, 66 to 35. The biggest single separator in this matchup is MuSR, where the scores are 82 and 29.

Which is better for knowledge tasks, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 30.5. Inside this category, MMLU is the benchmark that creates the most daylight between them.

Which is better for coding, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for coding in this comparison, averaging 47.1 versus 14.8. Inside this category, HumanEval is the benchmark that creates the most daylight between them.

Which is better for math, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for math in this comparison, averaging 84.5 versus 44.2. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.

Which is better for reasoning, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for reasoning in this comparison, averaging 78.3 versus 40.7. Inside this category, MuSR is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for agentic tasks in this comparison, averaging 60.2 versus 32.9. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

Which is better for multimodal and grounded tasks, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 66.7 versus 39.5. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for instruction following in this comparison, averaging 87 versus 67. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Which is better for multilingual tasks, Step 3.5 Flash or DeepSeek V3.1?

Step 3.5 Flash has the edge for multilingual tasks in this comparison, averaging 82.8 versus 60.8. Inside this category, MGSM is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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