Step 3.5 Flash vs Claude 3.5 Sonnet

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 60. 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 71.2. The single biggest benchmark swing on the page is MuSR, 82 to 61. Claude 3.5 Sonnet does hit back in multimodal & grounded, so the answer changes if that is the part of the workload you care about most.

Step 3.5 Flash gives you the larger context window at 256K, compared with 200K for Claude 3.5 Sonnet.

Quick Verdict

Pick Step 3.5 Flash if you want the stronger benchmark profile. Claude 3.5 Sonnet only becomes the better choice if multimodal & grounded is the priority.

Agentic

Step 3.5 Flash

Step 3.5 Flash

60.2

Claude 3.5 Sonnet

55

62
Terminal-Bench 2.0
54
66
BrowseComp
62
54
OSWorld-Verified
51

Coding

Step 3.5 Flash

Step 3.5 Flash

47.1

Claude 3.5 Sonnet

37.8

77
HumanEval
57
48
SWE-bench Verified
36
45
LiveCodeBench
39
49
SWE-bench Pro
37

Multimodal & Grounded

Claude 3.5 Sonnet

Step 3.5 Flash

66.7

Claude 3.5 Sonnet

74.8

64
MMMU-Pro
77
70
OfficeQA Pro
72

Reasoning

Step 3.5 Flash

Step 3.5 Flash

78.3

Claude 3.5 Sonnet

67.7

82
SimpleQA
63
82
MuSR
61
83
BBH
83
74
LongBench v2
70
73
MRCRv2
70

Knowledge

Step 3.5 Flash

Step 3.5 Flash

60.8

Claude 3.5 Sonnet

50.8

84
MMLU
65
83
GPQA
65
81
SuperGPQA
63
79
OpenBookQA
61
76
MMLU-Pro
74
12
HLE
5
71
FrontierScience
59

Instruction Following

Step 3.5 Flash

Step 3.5 Flash

87

Claude 3.5 Sonnet

83

87
IFEval
83

Multilingual

Step 3.5 Flash

Step 3.5 Flash

82.8

Claude 3.5 Sonnet

80.5

86
MGSM
85
81
MMLU-ProX
78

Mathematics

Step 3.5 Flash

Step 3.5 Flash

84.5

Claude 3.5 Sonnet

71.2

85
AIME 2023
65
87
AIME 2024
67
86
AIME 2025
66
81
HMMT Feb 2023
61
83
HMMT Feb 2024
63
82
HMMT Feb 2025
62
84
BRUMO 2025
64
85
MATH-500
80

Frequently Asked Questions

Which is better, Step 3.5 Flash or Claude 3.5 Sonnet?

Step 3.5 Flash is ahead overall, 66 to 60. The biggest single separator in this matchup is MuSR, where the scores are 82 and 61.

Which is better for knowledge tasks, Step 3.5 Flash or Claude 3.5 Sonnet?

Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 50.8. Inside this category, MMLU is the benchmark that creates the most daylight between them.

Which is better for coding, Step 3.5 Flash or Claude 3.5 Sonnet?

Step 3.5 Flash has the edge for coding in this comparison, averaging 47.1 versus 37.8. Inside this category, HumanEval is the benchmark that creates the most daylight between them.

Which is better for math, Step 3.5 Flash or Claude 3.5 Sonnet?

Step 3.5 Flash has the edge for math in this comparison, averaging 84.5 versus 71.2. 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 Claude 3.5 Sonnet?

Step 3.5 Flash has the edge for reasoning in this comparison, averaging 78.3 versus 67.7. 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 Claude 3.5 Sonnet?

Step 3.5 Flash has the edge for agentic tasks in this comparison, averaging 60.2 versus 55. 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 Claude 3.5 Sonnet?

Claude 3.5 Sonnet has the edge for multimodal and grounded tasks in this comparison, averaging 74.8 versus 66.7. 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 Claude 3.5 Sonnet?

Step 3.5 Flash has the edge for instruction following in this comparison, averaging 87 versus 83. 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 Claude 3.5 Sonnet?

Step 3.5 Flash has the edge for multilingual tasks in this comparison, averaging 82.8 versus 80.5. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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