Step 3.5 Flash vs Llama 3.1 405B

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 59. 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 reasoning, where it averages 78.3 against 68.3. The single biggest benchmark swing on the page is MuSR, 82 to 66.

Step 3.5 Flash gives you the larger context window at 256K, compared with 128K for Llama 3.1 405B.

Quick Verdict

Pick Step 3.5 Flash if you want the stronger benchmark profile. Llama 3.1 405B 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

Llama 3.1 405B

53.9

62
Terminal-Bench 2.0
53
66
BrowseComp
58
54
OSWorld-Verified
52

Coding

Step 3.5 Flash

Step 3.5 Flash

47.1

Llama 3.1 405B

40.6

77
HumanEval
62
48
SWE-bench Verified
46
45
LiveCodeBench
37
49
SWE-bench Pro
43

Multimodal & Grounded

Step 3.5 Flash

Step 3.5 Flash

66.7

Llama 3.1 405B

62.3

64
MMMU-Pro
60
70
OfficeQA Pro
65

Reasoning

Step 3.5 Flash

Step 3.5 Flash

78.3

Llama 3.1 405B

68.3

82
SimpleQA
68
82
MuSR
66
83
BBH
82
74
LongBench v2
68
73
MRCRv2
65

Knowledge

Step 3.5 Flash

Step 3.5 Flash

60.8

Llama 3.1 405B

53.2

84
MMLU
70
83
GPQA
70
81
SuperGPQA
68
79
OpenBookQA
66
76
MMLU-Pro
71
12
HLE
7
71
FrontierScience
65

Instruction Following

Step 3.5 Flash

Step 3.5 Flash

87

Llama 3.1 405B

86

87
IFEval
86

Multilingual

Step 3.5 Flash

Step 3.5 Flash

82.8

Llama 3.1 405B

80.1

86
MGSM
84
81
MMLU-ProX
78

Mathematics

Step 3.5 Flash

Step 3.5 Flash

84.5

Llama 3.1 405B

74.9

85
AIME 2023
70
87
AIME 2024
72
86
AIME 2025
71
81
HMMT Feb 2023
66
83
HMMT Feb 2024
68
82
HMMT Feb 2025
67
84
BRUMO 2025
69
85
MATH-500
82

Frequently Asked Questions

Which is better, Step 3.5 Flash or Llama 3.1 405B?

Step 3.5 Flash is ahead overall, 66 to 59. The biggest single separator in this matchup is MuSR, where the scores are 82 and 66.

Which is better for knowledge tasks, Step 3.5 Flash or Llama 3.1 405B?

Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 53.2. Inside this category, MMLU is the benchmark that creates the most daylight between them.

Which is better for coding, Step 3.5 Flash or Llama 3.1 405B?

Step 3.5 Flash has the edge for coding in this comparison, averaging 47.1 versus 40.6. Inside this category, HumanEval is the benchmark that creates the most daylight between them.

Which is better for math, Step 3.5 Flash or Llama 3.1 405B?

Step 3.5 Flash has the edge for math in this comparison, averaging 84.5 versus 74.9. 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 Llama 3.1 405B?

Step 3.5 Flash has the edge for reasoning in this comparison, averaging 78.3 versus 68.3. 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 Llama 3.1 405B?

Step 3.5 Flash has the edge for agentic tasks in this comparison, averaging 60.2 versus 53.9. 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 Llama 3.1 405B?

Step 3.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 66.7 versus 62.3. Inside this category, OfficeQA Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, Step 3.5 Flash or Llama 3.1 405B?

Step 3.5 Flash has the edge for instruction following in this comparison, averaging 87 versus 86. 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 Llama 3.1 405B?

Step 3.5 Flash has the edge for multilingual tasks in this comparison, averaging 82.8 versus 80.1. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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