Llama 3.1 405B vs Seed 1.6 Flash

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

Llama 3.1 405B has the cleaner overall profile here, landing at 59 versus 56. It is a real lead, but still close enough that category-level strengths matter more than the headline number.

Llama 3.1 405B's sharpest advantage is in coding, where it averages 40.6 against 27.6. The single biggest benchmark swing on the page is SWE-bench Verified, 46 to 24. Seed 1.6 Flash does hit back in multimodal & grounded, so the answer changes if that is the part of the workload you care about most.

Seed 1.6 Flash is the reasoning model in the pair, while Llama 3.1 405B is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. Seed 1.6 Flash gives you the larger context window at 256K, compared with 128K for Llama 3.1 405B.

Quick Verdict

Pick Llama 3.1 405B if you want the stronger benchmark profile. Seed 1.6 Flash only becomes the better choice if multimodal & grounded is the priority or you need the larger 256K context window.

Agentic

Seed 1.6 Flash

Llama 3.1 405B

53.9

Seed 1.6 Flash

54.5

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

Coding

Llama 3.1 405B

Llama 3.1 405B

40.6

Seed 1.6 Flash

27.6

62
HumanEval
59
46
SWE-bench Verified
24
37
LiveCodeBench
25
43
SWE-bench Pro
31

Multimodal & Grounded

Seed 1.6 Flash

Llama 3.1 405B

62.3

Seed 1.6 Flash

73.1

60
MMMU-Pro
74
65
OfficeQA Pro
72

Reasoning

Llama 3.1 405B

Llama 3.1 405B

68.3

Seed 1.6 Flash

66.8

68
SimpleQA
61
66
MuSR
59
82
BBH
75
68
LongBench v2
70
65
MRCRv2
74

Knowledge

Llama 3.1 405B

Llama 3.1 405B

53.2

Seed 1.6 Flash

47.3

70
MMLU
65
70
GPQA
64
68
SuperGPQA
62
66
OpenBookQA
60
71
MMLU-Pro
65
7
HLE
3
65
FrontierScience
57

Instruction Following

Llama 3.1 405B

Llama 3.1 405B

86

Seed 1.6 Flash

81

86
IFEval
81

Multilingual

Llama 3.1 405B

Llama 3.1 405B

80.1

Seed 1.6 Flash

72.8

84
MGSM
76
78
MMLU-ProX
71

Mathematics

Llama 3.1 405B

Llama 3.1 405B

74.9

Seed 1.6 Flash

67.1

70
AIME 2023
64
72
AIME 2024
66
71
AIME 2025
65
66
HMMT Feb 2023
60
68
HMMT Feb 2024
62
67
HMMT Feb 2025
61
69
BRUMO 2025
63
82
MATH-500
72

Frequently Asked Questions

Which is better, Llama 3.1 405B or Seed 1.6 Flash?

Llama 3.1 405B is ahead overall, 59 to 56. The biggest single separator in this matchup is SWE-bench Verified, where the scores are 46 and 24.

Which is better for knowledge tasks, Llama 3.1 405B or Seed 1.6 Flash?

Llama 3.1 405B has the edge for knowledge tasks in this comparison, averaging 53.2 versus 47.3. Inside this category, FrontierScience is the benchmark that creates the most daylight between them.

Which is better for coding, Llama 3.1 405B or Seed 1.6 Flash?

Llama 3.1 405B has the edge for coding in this comparison, averaging 40.6 versus 27.6. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

Which is better for math, Llama 3.1 405B or Seed 1.6 Flash?

Llama 3.1 405B has the edge for math in this comparison, averaging 74.9 versus 67.1. Inside this category, MATH-500 is the benchmark that creates the most daylight between them.

Which is better for reasoning, Llama 3.1 405B or Seed 1.6 Flash?

Llama 3.1 405B has the edge for reasoning in this comparison, averaging 68.3 versus 66.8. Inside this category, MRCRv2 is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Llama 3.1 405B or Seed 1.6 Flash?

Seed 1.6 Flash has the edge for agentic tasks in this comparison, averaging 54.5 versus 53.9. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.

Which is better for multimodal and grounded tasks, Llama 3.1 405B or Seed 1.6 Flash?

Seed 1.6 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 73.1 versus 62.3. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, Llama 3.1 405B or Seed 1.6 Flash?

Llama 3.1 405B has the edge for instruction following in this comparison, averaging 86 versus 81. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Which is better for multilingual tasks, Llama 3.1 405B or Seed 1.6 Flash?

Llama 3.1 405B has the edge for multilingual tasks in this comparison, averaging 80.1 versus 72.8. Inside this category, MGSM is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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