Claude 3.5 Sonnet vs Seed 1.6 Flash

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

Claude 3.5 Sonnet is clearly ahead on the aggregate, 60 to 56. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude 3.5 Sonnet's sharpest advantage is in coding, where it averages 37.8 against 27.6. The single biggest benchmark swing on the page is LiveCodeBench, 39 to 25.

Seed 1.6 Flash is the reasoning model in the pair, while Claude 3.5 Sonnet 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 200K for Claude 3.5 Sonnet.

Quick Verdict

Pick Claude 3.5 Sonnet if you want the stronger benchmark profile. Seed 1.6 Flash only becomes the better choice if you need the larger 256K context window or you want the stronger reasoning-first profile.

Agentic

Claude 3.5 Sonnet

Claude 3.5 Sonnet

55

Seed 1.6 Flash

54.5

54
Terminal-Bench 2.0
52
62
BrowseComp
62
51
OSWorld-Verified
52

Coding

Claude 3.5 Sonnet

Claude 3.5 Sonnet

37.8

Seed 1.6 Flash

27.6

57
HumanEval
59
36
SWE-bench Verified
24
39
LiveCodeBench
25
37
SWE-bench Pro
31

Multimodal & Grounded

Claude 3.5 Sonnet

Claude 3.5 Sonnet

74.8

Seed 1.6 Flash

73.1

77
MMMU-Pro
74
72
OfficeQA Pro
72

Reasoning

Claude 3.5 Sonnet

Claude 3.5 Sonnet

67.7

Seed 1.6 Flash

66.8

63
SimpleQA
61
61
MuSR
59
83
BBH
75
70
LongBench v2
70
70
MRCRv2
74

Knowledge

Claude 3.5 Sonnet

Claude 3.5 Sonnet

50.8

Seed 1.6 Flash

47.3

65
MMLU
65
65
GPQA
64
63
SuperGPQA
62
61
OpenBookQA
60
74
MMLU-Pro
65
5
HLE
3
59
FrontierScience
57

Instruction Following

Claude 3.5 Sonnet

Claude 3.5 Sonnet

83

Seed 1.6 Flash

81

83
IFEval
81

Multilingual

Claude 3.5 Sonnet

Claude 3.5 Sonnet

80.5

Seed 1.6 Flash

72.8

85
MGSM
76
78
MMLU-ProX
71

Mathematics

Claude 3.5 Sonnet

Claude 3.5 Sonnet

71.2

Seed 1.6 Flash

67.1

65
AIME 2023
64
67
AIME 2024
66
66
AIME 2025
65
61
HMMT Feb 2023
60
63
HMMT Feb 2024
62
62
HMMT Feb 2025
61
64
BRUMO 2025
63
80
MATH-500
72

Frequently Asked Questions

Which is better, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet is ahead overall, 60 to 56. The biggest single separator in this matchup is LiveCodeBench, where the scores are 39 and 25.

Which is better for knowledge tasks, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for knowledge tasks in this comparison, averaging 50.8 versus 47.3. Inside this category, MMLU-Pro is the benchmark that creates the most daylight between them.

Which is better for coding, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for coding in this comparison, averaging 37.8 versus 27.6. Inside this category, LiveCodeBench is the benchmark that creates the most daylight between them.

Which is better for math, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for math in this comparison, averaging 71.2 versus 67.1. Inside this category, MATH-500 is the benchmark that creates the most daylight between them.

Which is better for reasoning, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for reasoning in this comparison, averaging 67.7 versus 66.8. Inside this category, BBH is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for agentic tasks in this comparison, averaging 55 versus 54.5. 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, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for multimodal and grounded tasks in this comparison, averaging 74.8 versus 73.1. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for instruction following in this comparison, averaging 83 versus 81. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Which is better for multilingual tasks, Claude 3.5 Sonnet or Seed 1.6 Flash?

Claude 3.5 Sonnet has the edge for multilingual tasks in this comparison, averaging 80.5 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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