Claude Opus 4.6 vs Seed 1.6 Flash

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

Claude Opus 4.6 is clearly ahead on the aggregate, 85 to 56. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude Opus 4.6's sharpest advantage is in coding, where it averages 75.1 against 27.6. The single biggest benchmark swing on the page is SWE-bench Verified, 80 to 24.

Claude Opus 4.6 is also the more expensive model on tokens at $15.00 input / $75.00 output per 1M tokens, versus $0.08 input / $0.30 output per 1M tokens for Seed 1.6 Flash. That is roughly 250.0x on output cost alone. Seed 1.6 Flash is the reasoning model in the pair, while Claude Opus 4.6 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. Claude Opus 4.6 gives you the larger context window at 1M, compared with 256K for Seed 1.6 Flash.

Quick Verdict

Pick Claude Opus 4.6 if you want the stronger benchmark profile. Seed 1.6 Flash only becomes the better choice if you want the cheaper token bill or you want the stronger reasoning-first profile.

Agentic

Claude Opus 4.6

Claude Opus 4.6

79.2

Seed 1.6 Flash

54.5

80
Terminal-Bench 2.0
52
85
BrowseComp
62
74
OSWorld-Verified
52

Coding

Claude Opus 4.6

Claude Opus 4.6

75.1

Seed 1.6 Flash

27.6

91
HumanEval
59
80
SWE-bench Verified
24
75
LiveCodeBench
25
74
SWE-bench Pro
31

Multimodal & Grounded

Claude Opus 4.6

Claude Opus 4.6

94.6

Seed 1.6 Flash

73.1

95
MMMU-Pro
74
94
OfficeQA Pro
72

Reasoning

Claude Opus 4.6

Claude Opus 4.6

93.1

Seed 1.6 Flash

66.8

95
SimpleQA
61
93
MuSR
59
94
BBH
75
92
LongBench v2
70
92
MRCRv2
74

Knowledge

Claude Opus 4.6

Claude Opus 4.6

78.9

Seed 1.6 Flash

47.3

99
MMLU
65
97
GPQA
64
95
SuperGPQA
62
93
OpenBookQA
60
92
MMLU-Pro
65
38
HLE
3
88
FrontierScience
57

Instruction Following

Claude Opus 4.6

Claude Opus 4.6

95

Seed 1.6 Flash

81

95
IFEval
81

Multilingual

Claude Opus 4.6

Claude Opus 4.6

94.7

Seed 1.6 Flash

72.8

96
MGSM
76
94
MMLU-ProX
71

Mathematics

Claude Opus 4.6

Claude Opus 4.6

97.2

Seed 1.6 Flash

67.1

99
AIME 2023
64
99
AIME 2024
66
98
AIME 2025
65
95
HMMT Feb 2023
60
97
HMMT Feb 2024
62
96
HMMT Feb 2025
61
96
BRUMO 2025
63
98
MATH-500
72

Frequently Asked Questions

Which is better, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 is ahead overall, 85 to 56. The biggest single separator in this matchup is SWE-bench Verified, where the scores are 80 and 24.

Which is better for knowledge tasks, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for knowledge tasks in this comparison, averaging 78.9 versus 47.3. Inside this category, HLE is the benchmark that creates the most daylight between them.

Which is better for coding, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for coding in this comparison, averaging 75.1 versus 27.6. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

Which is better for math, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for math in this comparison, averaging 97.2 versus 67.1. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.

Which is better for reasoning, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for reasoning in this comparison, averaging 93.1 versus 66.8. Inside this category, SimpleQA is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for agentic tasks in this comparison, averaging 79.2 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 Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for multimodal and grounded tasks in this comparison, averaging 94.6 versus 73.1. Inside this category, OfficeQA Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for instruction following in this comparison, averaging 95 versus 81. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Which is better for multilingual tasks, Claude Opus 4.6 or Seed 1.6 Flash?

Claude Opus 4.6 has the edge for multilingual tasks in this comparison, averaging 94.7 versus 72.8. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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