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 44. 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 48.3. The single biggest benchmark swing on the page is MuSR, 82 to 34.
Claude 4.1 Opus Thinking is the reasoning model in the pair, while Step 3.5 Flash 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. Step 3.5 Flash gives you the larger context window at 256K, compared with 200K for Claude 4.1 Opus Thinking.
Pick Step 3.5 Flash if you want the stronger benchmark profile. Claude 4.1 Opus Thinking only becomes the better choice if you want the stronger reasoning-first profile.
Step 3.5 Flash
60.2
Claude 4.1 Opus Thinking
46.7
Step 3.5 Flash
47.1
Claude 4.1 Opus Thinking
21.8
Step 3.5 Flash
66.7
Claude 4.1 Opus Thinking
59.3
Step 3.5 Flash
78.3
Claude 4.1 Opus Thinking
49.4
Step 3.5 Flash
60.8
Claude 4.1 Opus Thinking
34.3
Step 3.5 Flash
87
Claude 4.1 Opus Thinking
66
Step 3.5 Flash
82.8
Claude 4.1 Opus Thinking
58.7
Step 3.5 Flash
84.5
Claude 4.1 Opus Thinking
48.3
Step 3.5 Flash is ahead overall, 66 to 44. The biggest single separator in this matchup is MuSR, where the scores are 82 and 34.
Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 34.3. Inside this category, MMLU is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for coding in this comparison, averaging 47.1 versus 21.8. Inside this category, HumanEval is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for math in this comparison, averaging 84.5 versus 48.3. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for reasoning in this comparison, averaging 78.3 versus 49.4. Inside this category, MuSR is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for agentic tasks in this comparison, averaging 60.2 versus 46.7. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 66.7 versus 59.3. Inside this category, OfficeQA Pro is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for instruction following in this comparison, averaging 87 versus 66. Inside this category, IFEval is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for multilingual tasks in this comparison, averaging 82.8 versus 58.7. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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