Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
Claude Opus 4.5 is clearly ahead on the aggregate, 77 to 66. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Opus 4.5's sharpest advantage is in multimodal & grounded, where it averages 90.9 against 66.7. The single biggest benchmark swing on the page is MMMU-Pro, 94 to 64.
Step 3.5 Flash gives you the larger context window at 256K, compared with 200K for Claude Opus 4.5.
Pick Claude Opus 4.5 if you want the stronger benchmark profile. Step 3.5 Flash only becomes the better choice if you need the larger 256K context window.
Claude Opus 4.5
70.5
Step 3.5 Flash
60.2
Claude Opus 4.5
60.4
Step 3.5 Flash
47.1
Claude Opus 4.5
90.9
Step 3.5 Flash
66.7
Claude Opus 4.5
87.7
Step 3.5 Flash
78.3
Claude Opus 4.5
70.9
Step 3.5 Flash
60.8
Claude Opus 4.5
90
Step 3.5 Flash
87
Claude Opus 4.5
86.1
Step 3.5 Flash
82.8
Claude Opus 4.5
93.2
Step 3.5 Flash
84.5
Claude Opus 4.5 is ahead overall, 77 to 66. The biggest single separator in this matchup is MMMU-Pro, where the scores are 94 and 64.
Claude Opus 4.5 has the edge for knowledge tasks in this comparison, averaging 70.9 versus 60.8. Inside this category, MMLU is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for coding in this comparison, averaging 60.4 versus 47.1. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for math in this comparison, averaging 93.2 versus 84.5. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for reasoning in this comparison, averaging 87.7 versus 78.3. Inside this category, SimpleQA is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for agentic tasks in this comparison, averaging 70.5 versus 60.2. Inside this category, OSWorld-Verified is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for multimodal and grounded tasks in this comparison, averaging 90.9 versus 66.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for instruction following in this comparison, averaging 90 versus 87. Inside this category, IFEval is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for multilingual tasks in this comparison, averaging 86.1 versus 82.8. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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