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 62. 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 73.3. The single biggest benchmark swing on the page is MuSR, 82 to 63. Claude Haiku 4.5 does hit back in multimodal & grounded, so the answer changes if that is the part of the workload you care about most.
Claude Haiku 4.5 is also the more expensive model on tokens at $0.80 input / $4.00 output per 1M tokens, versus $0.10 input / $0.30 output per 1M tokens for Step 3.5 Flash. That is roughly 13.3x on output cost alone. Step 3.5 Flash gives you the larger context window at 256K, compared with 200K for Claude Haiku 4.5.
Pick Step 3.5 Flash if you want the stronger benchmark profile. Claude Haiku 4.5 only becomes the better choice if multimodal & grounded is the priority.
Step 3.5 Flash
60.2
Claude Haiku 4.5
56.7
Step 3.5 Flash
47.1
Claude Haiku 4.5
41.7
Step 3.5 Flash
66.7
Claude Haiku 4.5
78.4
Step 3.5 Flash
78.3
Claude Haiku 4.5
68.9
Step 3.5 Flash
60.8
Claude Haiku 4.5
53.6
Step 3.5 Flash
87
Claude Haiku 4.5
86
Step 3.5 Flash
82.8
Claude Haiku 4.5
80.1
Step 3.5 Flash
84.5
Claude Haiku 4.5
73.3
Step 3.5 Flash is ahead overall, 66 to 62. The biggest single separator in this matchup is MuSR, where the scores are 82 and 63.
Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 53.6. 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 41.7. 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 73.3. 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 68.9. 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 56.7. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Claude Haiku 4.5 has the edge for multimodal and grounded tasks in this comparison, averaging 78.4 versus 66.7. Inside this category, MMMU-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 86. 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 80.1. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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