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 30. 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 37. The single biggest benchmark swing on the page is HumanEval, 77 to 14.
Step 3.5 Flash is also the more expensive model on tokens at $0.10 input / $0.30 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for LFM2.5-1.2B-Instruct. That is roughly Infinityx on output cost alone. Step 3.5 Flash gives you the larger context window at 256K, compared with 32K for LFM2.5-1.2B-Instruct.
Pick Step 3.5 Flash if you want the stronger benchmark profile. LFM2.5-1.2B-Instruct only becomes the better choice if you want the cheaper token bill.
Step 3.5 Flash
60.2
LFM2.5-1.2B-Instruct
25.7
Step 3.5 Flash
47.1
LFM2.5-1.2B-Instruct
7.2
Step 3.5 Flash
66.7
LFM2.5-1.2B-Instruct
32.4
Step 3.5 Flash
78.3
LFM2.5-1.2B-Instruct
32.1
Step 3.5 Flash
60.8
LFM2.5-1.2B-Instruct
26
Step 3.5 Flash
87
LFM2.5-1.2B-Instruct
80
Step 3.5 Flash
82.8
LFM2.5-1.2B-Instruct
60.7
Step 3.5 Flash
84.5
LFM2.5-1.2B-Instruct
37
Step 3.5 Flash is ahead overall, 66 to 30. The biggest single separator in this matchup is HumanEval, where the scores are 77 and 14.
Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 26. 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 7.2. 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 37. 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 32.1. 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 25.7. 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 32.4. 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 80. 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 60.7. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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