Grok 4.1 Fast vs Step 3.5 Flash

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

Grok 4.1 Fast is clearly ahead on the aggregate, 76 to 66. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Grok 4.1 Fast's sharpest advantage is in multimodal & grounded, where it averages 87.4 against 66.7. The single biggest benchmark swing on the page is MMMU-Pro, 91 to 64.

Grok 4.1 Fast gives you the larger context window at 1M, compared with 256K for Step 3.5 Flash.

Quick Verdict

Pick Grok 4.1 Fast if you want the stronger benchmark profile. Step 3.5 Flash only becomes the better choice if its workflow or ecosystem matters more than the raw scoreboard.

Agentic

Grok 4.1 Fast

Grok 4.1 Fast

71

Step 3.5 Flash

60.2

74
Terminal-Bench 2.0
62
73
BrowseComp
66
66
OSWorld-Verified
54

Coding

Grok 4.1 Fast

Grok 4.1 Fast

59.5

Step 3.5 Flash

47.1

86
HumanEval
77
68
SWE-bench Verified
48
54
LiveCodeBench
45
63
SWE-bench Pro
49

Multimodal & Grounded

Grok 4.1 Fast

Grok 4.1 Fast

87.4

Step 3.5 Flash

66.7

91
MMMU-Pro
64
83
OfficeQA Pro
70

Reasoning

Grok 4.1 Fast

Grok 4.1 Fast

88.3

Step 3.5 Flash

78.3

90
SimpleQA
82
88
MuSR
82
87
BBH
83
87
LongBench v2
74
89
MRCRv2
73

Knowledge

Grok 4.1 Fast

Grok 4.1 Fast

69.2

Step 3.5 Flash

60.8

94
MMLU
84
92
GPQA
83
90
SuperGPQA
81
88
OpenBookQA
79
81
MMLU-Pro
76
20
HLE
12
83
FrontierScience
71

Instruction Following

Grok 4.1 Fast

Grok 4.1 Fast

90

Step 3.5 Flash

87

90
IFEval
87

Multilingual

Grok 4.1 Fast

Grok 4.1 Fast

84.8

Step 3.5 Flash

82.8

88
MGSM
86
83
MMLU-ProX
81

Mathematics

Grok 4.1 Fast

Grok 4.1 Fast

92.3

Step 3.5 Flash

84.5

96
AIME 2023
85
98
AIME 2024
87
97
AIME 2025
86
92
HMMT Feb 2023
81
94
HMMT Feb 2024
83
93
HMMT Feb 2025
82
95
BRUMO 2025
84
89
MATH-500
85

Frequently Asked Questions

Which is better, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast is ahead overall, 76 to 66. The biggest single separator in this matchup is MMMU-Pro, where the scores are 91 and 64.

Which is better for knowledge tasks, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast has the edge for knowledge tasks in this comparison, averaging 69.2 versus 60.8. Inside this category, FrontierScience is the benchmark that creates the most daylight between them.

Which is better for coding, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast has the edge for coding in this comparison, averaging 59.5 versus 47.1. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

Which is better for math, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast has the edge for math in this comparison, averaging 92.3 versus 84.5. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.

Which is better for reasoning, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast has the edge for reasoning in this comparison, averaging 88.3 versus 78.3. Inside this category, MRCRv2 is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast has the edge for agentic tasks in this comparison, averaging 71 versus 60.2. 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, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast has the edge for multimodal and grounded tasks in this comparison, averaging 87.4 versus 66.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast 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.

Which is better for multilingual tasks, Grok 4.1 Fast or Step 3.5 Flash?

Grok 4.1 Fast has the edge for multilingual tasks in this comparison, averaging 84.8 versus 82.8. Inside this category, MGSM is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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