Grok 4.1 Fast vs LFM2.5-1.2B-Instruct

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 30. 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 reasoning, where it averages 88.3 against 32.1. The single biggest benchmark swing on the page is HumanEval, 86 to 14.

Grok 4.1 Fast gives you the larger context window at 1M, compared with 32K for LFM2.5-1.2B-Instruct.

Quick Verdict

Pick Grok 4.1 Fast if you want the stronger benchmark profile. LFM2.5-1.2B-Instruct 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

LFM2.5-1.2B-Instruct

25.7

74
Terminal-Bench 2.0
22
73
BrowseComp
31
66
OSWorld-Verified
26

Coding

Grok 4.1 Fast

Grok 4.1 Fast

59.5

LFM2.5-1.2B-Instruct

7.2

86
HumanEval
14
68
SWE-bench Verified
9
54
LiveCodeBench
8
63
SWE-bench Pro
6

Multimodal & Grounded

Grok 4.1 Fast

Grok 4.1 Fast

87.4

LFM2.5-1.2B-Instruct

32.4

91
MMMU-Pro
27
83
OfficeQA Pro
39

Reasoning

Grok 4.1 Fast

Grok 4.1 Fast

88.3

LFM2.5-1.2B-Instruct

32.1

90
SimpleQA
24
88
MuSR
22
87
BBH
59
87
LongBench v2
34
89
MRCRv2
37

Knowledge

Grok 4.1 Fast

Grok 4.1 Fast

69.2

LFM2.5-1.2B-Instruct

26

94
MMLU
26
92
GPQA
25
90
SuperGPQA
23
88
OpenBookQA
21
81
MMLU-Pro
50
20
HLE
1
83
FrontierScience
30

Instruction Following

Grok 4.1 Fast

Grok 4.1 Fast

90

LFM2.5-1.2B-Instruct

80

90
IFEval
80

Multilingual

Grok 4.1 Fast

Grok 4.1 Fast

84.8

LFM2.5-1.2B-Instruct

60.7

88
MGSM
62
83
MMLU-ProX
60

Mathematics

Grok 4.1 Fast

Grok 4.1 Fast

92.3

LFM2.5-1.2B-Instruct

37

96
AIME 2023
24
98
AIME 2024
26
97
AIME 2025
25
92
HMMT Feb 2023
20
94
HMMT Feb 2024
22
93
HMMT Feb 2025
21
95
BRUMO 2025
23
89
MATH-500
54

Frequently Asked Questions

Which is better, Grok 4.1 Fast or LFM2.5-1.2B-Instruct?

Grok 4.1 Fast is ahead overall, 76 to 30. The biggest single separator in this matchup is HumanEval, where the scores are 86 and 14.

Which is better for knowledge tasks, Grok 4.1 Fast or LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for knowledge tasks in this comparison, averaging 69.2 versus 26. Inside this category, MMLU is the benchmark that creates the most daylight between them.

Which is better for coding, Grok 4.1 Fast or LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for coding in this comparison, averaging 59.5 versus 7.2. Inside this category, HumanEval is the benchmark that creates the most daylight between them.

Which is better for math, Grok 4.1 Fast or LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for math in this comparison, averaging 92.3 versus 37. 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 LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for reasoning in this comparison, averaging 88.3 versus 32.1. Inside this category, SimpleQA is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Grok 4.1 Fast or LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for agentic tasks in this comparison, averaging 71 versus 25.7. 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 LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for multimodal and grounded tasks in this comparison, averaging 87.4 versus 32.4. 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 LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for instruction following in this comparison, averaging 90 versus 80. 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 LFM2.5-1.2B-Instruct?

Grok 4.1 Fast has the edge for multilingual tasks in this comparison, averaging 84.8 versus 60.7. Inside this category, MGSM is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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