Grok 4.1 Fast (Reasoning) is the reasoning-enabled configuration of Grok 4.1 Fast, with extended thinking always active. The model produces explicit chain-of-thought traces before its final answer, delivering higher accuracy on complex analytical tasks at the cost of additional latency. It shares the same 2M-token context window and tool-calling capabilities as the standard variant, making it suited for tasks where correctness on difficult problems justifies the extra thinking time.
xAI SuperGrokxAI SuperGrok HeavyAPI|VisionReasoningWeb Search|Proprietary Model
Knowledge Cutoff
2025-06-01
Input → Output Format
Context Memory
2MIN33KOUT
AI Performance Evaluation
Arena Overall Score
1432
±4As of 2026-05-01
Overall Rank
No.63
48,702 Votes
Arena by Ability
Hard Prompts
1442±4No.77
Expert Knowledge
1441±11No.79
Instruction Following
1401±6No.94
Conversation Memory
1417±7No.87
Creative
1410±7No.53
Coding
1465±6No.81
Math
1423±11No.72
Arena by Occupation
Creative Writing
1403±6No.75
Social Sciences
1450±7No.62
Media
1400±7No.62
Business
1417±7No.76
Healthcare
1447±11No.72
Legal
1427±11No.80
Software
1460±5No.70
Mathematics
1423±13No.76
Source:Arena Intelligence
Overall
AA Intelligence Index
39%↓1%
LiveBench
60%↓1%
ForecastBench
60%↑1%
Reasoning & Math
AA Math Index
89%↑15%
GPQA Diamond
85%↑3%
HLE
18%↑0%
MMLU-Pro
85%↑4%
AIME 2025
89%↑15%
LB Reasoning
80%↑11%
LB Math
84%↑10%
LB Data
52%↓1%
Coding
AA Coding Index
31%↓6%
LiveCodeBench
82%↑17%
LB Coding
70%↓3%
LB Agentic
32%↓13%
TAU2
93%↑13%
TerminalBench
24%↓10%
SciCode
44%↑2%
Language & Instructions
IFBench
53%↓10%
AA-LCR
68%↑6%
Hallucination (HHEM)
19%↑9%
Factual (HHEM)
81%↓9%
LB Language
74%↑2%
LB IF
28%↓23%
Output Speed
Standard Mode
114tok/s↑37
First Output 0.30s
Reasoning Mode
94tok/s↑7
First Output 11.80s
