Noometry

Model comparison

Grok 4.1 Fast vs Kimi K2.5 Instant

Kimi K2.5 Instant is the stronger model overall, scoring 43.6 to 41.4 on the Noometry Index.

Last verified . 18 shared benchmarks.

Grok 4.1 Fast xAI

41.4

Rank #136 Confirmed

Kimi K2.5 Instant Moonshot AI

43.6

Rank #89 Confirmed

Summary

  • They share 18 benchmarks with published results for both. Grok 4.1 Fast scores higher in 1 category and Kimi K2.5 Instant in 8 categories; 9 gaps are clear of the uncertainty.
  • The widest gap is in reasoning, where Grok 4.1 Fast leads 43.4 to 29.7.
  • Kimi K2.5 Instant has downloadable open weights; the other is API-only.

Side by side

Grok 4.1 FastKimi K2.5 Instant
ProviderxAIMoonshot AI
Noometry Index41.443.6
Released2025-06-27—
WeightsProprietaryOpen
Context window128K—
Max output30K—
Input $ / M tokens$0.20—
Output $ / M tokens$0.50—
Results tracked3218

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Category by category

Coding Kimi K2.5 Instant leads

Grok 4.1 Fast: 34.1 (#245), Kimi K2.5 Instant: 42.6 (#97)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena WebDev12421404
LMArena Coding14111484
ALE-Bench394.93—

Agentic & Tool Use Not comparable

Grok 4.1 Fast: 36.3 (#39), Kimi K2.5 Instant: —

BenchmarkGrok 4.1 FastKimi K2.5 Instant
Berkeley Function Calling Leaderboard69.6%—
τ²-bench Banking13.1%—
LMArena Search1171—
Vending-Bench 21,107—

Reasoning Grok 4.1 Fast leads

Grok 4.1 Fast: 43.4 (#49), Kimi K2.5 Instant: 29.7 (#90)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Hard Prompts14071443
SimpleBench56%—
NYT Connections (extended)87.4%—
DTBench87.7%—
ForecastBench61—

Math Kimi K2.5 Instant leads

Grok 4.1 Fast: 31.9 (#221), Kimi K2.5 Instant: 39.4 (#105)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Math14081442
MathArena Final-Answer Competitions60.9%—
ProofBench4%—

Knowledge Kimi K2.5 Instant leads

Grok 4.1 Fast: 33.1 (#207), Kimi K2.5 Instant: 40.2 (#123)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Expert13991440
Vectara Hallucination Rate17.8%—

Multimodal Kimi K2.5 Instant leads

Grok 4.1 Fast: 37.0 (#76), Kimi K2.5 Instant: 40.2 (#50)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Vision12011254

Multilingual Kimi K2.5 Instant leads

Grok 4.1 Fast: 51.0 (#114), Kimi K2.5 Instant: 52.0 (#94)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Non-English13911406
LMArena Chinese14411449
LMArena French14151403
LMArena German14041413
LMArena Korean13611378
LMArena Russian13871404
LMArena Spanish14131447
LMArena Japanese1349—

Instruction Following Kimi K2.5 Instant leads

Grok 4.1 Fast: 72.7 (#133), Kimi K2.5 Instant: 75.3 (#65)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Instruction Following13761430

Long Context Kimi K2.5 Instant leads

Grok 4.1 Fast: 42.4 (#126), Kimi K2.5 Instant: 43.9 (#83)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Longer Query13901435

Writing & Preference Kimi K2.5 Instant leads

Grok 4.1 Fast: 57.2 (#131), Kimi K2.5 Instant: 60.6 (#95)

BenchmarkGrok 4.1 FastKimi K2.5 Instant
LMArena Text14081420
LMArena Creative Writing13941381
LMArena Multi-Turn13891427
EQ-Bench Creative Writing1327—

Frequently asked questions

Is Grok 4.1 Fast better than Kimi K2.5 Instant?

Kimi K2.5 Instant is the stronger model overall, scoring 43.6 to 41.4 on the Noometry Index.

Is Grok 4.1 Fast or Kimi K2.5 Instant better for coding?

Kimi K2.5 Instant scores higher on coding benchmarks: 42.6 versus 34.1 in the Noometry coding category.

How many benchmarks do Grok 4.1 Fast and Kimi K2.5 Instant share?

18 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Kimi K2.5 Instant has 18.

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