Noometry

Model comparison

Grok 4 Fast vs Mercury 2.5

Grok 4 Fast has enough public results to be ranked (#164); Mercury 2.5 does not yet, so treat this comparison as directional.

Last verified . 0 shared benchmarks.

Grok 4 Fast xAI

39.0

Rank #164 Confirmed

Mercury 2.5 Inception

30.2

Unranked Sparse

Summary

  • The widest gap is in math, where Grok 4 Fast leads 36.1 to 22.4.

Side by side

Grok 4 FastMercury 2.5
ProviderxAIInception
Noometry Index39.030.2
Released2025-09-192026-09-08
WeightsProprietaryProprietary
Context window—260K
Max output—66K
Input $ / M tokens—$0.04
Output $ / M tokens—$0.15
Results tracked302

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Category by category

Coding Not comparable

Grok 4 Fast: 32.3 (#264), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
LMArena WebDev1160—
WeirdML42.9%—
LMArena Coding1429—
ALE-Bench—301.65

Agentic & Tool Use Not comparable

Grok 4 Fast: 29.3 (#80), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
τ²-bench Banking15.7%—
Cybench30%—
LMArena Search1171—

Reasoning Not comparable

Grok 4 Fast: 22.5 (#179), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
ARC-AGI-25.3%—
Kagi LLM Benchmark66.1%—
ARC-AGI-148.5%—
LMArena Hard Prompts1413—
DTBench82.7%—
Epoch Capabilities Index144.21—
ForecastBench60.5—

Math Grok 4 Fast leads

Grok 4 Fast: 36.1 (#126), Mercury 2.5: 22.4

BenchmarkGrok 4 FastMercury 2.5
ProofBench—3%
LMArena Math1419—

Knowledge Not comparable

Grok 4 Fast: 31.5 (#211), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
Vectara Hallucination Rate19.7%—
LMArena Expert1411—

Multilingual Not comparable

Grok 4 Fast: 51.5 (#106), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
LMArena Non-English1397—
LMArena Chinese1458—
LMArena French1433—
LMArena German1383—
LMArena Japanese1358—
LMArena Korean1359—
LMArena Russian1387—
LMArena Spanish1414—

Instruction Following Not comparable

Grok 4 Fast: 73.4 (#116), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
LMArena Instruction Following1388—

Long Context Not comparable

Grok 4 Fast: 63.2 (#3), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
Fiction.LiveBench94.4%—
LMArena Longer Query1415—

Writing & Preference Not comparable

Grok 4 Fast: 60.2 (#96), Mercury 2.5: —

BenchmarkGrok 4 FastMercury 2.5
LMArena Text1407—
LMArena Creative Writing1388—
LMArena Multi-Turn1414—

Frequently asked questions

Is Grok 4 Fast better than Mercury 2.5?

Grok 4 Fast has enough public results to be ranked (#164); Mercury 2.5 does not yet, so treat this comparison as directional.

How many benchmarks do Grok 4 Fast and Mercury 2.5 share?

0 benchmarks have published results for both models. Grok 4 Fast has 30 scored results on Noometry and Mercury 2.5 has 2.

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