Noometry

Model comparison

Claude Fable 5.1 vs Step 3

Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 40.5 on the Noometry Index.

Last verified . 16 shared benchmarks.

Claude Fable 5.1 Anthropic

69.0

Rank #2 Confirmed

Step 3 StepFun

40.5

Rank #149 Confirmed

Summary

  • They share 16 benchmarks with published results for both. Claude Fable 5.1 scores higher in 9 categories and Step 3 in 0 categories; 9 gaps are clear of the uncertainty.
  • The widest gap is in math, where Claude Fable 5.1 leads 89.6 to 37.6.
  • Step 3 has downloadable open weights; the other is API-only.

Side by side

Claude Fable 5.1Step 3
ProviderAnthropicStepFun
Noometry Index69.040.5
Released2026-09-01—
WeightsProprietaryOpen
Context window1M—
Max output128K—
Input $ / M tokens$10—
Output $ / M tokens$50—
Results tracked5217

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Category by category

Coding Claude Fable 5.1 leads

Claude Fable 5.1: 74.7 (#1), Step 3: 40.1 (#147)

BenchmarkClaude Fable 5.1Step 3
LMArena Coding15281367
FrontierCode50.9%—
CursorBench51.8%—
LMArena WebDev1744—
FrontierSWE56.3%—
SciCode63.1%—
GSO88.2%—
WeirdML92.9%—
MirrorCode73.3%—
ALE-Bench2,143—

Agentic & Tool Use Not comparable

Claude Fable 5.1: 50.7 (#5), Step 3: —

BenchmarkClaude Fable 5.1Step 3
APEX-Agents68.6%—
Remote Labor Index17.9%—
GDP.pdf29.6%—
Vending-Bench 25,422—

Reasoning Claude Fable 5.1 leads

Claude Fable 5.1: 76.7 (#7), Step 3: 28.4 (#105)

BenchmarkClaude Fable 5.1Step 3
LMArena Hard Prompts15261355
ARC-AGI-290%—
Kagi LLM Benchmark—62.3%
NYT Connections (extended)90%—
ARC-AGI-197.5%—
CritPt31.1%—
Chess Puzzles47%—
EBR-Bench57.1%—
Mystery Game Puzzles58%—
DTBench97.6%—
LMCA65.5%—
Epoch Capabilities Index164.7—

Math Claude Fable 5.1 leads

Claude Fable 5.1: 89.6 (#4), Step 3: 37.6 (#148)

BenchmarkClaude Fable 5.1Step 3
LMArena Math15251366
FrontierMath (Tiers 1-3)90.2%—
FrontierMath Tier 487.8%—
OTIS Mock AIME 2024-2025100%—
ProofBench100%—
FrontierMath Erdős0%—

Knowledge Claude Fable 5.1 leads

Claude Fable 5.1: 69.6 (#6), Step 3: 36.8 (#164)

BenchmarkClaude Fable 5.1Step 3
LMArena Expert15351333
Humanity's Last Exam46.5%—
SimpleQA Verified70.8%—

Multimodal Claude Fable 5.1 leads

Claude Fable 5.1: 53.9 (#4), Step 3: 35.5 (#86)

BenchmarkClaude Fable 5.1Step 3
LMArena Vision13181177
Blueprint-Bench 241.9%—
Furniture Assembly70%—
LMArena Document1513—

Multilingual Claude Fable 5.1 leads

Claude Fable 5.1: 59.1 (#3), Step 3: 46.3 (#159)

BenchmarkClaude Fable 5.1Step 3
LMArena Non-English15071327
LMArena Chinese15861397
LMArena German15001371
LMArena Korean15341269
LMArena Russian15211331
LMArena Spanish15161371
LMArena French1525—
LMArena Japanese1543—

Instruction Following Claude Fable 5.1 leads

Claude Fable 5.1: 79.2 (#6), Step 3: 70.4 (#164)

BenchmarkClaude Fable 5.1Step 3
LMArena Instruction Following15171332

Long Context Claude Fable 5.1 leads

Claude Fable 5.1: 46.7 (#20), Step 3: 40.3 (#157)

BenchmarkClaude Fable 5.1Step 3
LMArena Longer Query15221326

Writing & Preference Claude Fable 5.1 leads

Claude Fable 5.1: 79.2 (#2), Step 3: 54.3 (#151)

BenchmarkClaude Fable 5.1Step 3
LMArena Text15101350
LMArena Creative Writing15071321
LMArena Multi-Turn14921341
EQ-Bench Creative Writing2162—

Frequently asked questions

Is Claude Fable 5.1 better than Step 3?

Claude Fable 5.1 is the stronger model overall, scoring 69.0 to 40.5 on the Noometry Index.

Is Claude Fable 5.1 or Step 3 better for coding?

Claude Fable 5.1 scores higher on coding benchmarks: 74.7 versus 40.1 in the Noometry coding category.

How many benchmarks do Claude Fable 5.1 and Step 3 share?

16 benchmarks have published results for both models. Claude Fable 5.1 has 52 scored results on Noometry and Step 3 has 17.

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