> Claude Fable 5.1 vs Step 5 Preview: index scores 192 and ~175 (GPT-4 = 100), API prices, context windows and results on the same independent tests, side by side.

Up to four models

# Compare

Side by side on the same independent tests, with price and context. The link in your address bar shares this exact comparison.

[Claude Fable 5.1](https://themodelindex.org/models/claude-fable-5-1/)

[Step 5 Preview](https://themodelindex.org/models/step-5-preview/)

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Next to Claude Fable 5.1

Cheapest at this level

Claude Sonnet 5.5

Best open model, measured

Kimi K3

Closest rival, another lab

Gemini 4 Argon

Stronger for the same price

Claude Opus 5.5

The version it replaced

Claude Fable 5

Presets

Best open vs best closed (measured)

Today vs GPT-4 (2023)

Top three labs

US vs China, best of each

[Claude Fable 5.1](https://themodelindex.org/models/claude-fable-5-1/)

192

181–203

Weights

Closed

Released

Sep 2026

Price in / out

$10 / $50

Context

1M

Core tests taken

4 of 8

[Step 5 Preview](https://themodelindex.org/models/step-5-preview/)

~175

estimated

Weights

Closed

Released

Sep 2026

Price in / out

–

Context

–

Core tests taken

–

Claude Fable 5.1 leads Step 5 Preview by 17 points (one score is an estimate).

## Test by test · independent results · Epoch AI

Claude Fable 5.1

Step 5 Preview

These models share no independent tests yet.

Only tests that at least two of these models have taken. Bold rows are the core tests shown on every profile; all of these results inform the index score. Task length (METR) is listed below the chart because it is a duration, not a percentage.

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Source: https://themodelindex.org/compare/claude-fable-5-1-vs-step-5-preview/ · The Model Index · data as of 2026-10-01