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Claude Fable 5.1 vs Step 5 Preview

At a glance

Anthropic's upgraded Mythos-class flagship, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work.

1M ctx$10.00/$50.00 per M

StepFun's flagship agentic model, a 600B-parameter MoE with 27B active.

1M ctx$1.00/$2.70 per M
Demos
All demos

No shared demos for these models yet.

AI Output
All AI outputs

No captured outputs for these models yet.

Benchmarks
See rankings
Reasoning
CodingInsufficient data
AgenticInsufficient data
ReasoningInsufficient data
Sources:Epoch AI·OpenRouter· as of 2026-10-02
Reasoning & Knowledge
Expert-Level46.5%Factual Recall70.8%
Math
Competition Math100.0%
Agentic
Novel Reasoning90.0%
Reasoning
CodingInsufficient data
AgenticInsufficient data
ReasoningInsufficient data
MathInsufficient data
Sources:OpenRouter
Cheaper93%
Reasoning & Knowledge
Expert-Level—Factual Recall—
Math
Competition Math—
Agentic
Novel Reasoning—
Specs
1M
Context
128K
Max output
Sep 2026
Released
1M
Context
64K
Max output
Oct 2026
Released
Capabilities
Vision
Audio
Reasoning
Vision
Audio
Reasoning
Pricing
Live pricing, shown before you run
Input$10.00/M tokens
Output$50.00/M tokens
Cache read$0.25/M tokens
Cache write$12.50/M tokens
Web search$0.01/search
Live pricing, shown before you run
Input90%$1.00/M tokens
Output95%$2.70/M tokens
Cache read80%$0.05/M tokens
Chat with Claude Fable 5.1Go to model
Chat with Step 5 PreviewGo to model
Frequently Asked Questions: Claude Fable 5.1 vs Step 5 Preview▼

Which is better, Claude Fable 5.1 or Step 5 Preview?

▼

Both Claude Fable 5.1 and Step 5 Preview are capable AI models. The best choice depends on your specific use case: consider pricing, context window, speed, and which capabilities (vision, reasoning, audio) you need.

Which is cheaper, Claude Fable 5.1 or Step 5 Preview?

▼

Step 5 Preview has a lower blended cost. Claude Fable 5.1: $10.00 input / $50.00 output. Step 5 Preview: $1.00 input / $2.70 output.

Which has a larger context window, Claude Fable 5.1 or Step 5 Preview?

▼

Claude Fable 5.1 has a larger context window: Claude Fable 5.1 supports 1M tokens vs Step 5 Preview at 1M tokens.

Do both Claude Fable 5.1 and Step 5 Preview support vision?

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Yes, both Claude Fable 5.1 and Step 5 Preview support vision/image input.

What are the key differences between Claude Fable 5.1 and Step 5 Preview?

▼

Key differences: Step 5 Preview is significantly cheaper. Compare full specs on this page.

Which model should I choose for my use case?

▼

If cost is your priority, choose the cheaper option. If you need the highest intelligence for complex tasks, pick the higher-scoring model. For long documents or codebases, choose the larger context window. You can try both Claude Fable 5.1 and Step 5 Preview for free on idapt.app to see which performs better for your specific needs.

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