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Grok 4 Fast vs Claude Fable 5.1

At a glance

Fast version of Grok 4 with SOTA cost-efficiency and 2M-token context.

772M ctx#36/92

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
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
CodingInsufficient data
AgenticInsufficient data
ReasoningInsufficient data
MathInsufficient data
Sources:Epoch ECI·Epoch AI· as of 2026-07-10
Capability
CapabilityECI77.0
Agentic
Novel Reasoning5.3%
Reasoning
CodingInsufficient data
AgenticInsufficient data
ReasoningInsufficient data
MathInsufficient data
Sources:OpenRouter
Capability
Capability—
Agentic
Novel Reasoning—
Specs
2M
Context
33K
Max output
—
Released
1M
Context
128K
Max output
Sep 2026
Released
Capabilities
Vision
Audio
Reasoning
Vision
Audio
Reasoning
Pricing
Pricing not available
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
Chat with Grok 4 FastGo to model
Chat with Claude Fable 5.1Go to model
Frequently Asked Questions: Grok 4 Fast vs Claude Fable 5.1▼

Which is better, Grok 4 Fast or Claude Fable 5.1?

▼

Both Grok 4 Fast and Claude Fable 5.1 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 has a larger context window, Grok 4 Fast or Claude Fable 5.1?

▼

Grok 4 Fast has a larger context window: Grok 4 Fast supports 2M tokens vs Claude Fable 5.1 at 1M tokens.

Do both Grok 4 Fast and Claude Fable 5.1 support vision?

▼

Yes, both Grok 4 Fast and Claude Fable 5.1 support vision/image input.

What are the key differences between Grok 4 Fast and Claude Fable 5.1?

▼

Key differences: only Claude Fable 5.1 offers extended reasoning mode. 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 Grok 4 Fast and Claude Fable 5.1 for free on idapt.app to see which performs better for your specific needs.

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