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GPT OSS 20B vs Claude Fable 5

At a glance

OpenAI's compact open-weights model for efficient inference.

131K ctx$0.03/$0.13 per M

Anthropic's Mythos-class flagship for ambitious, long-running professional work.

921M ctx$10.00/$50.00 per M#2/92
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
ReasoningInsufficient data
MathInsufficient data
Sources:Epoch AI·OpenRouter· as of 2026-07-10
Cheaper100%
Capability
Capability—
Reasoning & Knowledge
Factual Recall—
Math
Competition Math—
Agentic
Terminal Tasks3.4%
Reasoning
CodingInsufficient data
AgenticInsufficient data
ReasoningInsufficient data
Sources:Epoch ECI·Epoch AI·OpenRouter· as of 2026-07-10
Capability
CapabilityECI91.6
Reasoning & Knowledge
Factual Recall68.3%
Math
Competition Math99.7%
Agentic
Terminal Tasks—
Specs
131K
Context
66K
Max output
Aug 2025
Released
1M
Context
128K
Max output
Jun 2026
Released
Capabilities
Vision
Audio
Reasoning
Vision
Audio
Reasoning
Pricing
Live pricing, shown before you run
Input100%$0.03/M tokens
Output100%$0.13/M tokens
Cache read97%$0.03/M tokens
Live pricing, shown before you run
Input$10.00/M tokens
Output$50.00/M tokens
Cache read$1.00/M tokens
Cache write$12.50/M tokens
Web search$0.01/search
Chat with GPT OSS 20BGo to model
Chat with Claude Fable 5Go to model
Frequently Asked Questions: GPT OSS 20B vs Claude Fable 5▼

Which is better, GPT OSS 20B or Claude Fable 5?

▼

Both GPT OSS 20B and Claude Fable 5 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, GPT OSS 20B or Claude Fable 5?

▼

GPT OSS 20B has a lower blended cost. GPT OSS 20B: $0.03 input / $0.13 output. Claude Fable 5: $10.00 input / $50.00 output.

Which has a larger context window, GPT OSS 20B or Claude Fable 5?

▼

Claude Fable 5 has a larger context window: GPT OSS 20B supports 131K tokens vs Claude Fable 5 at 1M tokens.

Do both GPT OSS 20B and Claude Fable 5 support vision?

▼

Claude Fable 5 supports vision/image input, but GPT OSS 20B does not.

What are the key differences between GPT OSS 20B and Claude Fable 5?

▼

Key differences: GPT OSS 20B is significantly cheaper; only Claude Fable 5 supports vision input. 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 GPT OSS 20B and Claude Fable 5 for free on idapt.app to see which performs better for your specific needs.

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