GPT-5.5 Pro vs Claude Fable 5

Head-to-head technical comparison of intelligence, capabilities, and API pricing.

GPT-5.5 Pro

OpenAI

AI Mastery Index94.2

LMSYS Arena1468

Technical (MMLU-Pro)94.2%

Cost per 1M Tokens$30

Claude Fable 5

Anthropic

AI Mastery Index96.4

LMSYS Arena1494

Technical (MMLU-Pro)95.6%

Cost per 1M Tokens$10

Architect's Verdict

When comparing GPT-5.5 Pro and Claude Fable 5, Claude Fable 5 edges out in overall capabilities according to the AI Mastery Index. However, for cost-sensitive workloads, Claude Fable 5 offers a more economical API at $10 per 1M tokens. Your choice should depend heavily on whether you prioritize raw reasoning (MMLU) or scalable deployment economics.