Claude Fable 5.1 (Medium, Default Fallback) vs GPT-5.6 Luna (Xhigh)
Which is better for the money: Claude Fable 5.1 (Medium, Default Fallback) by Anthropic or GPT-5.6 Luna (Xhigh) by OpenAI? Intelligence, total benchmark cost, and end-to-end time from Artificial Analysis & other sources, snapshot 2026-10-27.
Depends on your budget
Claude Fable 5.1 (Medium, Default Fallb… scores 14.3 points higher (48.9 vs 34.6) but costs 22× as much to run the benchmark ($3983 vs $179; flagship vs mid-range cost classes). They are not alternatives at one budget: pick Claude Fable 5.1 (Medium, Default Fallb… when you need intelligence above 34.6, and GPT-5.6 Luna (Xhigh) when 34.6 is enough.
| Metric | Claude Fable 5.1 (Medium, Default Fallback) | GPT-5.6 Luna (Xhigh) | Difference |
|---|---|---|---|
| Intelligence (higher is better) | 48.9 | 34.6 | −29.2% GPT-5.6 Luna (Xhigh) is 29.2% less intelligent |
| Total AA cost (lower is better) | $3,983.28 | $179.33 | −95.5% GPT-5.6 Luna (Xhigh) is 95.5% cheaper |
| End-to-end time (lower is better) | 22.02s | 39.18s | +77.9% GPT-5.6 Luna (Xhigh) is 77.9% slower |
| Price per 1M tokens (in / out) | $10.0 / $50.0 | $0.20 / $1.20 | |
| Input modalities | Text, Image | Text, Image |
GPT-5.6 Luna (Xhigh) vs Claude Fable 5.1 (Medium, Default Fallback): 29.2% less intelligence, 95.5% less cost to run the AA benchmark, and 77.9% slower end-to-end.
Against the frontier
- Claude Fable 5.1 (Medium, Default Fallback) is off the frontier: at the same or lower cost, Kimi K3.1 Pro scores 55.10 for $3117.
- GPT-5.6 Luna (Xhigh) is off the frontier: at the same or lower cost, GPT-6.1 Terra (Medium) scores 41.30 for $175.
Compare something else
Accept: text/markdown or ?format=md returns this page as Markdown. JSON: /api/v1/compare/claude-fable-5-1-medium/gpt-5-6-luna-xhigh · Markdown: /api/v1/compare/claude-fable-5-1-medium/gpt-5-6-luna-xhigh?format=md · llms.txt · agent skill