Which is cheaper, Claude Fable 5 or GPT-6 Luna?

Claude Fable 5 lists at $10 input / $50 output per 1M tokens; GPT-6 Luna lists at $0.10 input / $0.50 output per 1M tokens. GPT-6 Luna has the lower list price.

Which is used more, Claude Fable 5 or GPT-6 Luna?

GPT-6 Luna, with 1.4% of the AI-written code reviewed by cubic in the week of Oct 12, 2026, against 0.2% for Claude Fable 5.

Updated Oct 20, 2026

Claude Fable 5 vs GPT-6 Luna

Claude Fable 5 is no longer ranked because it now writes under 0.5% of AI-attributed lines.

Claude Fable 5 and GPT-6 Luna compared on relative bug rate and on price and usage.
Bug rate
	Claude Fable 5	GPT-6 Luna
Relative bug rate	No longer ranked	0.45
Details
Provider	Anthropic	OpenAI
Released	Jun 9, 2026	Sep 22, 2026
List price	$10 input / $50 output per 1M tokens	$0.10 input / $0.50 output per 1M tokens
Share of AI-written code, week of Oct 12	0.2%	1.4%

1.00 = average · lower is better

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Questions and answers

Which has fewer bugs, Claude Fable 5 or GPT-6 Luna?: Claude Fable 5 is no longer ranked because it now writes under 0.5% of AI-attributed lines.
Which is cheaper, Claude Fable 5 or GPT-6 Luna?: Claude Fable 5 lists at $10 input / $50 output per 1M tokens; GPT-6 Luna lists at $0.10 input / $0.50 output per 1M tokens. GPT-6 Luna has the lower list price.
Which is used more, Claude Fable 5 or GPT-6 Luna?: GPT-6 Luna, with 1.4% of the AI-written code reviewed by cubic in the week of Oct 12, 2026, against 0.2% for Claude Fable 5.