Which has fewer bugs, Claude Fable 5.1 or Claude Opus 4.8?

Claude Opus 4.8 had 25% fewer counted bugs per line than Claude Fable 5.1 (0.88 vs 1.17). Claude Opus 4.8 ranks #2 of 7 and Claude Fable 5.1 #4.

Which is used more, Claude Fable 5.1 or Claude Opus 4.8?

Claude Fable 5.1, with 19.4% of the AI-written code reviewed by cubic in the week of Sep 14, 2026, against 1.9% for Claude Opus 4.8.

Updated Sep 26, 2026

Claude Opus 4.8 had 25% fewer counted bugs per line than Claude Fable 5.1 (0.88 vs 1.17).

Claude Fable 5.1 and Claude Opus 4.8 compared on relative bug rate, by coding agent, bug type, and language, and on price and usage.
Bug rate
	Claude Fable 5.1	Claude Opus 4.8
Relative bug rate	1.17	0.88
Rank	#4 of 7	#2 of 7
By coding agent
Claude Code	1.17	0.86
Details
Share of AI-written code, week of Sep 14	19.4%	1.9%

1.00 = average · lower is better

Which has fewer bugs, Claude Fable 5.1 or Claude Opus 4.8?: Claude Opus 4.8 had 25% fewer counted bugs per line than Claude Fable 5.1 (0.88 vs 1.17). Claude Opus 4.8 ranks #2 of 7 and Claude Fable 5.1 #4.
Which is used more, Claude Fable 5.1 or Claude Opus 4.8?: Claude Fable 5.1, with 19.4% of the AI-written code reviewed by cubic in the week of Sep 14, 2026, against 1.9% for Claude Opus 4.8.