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GMMLU

Data updated 24 Sept 2026

Bucket: Knowledge
Unit: percent
Direction: Higher is better
Version: —
Display harness: Claude Fable 5.1 and Claude Mythos 5.1 System Card
Board: https://www.anthropic.com/claude-fable-5-1-mythos-5-1-system-card

Compare published benchmark results with category weights →

Models

Published configurations retain their source and harness labels. Missing results remain unknown.

1–4 of 4 entries

Model	Score	Harness	Evidence	Source-recorded date
Claude Fable 5.1Anthropic	94% Reported settings & source Mean accuracy42languages; adaptive max; one trial; no tools/custom system prompts. Fable is the safeguarded deployed configuration; selected tasks may use disclosed Opus fallback, except evaluations explicitly counting safety blocks as failures. Claude Fable 5.1 and Claude Mythos 5.1 System Card · 8.18.1 · reviewed 2026-09-24	Claude Fable 5.1 and Claude Mythos 5.1 System Card	lab self-report	2026-09-24
Claude Fable 5Anthropic	93.6% Reported settings & source Mean accuracy42languages; adaptive max; one trial; no tools/custom system prompts. Fable is the safeguarded deployed configuration; selected tasks may use disclosed Opus fallback, except evaluations explicitly counting safety blocks as failures. Claude Fable 5.1 and Claude Mythos 5.1 System Card · 8.18.1 · reviewed 2026-09-24	Claude Fable 5.1 and Claude Mythos 5.1 System Card	lab self-report	2026-09-24
Claude Opus 5Anthropic	92.5% Reported settings & source Mean accuracy42languages; adaptive max; one trial; no tools/custom system prompts. Claude Fable 5.1 and Claude Mythos 5.1 System Card · 8.18.1 · reviewed 2026-09-24	Claude Fable 5.1 and Claude Mythos 5.1 System Card	lab self-report	2026-09-24
Claude Opus 5.5Anthropic	94.3% Reported settings & source Average accuracy across 42 languages; adaptive thinking at max effort; single trial; no tools or custom system prompt. Provider-published lab self-report from the Claude Opus 5.5 system card (SHA256 7311c9c6bbb16d012f1c12c7418b05949fcf7ae3e30d2c40f22050074b2a7378). Not an independent board. Comparison limit: Provider-published lab self-report. Shown as a labeled claim and not admitted as a matched board comparison. Claude Opus 5.5 System Card · section 8.16.1; Figure 8.16.1.A · reviewed 2026-09-22	Claude Opus 5.5 System Card	lab self-report	2026-09-22