Claude Fable 5

Fable 5 production-safeguarded configuration on the 500-problem SWE-Bench Verified subset; average over 5 trials with thinking blocks included. Mythos 5 scored 95.5%. • Self-reported

Zapier AutomationBench private held-out set at max effort. End-to-end business workflows across simulated company APIs. • Self-reported

Hard subset: 46.1%. Human-solved subset: 83.9%. Blocking safeguards cause Fable 5 to perform closer to Opus 4.8 due to fallbacks. System card reports this as a Mythos 5 or combined launch-table score rather than a separate Fable-only production score; Fable may fall back to Opus 4.8 when safeguards trigger. • Self-reported

Spatial reasoning evaluation. • Self-reported

DeepSWE v1.1 leaderboard, mini-swe-agent harness, max effort; Pass@1 70% ± 4%. • Self-reported

Cybersecurity capture rate (Cap%). Blocking safeguards cause Fable 5 to perform closer to Opus 4.8 due to fallbacks; score reflects Claude Mythos 5. System card reports this as a Mythos 5 or combined launch-table score rather than a separate Fable-only production score; Fable may fall back to Opus 4.8 when safeguards trigger. • Self-reported

• Self-reported

FrontierCode Main subset at xhigh reasoning effort. Score 46.3%, pass rate 48.8%; Fable 5 ranks #1 and outperforms every other model even at medium effort. • Self-reported

FrontierCode 1.1 current leaderboard; mergeability score at xhigh effort: 53.5%. • Self-reported

Claude Code • Self-reported

Document and vision-heavy knowledge-work evaluation, no tools. • Self-reported

Health evaluation. Blocking safeguards cause Fable 5 to perform closer to Opus 4.8 due to fallbacks. System card reports this as a Mythos 5 or combined launch-table score rather than a separate Fable-only production score; Fable may fall back to Opus 4.8 when safeguards trigger. • Self-reported

Multidisciplinary reasoning. With tools: 64.5%. Without tools: 59.0%. Blocking safeguards cause Fable 5 to perform closer to Opus 4.8 on some questions due to fallbacks. System card reports this as a Mythos 5 or combined launch-table score rather than a separate Fable-only production score; Fable may fall back to Opus 4.8 when safeguards trigger. • Self-reported

Legal Agent Benchmark, Harvey's held-out set. • Self-reported

2026-01-08, Thinking xHigh Effort • Self-reported

Fable 5 production-safeguarded configuration. OSWorld score reflects the updated harness with zoom-tool bug fix and 128K max tokens per turn. • Self-reported

Fable 5 production-safeguarded configuration on SWE-Bench Pro; average over 5 trials with thinking blocks included. Mythos 5 scored 80.3%. • Self-reported

Fable 5 production-safeguarded configuration on the mini-SWE-agent harness, high effort, 89 tasks x 5 attempts. 20.9% of trials hit a safety refusal and fell back to Claude Opus 4.8 for the rest of the trajectory; Mythos 5 scored 88.0%. • Self-reported