RankingLegal Agent Benchmark · 120-task held-out subset

Legal Agent Benchmark · 120-task held-out subset

Data updated 24 Sept 2026

Bucket: Supporting evidence
Unit: percent
Direction: Higher is better
Version: 120-task held-out subset
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

The available records have no admitted matched comparison in the capability core. Raw results remain available below.

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	16.7% Reported settings & source all-pass; Artificial Analysis harness; xhigh effort. 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 · 8.15.2 · reviewed 2026-09-24	Claude Fable 5.1 and Claude Mythos 5.1 System Card	lab self-report	2026-09-24
Claude Fable 5.1Anthropic	93.3% Reported settings & source criterion-pass; Artificial Analysis harness; xhigh effort. 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 · 8.15.2 · 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	8.3% Reported settings & source All-pass rate on Harvey's held-out 120 tasks; max effort. Artificial Analysis harness, as in the previous system card. 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 8.14.2 · reviewed 2026-09-22	Claude Opus 5.5 System Card	lab self-report	2026-09-22
Claude Opus 5.5Anthropic	91.2% Reported settings & source Mean criterion-pass rate on Harvey's held-out 120 tasks; max effort. Artificial Analysis harness, as in the previous system card. 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 8.14.2 · reviewed 2026-09-22	Claude Opus 5.5 System Card	lab self-report	2026-09-22