Anthropic / MODEL EVIDENCE

Claude Opus 5.5 (unknown)

2 benchmarks · 2 observations · 2 sources · released 2026-09-22

Scores at a glance

2 benchmarks · large dot: Claude Opus 5.5 (unknown); small dots: closest models where reported

Closest models by score

Similar positions on shared benchmark leaderboards. Smaller gaps are closer.

4.9 percentile-point gap

2 of 2 shared benchmark comparisons

How similarity is measured

Mean absolute gap in percentile positions on shared benchmark settings; lower is closer. At least 60% overlap is required, with a minimum of three when available. Independent evaluations are used when there are at least three; otherwise published report comparisons are used. Repeated model observations within one setting are averaged before ranking. Writing-style traits and composite indices are excluded. This describes similarity, not an overall quality ranking.

POST-TRAINING / SOURCE DISCLOSURE

What the Claude Opus 5.5 report says

Anthropic describes fine-tuning after pretraining to align the assistant with Claude’s constitution. The system card also documents human preference selection, safety evaluation and adversarial testing.

  • Post-training and fine-tuning guided by Claude’s constitution
  • Human preference and safety-evaluation data

The system card does not disclose a production PPO, DPO or GRPO recipe. Constitutional AI is a related method note; its particular SL-CAI/RL-CAI implementation is not asserted for this release.

  1. Claude Opus 5.5 System Card ↗

    Anthropic · 2026

Sources

Every plotted observation links to its evaluation. Reported configurations, benchmark versions and task subsets can differ; similarity describes shared scores, not training lift.

  1. Blueprint-Bench 2 | Andon Labs ↗

    Andon Labs

  2. Remote Labor Index ↗

    Epoch AI

Names used in source tables

Claude Opus 5.5 (unknown)