# Protein domain identification (Protein Domain ID)

> Anthropic's protein-understanding test: from an amino acid sequence alone, choose the correct Pfam domain family among similar distractors, without tools.

Canonical page: https://benchlm.ai/benchmarks/proteindomainidentification

- Category: [Knowledge](/knowledge)
- Last updated: November 11, 2026

## About Protein Domain ID

- Year: 2026
- Tasks: Multiple-choice Pfam family questions
- Format: Accuracy
- Difficulty: Protein understanding
- Paper: [Claude Fable 5.2 and Claude Mythos 5.2 system card](https://assets.claude.com/27d60918d218125e7504bc7354c4b4626ec56b11.pdf)

Introduced in the Claude Fable 5.2 and Mythos 5.2 system card and run on Mythos 5.2 with biology safeguards off. Internal, so display-only.

Protein Domain ID is currently displayed on BenchLM for reference, but it is excluded from the weighted scoring formula.

## Leaderboard (3 models)

| Rank | Model | Creator | Score |
|------|-------|---------|-------|
| 1 | [Claude Mythos 5.2](/models/claude-mythos-5-2) | Anthropic | 91.8% |
| 2 | [Claude Opus 5.5](/models/claude-opus-5-5) | Anthropic | 73.6% |
| 3 | [Claude Mythos 5.1](/models/claude-mythos-5-1) | Anthropic | 63.5% |

## FAQ

### What does Protein Domain ID measure?

Anthropic's protein-understanding test: from an amino acid sequence alone, choose the correct Pfam domain family among similar distractors, without tools.

### Which model scores highest on Protein Domain ID?

Claude Mythos 5.2 by Anthropic currently leads with a score of 91.8% on Protein Domain ID.

### How many models are evaluated on Protein Domain ID?

3 AI models have published results on Protein Domain ID in the BenchLM catalog.

### Does Protein Domain ID affect BenchLM's overall score?

Not directly. Protein Domain ID is still displayed on BenchLM for reference, but it is excluded from the weighted scoring formula.

## Compare Top Models on Protein Domain ID

- [Claude Mythos 5.2 vs Claude Opus 5.5](/compare/claude-mythos-5-2-vs-claude-opus-5-5)
- [Claude Opus 5.5 vs Claude Mythos 5.1](/compare/claude-mythos-5-1-vs-claude-opus-5-5)