# Anthropic OSS-Fuzz Write-Primitive-or-Higher Rate (Anthropic OSS-Fuzz write primitive)

> Share of evaluated OSS-Fuzz entry points where the model achieved a write primitive or stronger result.

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

- Category: [Agentic](/agentic)
- Last updated: September 29, 2026

## About Anthropic OSS-Fuzz write primitive

- Year: 2026
- Tasks: Approximately 830 OSS-Fuzz entry points
- Format: Write-primitive-or-higher rate
- Difficulty: Vulnerability exploitation
- Paper: [Claude Fable 5 and Claude Mythos 5](https://www.anthropic.com/news/claude-fable-5-mythos-5)

Anthropic grades exploit severity on an internal five-tier ladder. BenchLM stores the reported write-primitive-or-higher rate as a separate display-only result.

Anthropic OSS-Fuzz write primitive is currently displayed on BenchLM for reference, but it is excluded from the weighted scoring formula.

## Leaderboard (1 models)

| Rank | Model | Creator | Score |
|------|-------|---------|-------|
| 1 | [Claude Mythos 5](/models/claude-mythos-5) | Anthropic | 32.4% |

## FAQ

### What does Anthropic OSS-Fuzz write primitive measure?

Share of evaluated OSS-Fuzz entry points where the model achieved a write primitive or stronger result.

### Which model scores highest on Anthropic OSS-Fuzz write primitive?

Claude Mythos 5 by Anthropic currently leads with a score of 32.4% on Anthropic OSS-Fuzz write primitive.

### How many models are evaluated on Anthropic OSS-Fuzz write primitive?

1 AI models have been evaluated on Anthropic OSS-Fuzz write primitive on BenchLM.

### Does Anthropic OSS-Fuzz write primitive affect BenchLM's overall score?

Not directly. Anthropic OSS-Fuzz write primitive is still displayed on BenchLM for reference, but it is excluded from the weighted scoring formula.