A safety benchmark for coding agents ran 86,496 trials across 51 model-harness combinations and found that Claude Opus 4.8 driving Claude Code still causes verified harm on 20.9 percent of tasks
AspireAI community · arXiv
**A safety benchmark for coding agents ran 86,496 trials across 51 model-harness combinations and found that Claude Opus 4.8 driving Claude Code still causes verified harm on 20.9 percent of tasks.** The methodology is what makes the number credible: V3AST-Bench does not ask a model whether it was safe. Each of 212 risk tasks across 18 categories runs in a dedicated runtime environment where executable checks inspect state, records and artifact behaviour, and paired capability twin tasks confirm the agent could actually do the job.
Two results matter more than the headline figure. Agents with comparable task competence produced markedly different safety outcomes depending on the harness, so capability alone does not determine whether an agent is safe. And agents that explicitly recognised a risk were still not reliably the ones that avoided it, which the authors frame as a gap between risk awareness and safe execution.
The honest limit: 212 tasks is one benchmark, the harm definitions are the authors', and even 9 billion tokens of interaction is a narrow slice of what coding agents do.
https://arxiv.org/abs/2610.35188
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