5 hours ago
- Claude Opus 5 aims to match or exceed Fable 5's performance on many tasks while being faster and half the price.
- Opus 5 shows substantial gains over Opus 4.8 in agentic coding, computer use, and long-horizon knowledge work, setting new state-of-the-art benchmarks.
- Opus 5 lacks full 'Juice' for cyber offense and bio threats due to deliberate avoidance of cyber training and smaller model size.
- Safety classifiers trigger 85% less often than Fable's, permitting source code vulnerability analysis but blocking binary vulnerability discovery.
- Opus 5 shows improved prompt injection resistance, reducing attack success rate from 7.14% to 0.54% in computer use environments.
- Alignment scores are up, with reduced circumvention and reckless tool use, but concerns include overconfidence and overdramatic phrasing.
- Automated alignment tests show high scores, but the report warns against conflating benchmark scores with true alignment, urging caution in messaging.