Anthropic on Friday rolled out Claude Opus 5, pitching it as a cheaper alternative to its top-tier Fable 5 model. In cybersecurity, the new model is nearly as good as Mythos 5 at spotting software vulnerabilities, but remains well behind it in turning those findings into working exploits, according to Anthropic’s OSS-Fuzz-based evaluation. Opus 5 identifies vulnerabilities at a rate close to Mythos 5, but its exploit-development score trails considerably, which Anthropic frames as a deliberate outcome of avoiding training on offensive cyber tasks. Opus 5’s safety classifiers are tuned to be less restrictive than those on Fable 5, with Anthropic expecting roughly 85 percent fewer interventions. The model is permitted to search for vulnerabilities directly in source code, but binary-based vulnerability scanning, penetration testing, and exploit generation remain blocked. Requests that trip those classifiers fall back automatically to the older Opus 4.8 model. Enterprises and researchers in Anthropic’s Cyber Verification Program can get a version with restrictions loosened further. Mythos 5 remains withheld from general release, while Fable 5 is the safeguarded, publicly available counterpart. Both models were taken offline last month due to the Trump administration’s concerns over their use by foreign nationals, with restrictions later lifted. Pricing for Opus 5 holds at $5 per million input tokens and $25 per million output tokens, with a faster-response mode at double the base rate.