The decision marks a significant shift from the company's initial assessment in April, when it launched Project Glasswing—a controlled consortium including Amazon, Apple, Google, Microsoft, and other major firms—to contain what it described as unprecedented risks posed by the model's autonomous hacking capabilities.
According to Anthropic, Fable 5 is now available to enterprise customers and paid subscribers, but with substantial safeguards: queries on high-risk topics including cybersecurity, biology, and chemistry are automatically routed to Claude Opus 4.8, a less capable model. The company said it developed these classifiers over the past two months and subjected them to extensive testing, including what it described as over 1,000 hours of internal red-teaming without discovering a universal jailbreak. The safeguards trigger in less than 5% of sessions on average, though Anthropic acknowledged they remain "stricter than would be ideal" and sometimes block benign requests.
The release comes amid competitive and commercial pressures. As CNBC reported, Anthropic filed confidentially for an IPO days before the launch, following a funding round that valued the company at $965 billion and revenue projections reaching $47 billion annually. The timing also places Anthropic ahead of OpenAI, which announced its own IPO filing on 8 June. Industry observers have noted the tension between the company's stated safety commitments and its need to monetize frontier capabilities—Fable 5 is priced at $10 per million input tokens, double the cost of Opus 4.8.
The original Mythos Preview had drawn warnings from cybersecurity experts and policymakers. In April, the Council on Foreign Relations characterized the model as an inflection point, noting its ability to autonomously discover zero-day vulnerabilities across major operating systems and browsers without human direction. Bain & Company argued in May that the launch signalled the arrival of AI-powered attacks at scale, warning that organizations would need to double cybersecurity spending to meet the threat. The London School of Economics questioned whether containment strategies were viable, noting that if Anthropic could develop such capabilities, competitors would likely follow—potentially without equivalent safety measures.
What remains unclear is whether the safeguards represent a robust technical solution or a compromise driven by commercial imperatives. NBC News noted that the model's underlying capabilities remain unchanged from the restricted Mythos Preview, with only the addition of classifiers to block certain queries. TechCrunch highlighted that the release came just days after Anthropic publicly warned that frontier AI systems were advancing so rapidly they might soon achieve recursive self-improvement. The company is also implementing a new 30-day data retention policy for all Fable 5 and Mythos 5 traffic—even for enterprises that previously had zero-retention agreements—a move framed as necessary to detect novel jailbreaks but which sets a precedent for mandatory surveillance of frontier model usage.