Anthropic launches Opus 5 as cost-effective alternative to Fable 5
The release positions Opus 5 as a practical workhorse for developers, excluding it from data retention policies and introducing an effort-based efficiency menu.
Anthropic has officially released Opus 5, a new large language model designed to deliver performance metrics close to its flagship Fable 5 at half the cost. The release arrives two months after the availability of Opus 4.8 and follows the June debut of other models in the 5 series, including Mythos 5, Fable 5, and Sonnet 5. The company states that Opus 5 is substantially better at complex coding tasks than its predecessor and excels in knowledge work compared to past iterations.
Pricing for the new model remains consistent with previous versions, set at $5 per one million input tokens and $25 per one million output tokens. This rate positions Opus 5 at half the cost of Fable 5 and slightly cheaper than OpenAI’s GPT-5.6. The model is included in all of Anthropic’s paid subscription tiers, offering broad access that competitors such as Moonshot’s Kimi K3 currently do not provide, despite the latter offering Fable-like performance at $15 per million output tokens.
A key differentiator for Opus 5 is its safety architecture. The model features less restrictive safeguards than Fable 5, with Anthropic expecting classifier interventions to occur 85% less frequently, particularly in cybersecurity and biology tasks. The company has strengthened guardrails along a narrow range of specific tasks to allow beneficial uses in these fields, noting that Opus 5 exhibits the lowest rates of deceptive behavior and is more resistant to being tricked than previous versions.
Unlike the limited-access Mythos model, Opus 5 was not specifically trained on cyber-related tasks. While it is broadly better at identifying vulnerabilities than its predecessor, Anthropic states it remains substantially behind Fable 5 in exploiting them. The model is also excluded from the company’s recently announced 30-day data retention policy, which applies to Fable and Mythos 5, addressing concerns regarding data privacy for enterprise users.
Anthropic has introduced an "effort" menu for Opus 5, allowing users to toggle between thoroughness and speed or efficiency to conserve tokens. A Fast mode option is also available in the research preview. The company expects Opus 5 to become the default choice for general workloads, aiming to address user frustrations with the heavy-handed restrictions previously associated with the Fable model.
