Three months after launching its top-tier model, Anthropic has given Claude another notable upgrade. The company is rolling out Fable 5.1 today. The new version brings noticeable improvements in coding and long-term problem solving compared to its predecessor. This update makes the system the most capable tier for users needing advanced assistance, sitting comfortably above smaller options like Haiku, Sonnet, and Opus.
Fable 5.1 drops costs while fixing complex software issues
The new Fable 5.1 model is built to avoid taking shortcuts that lead to lower quality work. Anthropic says its system can now identify and resolve the root causes of deep software bugs. During early testing, an investment firm named Millennium used Fable 5.1 to uncover the source of a rare system crash. Human engineers and other AI models could not figure out the problem for several years.
Alongside the performance bump, the company is dropping the price for running these tasks. Fable 5.1 costs about 25 percent less than the previous version for standard workloads. This price drop comes from making cache reads cheaper, which happens when the artificial intelligence reuses context it has already processed. For tasks requiring heavy automated agent work, the savings can reach up to 45 percent.
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Anthropic is also releasing a parallel version called Mythos 5.1. While Fable 5.1 is available to the general public, Mythos 5.1 is locked behind trusted access programs. It shares the same underlying technology but includes specific safeguards tailored for sensitive work in cybersecurity and life sciences.
The update makes high-tier automation more accessible for everyday users and developers. Lowering the barrier to entry with cheaper cache reads means smaller teams can now run complex coding tasks without breaking the budget.
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