anthropic has introduced Claude Fable 5a version of its Mythos-class model architecture with enhanced security features.
The model is available to Pro, Max and Enterprise customers at no additional charge until June 22. After that date, pricing will be based on usage. Fable 5 uses tokens at a much faster rate than previous Claude models.
This release comes after Anthropic’s April announcement of Mythos, which the company noted could raise security concerns if released without restrictions.
Fable 5 is the first widely accessible version of that kind of model, with security measures that prevent or redirect sensitive queries related to offensive cybersecurity, biology or chemistry to the previous model Opus 4.8.
How Claude Fable 5 is different and how quickly it burns chips
Claude Mythos is only available to a select group of trusted partners, including government cyber defense teams and certain life sciences researchers.
Fable 5 uses the same basic model but incorporates security measures that prevent it from handling the most sensitive types of queries. According to Anthropic, these security features redirect sensitive requests to Opus 4.8 instead of attempting to respond to them directly.
Fable 5 is Anthropic’s most computationally demanding model, using tokens at a significantly higher rate than Opus 4.8. During typical conversational use, token consumption is approximately double that of Opus. When used with Workflow mode and settings set to High or High Effort, the consumption rate increases significantly.
BleepingComputer tested the model and found that Fable 5 used around 1 million tokens in eight minutes during a workflow session. This used up the daily allotment of a maximum $100 subscription in just under nine minutes. Workflow is a new system that breaks complex prompts into smaller tasks and runs parallel subagents to handle them.
The high computational cost is the main reason why Anthropic cannot offer Fable 5 on the same terms as Opus 4.8 and other models.
Availability and prices
Fable 5 is now available for free for Pro, Max, and Enterprise customers until June 22. After that date, the model will change to a usage-based pricing plan. Anthropic has not yet announced the per-token costs that will apply once the free period ends.
Claude Code, Anthropic’s command-line coding tool, now features Fable 5 as a selectable model option.
To manage token usage during the free period, users should use Fable 5 in standard conversation mode instead of Workflow with high effort settings, which can quickly exhaust daily limits.
