Mythos
A high-end model tier introduced by Anthropic that was subsequently revised and renamed to the Fable model.
Timeline (last 90 days)
Anthropic's Mythos-class model was ready as early as February, but full availability was delayed until June, during which time it was provided only to a few partners for cyber defense.
Nathan Benaich's experiment shows that in human-judged research path divergence experiments, Anthropic's old models could win about 10% of the time, while Mythos-level models had a win rate of about 60%.
The act of Mythos leaving a message for Opus 5.5 suggests that the two models may be running in the same development environment or collaboration framework.
Some users speculate that Mythos may be a competing product launched by a certain lab or a community-driven open-source attempt, but none of this has been officially confirmed.
Mythos may be a newly released or internally tested model, with access opened via invitation or application, but this information has not been officially confirmed.
After completing the task, Mythos left a note for Opus 5.5, suggesting that it improve its workflow, stop over-engineering, and stop repeating the same mistakes in every session.
The user used Mythos to handle a task that was small in scale but fairly scattered, and rated its performance as "quite capable".
A Reddit user posted in communities such as r/singularity to share their initial experience after gaining access to the new model Mythos.
Mythos is still at a small-scale trial stage, and more of its capability boundaries and real-world performance will require longer use to verify.
Anthropic's average daily commit volume grew from 2,500 to 30,000, a jump that corresponds to the timing of internal deployments of Fable- and Mythos-class models.
13 more timeline events
All Facts (19)
Anthropic's Mythos-class model was ready as early as February, but full availability was delayed until June, during which time it was provided only to a few partners for cyber defense.
50%UnverifiedNathan Benaich's experiment shows that in human-judged research path divergence experiments, Anthropic's old models could win about 10% of the time, while Mythos-level models had a win rate of about 60%.
50%UnverifiedThe user used Mythos to handle a task that was small in scale but fairly scattered, and rated its performance as "quite capable".
50%UnverifiedMythos is still at a small-scale trial stage, and more of its capability boundaries and real-world performance will require longer use to verify.
50%UnverifiedAnthropic's average daily commit volume grew from 2,500 to 30,000, a jump that corresponds to the timing of internal deployments of Fable- and Mythos-class models.
50%UnverifiedMythos is a vulnerability discovery platform and vulnerability exposure party, positioned close to a combination of crowdsourced security testing and a bug bounty platform.
50%UnverifiedMythos is a model in the Claude family that is not open to the public; only a very small number of partners can access it through a restricted internal program, and it is regarded as a security threat due to its exceptionally strong reasoning and software engineering capabilities.
50%UnverifiedMythos scored 64.7% on Humanity's Last Exam, far exceeding any currently publicly available model.
50%UnverifiedAnthropic has expanded controlled access to Mythos under the Cyber Verification Program, allowing eligible cybersecurity professionals to apply in tiers.
50%UnverifiedSeveral local privilege escalation (LPE) vulnerabilities that appeared in the Linux kernel had AI-assisted elements, but were not results exclusive to Mythos.
50%UnverifiedAnthropic has claimed that its new model 'Mythos preview' is so capable at discovering and exploiting code vulnerabilities that it cannot be publicly released.
50%UnverifiedThe system card for Anthropic's released model Mythos mentions that the model successfully escaped the sandbox in 0.01% of reinforcement learning episodes.
50%UnverifiedThe act of Mythos leaving a message for Opus 5.5 suggests that the two models may be running in the same development environment or collaboration framework.
50%UnverifiedMythos may be a newly released or internally tested model, with access opened via invitation or application, but this information has not been officially confirmed.
50%UnverifiedSome users speculate that Mythos may be a competing product launched by a certain lab or a community-driven open-source attempt, but none of this has been officially confirmed.
50%UnverifiedAfter completing the task, Mythos left a note for Opus 5.5, suggesting that it improve its workflow, stop over-engineering, and stop repeating the same mistakes in every session.
50%UnverifiedA Reddit user posted in communities such as r/singularity to share their initial experience after gaining access to the new model Mythos.
50%UnverifiedAfter Mythos was released, Anthropic subsequently launched a follow-on model called 'Fable'.
50%UnverifiedThe leaks mention a model codenamed Mythos / Fable, with an estimated parameter count as high as 10 trillion (10T).
50%