A model name is a product decision. It is not a sort key.
Claude Fable 5.2 and Claude Mythos 5.2 are the same underlying model. Anthropic says so on the launch page. Fable is the one anyone can use, because the cybersecurity and biology safeguards stay on. Mythos is that model without certain of those safeguards. Organizations apply for it through the cyber and life-sciences verification programs, for beneficial work in those fields.
Two names. One brain. The difference is the lock.
The page then tells you not to start on either of them. For most coding and knowledge tasks, start with Claude Opus 5.5. They call it their strongest daily driver. Higher version number. Smaller job. Move up to Fable or Mythos when the work is actually ambitious and open-ended. Move down to Sonnet 5.5 or Haiku 5.5 when it is not.
Fable can also sit as an advisor that Haiku, Sonnet, or Opus consults on the hard part. Or as an orchestrator that hands the easy slices back to a smaller model.
Their chart still says Fable 5.2 is a step above Opus 5.5 on almost every capability they evaluated. A higher score is not a default. You do not book the fastest machine in the fleet to rename a file. You do not send every prompt to the model they reserved for the ugly, open-ended jobs.
The version number is how the SKU is labeled. The safeguard line is who is allowed to hold it. The routing paragraph is which one you should call. Read those backwards and you will act surprised that 5.2 is the flagship and 5.5 is Tuesday.
If you are wiring a model picker, store a job, not a rank. "Daily coding" points at Opus. "Hard, open-ended technical work" points at Fable. "Cyber or biology work that Fable's safeguards block" points at Mythos, and only if the org is actually in the program. A picker that sorts by version ships the wrong brain to the wrong lock.
- Do not rank models by the number after the dot.
- Do not treat two product names as two brains when the vendor says they share weights.
- Do not read "fewer safeguards" as "smarter."
- Do not leave every session on the launch model because the post was loud.
- Do not skip the paragraph that names the default.
Read the routing note before you read the chart.
Claude Fable 5.2 and Mythos 5.2
This post was generated automatically from public Hacker News data.
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