Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on 9 November, its top models for hard technical work, and cut API prices.
Both are the same underlying model. Anthropic says Fable’s cybersecurity and biology safeguards let it offer the model to all users, while Mythos goes only to vetted organisations. Even so, Anthropic isn’t pitching Fable as everyone’s default. For most coding and knowledge tasks, it recommends starting with Claude Opus 5.5, “our strongest daily driver”. It suggests moving up to Fable or Mythos for the most ambitious, open-ended work.
Output tokens cost $40 per million, down from $50 for the 5.1 generation, and input tokens fall to $8 from $10. Anthropic says the new models generate outputs up to 30% faster. An optional fast mode speeds generation up to 2.5 times for $16 per million input and $80 per million output tokens. Anthropic says that in early testing on FrontierCode 2.0, Fable 5.2 at High effort scored about as well as Opus 5.5 at Max effort. That comparison costs roughly half as much per task. For teams paying per task, that saving could count for more than the headline scores.
Anthropic’s own benchmark table, run with safeguards on, puts Fable 5.2 a step above Opus 5.5 on almost every test. Those are Anthropic’s own numbers, and we haven’t seen independent results yet.
| Test (Anthropic’s figures) | Fable 5.2 | Fable 5.1 | Opus 5.5 |
|---|---|---|---|
| FrontierCode 2.0 (agentic coding) | 49.1% | 32.4% | 45.5% |
| FrontierSWE v2 (agentic coding) | 69.9% | 56.3% | 62.3% |
| AutomationBench (business workflows) | 51.4% | 31.4% | 42.5% |
| Humanity’s Last Exam (with tools) | 74.2% | 65.6% | 67.7% |
| Remote Labor Index | 41.3% | 17.9% | 21.3% |
You can just throw Claude Fable 5.2 at new, ambiguous systems it has never seen before, and it will figure out how to actually work within them.
Matt Lee, Senior Staff Engineer, Datadog
Developers can call Fable 5.2 as claude-fable-5-2 on the Claude Platform, and it’s also on Amazon Web Services, Google Cloud, and Microsoft Azure. Mythos is different: organisations doing beneficial work in cybersecurity or biomedical research have to apply through Anthropic’s Life Sciences and Cyber Verification Programs. Subscribers on plans that include Fable get one to three Fable usage resets, depending on how long they’ve subscribed.
It’s the second big update to Fable 5 since the model class arrived in June. The first was Fable 5.1 in September. The line had a rocky start. In June, Anthropic pulled Fable 5 and Mythos 5 worldwide after a US government order. CNBC reports that Anthropic is readying a potential IPO that could happen as soon as next week, and the new release lands in the middle of that run-up.
Anthropic also uses the models internally. It says Claude now writes over 90% of the changes merged into its core codebase, with human guidance. Agents on an earlier Fable 5.2 build moved a production service from Python to Rust, and the service now starts about 26 times faster.
