introducing-claude-fable-5-and-claude-mythos-5 changedmodels/fable-5/introducing-claude-fable-5-and-claude-mythos-5
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1515Claude Fable 5 is built for demanding reasoning and long-horizon agentic work. Claude Mythos 5 shares the same capabilities and is available only in limited release through [Project Glasswing](https://anthropic.com/glasswing).
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17The headline change for integrations: Claude Fable 5 includes safety classifiers that can decline requests. Claude Mythos 5 does not include these classifiers. If your integration calls Claude Fable 5, plan for three changes: new response handling for refusals, fallback options for retrying on another Claude model, and new billing rules. [Refusals, fallback, and billing on Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/introducing-claude-fable-5-and-claude-mythos-5#refusals-fallback-and-billing-on-claude-fable-5) summarizes all three.
17The headline change for integrations: Claude Fable 5 includes safety classifiers that can decline requests. If your integration calls Claude Fable 5, plan for three changes: new response handling for refusals, fallback options for retrying on another Claude model, and new billing rules. [Refusals, fallback, and billing on Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/introducing-claude-fable-5-and-claude-mythos-5#refusals-fallback-and-billing-on-claude-fable-5) summarizes all three.
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1919## Models
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21| Model | API model ID | Description |
22| --------------- | ----------------- | --------------------------------------------------------------------------------------------------------------------------------------------- |
23| Claude Fable 5 | `claude-fable-5` | Built for demanding reasoning and long-horizon agentic work |
24| Claude Mythos 5 | `claude-mythos-5` | Shares Claude Fable 5's capabilities without the safety classifiers. Available through Project Glasswing. Successor to Claude Mythos Preview. |
21| Model | API model ID | Description |
22| --------------- | ----------------- | -------------------------------------------------------------------------------------------------------------- |
23| Claude Fable 5 | `claude-fable-5` | Built for demanding reasoning and long-horizon agentic work |
24| Claude Mythos 5 | `claude-mythos-5` | Shares Claude Fable 5's capabilities. Available through Project Glasswing. Successor to Claude Mythos Preview. |
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2626Claude Fable 5 and Claude Mythos 5 share the same specs and pricing:
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3333## Refusals, fallback, and billing on Claude Fable 5
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35Claude Fable 5 includes safety classifiers that can decline certain requests. Claude Mythos 5 does not include these classifiers, so this section applies to Claude Fable 5 only. The following sections summarize what refusals mean for your integration. Each links to the full guide.
35Claude Fable 5 includes safety classifiers that can decline certain requests. The following sections summarize what refusals mean for your integration. Each links to the full guide.
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3737### Refusals
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