overview changedmodels/fable-5-1/overview
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77**Legacy.** Released September 1, 2026.
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9For demanding reasoning and long-horizon agentic work
9Although Claude Fable 5.1 is still available, you should consider migrating to Claude Fable 5.2. [See Claude Fable 5.2](https://platform.claude.com/docs/en/models/fable-5-2/overview) · [Migrate to Claude Fable 5.2](https://platform.claude.com/docs/en/models/fable-5-2/migration-guide#migrating-from-claude-fable-5-1-to-claude-fable-5-2)
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11Although Claude Fable 5.1 is still available, you should consider migrating to Claude Fable 5.2. [See Claude Fable 5.2](https://platform.claude.com/docs/en/models/fable-5-2/overview) · [Migrate to Claude Fable 5.2](https://platform.claude.com/docs/en/models/fable-5-2/migration-guide)
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1311Model ID: `claude-fable-5-1`
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1513Context window: 1M tokens · Max output: 128K tokens · Input pricing: $10 / MTok · Output pricing: $50 / MTok
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103101 When this model’s thinking blocks stay usable: across model switches and across changes to the conversation.
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106 <Card title="Per-message effort" icon="sliders" href="https://platform.claude.com/docs/en/build-with-claude/effort#change-effort-mid-conversation-beta">
104 <Card title="Per-message effort" icon="sliders" href="https://platform.claude.com/docs/en/build-with-claude/effort-per-message">
107105 Change the effort level partway through a conversation without invalidating the prompt cache.
108106 </Card>
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