## Token counts on Claude Fable and Claude Mythos models ## Token counts on Claude Fable 5 and Claude Mythos 5
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2929### Supported models
3030
31All [active models](https://platform.claude.com/docs/en/models/overview) support token counting, including Claude Opus 5 and Claude Sonnet 5.
31All [active models](https://platform.claude.com/docs/en/models/overview) support token counting.
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3333<Note>
3434 Claude 4.7 and later models and Claude Mythos Preview use a newer tokenizer. The same input text produces approximately 30 percent more tokens than on earlier models. The exact increase depends on the content and workload shape. Recount prompts against the model you plan to use rather than reusing counts measured against earlier models.
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1397## Token counts on Claude Fable 5 and Claude Mythos 5
1397## Token counts on Claude Fable and Claude Mythos models
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1399Claude Fable 5 and Claude Mythos 5 use the tokenizer introduced with Claude Opus 4.7, which produces roughly 30 percent more tokens than models before Claude Opus 4.7 for the same text. The exact increase depends on the content and workload shape. The token counting endpoint returns the count under the tokenizer of the `model` you pass, so to measure the difference for your workload, count the same request twice: once with your current model and once with `model: "claude-fable-5"` (or `"claude-mythos-5"`), and compare the two `input_tokens` values.
1399Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, and Claude Mythos 5 share the tokenizer introduced with Claude Opus 4.7. A prompt counts the same on all four, and roughly 30 percent higher than on models before Claude Opus 4.7 (the exact increase depends on the content). The token counting endpoint counts under the tokenizer of the `model` you pass. To measure the difference for your workload, count the same request twice, once with your current model and once with the model you plan to move to, and compare the two `input_tokens` values.
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14011401<Note>
1402 **Billing and migration:** Usage and billing on Claude Fable 5 and Claude Mythos 5 reflect this tokenizer's counts. If you're migrating from a model before Claude Opus 4.7, the same content consumes roughly 30 percent more tokens. The exact increase depends on the content and workload shape. When migrating a workload to Claude Fable 5 and Claude Mythos 5, don't reuse token counts measured on a model before Claude Opus 4.7 to estimate costs or context window fit. Count your prompts with `model: "claude-fable-5"` (or `"claude-mythos-5"`).
1402 **Billing and migration:** Usage and billing on these models reflect this tokenizer's counts. When migrating from a model before Claude Opus 4.7, don't reuse token counts measured on the older model to estimate costs or context window fit. Count your prompts with the `model` ID you plan to use (for example, `"claude-fable-5-1"`).
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