This entry is a serving variant of Anthropic: Claude Fable 5. A variant shares its base model's tokenizer by construction, so the measurement lives on the base record and this page inherits it.
| Signal | Result | Reference |
|---|---|---|
| Tokenizer signature | Not measured | – |
| API surface | No other entry shares this exact contract | api_21c18cd3 |
| Context and output | 1,000,000 context · 128,000 max output | declared |
| Reasoning contract | Mandatory · efforts max, xhigh, high, medium, low · default high | declared |
| Serving providers observed | None recorded yet | – |
Claude Fable 5 is a Mythos-class model from Anthropic, built for autonomous knowledge work and coding. It supports text, image, and file inputs with text output, with reasoning support and...
Supported parameters
include_reasoningmax_tokensreasoningreasoning_effortresponse_formatstopstructured_outputstool_choicetoolsverbosity
defaults: {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null}
Cite this page as the evidence record for Anthropic: Claude Fable 5 (batch): the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings. The raw data behind every figure is on the data page.
