Anthropic: Claude Fable 5

anthropic/claude-fable-5 · AnthropicNot yet established

Declared family: Claude
Evidence confidence: Unknown
Declared tokenizer tag: Claude
Entered catalogue: 9 June 2026
Last tested: Not yet measured
Measurement: Awaiting measurement

Evidence stack

Signals of different kinds, weighed together

Signal	Result	Reference
Tokenizer signature	Not measured	–
API surface	Identical contract to 1 other entry	api_225f0dab
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	–

Declared record

What the catalogue claims about this model

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...

Modalities: text+image+file->text
Declared tokenizer: Claude
Prompt price: $10.0 / M tokens
Completion price: $50.0 / M tokens

Supported parameters

include_reasoningmax_completion_tokensmax_tokensreasoningreasoning_effortresponse_formatstopstructured_outputstool_choicetoolsverbosity

defaults: {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null}

Catalogue entry

History

Every observation, kept as taken

9 June 2026Enters the OpenRouter catalogue declared as Claude.

Cite this page as the evidence record for Anthropic: Claude Fable 5: 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.