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Anthropic · Language model

Claude Fable 5

anthropic/claude-fable-5
  • Language
Released Jun 9, 2026

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...

Specifications

Context window
1,000,000 tokens
Max output
128,000 tokens
Input
text, image, file
Output
text
Reasoning effort
max, xhigh, high, medium, low (always on)
Tokenizer
Claude
Moderation
provider-moderated

Supported parameters

Accepted by the model and forwarded as-is by the gateway.

  • max_completion_tokens
  • max_tokens
  • reasoning
  • reasoning_effort
  • response_format
  • stop
  • structured_outputs
  • tool_choice
  • tools
  • verbosity

Use it

POST /api/v1/chat/completions · MCP chat · full reference

curl https://omnirail.org/api/v1/chat/completions \
  -H "Authorization: Bearer $OMNIRAIL_KEY" -H "Content-Type: application/json" \
  -d '{"model":"anthropic/claude-fable-5","messages":[{"role":"user","content":"Hello"}],"max_tokens":300}'