About Claude Fable 5
Claude Fable 5 introduces Anthropic's Claude 5 generation and Mythos-class model tier, built for demanding reasoning and long-horizon agentic work. It is built to sustain days-long, complex, and asynchronous tasks that earlier models could not, with strong performance across software engineering, knowledge work, vision, and computer use.
Claude Fable 5 is a Mythos-class model made safe for general use, with conservative safeguards in cybersecurity, biology, and chemistry. Flagged requests in those domains can be routed to Claude Opus 4.8 via server-side fallback. It uses adaptive thinking (always on), does not support extended thinking, and ships with a native 1M-token context window and up to 128k output tokens.
| Metric | Value |
|---|---|
| Context Length | 1,000,000 tokens |
| Max Output | 128,000 tokens |
| Multilingual | Yes |
Ready to build with Claude Fable 5?
Try Claude Fable 5 in the Workbench to prompt it, compare outputs, and iterate on prompts without writing any code. When you're ready to ship, call the same model from our API and build your own apps on top of it.
curl -sSf -X POST https://hub.oxen.ai/api/ai/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $OXEN_API_KEY" \
-d '{
"model": "claude-fable-5",
"messages": [
{
"role": "user",
"content": "Try sending a message."
}
]
}'API endpoint
See the API reference for request and response formats.
https://hub.oxen.ai/api/ai/chat/completions