Claude Fable 5 (Adaptive Reasoning, Opus 4.8 Fallback)
FrontierClosed weightsTextAdaptive reasoning
Claude Fable family model by Anthropic.
Opus 4.8 Fallback
About the Claude Fable family
A specialty line in Anthropic's Claude 5 generation, run at max adaptive-reasoning effort with an Opus 4.8 fallback — oriented toward rich long-form reasoning and creative/analytical work.
All Claude Fable modelsHow this one is configured
This configuration uses adaptive reasoning (decides per-question how much to think); version/snapshot: Opus 4.8 Fallback.
Also runs at: max effort
Effort controls how long the model thinks before answering — higher effort usually means better answers on hard problems, at the cost of speed and money. Same model underneath, so they share this page.