Claude Fable 5.1 from @AnthropicAI is live on OpenRouter.
A direct upgrade for Fable 5 workloads, with the biggest gains in agentic coding, long-running workflows, visual code generation, finance, and analysis.
Try it: https://t.co/a07gfACbQe
On pricing: Fable 5.1 keeps Fable 5 pricing at $10/M input tokens and $50/M output tokens.
Prompt cache reads drop to $0.25/M tokens, 75% below the old cache-read rate.
Read more: https://t.co/EZjBphBEIS
token — The chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
Why it matters
Headline pricing matches Fable 5, but prompt cache reads drop to $0.25 per million tokenThe chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.Full definition →, a 75% cut that materially lowers the cost of AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition → loops replaying large contexts.
