About Claude Fable 5
Claude Fable 5 is the first model in Anthropic's Mythos class, a capability tier the company introduced above its Opus class — Anthropic describes Fable as a Mythos-class model made safe for general availability, with additional safeguards distinguishing it from the restricted-access Claude Mythos 5 it shares its underlying model with. Anthropic positions it as next-generation intelligence for long-running agents, with particular strength in software engineering, knowledge work, vision and scientific research.
It reads text and images, writes text, runs adaptive thinking that is always on, and carries the family's million-token context window with the largest output allowance in Anthropic's lineup. Anthropic lists it among its legacy models — still available — with Claude Fable 5.1 named as its successor.
Fable sits at the top of Anthropic's price list — double Opus rates on both input and output — and its always-on adaptive thinking bills as output tokens, so hard problems cost more than their visible answers suggest. One subtlety matters when comparing against older Claude models: Fable uses the tokenizer Anthropic introduced with Claude Opus 4.7, which produces roughly a third more tokens from the same text than earlier Claude tokenizers did, so per-token price understates the per-request difference. Prompt caching discounts repeated input by an order of magnitude, and batch processing halves standard rates. Reserve it for work that genuinely exceeds Opus, and note that its successor keeps the same input and output rates while charging less for cache reads, which tilts long agentic sessions toward Claude Fable 5.1.
Frequently asked questions
How much does the Claude Fable 5 API cost?
Claude Fable 5 costs $10 per million input tokens and $50 per million output tokens, with cached input at $1 per million (90% off). Note: Anthropic lists Fable 5 as a legacy model (still available); Claude Fable 5.1 succeeds it at the same input/output rates with cheaper cache reads.
How much does a typical chat message cost with Claude Fable 5?
A short chat message (about 500 input and 250 output tokens) costs roughly $0.018 with Claude Fable 5. At 1,000 such requests a day, that is about $525.00 per month.
Is Claude Fable 5 cheap compared to similar models?
Claude Fable 5 has the #28 cheapest input rate of the 29 models we track. On a mixed workload (10K input / 2K output), it costs $0.200 per request, versus $0.045 for GPT-4o.
What does Claude Fable 5 cost per 1,000 tokens?
Per 1,000 tokens, Claude Fable 5 costs $0.0100 for input and $0.0500 for output, or $0.0010 for cached input. Providers quote rates per million tokens ($10/M in, $50/M out here), so divide by a thousand for the per-1K figure older pricing pages used.
How large a prompt can Claude Fable 5 take?
Claude Fable 5 accepts up to 977K tokens of input context and can generate up to 125K tokens of output per request. At its input rate, filling the entire 977K-token window costs about $10.00 per request before any output.
Related
Compare all models at once ·Count tokens in your prompt · Claude Fable 5 vs GPT-5.6 Sol head-to-head
All Anthropic model costs: Claude Fable 5.1 · Claude Opus 5 · Claude Sonnet 5 · Claude Haiku 4.5 · Claude Opus 4.8
Last updated 2026-09-03. Prices verified against Anthropic's official pricing page; see the methodology.