Claude Fable 5.1
Chat model · Anthropic ·
Claude Fable 5.1 is a chat model by Anthropic. In Endless it costs 810 credits per 1M input tokens and 4050 per 1M output tokens, on the Hobby plan and up.
Claude Fable 5.1 is Anthropic's most capable widely released model, built for demanding reasoning, multi-hour coding and multistep research.
- Price
- 810 credits per 1M input tokens
- 4050 credits per 1M output tokens
- Availability
- Available on Hobby and above
- Context window
- 1M tokens
- Max output
- 128K tokens
- Inputs
- Text, images
- Outputs
- Text
About Claude Fable 5.1
Claude Fable 5.1 is the top tier of the Claude lineup, released in September 2026 as the successor to Claude Fable 5. It reads text and images, holds up to 1M tokens of context and writes up to 128K tokens in one reply. Thinking is always on. It avoids shortcuts that lead to weaker work and goes after the root cause of a problem instead of patching the symptom.
Reach for it when a task runs long and needs little supervision: chasing down a crash nobody has managed to explain, or working through research that spans many sources and steps. It also builds slide decks and spreadsheet models from financial documents, and it stays more comfortable than Fable 5 on long, unattended work.
Claude Opus 5.5 performs at a similar level on most work and responds faster, so it makes a good starting point. Move to Fable 5.1 when a job needs the deepest reasoning or the longest autonomous run. In Endless both sit in the same chat, so you can switch between them inside one workspace.
Best for
- Multi-hour coding tasks that need a root-cause fix
- Research that pulls together many sources over many steps
- Slide decks and spreadsheet models built from financial documents
- Problems where a faster model keeps falling short
Questions about Claude Fable 5.1
- What is the difference between Claude Fable 5.1 and Claude Fable 5?
- Fable 5.1 is the newer release in the same tier. It is stronger at long-running agentic coding, multistep research and document, spreadsheet and slide work, and its knowledge runs through June 2026 instead of January 2026.
- Should I use Claude Fable 5.1 or Claude Opus 5.5?
- Start with Opus 5.5 for most work, since it performs close to Fable 5.1 on most tasks and responds faster. Choose Fable 5.1 for the hardest reasoning and for long agent runs where Opus 5.5 still falls short.
- How much text can Claude Fable 5.1 read at once?
- It has a 1M-token context window, roughly 555,000 words. It can write up to 128K tokens in a single reply.
Related models
Claude Opus 5.5
by Anthropic
Long agentic coding and research work over a 1M-token context
324 / 1620 credits per 1M tokens
Claude Haiku 5.5
by Anthropic
Fast summaries, routing and subagent tasks at high volume
40.5 / 202.5 credits per 1M tokens
Claude Fable 5
by Anthropic
Long autonomous sessions that stay focused across millions of tokens
810 / 4050 credits per 1M tokens
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