Claude Fable 5.1
A good performance / EU-hosting balance for a European company.
Overview
Claude Fable 5.1 was released on 1 September 2026 as the successor to Claude Fable 5. According to Anthropic, it improves long-running agentic coding, multistep research and work on documents, spreadsheets and slides. Pricing is unchanged from Fable 5 at $10 input and $50 output per million tokens, with cheaper cache reads. The context window is 1 million tokens and output reaches 128,000 tokens. Anthropic recommends starting with Claude Opus 5 for most workloads and keeping Fable 5.1 for cases where Opus 5 is not enough. Claude Mythos 5.1 is the same model with a different level of safeguards, available only to Project Glasswing participants.
Skill profile
Not disclosed
Three independent measures
What people prefer, what the model can do, what the market uses. Each source has its biases and none is enough on its own: we show them side by side, never blended.
Strengths
- World-class on Arena
- Very long context
Limitations
- High output cost
Who is it for
- your data must stay in the EU
- your budget is tight
Access & availability
Key specifications
What it costs per month
Estimate from sourced API prices and a hardware tier for self-hosting. Assumptions are editable.
Assumptions: 36-month amortisation, 0.25 €/kWh, 22 days/month, 1 $ = 0.92 €. Excludes labour, software licences, redundancy.
nAIvigate Trust Index
What the vendor offers and documents for professional use in Europe. An undocumented criterion counts as zero and stays visible: the score rises when the vendor publishes, not when we assume.
19/20 criteria documented · 95 %
See the criteria▾
Trust Index badge
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[](https://naivigate.com/en/model/claude-fable-5-1)Data & compliance
What we know, line by line, with source and date. These lines feed the Data and Enterprise families of the Trust Index above. GDPR compliance depends on your processing, not on the model alone.
| EU data residency | No |
| Data processing agreement (DPA) | Yes |
| Transfer outside the EU | Yes |
| Training on your data | No |
| Configurable retention | Yes |
| Zero Data Retention | On request |
| Self-hostable | No |
| Declared hosting | US |
Quality of this card’s data
This score measures the quality of the data on this card: price, context, Elo, licence, documented, sourced and fresh. It measures neither the model nor its compliance: for that, see the Trust Index above.
5/6 documented · 3/6 primary sources
Advanced data · for expertsArchitecture, modalities, detailed cost, full benchmarks▾
| Arena Elo | 1501 |
| MMLU | — |
| GPQA | — |
| HumanEval | — |
| SWE-Bench | — |
| MATH | — |