Fable 5, Now Available in :Harvey:
Announcing Anthropic's Fable 5 in Harvey
Today Anthropic released Fable 5, the most powerful model in the Claude family, and Harvey customers can opt in to early access.
Fable 5 scored new highs on both LAB and BigLaw Bench, our benchmarks for evaluating model performance on complex legal tasks.
It also comes with some security and data privacy considerations that differ from Harvey’s core offerings. We're flagging these transparently so customers can make an informed decision about whether and when to enable it.
Fable 5 Sets a New Bar
On Harvey's Legal Agent Benchmark (LAB), which measures end-to-end completion of complex legal tasks under a strict all-pass standard, Fable 5 scored 13.3% — an all-time high-score, up from Opus 4.8’s 10.4%.
In our internal evaluation using BigLaw Bench, Harvey's proprietary legal benchmark, Fable 5 scored 93.4% overall, a new high for the Anthropic model family.
Our lawyer evaluators highlighted the model's strength in drafting and markup analysis. Fable 5 produced well-structured legal documents across practice areas and reliably identified term sheet deviations, off-market provisions, and internal inconsistencies when reviewing counterparty redlines. The model also handled large, multi-document scenarios well, accurately tracing provisions and defined terms across large sets of source documents per task and catching inconsistencies between them. Performance on complex quantitative analysis — such as multi-step tax calculations and fund waterfall modeling — was more mixed, consistent with what we've observed across frontier models in those categories.
“Fable 5 reached a new high on our Legal Agent Benchmark, scoring 13.3%, with particular strengths in drafting and long-horizon agent work. For the kind of complex, multi-step matters our customers run every day, that's a meaningful step up. We're making Fable 5 available to customers who want to explore what it has to offer.”
Niko Grupen
Head of Applied Research at Harvey
What to Know Before Enabling Fable 5
The use of Fable 5 involves data processing practices that differ from data commitments we made in our existing customer agreements. Specifically, Anthropic will retain data and contents (inputs, outputs, and documents) and may review such data for safety reasons. Anthropic has informed us that this data will generally be deleted after 30 days, unless a longer retention period is required for legal or safety reasons. If Anthropic does access customer data it will be through a scoped viewer with no export, copy, or download capability.
Anthropic does not offer any regional processing for Fable 5 so all data will be processed in the United States. For more information, see Anthropic’s help center article here.
We are making this model available as an opt-in option vs. by default, and will be monitoring usage and cost during the early access period. Our goal is to give customers access to a highly capable model while preserving their ability to decide what’s right for their organization.
If you have questions or are interested in enabling Fable 5 for your organization, please reach out to your account team.