Use Fable 5 in Harvey
Learn what Fable 5 is, how admins enable it, and how to use it in the model selector.
Last updated: Aug 4, 2026
Overview
Fable 5 is a frontier Mythos-grade model from Anthropic, available in Harvey as a premium option. It is built for long-horizon, autonomous work, demonstrating strong performance across legal tasks as measured by Harvey’s benchmarks (LAB and BigLaw Bench).
Because it processes your data differently than Harvey's core services, Fable 5 is governed by Harvey's Extended AI Features framework and is off by default. A workspace admin must opt in before anyone can use it.
Important: Fable 5 usage is billed separately from your Harvey subscription and requires a signed contract addendum. Contact your Customer Success Manager or account team for more details if you want to turn Fable 5 on for your workspace.
Before You Enable Fable 5
There are two key areas to review with your organization before turning Fable 5 on: data retention and regional processing.
Data retention
Unlike other models in Harvey, Fable 5 cannot be used with Zero Data Retention (ZDR). Anthropic requires extended retention to run the safety classifiers that protect against misuse of the model.
Category | Details |
|---|---|
Retention period | Prompts and outputs are retained for 30 days, then deleted. |
Longer retention | Only if content is flagged by a safety classifier, or if Anthropic is legally required to retain it |
Human review | No Anthropic employee has default access. A small set of approved reviewers may access content only if it is flagged for potential serious harm, or at your written request. Every access is recorded in a tamper-proof log |
Training | Retained data is not used to train Anthropic's models, and is not shared with other customers |
Fable 5 access is isolated to a dedicated Anthropic workspace. Enabling Fable 5 does not affect ZDR for any other model — you can continue using other Anthropic models in Harvey with ZDR enabled.
For the full data-handling detail, see Extended AI Features.
Regional processing
Fable 5 supports US-based processing only. Anthropic does not currently offer regional processing for Fable 5.
This means that if your workspace is hosted outside the US, you can still enable and use Fable 5, but every Fable 5 query will be processed in the United States, and stored in the US. Your queries to all other models continue to follow your workspace's normal regional processing configuration.
Enabling Fable 5 and Monitoring Usage (For Admins)
Enabling Fable 5 is a two-step process.
Step 1: Contact Harvey to Enable Extended AI Features
The Extended AI Features setting is not visible in your workspace until Harvey enables it.
- Contact your account team to have Extended AI Features enabled for your workspace.
- Your Harvey team will walk you through the data retention and processing terms above, and the commercial terms for Fable 5 usage.
- Once complete, the Extended AI Features toggle appears in your admin settings.
Note: The Extended AI Features setting is subject to Harvey's Service Terms.
Step 2: Turn on Extended AI Features and enable Fable 5
- Go to Settings → Models.
- Turn on Extended AI Features.
- Enable Fable 5 for either your entire workspace or for specific users.
Fable 5 appears in the model selector only for users you have enabled it for.
Monitoring Usage
You can view your organization's Fable 5 usage in the Credit Usage page within Settings.
- Go to Settings → Credit Usage
- In the Credit usage by model panel, review Fable 5 consumption over time.
Using Fable 5 in Harvey
Fable 5 appears as a named model in the model selector, alongside the other models available to you.
Note: Your workspace must have the model selector enabled to choose it — see How to Choose an AI Model in Harvey.
In Assistant:
- Select the customize button.
- In the models list, select Fable 5.
In a Vault review table:
- Create a new column query and select Continue.
- From the model selector, choose Fable 5.
When you select Fable 5 directly, Harvey routes your query to Fable 5, and the model used is shown in your thread. If Fable 5 is temporarily unavailable, Harvey displays a notice and automatically routes the query to another model that is well-suited to the task.
Note: Fable 5 is not part of Auto mode and is not Harvey's default model. If you don't explicitly choose Fable 5, your queries will not run on it.
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