# AWS Bedrock Requires Mandatory 30-Day Anthropic Data Sharing for Claude Fable 5 and Mythos 5 — Customers Must Set Their Bedrock Account or Project to provider_data_share Before Invoking the Models, and Future Mythos-Class Releases Will Inherit the Same Policy

> Mythos-class capability on Bedrock comes with a new condition: your prompts leave AWS and live with Anthropic for 30 days.

- Org: Amazon Web Services
- Date: 2026-06-09
- Category: security, ecosystem
- Source: https://aws.amazon.com/blogs/aws/anthropic-claude-fable-5-on-aws-mythos-class-capabilities-with-built-in-safeguards-now-available/
- Canonical page: https://ai-tldr.dev/releases/aws-bedrock-mythos-fable-data-retention-jun9/

## In short

AWS Bedrock now blocks Claude Fable 5 and Mythos 5 unless customers opt their account or project into provider_data_share. Prompts and completions leave AWS, sit with Anthropic for up to 30 days, and the same rule applies to future Mythos-class models.

## What it is

A Bedrock platform change tied to the June 9 launch of Anthropic's Mythos-class models (Claude Fable 5 and the limited-availability Mythos 5). Bedrock now exposes a Data Retention API with four modes (default, provider_data_share, none, inherit), and Fable 5 and Mythos 5 declare allowed_modes of only provider_data_share. Any account or project still on default, none, or inherit sees those models return status: unavailable.

## How it works

Customers set the mode via PUT /v1/data_retention at the account level or POST /v1/organization/projects/{id} at the project level. Once enabled, user prompts and Claude completions are stored by Anthropic for up to 30 days for trust-and-safety review, including human review and use in misuse pattern detection. When a Fable 5 request is rerouted to Opus 4.8 by a safety classifier, the fallback exchange is still retained under Fable 5's rules. AWS exposes a bedrock-mantle:DataRetentionMode IAM condition key so organizations can lock the mode via SCP.

## Why it matters

Bedrock's pitch has been that customer data does not leave the AWS boundary. Fable 5 and Mythos 5 are the first Bedrock-hosted models to break that promise by design. Regulated buyers with zero-data-retention agreements lose access to the Mythos tier unless they request a per-account ZDR exception through their AWS account team. Anthropic frames the retention as the only way to catch cross-conversation misuse that single-prompt classifiers miss.

## Who it's for

Bedrock buyers, AWS solutions architects, compliance teams, AI procurement

## Try it

curl -X PUT https://bedrock-mantle.us-east-1.api.aws/v1/data_retention -H "x-api-key: $BEDROCK_API_KEY" -d '{"mode":"provider_data_share"}'

## Links

- [AWS Blog](https://aws.amazon.com/blogs/aws/anthropic-claude-fable-5-on-aws-mythos-class-capabilities-with-built-in-safeguards-now-available/)
- [Bedrock Data Retention Docs](https://docs.aws.amazon.com/bedrock/latest/userguide/data-retention.html)
- [Anthropic Retention Policy](https://support.claude.com/en/articles/15425996-data-retention-practices-for-mythos-class-models)
- [HN Discussion](https://news.ycombinator.com/item?id=48473166)