Anthropic EFS 2026: what Enterprise Frontier Safeguards are
EFS keeps monitoring logs in the customer cloud. Detection stays automated at Anthropic. Full rollout is later this fall.
On 1 September 2026 Anthropic published the enterprise condition hereink readers keep asking about: Enterprise Frontier Safeguards keep monitoring logs in the customer cloud, not at the model vendor.
The query is Anthropic EFS. It is not a new model drop. It is a custody and misuse-detection design for Covered Models such as Claude Fable 5 and 5.1. The facts sit in Anthropic’s post and the AWS Machine Learning blog.
It splits custody, not the model
The customer holds the logs
Activity data can live in the customer’s own Amazon S3, Azure Blob, or Google Cloud Storage under customer keys, access policy, and audit logs. Anthropic does not charge for EFS. The cloud bill covers storage, I/O, and egress.
The lab still runs detection
Automated systems scan a rolling window for serious misuse, including attempts at offensive cyber or biological work and signs of stolen credentials. Flags go to the customer. Anthropic human review is not required.
Detection stays with the lab. Logs stay in the customer account.
What is actually live
| Layer | What the vendors wrote | Status |
|---|---|---|
| EFS itself | Phased rollout, broader availability later this fall | Request access; not default GA |
| Bridge ZDR | Eligible customers can run Fable 5 / 5.1 with zero data retention first | AWS: internal use through 2026-12-31 |
| Surfaces | Claude Code, Claude Enterprise, Claude Platform, Bedrock, Google Agent Platform, Microsoft Foundry | Parity promised across the three clouds |
| Price and behavior | Customer storage, CMEK, and automated review are each opt-in | No change to model behavior, API price, or limits |
How a buyer should read the note
- 01Check the Covered Model label
Fable 5.1 is a Covered Model: retention can run up to 30 days so misuse can be correlated across sessions and accounts. Anthropic says this is not a path to train on enterprise data.
- 02Ask whose account holds the logs
Regulated buyers often cannot add another trusted data vendor. EFS’s pitch is that monitoring data lands in the cloud they already run. Without eligibility, each cloud’s retention mode still applies.
- 03Ask who does human review
On Bedrock, AWS says the default Covered Model path uses aws_review, with Amazon staff reviewing inside the AWS boundary. EFS routes flags to the customer’s own security team.
- Who should track this
- Security and compliance teams in banking, health, telecom, law, and the public sector that already want Fable 5.1 but stalled on 30-day retention.
- What the posts do not settle
- SLAs, which sectors auto-qualify, and when third-party resellers match the same split. Anthropic only says it is working with cloud partners and some third-party offerings.
EFS = customer-held logs + Anthropic automated detectionDraw the custody line
Who holds the keys and who sees the flags belongs on one sheet. A short room does not need an account; see no account needed.