---
title: "Anthropic Fingerprint storage requires the diagnostics object: 2026-09-09 | Harbyn"
description: "Anthropic Fingerprint storage requires the diagnostics object, announced Sep 9, 2026."
canonical: "https://harbyn.com/changes/anthropic/2026-09-09-fingerprint-storage-requires-the-diagnostics-object"
last-updated: 2026-09-24
---

# Anthropic Fingerprint storage requires the diagnostics object

Markdown version of <https://harbyn.com/changes/anthropic/2026-09-09-fingerprint-storage-requires-the-diagnostics-object>.

Behavior change - Anthropic. medium severity. Announced.

The API now stores a request's fingerprint only when the request includes the diagnostics object. A request that sends only the cache-diagnosis-2026-04-07 beta header is still accepted, but no fingerprint is stored; a later turn that points previous\_message\_id at it reports previous\_message\_not\_found.

## Facts

| Fact | Value |
| --- | --- |
| Vendor | [Anthropic](https://harbyn.com/vendors/anthropic.md) |
| Kind | Behavior change |
| Severity | medium |
| Status | Announced |
| Announced | Sep 9, 2026 |
| Added to Harbyn | Sep 24, 2026 |
| Lead time | No dated deadline |
| Symbols | `cache-diagnosis-2026-04-07`, `diagnostics`, `previous_message_id`, `previous_message_not_found` |
| Review | Automated, extracted by a model |

## Find it in your code

```sh
npx harbyn scan
```

This change names no identifier the scanner can match line by line, so the scan tells you whether your repository uses Anthropic, from its packages and API hosts. Nothing leaves your machine.

## Sources

Where this event comes from: the page we read, when we read it, and the hash of that snapshot.

- <https://platform.claude.com/docs/en/release-notes/overview.md> (changelog, fetched 2026-09-24 17:16 UTC, sha256 `62f890350b58e6da475adcc09e72e9a16dbad42f99c96e39f3d2543575c3423c`)

## Related changes

### More from Anthropic

- [Claude Enterprise Admin, Analytics and Compliance API requests should send the anthropic-version header](https://harbyn.com/changes/anthropic/2026-09-01-enterprise-admin-and-compliance-api-requests-must-send-api-version-header.md) (Behavior change, announced Sep 1, 2026)
- [Tool choice restriction on Fable 5.1 and Mythos 5.1](https://harbyn.com/changes/anthropic/2026-09-01-tool-choice-restriction-on-fable-5-1-and-mythos-5-1.md) (Behavior change, announced Sep 1, 2026)
- [SDK beta headers removal for files and skills](https://harbyn.com/changes/anthropic/2026-08-27-sdk-beta-headers-removal-for-files-and-skills.md) (Deprecation, announced Aug 27, 2026)
- [Cache diagnostics is out of beta](https://harbyn.com/changes/anthropic/2026-09-23-cache-diagnostics-is-out-of-beta.md) (Behavior change, announced Sep 23, 2026)

### Changes at other vendors

- [Amazon Selling Partner API: ORDER\_CHANGE notifications add PreFulfillmentStatusChange for Amazon Autos](https://harbyn.com/changes/amazon-sp-api/2026-10-14-sp-api-updates-new-listings-items-api-ivp-values-in-eu5-jp-and-ca-stores-oct-3.md) (effective Oct 28, 2026)
- [BigCommerce: 301 redirects will apply only to storefront channels](https://harbyn.com/changes/bigcommerce/2026-10-07-301-redirects-now-apply-to-storefront-channels-only.md) (effective Nov 10, 2026)
- [GitHub: Secret scanning audit log business field changes to enterprise slug](https://harbyn.com/changes/github/2026-10-20-updates-to-github-secret-scanning-7.md) (effective Nov 12, 2026)
- [Jira / Atlassian Cloud: New IP address ranges in use from January 1, 2027](https://harbyn.com/changes/atlassian-jira/2026-10-16-atlassian-cloud-adds-new-ip-address-ranges.md) (effective Jan 1, 2027)

[All upcoming deadlines](https://harbyn.com/deadlines.md)