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Area

admin/api

Describe the bug

In the latest release of Keycloak, 26.2.4, the POST /admin/realms API now returns a 400 status code if the realm already exists instead of the 409 status code returned previously.

This is the full response:

400: b'{"errorMessage":"Realm <name> already exists"}'

This API changes breaks a number of keycloak clients that expect a 409 status code to be returned when a realm already exists.

Version

26.2.4

Regression

[x] The issue is a regression

Expected behavior

If the realm already exists, the API should return a 409 status code.

Actual behavior

The API returns a 400 status code when the realm exists.

How to Reproduce?

Call the POST /admin/realms API with the name of a realm that already exists, and the response status code will be 400 instead of 409.

Anything else?

No response

Example in postman:

<img width="1397" alt="Image" src="https://github.com/user-attachments/assets/56879c51-a4ff-4616-b773-a28157cf41be" />