What happened?

1. Verify a published article category exists (e.g., id=24).
2. Send the following request (body copied verbatim from the official docs at https://docs.joomla.org/J4.x:Joomla_Core_APIs):

POST https://[domain]/api/index.php/v1/content/articles

Headers:
  X-Joomla-Token: <valid super-user token>
  Content-Type: application/json
  Accept: application/vnd.api+json

Body:
{
  "alias": "my-article",
  "articletext": "My text",
  "catid": 24,
  "language": "*",
  "metadesc": "",
  "metakey": "",
  "title": "Here is an article"
}

Version

6.1

Expected result

New article created.

Actual result

{
    "errors": [
        {
            "title": "Field required: Title"
        }
    ]
}

System Information

• Joomla! version: 6.1.0 Stable [Nyota]
• PHP Version: 8.3.30
• Web Server: Apache (apache2handler)
• Database: MySQL 8.4.6
• Database Collation: utf8mb4_0900_ai_ci
• Joomla Backward Compatibility Plugin: Enabled (classes_aliases:"1", legacy_classes:"1")

Additional Comments

The API validator partially sees the body: when catid is also omitted, the error becomes:

{
    "errors": [
        {
            "title": "Field required: Title\nField required: Category"
        }
    ]
}

Removing catid adds a Category error, so the body is being parsed, but the title field always fails the required check even when a non-empty string is supplied.

Tested variations (all fail with the same Field required: Title error)

• Different title values: plain text, with/without apostrophe, short strings, long strings
• Different unique aliases
• Content-Type application/json and application/vnd.api+json
• Postman and direct curl