[Bug]: mime_content_type(): Icewind\\Streams\\CallbackWrapper::stream_cast is not implemented

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I'm getting this error where requesting /ocs/v2.php/taskprocessing/tasks_provider/{task}/file/{fileid}

{
  "reqId": "**REDACTED**",
  "level": 2,
  "time": "2025-08-26T15:19:52+00:00",
  "remoteAddr": "10.9.0.200",
  "user": "--",
  "app": "PHP",
  "method": "GET",
  "url": "/ocs/v2.php/taskprocessing/tasks_provider/1469/file/992499?format=json",
  "message": "mime_content_type(): Icewind\\Streams\\CallbackWrapper::stream_cast is not implemented! at /var/www/nextcloud/core/Controller/TaskProcessingApiController.php#411",
  "userAgent": "ExApp/stt_whisper2/2.2.1 (httpx/0.28.1)",
  "version": "31.0.8.1",
  "data": {
    "app": "PHP"
  }

The file is an opus ogg audio file, manually running mime_content_type('file.opus'); returns audio/ogg

Steps to reproduce

HTTP GET to /ocs/v2.php/taskprocessing/tasks_provider/{task}/file/{fileid} where file is an opus file.

Expected behavior

mime_content_type() should return 'audio/ogg' without any error or warning.

Nextcloud Server version

31

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.3

Web server

Apache (supported)

Database engine version

MySQL

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

Start at core/Controller/TaskProcessingApiController.php line 411 and reproduce the GET request for an opus file at the task-processing file endpoint. Trace the stream passed to mime_content_type(); done means the request identifies the file as audio/ogg without the stream_cast warning.