LiteLLM doesn't seem to pass user email to Openmeter when using OpenWebUI

[ianaware]

We have OpenWebUI as the LLM front-end that we have connected to LiteLLM and we want to now add Openmeter and set up per email address cost/token tracking.

Environment:

LiteLLM version: ghcr.io/berriai/litellm:main-stable
Deployment: Kubernetes (EKS)
OpenWebUI with ENABLE_FORWARD_USER_INFO_HEADERS=True

Issue:
OpenMeter integration throws Exception: OpenMeter: user is required even though the user email is present in the request metadata.

My config:

litellm_settings:
  callbacks: ["openmeter"]
  openmeter_subject_headers: ["X-OpenWebUI-User-Email"]
  
general_settings:
  store_model_in_db: true
  user_header_name: X-OpenWebUI-User-Email
  user_header_mappings:
    - header_name: X-OpenWebUI-User-Email
      litellm_user_role: customer

What I see in the logs:

1. The header is being received:

'x-openwebui-user-email': 'my_user_email_address@email_address.com'

2. The user data is in metadata:

'metadata': {
  'user_api_key_end_user_id': 'my_user_email_address@email_address.com',
  'user_api_key_user_email': 'my_user_email_address@email_address.comh',
  ...
}

3. But OpenMeter still fails:

File "/usr/lib/python3.13/site-packages/litellm/integrations/openmeter.py", line 80, in _common_logic
  raise Exception("OpenMeter: user is required")

The Problem:
Looking at the OpenMeter integration code (openmeter.py lines 65-80), it expects:

kwargs.get("user") OR
kwargs["litellm_params"]["metadata"]["user_api_key_user_id"]

But in my logs, the metadata is at:

kwargs["metadata"]["user_api_key_end_user_id"] (not nested under litellm_params)

**Question:**

How do I configure LiteLLM to properly set the user parameter that OpenMeter needs when using OpenWebUI headers? The user_header_name setting doesn't seem to populate kwargs["user"] in a way that OpenMeter can access it.
Is there a configuration option I'm missing, or does the OpenMeter integration need to be updated to look for user data in the correct location in kwargs?

Any help on how to fix this and link it all together or how to solve this would be very much appreciated.

I have made this as a separate issue topic, so I apologise if this qna is not the right way to do it.