How to pass LiteLLM user email to Openmeter as 'user' value?

[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.

In my litellm request logs the user email address passed to it from OpenWebUI is under 'End User'.

Sample LiteLLM log:

Time	Status	Session ID	Request ID	Cost	Duration (s)	Team Name	Key Hash	Key Name	Model	Tokens	Internal User	End User	Tags

11/09/2025 03:57:41 PM	Success	<Session ID>
<Request ID>
$0.000028	
0.916
Dev
<Key Hash>
<Key Name>

gpt-4.1-nano
225(208+17)	
<Internal User value>
[email protected] - this is what I need to send to Openmeter
0: User-Agent: Python +1

This proves that OpenWebUI correctly passes the data to LiteLLM (I think), but, with Openmeter, I get the error below.

raise Exception("OpenMeter: user is required") Exception: OpenMeter: user is required`

It seems Openmeter looks for "user" but OpenWebUI puts the email address under 'End_User' so there is a mismatch. However, I am no expert here on how this works with openmeter/openwebui .

How can I get it to use 'end_user' from LiteLLM? Is there some config setting I must add that does this or a config setting that passes the end_user value to the "user" value Openmeter expects to stop this error from happening and pass the email address data correctly from LiteLLM to Openmeter?

In my k8s.yaml for LiteLLM I have, under litellm_settings:

callbacks: ["openmeter"]
openmeter_subject_headers: ["X-OpenWebUI-User-Email"]

under general_settings I have:

user_header_name: X-OpenWebUI-User-Email

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