[Bug]: Default encoding_format list in model parameters triggers vLLM failure

[ndjones]

Check for existing issues

• I have searched the existing issues and checked that my issue is not a duplicate.

What happened?

Including encoding_format as a list within model parameters leads to a vLLM failure on model calls that don't explicitly set a specific encoding_format, as by default LiteLLM passes the whole list to vLLM as a string.

 "encoding_format": [
    "float",
    "base64",
    "ubyte",
    "int8"
  ]

The model Test Connection behaves in this default way, and displays this error

Error testing connection: litellm.BadRequestError: Hosted_vllmException - {"error":{"message":"3 validation errors:\n {'type'...

Using the Swagger API you can reproduce this error by not setting encoding_format or otherwise setting it.

Steps to Reproduce

1. Set encoding_format to a list on an embedding model
2. Make a call to the embeddings endpoint without specifying an encoding_format
3. Make a call to the embeddings endpoint with specifying an encoding format

Relevant log output

What part of LiteLLM is this about?

Proxy

What LiteLLM version are you on ?

v1.83.14

Twitter / LinkedIn details

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