From eb28ed1dc6da783dfe73ac066d9da8fd68911427 Mon Sep 17 00:00:00 2001
From: PRABHU KIRAN VANDRANKI <72809214+VANDRANKI@users.noreply.github.com>
Date: Tue, 19 May 2026 20:19:16 -0400
Subject: [PATCH] fix(embedding): normalize list encoding_format from model
 config to first element

When `encoding_format` is configured as a list in model litellm_params (e.g.
`encoding_format: [float, base64]` to declare supported formats), the list was
forwarded verbatim to the upstream embedding API, causing vLLM to reject the
request with validation errors.

Normalize `encoding_format` to its first element when it arrives as a list,
matching the function's `Optional[str]` contract. If the list is empty, treat
it as `None` (unset). This affects all providers (hosted_vllm, openai, azure,
etc.) uniformly.

Fixes #28239
---
 litellm/main.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/litellm/main.py b/litellm/main.py
index c3d1c2e05b0..660559baf6a 100644
--- a/litellm/main.py
+++ b/litellm/main.py
@@ -4809,6 +4809,8 @@ def embedding(  # noqa: PLR0915
     mock_response: Optional[List[float]] = kwargs.get("mock_response", None)  # type: ignore
     azure_ad_token_provider = kwargs.get("azure_ad_token_provider", None)
     aembedding: Optional[bool] = kwargs.get("aembedding", None)
+    if isinstance(encoding_format, list):
+        encoding_format = encoding_format[0] if encoding_format else None
     extra_headers = kwargs.get("extra_headers", None)
     headers = kwargs.get("headers", None) or extra_headers
     if headers is None: