fix(embedding): omit null encoding_format for openai requests (#25395)

litellm/main.py

@@ -4913,9 +4913,6 @@ def embedding(  # noqa: PLR0915
 
             if encoding_format is not None:
                 optional_params["encoding_format"] = encoding_format
-            else:
-                # Omiting causes openai sdk to add default value of "float"
-                optional_params["encoding_format"] = None
 
             api_version = None
 

tests/test_litellm/llms/openai/embeddings/test_openai_embeddings_encoding_format.py

@@ -0,0 +1,34 @@
+from unittest.mock import patch
+
+import litellm
+
+
+@patch("litellm.main.openai_chat_completions.embedding", return_value={"ok": True})
+def test_openai_embedding_does_not_send_encoding_format_when_unset(mock_embedding):
+    """Regression test: do not send encoding_format=null to OpenAI-compatible APIs."""
+    litellm.embedding(
+        model="text-embedding-3-small",
+        input=["hello"],
+        api_base="https://example.com/v1",
+        api_key="test-key",
+        custom_llm_provider="openai",
+    )
+
+    optional_params = mock_embedding.call_args.kwargs["optional_params"]
+    assert "encoding_format" not in optional_params
+
+
+@patch("litellm.main.openai_chat_completions.embedding", return_value={"ok": True})
+def test_openai_embedding_preserves_explicit_encoding_format(mock_embedding):
+    """Explicit encoding_format should still be forwarded."""
+    litellm.embedding(
+        model="text-embedding-3-small",
+        input=["hello"],
+        api_base="https://example.com/v1",
+        api_key="test-key",
+        custom_llm_provider="openai",
+        encoding_format="float",
+    )
+
+    optional_params = mock_embedding.call_args.kwargs["optional_params"]
+    assert optional_params["encoding_format"] == "float"