diff --git a/litellm/litellm_core_utils/mock_functions.py b/litellm/litellm_core_utils/mock_functions.py
index 94d0ef8e423..4d33008d692 100644
--- a/litellm/litellm_core_utils/mock_functions.py
+++ b/litellm/litellm_core_utils/mock_functions.py
@@ -1,5 +1,7 @@
 from collections.abc import Sequence
+from typing import Final
 
+from ..exceptions import BadRequestError
 from ..types.utils import (
     Embedding,
     EmbeddingResponse,
@@ -8,13 +10,15 @@ from ..types.utils import (
     Usage,
 )
 
+# OpenAI caps an embedding input array at 2048 items, as of 2026-10-05:
+# https://platform.openai.com/docs/api-reference/embeddings/create
+_MAX_EMBEDDING_INPUTS: Final = 2048
+
 
 def _embedding_input_count(embedding_input: str | Sequence[str] | Sequence[int] | Sequence[Sequence[int]]) -> int:
-    match embedding_input:
-        case str() | [int(), *_]:
-            return 1
-        case _:
-            return len(embedding_input)
+    if isinstance(embedding_input, str) or (len(embedding_input) > 0 and isinstance(embedding_input[0], int)):
+        return 1
+    return len(embedding_input)
 
 
 def mock_embedding(
@@ -26,12 +30,17 @@ def mock_embedding(
         mock_response = [0.0] * 1536
     elif mock_response == "error":
         raise Exception("Mock error")
+    input_count: Final = _embedding_input_count(embedding_input)
+    if not 1 <= input_count <= _MAX_EMBEDDING_INPUTS:
+        raise BadRequestError(
+            message=f"input must contain between 1 and {_MAX_EMBEDDING_INPUTS} items, got {input_count}",
+            model=model,
+            llm_provider=None,
+            body={"param": "input"},
+        )
     return EmbeddingResponse(
         model=model,
-        data=[
-            Embedding(embedding=mock_response, index=index, object="embedding")
-            for index in range(_embedding_input_count(embedding_input))
-        ],
+        data=[Embedding(embedding=mock_response, index=index, object="embedding") for index in range(input_count)],
         usage=Usage(prompt_tokens=10, completion_tokens=0),
     )
 
diff --git a/tests/unit/litellm_core_utils/test_mock_functions.py b/tests/unit/litellm_core_utils/test_mock_functions.py
index 841336f9917..e362ae98055 100644
--- a/tests/unit/litellm_core_utils/test_mock_functions.py
+++ b/tests/unit/litellm_core_utils/test_mock_functions.py
@@ -3,6 +3,7 @@ from typing import Final
 import pytest
 
 import litellm
+from litellm.exceptions import BadRequestError
 
 
 @pytest.mark.parametrize(
@@ -21,3 +22,9 @@ def test_mock_embedding_returns_one_embedding_per_input(embedding_input: object,
 
     assert [row["index"] for row in response.data] == list(range(expected_count))
     assert [row["embedding"] for row in response.data] == [vector] * expected_count
+
+
+@pytest.mark.parametrize("embedding_input", [[], ["text"] * 2049])
+def test_mock_embedding_rejects_input_count_a_provider_would_reject(embedding_input: list[str]) -> None:
+    with pytest.raises(BadRequestError, match="between 1 and 2048 items"):
+        litellm.embedding(model="openai/test-model", input=embedding_input, mock_response=[0.1, 0.2])