diff --git a/src/openai/lib/_parsing/_embeddings.py b/src/openai/lib/_parsing/_embeddings.py
index acb890fa52..5fd8aea2c3 100644
--- a/src/openai/lib/_parsing/_embeddings.py
+++ b/src/openai/lib/_parsing/_embeddings.py
@@ -20,11 +20,15 @@ def parse_embedding_response(
     if not obj.data:
         raise ValueError("No embedding data received")
 
+    use_numpy: bool | None = None
+
     for embedding in obj.data:
         data = cast(object, embedding.embedding)
         if not isinstance(data, str):
             continue
-        if not has_numpy():
+        if use_numpy is None:
+            use_numpy = has_numpy()
+        if not use_numpy:
             # use array for base64 optimisation
             embedding.embedding = array.array("f", base64.b64decode(data)).tolist()
         else:
diff --git a/tests/lib/test_embeddings.py b/tests/lib/test_embeddings.py
index 787d580716..fab3a96e65 100644
--- a/tests/lib/test_embeddings.py
+++ b/tests/lib/test_embeddings.py
@@ -63,6 +63,37 @@ def test_decode_preserves_response_and_non_string_vectors(encoding_format: Omit
     assert parsed.model == "text-embedding-3-small"
 
 
+@pytest.mark.parametrize("encoding_format", [omit, not_given], ids=["omit", "not-given"])
+def test_decoder_is_inspected_once(encoding_format: Omit | NotGiven, monkeypatch: pytest.MonkeyPatch) -> None:
+    calls = 0
+
+    def counting_decoder() -> bool:
+        nonlocal calls
+        calls += 1
+        return False
+
+    monkeypatch.setattr(embeddings_parser, "has_numpy", counting_decoder)
+    response = make_response(ENCODED, ENCODED, ENCODED)
+
+    parsed = embeddings_parser.parse_embedding_response(response, encoding_format=encoding_format)
+
+    assert calls == 1
+    assert [cast(object, item.embedding) for item in parsed.data] == [VALUES, VALUES, VALUES]
+
+
+@pytest.mark.parametrize("encoding_format", [omit, not_given], ids=["omit", "not-given"])
+def test_float_vectors_skip_the_decoder(encoding_format: Omit | NotGiven, monkeypatch: pytest.MonkeyPatch) -> None:
+    def unexpected_decoder() -> bool:
+        raise AssertionError("a response without string vectors must not inspect the decoder")
+
+    monkeypatch.setattr(embeddings_parser, "has_numpy", unexpected_decoder)
+    response = make_response(VALUES, [4.0, 5.0])
+
+    parsed = embeddings_parser.parse_embedding_response(response, encoding_format=encoding_format)
+
+    assert [cast(object, item.embedding) for item in parsed.data] == [VALUES, [4.0, 5.0]]
+
+
 @pytest.mark.parametrize("encoding_format", ["float", "base64", None])
 @pytest.mark.parametrize("vectors", [(ENCODED,), ("abc",), ()], ids=["encoded", "invalid", "empty"])
 def test_explicit_format_is_untouched(