fix(databricks): tighten endpoint guard, pass api_base to transcription auth, drop no-op override

- endpoint-name guard drops '.' so '..' and dot-traversal can no longer
  shape the invoke path; invalid-name test now covers databricks/.. too
- _prepare_audio_transcription_request passes api_base into
  validate_environment (chat-handler convention), so an explicit api_base
  authenticates without DATABRICKS_API_BASE; regression test dispatches
  with per-call api_base and no env var
- remove has_native_transcription_endpoint override: databricks is not in
  OPENAI_AUDIO_TRANSCRIPTION_PROVIDERS, so the base-class default is what
  main.py already reads; cover the non-text predictions element branch

litellm/llms/custom_httpx/llm_http_handler.py

@@ -1417,6 +1417,7 @@ class BaseLLMHTTPHandler:
             model=model,
             messages=[],
             optional_params=optional_params,
+            api_base=api_base,
             litellm_params=litellm_params,
         )
 

litellm/llms/databricks/audio_transcription/transformation.py

@@ -35,9 +35,10 @@ from ..common_utils import DatabricksBase, DatabricksException
 
 _OBJECT_LIST: Final = TypeAdapter(list[object])
 _STRING_OBJECT_DICT: Final = TypeAdapter(dict[str, object])
-# Databricks serving endpoint names use [a-z0-9-]; the guard stays minimal
-# (also permitting dots and underscores) so no valid name can ever be rejected
-_ENDPOINT_NAME: Final = re.compile(r"[A-Za-z0-9._-]+")
+# Databricks serving endpoint names use [a-z0-9-]; underscores are also
+# permitted so no plausible name is rejected. Dots are excluded: allowing
+# them would admit path-shaping inputs such as "..".
+_ENDPOINT_NAME: Final = re.compile(r"[A-Za-z0-9_-]+")
 
 
 class DatabricksAudioTranscriptionConfig(BaseAudioTranscriptionConfig, DatabricksBase):
@@ -73,15 +74,6 @@ class DatabricksAudioTranscriptionConfig(BaseAudioTranscriptionConfig, Databrick
     ) -> BaseLLMException:
         return DatabricksException(message=error_message, status_code=status_code, headers=headers)
 
-    @property
-    def has_native_transcription_endpoint(self) -> bool:
-        # Databricks is not in OPENAI_AUDIO_TRANSCRIPTION_PROVIDERS today, so
-        # the main.py transport dispatch reads this as a no-op; it is set for
-        # parity with the xai transcription config (the precedent, where it
-        # IS load-bearing) and keeps this provider on the native handler if
-        # databricks ever joins the OpenAI-compatible audio list.
-        return True
-
     def validate_environment(
         self,
         headers: dict[str, object],  # mutable-ok: base class signature takes and returns dict
@@ -122,7 +114,7 @@ class DatabricksAudioTranscriptionConfig(BaseAudioTranscriptionConfig, Databrick
                 status_code=400,
                 message=(
                     f"Invalid Databricks endpoint name {endpoint!r}: names may only contain "
-                    "letters, digits, dots, underscores, and hyphens."
+                    "letters, digits, underscores, and hyphens."
                 ),
             )
         resolved_base: Final = self._get_api_base(api_base or os.getenv("DATABRICKS_API_BASE")).rstrip("/")

tests/test_litellm/llms/databricks/audio_transcription/test_databricks_audio_transcription_transformation.py

@@ -121,12 +121,17 @@ def test_get_complete_url_from_env(monkeypatch):
     assert url == INVOKE_URL
 
 
-def test_get_complete_url_rejects_path_shaping():
+@pytest.mark.parametrize(
+    "model",
+    ["databricks/../x", "databricks/.."],
+    ids=["dotdot-path", "dotdot-only"],
+)
+def test_get_complete_url_rejects_path_shaping(model):
     with pytest.raises(DatabricksException, match="Invalid Databricks endpoint name") as exc_info:
         CONFIG.get_complete_url(
             api_base=API_BASE,
             api_key=None,
-            model="databricks/../x",
+            model=model,
             optional_params={},
             litellm_params={},
         )
@@ -249,7 +254,11 @@ def test_transform_response_empty_transcript_is_valid():
     assert response.text == ""
 
 
-@pytest.mark.parametrize("payload", [{"predictions": []}, {}], ids=["empty-list", "missing-key"])
+@pytest.mark.parametrize(
+    "payload",
+    [{"predictions": []}, {}, {"predictions": [42]}],
+    ids=["empty-list", "missing-key", "non-text-element"],
+)
 def test_transform_response_empty_predictions_raises(payload):
     raw = httpx.Response(200, json=payload, request=httpx.Request("POST", INVOKE_URL))
     with pytest.raises(DatabricksException, match="no prediction text") as exc_info:
@@ -336,6 +345,35 @@ def test_transcription_dispatches_to_databricks_invoke(monkeypatch):
     assert response.text == "transcribed text"
 
 
+def test_transcription_uses_per_call_api_base_for_auth(monkeypatch):
+    # no DATABRICKS_API_BASE env var (the autouse fixture clears it): an
+    # explicit api_base= must reach validate_environment, otherwise auth
+    # falls into the SDK fallback even though the caller supplied a base
+    captured: dict = {}
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        captured["request"] = request
+        return httpx.Response(
+            200,
+            json={"predictions": ["transcribed text"]},
+            request=request,
+        )
+
+    http_handler = HTTPHandler(client=httpx.Client(transport=httpx.MockTransport(handler)))
+    response = litellm.transcription(
+        model="databricks/whisper-t",
+        file=("sample.wav", WAV_BYTES, "audio/wav"),
+        api_key="dapi-test",
+        api_base=API_BASE,
+        client=http_handler,
+    )
+
+    request = captured["request"]
+    assert str(request.url) == INVOKE_URL
+    assert request.headers["Authorization"] == "Bearer dapi-test"
+    assert response.text == "transcribed text"
+
+
 async def test_atranscription_dispatches_to_databricks_invoke(monkeypatch):
     monkeypatch.setenv("DATABRICKS_API_BASE", API_BASE)
     captured: dict = {}