fix(vertex_ai): keep batch output_file_id null until Vertex reports outputInfo (#43030)

* fix(vertex_ai): keep batch output_file_id null until Vertex reports outputInfo

Vertex only sets outputInfo.gcsOutputDirectory once a batch job has written
output. Falling back to outputConfig's outputUriPrefix named the per-model
directory shared by every batch of the deployment, an object that never
exists, so the proxy minted a managed file for it under the first key and
every other key's file calls on that id were 403s

* fix(vertex_ai): treat a null gcsOutputDirectory as no output file yet

---------

Co-authored-by: mateo-berri <277851410+mateo-berri@users.noreply.github.com>

litellm/llms/vertex_ai/batches/transformation.py

@@ -253,30 +253,15 @@ class VertexAIBatchTransformation:
         return uris[0]
 
     @classmethod
-    def _get_output_file_id_from_vertex_ai_batch_response(cls, response: VertexBatchPredictionResponse) -> str:
+    def _get_output_file_id_from_vertex_ai_batch_response(cls, response: VertexBatchPredictionResponse) -> str | None:
         """
-        Gets the output file id from the Vertex AI Batch response
+        Gets the output file id from the Vertex AI Batch response, None until Vertex reports outputInfo
         """
-
         output_info: Final = response.get("outputInfo") or OutputInfo()
-        output_file_id: str = output_info.get("gcsOutputDirectory", "")
-        if output_file_id:
-            output_file_id = output_file_id.rstrip("/") + "/predictions.jsonl"
-        if output_file_id and output_file_id != "/predictions.jsonl":
-            return output_file_id
-
-        output_config: Final = response.get("outputConfig")
-        if output_config is None:
-            return output_file_id
-
-        gcs_destination: Final = output_config.get("gcsDestination")
-        if gcs_destination is None:
-            return output_file_id
-
-        output_uri_prefix: Final = gcs_destination.get("outputUriPrefix", "")
-        if output_uri_prefix.endswith("/predictions.jsonl"):
-            return output_uri_prefix
-        return output_uri_prefix.rstrip("/") + "/predictions.jsonl"
+        gcs_output_directory: Final = (output_info.get("gcsOutputDirectory") or "").rstrip("/")
+        if not gcs_output_directory:
+            return None
+        return f"{gcs_output_directory}/predictions.jsonl"
 
     @classmethod
     def _get_batch_job_status_from_vertex_ai_batch_response(

tests/integration/providers/test_vertex_batch_output_info_wire.py

@@ -116,7 +116,7 @@ def test_vertex_batch_create_survives_explicit_null_output_info(gateway: Gateway
             "batch",
             "validating",
             _encoded(INPUT_FILE_ID, model, "file-"),
-            _encoded(f"{OUTPUT_PREFIX}/predictions.jsonl", model, "file-"),
+            None,
             None,
             "24h",
         ), response.text

tests/test_litellm/llms/vertex_ai/batches/test_transformation.py

@@ -13,6 +13,8 @@ There are no real I/O seams here; ``uuid.uuid4`` is the only nondeterministic
 dependency and is patched where the displayName is asserted.
 """
 
+from collections.abc import Mapping
+from typing import Final
 from unittest.mock import patch
 
 import pytest
@@ -35,8 +37,7 @@ INPUT_FILE = (
 
 ENDPOINT_ID = "7768560373388541952"
 ENDPOINT_INPUT_FILE = (
-    f"gs://litellm-testing-bucket/litellm-vertex-files/endpoints/{ENDPOINT_ID}/"
-    "e9412502-2c91-42a6-8e61-f5c294cc0fc8"
+    f"gs://litellm-testing-bucket/litellm-vertex-files/endpoints/{ENDPOINT_ID}/e9412502-2c91-42a6-8e61-f5c294cc0fc8"
 )
 
 
@@ -248,9 +249,78 @@ def test_get_input_file_id_empty_uris():
 
 
 # =========================================================================== #
-# _get_output_file_id_from_vertex_ai_batch_response
+# _get_output_file_id_from_vertex_ai_batch_response: None until Vertex reports outputInfo
 # =========================================================================== #
 
+SHARED_OUTPUT_PREFIX: Final = "gs://bucket/litellm-vertex-files/publishers/google/models/gemini-2.5-flash"
+SUCCEEDED_OUTPUT_DIRECTORY: Final = f"{SHARED_OUTPUT_PREFIX}/prediction-model-2026-09-24T19:41:00.000000Z"
+
+
+def _vertex_job(state: str) -> dict[str, object]:
+    return {
+        "name": "projects/510528649030/locations/us-central1/batchPredictionJobs/3814889423749775360",
+        "state": state,
+        "createTime": "2026-09-24T19:37:25.775603Z",
+        "inputConfig": {
+            "instancesFormat": "jsonl",
+            "gcsSource": {"uris": [f"{SHARED_OUTPUT_PREFIX}/0586ba52-4f8b-4988-aa8d-3573550a4b0f"]},
+        },
+        "outputConfig": {
+            "predictionsFormat": "jsonl",
+            "gcsDestination": {"outputUriPrefix": SHARED_OUTPUT_PREFIX},
+        },
+    }
+
+
+@pytest.mark.parametrize(
+    "vertex_state,output_info_field,expected_status,expected_output_file_id",
+    [
+        ("JOB_STATE_PENDING", {}, "validating", None),
+        ("JOB_STATE_RUNNING", {"outputInfo": {}}, "in_progress", None),
+        ("JOB_STATE_CANCELLED", {"outputInfo": None}, "cancelled", None),
+        (
+            "JOB_STATE_SUCCEEDED",
+            {"outputInfo": {"gcsOutputDirectory": SUCCEEDED_OUTPUT_DIRECTORY}},
+            "completed",
+            f"{SUCCEEDED_OUTPUT_DIRECTORY}/predictions.jsonl",
+        ),
+    ],
+    ids=["create_or_pending", "running", "cancelled", "succeeded"],
+)
+def test_transform_vertex_response_output_file_id_is_none_until_output_info(
+    vertex_state: str,
+    output_info_field: Mapping[str, object],
+    expected_status: str,
+    expected_output_file_id: str | None,
+) -> None:
+    batch: Final = T.transform_vertex_ai_batch_response_to_openai_batch_response(
+        {**_vertex_job(vertex_state), **output_info_field}
+    )
+
+    assert batch.status == expected_status
+    assert batch.output_file_id == expected_output_file_id
+
+
+@pytest.mark.parametrize(
+    "response",
+    [
+        {},
+        {"outputConfig": {}},
+        {"outputInfo": None},
+        {"outputInfo": {"gcsOutputDirectory": ""}},
+        {"outputInfo": {"gcsOutputDirectory": None}},
+    ],
+    ids=[
+        "no_fields",
+        "output_config_without_destination",
+        "null_output_info",
+        "empty_output_directory",
+        "null_output_directory",
+    ],
+)
+def test_get_output_file_id_is_none_without_output_directory(response: Mapping[str, object]) -> None:
+    assert T._get_output_file_id_from_vertex_ai_batch_response(response) is None
+
 
 def test_get_output_file_id_from_output_info():
     # outputInfo branch: rstrip trailing slash, append predictions.jsonl
@@ -267,49 +337,7 @@ def test_get_output_file_id_output_info_no_trailing_slash():
     )
 
 
-def test_get_output_file_id_empty_output_info_falls_through_to_output_config():
-    # gcsOutputDirectory missing -> "" -> the "/predictions.jsonl" guard skips
-    # the outputInfo branch, falls through to outputConfig
-    resp = {
-        "outputInfo": {},
-        "outputConfig": {"gcsDestination": {"outputUriPrefix": "gs://b/cfg"}},
-    }
-    assert T._get_output_file_id_from_vertex_ai_batch_response(resp) == "gs://b/cfg/predictions.jsonl"
-
-
-def test_get_output_file_id_output_info_explicit_none_falls_through_to_output_config():
-    resp = {
-        "outputInfo": None,
-        "outputConfig": {"gcsDestination": {"outputUriPrefix": "gs://b/cfg"}},
-    }
-    assert T._get_output_file_id_from_vertex_ai_batch_response(resp) == "gs://b/cfg/predictions.jsonl"
-
-
-def test_get_output_file_id_output_info_explicit_none_and_no_output_config():
-    assert T._get_output_file_id_from_vertex_ai_batch_response({"outputInfo": None}) == ""
-
-
-def test_get_output_file_id_no_output_info_and_no_output_config():
-    assert T._get_output_file_id_from_vertex_ai_batch_response({}) == ""
-
-
-def test_get_output_file_id_output_config_missing_gcs_destination():
-    # outputConfig present but no gcsDestination -> returns the running "" value
-    assert T._get_output_file_id_from_vertex_ai_batch_response({"outputConfig": {}}) == ""
-
-
-def test_get_output_file_id_output_config_already_has_suffix():
-    # outputUriPrefix already ends in /predictions.jsonl -> returned as-is (no double append)
-    resp = {"outputConfig": {"gcsDestination": {"outputUriPrefix": "gs://b/cfg/predictions.jsonl"}}}
-    assert T._get_output_file_id_from_vertex_ai_batch_response(resp) == "gs://b/cfg/predictions.jsonl"
-
-
-def test_get_output_file_id_output_config_strips_trailing_slash():
-    resp = {"outputConfig": {"gcsDestination": {"outputUriPrefix": "gs://b/cfg/"}}}
-    assert T._get_output_file_id_from_vertex_ai_batch_response(resp) == "gs://b/cfg/predictions.jsonl"
-
-
-def test_get_output_file_id_output_info_takes_precedence_over_output_config():
+def test_get_output_file_id_output_info_ignores_output_uri_prefix():
     resp = {
         "outputInfo": {"gcsOutputDirectory": "gs://from-info"},
         "outputConfig": {"gcsDestination": {"outputUriPrefix": "gs://from-config"}},

tests/test_litellm/llms/vertex_ai/test_vertex_ai_batch_transformation.py

@@ -26,12 +26,12 @@ def test_output_file_id_uses_predictions_jsonl_with_output_info():
     )
 
 
-def test_output_file_id_falls_back_to_output_uri_prefix_with_predictions_jsonl():
+def test_output_file_id_is_none_until_output_info():
     response = {
         "outputInfo": {},
         "outputConfig": {
             "gcsDestination": {
-                "outputUriPrefix": "gs://test-bucket/litellm-vertex-files/publishers/google/models/gemini-2.5-pro/prediction-model-456"
+                "outputUriPrefix": "gs://test-bucket/litellm-vertex-files/publishers/google/models/gemini-2.5-pro"
             }
         },
     }
@@ -42,10 +42,7 @@ def test_output_file_id_falls_back_to_output_uri_prefix_with_predictions_jsonl()
         )
     )
 
-    assert (
-        output_file_id
-        == "gs://test-bucket/litellm-vertex-files/publishers/google/models/gemini-2.5-pro/prediction-model-456/predictions.jsonl"
-    )
+    assert output_file_id is None
 
 
 def test_vertex_ai_cancel_batch():