diff --git a/enterprise/litellm_enterprise/proxy/hooks/managed_files.py b/enterprise/litellm_enterprise/proxy/hooks/managed_files.py
index f1b4c6b5b17..7a132c01399 100644
--- a/enterprise/litellm_enterprise/proxy/hooks/managed_files.py
+++ b/enterprise/litellm_enterprise/proxy/hooks/managed_files.py
@@ -41,6 +41,7 @@ from litellm.proxy._types import (
     CallTypes,
     LiteLLM_ManagedFileTable,
     LiteLLM_ManagedObjectTable,
+    ProxyException,
     UserAPIKeyAuth,
 )
 from litellm.proxy.openai_files_endpoints.common_utils import (
@@ -423,13 +424,23 @@ class _PROXY_LiteLLMManagedFiles(CustomLogger, BaseFileEndpoints):
         # This is because the encoded object ids stored in the managed objects table do not contain the provider information
         # To support provider filtering, we would need to store the provider information in the encoded object ids
         if provider:
-            raise Exception("Filtering by 'provider' is not supported when using managed batches.")
+            raise ProxyException(
+                message="Filtering by 'provider' is not supported when using managed batches.",
+                type="invalid_request_error",
+                param="provider",
+                code=400,
+            )
 
         # Model name filtering is not supported for managed batches
         # This is because the encoded object ids stored in the managed objects table do not contain the model name
         # A hash of the model name + litellm_params for the model name is encoded as the model id. This is not sufficient to reliably map the target model names to the model ids.
         if target_model_names:
-            raise Exception("Filtering by 'target_model_names' is not supported when using managed batches.")
+            raise ProxyException(
+                message="Filtering by 'target_model_names' is not supported when using managed batches.",
+                type="invalid_request_error",
+                param="target_model_names",
+                code=400,
+            )
 
         owner_filter = build_owner_filter(user_api_key_dict)
         if owner_filter is None:
diff --git a/litellm/proxy/batches_endpoints/endpoints.py b/litellm/proxy/batches_endpoints/endpoints.py
index 623900322be..f8b4e65c270 100644
--- a/litellm/proxy/batches_endpoints/endpoints.py
+++ b/litellm/proxy/batches_endpoints/endpoints.py
@@ -5,6 +5,8 @@
 
 ######################################################################
 import asyncio
+import os
+from collections.abc import Mapping
 from typing import Any, Final, cast
 
 from fastapi import APIRouter, Depends, HTTPException, Path, Request, Response
@@ -48,6 +50,23 @@ from litellm.types.llms.openai import LiteLLMBatchCreateRequest
 router: Final = APIRouter()
 
 
+def _raise_not_found_when_openai_fallback_unservable(
+    requested_provider: "str | None",
+    data: Mapping[str, object],
+    not_found_message: str,
+) -> None:
+    if requested_provider is not None:
+        return
+    if data.get("api_key") or litellm.api_key or litellm.openai_key or os.getenv("OPENAI_API_KEY"):
+        return
+    raise ProxyException(
+        message=not_found_message,
+        type="invalid_request_error",
+        param=None,
+        code=404,
+    )
+
+
 async def _resolve_managed_input_file_storage_url(input_file_id: str) -> "str | None":
     """Resolve a managed (unified) input_file_id to its backend storage_url.
 
@@ -150,12 +169,12 @@ async def create_batch(
             router_model = data.get("model", None)
             is_router_model = is_known_model(model=router_model, llm_router=llm_router)
 
-        custom_llm_provider: Final = (
+        requested_provider: Final = (
             provider
             or data.pop("custom_llm_provider", None)
             or get_custom_llm_provider_from_request_headers(request=request)
-            or "openai"
         )
+        custom_llm_provider: Final = requested_provider or "openai"
         _create_batch_data: Final = LiteLLMBatchCreateRequest(**data)
 
         # Apply team-level batch output expiry enforcement
@@ -317,6 +336,11 @@ async def create_batch(
                     user_api_key_dict=user_api_key_dict,
                     custom_llm_provider=custom_llm_provider,
                 )
+                _raise_not_found_when_openai_fallback_unservable(
+                    requested_provider=requested_provider,
+                    data=cast(dict, _create_batch_data),  # cast-ok: TypedDict is a dict at runtime
+                    not_found_message=f"No such File object: {input_file_id}",
+                )
                 response = await litellm.acreate_batch(
                     custom_llm_provider=custom_llm_provider,
                     **_create_batch_data,
@@ -566,18 +590,23 @@ async def retrieve_batch(
 
         # SCENARIO 3: Fallback to custom_llm_provider (uses env variables)
         else:
-            custom_llm_provider: Final = (
+            requested_provider: Final = (
                 provider
                 or get_custom_llm_provider_from_request_headers(request=request)
                 or get_custom_llm_provider_from_request_query(request=request)
-                or "openai"
             )
+            custom_llm_provider: Final = requested_provider or "openai"
             apply_team_provider_credentials(
                 data=data,
                 llm_router=llm_router,
                 user_api_key_dict=user_api_key_dict,
                 custom_llm_provider=custom_llm_provider,
             )
+            _raise_not_found_when_openai_fallback_unservable(
+                requested_provider=requested_provider,
+                data=data,
+                not_found_message=f"No batch found with id '{batch_id}'.",
+            )
             response = await litellm.aretrieve_batch(
                 custom_llm_provider=custom_llm_provider,
                 **data,
@@ -970,13 +999,13 @@ async def cancel_batch(
         # SCENARIO 3: Fallback to custom_llm_provider (uses env variables)
         else:
             body_custom_llm_provider = data.pop("custom_llm_provider", None)
-            custom_llm_provider: Final = (
+            requested_provider: Final = (
                 provider
                 or body_custom_llm_provider
                 or get_custom_llm_provider_from_request_headers(request=request)
                 or get_custom_llm_provider_from_request_query(request=request)
-                or "openai"
             )
+            custom_llm_provider: Final = requested_provider or "openai"
             # Extract batch_id from data to avoid "multiple values for keyword argument" error
             # data was cast from CancelBatchRequest which already contains batch_id
             data.pop("batch_id", None)
@@ -986,6 +1015,11 @@ async def cancel_batch(
                 user_api_key_dict=user_api_key_dict,
                 custom_llm_provider=custom_llm_provider,
             )
+            _raise_not_found_when_openai_fallback_unservable(
+                requested_provider=requested_provider,
+                data=data,
+                not_found_message=f"No batch found with id '{batch_id}'.",
+            )
             _cancel_batch_data: Final = CancelBatchRequest(batch_id=batch_id, **data)
             response = await litellm.acancel_batch(
                 custom_llm_provider=custom_llm_provider,
diff --git a/tests/enterprise/litellm_enterprise/proxy/hooks/test_managed_files.py b/tests/enterprise/litellm_enterprise/proxy/hooks/test_managed_files.py
index fde1feb80e2..22d5afd5d42 100644
--- a/tests/enterprise/litellm_enterprise/proxy/hooks/test_managed_files.py
+++ b/tests/enterprise/litellm_enterprise/proxy/hooks/test_managed_files.py
@@ -3147,3 +3147,43 @@ async def test_file_list_cursors_follow_the_owner_scoped_page():
     assert response.first_id == "litellm_proxy:mine"
     assert response.last_id == "litellm_proxy:mine"
     assert response.has_more is False
+
+
+@pytest.mark.asyncio
+async def test_list_user_batches_provider_filter_rejected_with_400():
+    from litellm.proxy._types import ProxyException, UserAPIKeyAuth
+
+    proxy_managed_files = _PROXY_LiteLLMManagedFiles(
+        DualCache(), prisma_client=MagicMock()
+    )
+
+    with pytest.raises(ProxyException) as exc:
+        await proxy_managed_files.list_user_batches(
+            user_api_key_dict=UserAPIKeyAuth(user_id="123"),
+            provider="openai",
+        )
+
+    assert exc.value.code == "400"
+    assert exc.value.type == "invalid_request_error"
+    assert exc.value.param == "provider"
+    assert exc.value.message == "Filtering by 'provider' is not supported when using managed batches."
+
+
+@pytest.mark.asyncio
+async def test_list_user_batches_target_model_names_filter_rejected_with_400():
+    from litellm.proxy._types import ProxyException, UserAPIKeyAuth
+
+    proxy_managed_files = _PROXY_LiteLLMManagedFiles(
+        DualCache(), prisma_client=MagicMock()
+    )
+
+    with pytest.raises(ProxyException) as exc:
+        await proxy_managed_files.list_user_batches(
+            user_api_key_dict=UserAPIKeyAuth(user_id="123"),
+            target_model_names="gpt-4o",
+        )
+
+    assert exc.value.code == "400"
+    assert exc.value.type == "invalid_request_error"
+    assert exc.value.param == "target_model_names"
+    assert exc.value.message == "Filtering by 'target_model_names' is not supported when using managed batches."
diff --git a/tests/test_litellm/proxy/batches_endpoints/test_endpoints.py b/tests/test_litellm/proxy/batches_endpoints/test_endpoints.py
index b720ea16968..e7e754c0d8f 100644
--- a/tests/test_litellm/proxy/batches_endpoints/test_endpoints.py
+++ b/tests/test_litellm/proxy/batches_endpoints/test_endpoints.py
@@ -117,6 +117,21 @@ class FakeRequest:
         self.query_params = query or {}
 
 
+@pytest.fixture
+def openai_env_creds(monkeypatch):
+    """Deterministic env creds so the implicit-openai fallback forwards instead
+    of tripping the no-creds 404 gate, regardless of the host environment."""
+    monkeypatch.setenv("OPENAI_API_KEY", "sk-env-openai")
+
+
+@pytest.fixture
+def no_openai_creds(monkeypatch):
+    """Neutralize every credential source the 404 gate checks."""
+    monkeypatch.delenv("OPENAI_API_KEY", raising=False)
+    monkeypatch.setattr(litellm, "api_key", None)
+    monkeypatch.setattr(litellm, "openai_key", None)
+
+
 @dataclass
 class Harness:
     """Holds every mocked seam so a test can configure inputs and assert calls."""
@@ -409,7 +424,7 @@ async def test_create__body_model_beats_header_and_query(harness):
 
 
 @pytest.mark.asyncio
-async def test_create__fallback_default_openai(harness):
+async def test_create__fallback_default_openai(harness, openai_env_creds):
     set_body(
         harness,
         {
@@ -427,6 +442,63 @@ async def test_create__fallback_default_openai(harness):
     assert harness.acreate_kwargs()["custom_llm_provider"] == "openai"
 
 
+@pytest.mark.asyncio
+async def test_create__fallback_no_creds_404(harness, no_openai_creds):
+    set_body(
+        harness,
+        {
+            "input_file_id": "file-plain",
+            "endpoint": "/v1/chat/completions",
+            "completion_window": "24h",
+        },
+    )
+
+    with pytest.raises(ProxyException) as exc:
+        await call_create(harness)
+
+    assert exc.value.code == "404"
+    assert exc.value.type == "invalid_request_error"
+    assert exc.value.param is None
+    assert exc.value.message == "No such File object: file-plain"
+    harness.litellm_acreate.assert_not_called()
+    harness.router_acreate.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_create__fallback_explicit_provider_bypasses_not_found_gate(harness, no_openai_creds):
+    set_body(
+        harness,
+        {
+            "input_file_id": "file-plain",
+            "endpoint": "/v1/chat/completions",
+            "completion_window": "24h",
+        },
+    )
+
+    await call_create(harness, provider="anthropic")
+
+    assert harness.acreate_kwargs()["custom_llm_provider"] == "anthropic"
+
+
+@pytest.mark.asyncio
+async def test_create__fallback_env_key_alone_forwards(harness, monkeypatch):
+    monkeypatch.setattr(litellm, "api_key", None)
+    monkeypatch.setattr(litellm, "openai_key", None)
+    monkeypatch.setenv("OPENAI_API_KEY", "sk-env-openai")
+    set_body(
+        harness,
+        {
+            "input_file_id": "file-plain",
+            "endpoint": "/v1/chat/completions",
+            "completion_window": "24h",
+        },
+    )
+
+    await call_create(harness)
+
+    assert harness.acreate_kwargs()["custom_llm_provider"] == "openai"
+
+
 @pytest.mark.asyncio
 async def test_create__fallback_provider_path_param(harness):
     set_body(
@@ -795,7 +867,7 @@ def _user_with_expiry(expiry: Any) -> UserAPIKeyAuth:
 
 
 @pytest.mark.asyncio
-async def test_create__team_expiry_injected(harness):
+async def test_create__team_expiry_injected(harness, openai_env_creds):
     set_body(
         harness,
         {
@@ -814,7 +886,7 @@ async def test_create__team_expiry_injected(harness):
 
 
 @pytest.mark.asyncio
-async def test_create__no_team_expiry_not_injected(harness):
+async def test_create__no_team_expiry_not_injected(harness, openai_env_creds):
     set_body(
         harness,
         {
@@ -862,7 +934,7 @@ async def test_create__team_expiry_malformed_500(harness, expiry):
 
 
 @pytest.mark.asyncio
-async def test_create__uses_acreate_batch_route_type(harness):
+async def test_create__uses_acreate_batch_route_type(harness, openai_env_creds):
     set_body(
         harness,
         {
@@ -878,7 +950,7 @@ async def test_create__uses_acreate_batch_route_type(harness):
 
 
 @pytest.mark.asyncio
-async def test_create__metadata_sanitized_before_forwarding(harness):
+async def test_create__metadata_sanitized_before_forwarding(harness, openai_env_creds):
     set_body(
         harness,
         {
@@ -896,7 +968,7 @@ async def test_create__metadata_sanitized_before_forwarding(harness):
 
 
 @pytest.mark.asyncio
-async def test_create__exception_calls_failure_hook(harness):
+async def test_create__exception_calls_failure_hook(harness, openai_env_creds):
     set_body(
         harness,
         {
@@ -1204,7 +1276,7 @@ async def test_retrieve__loadbalancing_raw_id_routes_to_router(retrieve_harness)
 
 
 @pytest.mark.asyncio
-async def test_retrieve__fallback_default_openai(retrieve_harness):
+async def test_retrieve__fallback_default_openai(retrieve_harness, openai_env_creds):
     await call_retrieve(retrieve_harness, "batch-raw-xyz")
 
     assert retrieve_harness.litellm_aretrieve.call_count == 1
@@ -1217,6 +1289,40 @@ async def test_retrieve__fallback_default_openai(retrieve_harness):
     assert retrieve_harness.update_batch_in_db.call_count == 1
 
 
+@pytest.mark.asyncio
+async def test_retrieve__fallback_no_creds_404(retrieve_harness, no_openai_creds):
+    with pytest.raises(ProxyException) as exc:
+        await call_retrieve(retrieve_harness, "batch-raw-xyz")
+
+    assert exc.value.code == "404"
+    assert exc.value.type == "invalid_request_error"
+    assert exc.value.param is None
+    assert exc.value.message == "No batch found with id 'batch-raw-xyz'."
+    retrieve_harness.litellm_aretrieve.assert_not_called()
+    retrieve_harness.router_aretrieve.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_retrieve__fallback_explicit_provider_bypasses_not_found_gate(retrieve_harness, no_openai_creds):
+    await call_retrieve(retrieve_harness, "batch-raw-xyz", provider="anthropic")
+
+    assert retrieve_harness.aretrieve_kwargs()["custom_llm_provider"] == "anthropic"
+
+
+@pytest.mark.asyncio
+async def test_retrieve__fallback_env_key_alone_forwards(retrieve_harness, monkeypatch):
+    monkeypatch.setattr(litellm, "api_key", None)
+    monkeypatch.setattr(litellm, "openai_key", None)
+    monkeypatch.setenv("OPENAI_API_KEY", "sk-env-openai")
+
+    await call_retrieve(retrieve_harness, "batch-raw-xyz")
+
+    assert retrieve_harness.aretrieve_kwargs() == {
+        "custom_llm_provider": "openai",
+        "batch_id": "batch-raw-xyz",
+    }
+
+
 @pytest.mark.asyncio
 async def test_retrieve__fallback_provider_path_param(retrieve_harness):
     await call_retrieve(retrieve_harness, "batch-raw-xyz", provider="anthropic")
@@ -1302,7 +1408,7 @@ async def test_retrieve__db_terminal_unified_resolves_file_ids(retrieve_harness)
 
 
 @pytest.mark.asyncio
-async def test_retrieve__db_non_terminal_state_syncs_with_provider(retrieve_harness):
+async def test_retrieve__db_non_terminal_state_syncs_with_provider(retrieve_harness, openai_env_creds):
     """A non-terminal DB row must NOT short-circuit; the endpoint syncs with the
     provider to refresh state."""
     db_response = make_batch(id="batch-from-db", status="validating")
@@ -1321,14 +1427,14 @@ async def test_retrieve__db_non_terminal_state_syncs_with_provider(retrieve_harn
 
 
 @pytest.mark.asyncio
-async def test_retrieve__uses_aretrieve_batch_route_type(retrieve_harness):
+async def test_retrieve__uses_aretrieve_batch_route_type(retrieve_harness, openai_env_creds):
     await call_retrieve(retrieve_harness, "batch-raw-xyz")
 
     assert retrieve_harness.pre_call.call_args.kwargs["route_type"] == "aretrieve_batch"
 
 
 @pytest.mark.asyncio
-async def test_retrieve__exception_calls_failure_hook(retrieve_harness):
+async def test_retrieve__exception_calls_failure_hook(retrieve_harness, openai_env_creds):
     retrieve_harness.litellm_aretrieve.side_effect = ValueError("provider boom")
 
     with pytest.raises(Exception):
@@ -1609,7 +1715,9 @@ async def test_list__target_model_names_takes_first_only(list_harness):
 
 
 @pytest.mark.asyncio
-async def test_list__fallback_default_openai(list_harness):
+async def test_list__fallback_default_openai(list_harness, no_openai_creds):
+    """list stays ungated by the no-creds 404 guard: it answers about a
+    collection, not a specific id, so there is nothing to 404 about."""
     await call_list(list_harness)
 
     assert list_harness.litellm_alist.call_count == 1
@@ -1960,7 +2068,7 @@ async def test_cancel__unified_no_router_500(cancel_harness):
 
 
 @pytest.mark.asyncio
-async def test_cancel__fallback_default_openai(cancel_harness):
+async def test_cancel__fallback_default_openai(cancel_harness, openai_env_creds):
     await call_cancel(cancel_harness, "batch-raw-xyz")
 
     assert cancel_harness.litellm_acancel.call_count == 1
@@ -1974,6 +2082,40 @@ async def test_cancel__fallback_default_openai(cancel_harness):
     assert cancel_harness.update_batch_in_db.call_count == 1
 
 
+@pytest.mark.asyncio
+async def test_cancel__fallback_no_creds_404(cancel_harness, no_openai_creds):
+    with pytest.raises(ProxyException) as exc:
+        await call_cancel(cancel_harness, "batch-raw-xyz")
+
+    assert exc.value.code == "404"
+    assert exc.value.type == "invalid_request_error"
+    assert exc.value.param is None
+    assert exc.value.message == "No batch found with id 'batch-raw-xyz'."
+    cancel_harness.litellm_acancel.assert_not_called()
+    cancel_harness.router_acancel.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_cancel__fallback_explicit_provider_bypasses_not_found_gate(cancel_harness, no_openai_creds):
+    await call_cancel(cancel_harness, "batch-raw-xyz", provider="anthropic")
+
+    assert cancel_harness.acancel_kwargs()["custom_llm_provider"] == "anthropic"
+
+
+@pytest.mark.asyncio
+async def test_cancel__fallback_env_key_alone_forwards(cancel_harness, monkeypatch):
+    monkeypatch.setattr(litellm, "api_key", None)
+    monkeypatch.setattr(litellm, "openai_key", None)
+    monkeypatch.setenv("OPENAI_API_KEY", "sk-env-openai")
+
+    await call_cancel(cancel_harness, "batch-raw-xyz")
+
+    assert cancel_harness.acancel_kwargs() == {
+        "custom_llm_provider": "openai",
+        "batch_id": "batch-raw-xyz",
+    }
+
+
 @pytest.mark.asyncio
 async def test_cancel__fallback_provider_path_param(cancel_harness):
     await call_cancel(cancel_harness, "batch-raw-xyz", provider="anthropic")
@@ -2028,14 +2170,14 @@ async def test_cancel__fallback_provider_precedence_path_over_body(cancel_harnes
 
 
 @pytest.mark.asyncio
-async def test_cancel__uses_acancel_batch_route_type(cancel_harness):
+async def test_cancel__uses_acancel_batch_route_type(cancel_harness, openai_env_creds):
     await call_cancel(cancel_harness, "batch-raw-xyz")
 
     assert cancel_harness.pre_call.call_args.kwargs["route_type"] == "acancel_batch"
 
 
 @pytest.mark.asyncio
-async def test_cancel__exception_calls_failure_hook(cancel_harness):
+async def test_cancel__exception_calls_failure_hook(cancel_harness, openai_env_creds):
     cancel_harness.litellm_acancel.side_effect = ValueError("provider boom")
 
     with pytest.raises(Exception):
@@ -2357,7 +2499,7 @@ async def test_create__model_encoded_input_file_id_rejected_when_managed_files_r
 
 
 @pytest.mark.asyncio
-async def test_create__raw_input_file_id_allowed_when_managed_files_not_required(harness):
+async def test_create__raw_input_file_id_allowed_when_managed_files_not_required(harness, openai_env_creds):
     set_body(
         harness,
         {
@@ -2459,7 +2601,7 @@ async def test_retrieve__managed_batch_still_accounts_inline_without_a_poller(re
 
 
 @pytest.mark.asyncio
-async def test_retrieve__raw_batch_id_is_untouched_by_the_poller_handoff(retrieve_harness):
+async def test_retrieve__raw_batch_id_is_untouched_by_the_poller_handoff(retrieve_harness, openai_env_creds):
     with patch.object(endpoints, "batch_cost_poller_is_active", MagicMock(return_value=True)):
         await call_retrieve(retrieve_harness, "batch-raw-xyz")
 
diff --git a/tests/test_litellm/proxy/test_batch_x_litellm_model_encoding.py b/tests/test_litellm/proxy/test_batch_x_litellm_model_encoding.py
index 101dc48603a..3d1831bb4cd 100644
--- a/tests/test_litellm/proxy/test_batch_x_litellm_model_encoding.py
+++ b/tests/test_litellm/proxy/test_batch_x_litellm_model_encoding.py
@@ -287,13 +287,15 @@ async def test_create_batch_with_x_litellm_model_encodes_output_and_error_file_i
 
 
 @pytest.mark.asyncio
-async def test_create_batch_without_x_litellm_model_returns_raw_ids():
+async def test_create_batch_without_x_litellm_model_returns_raw_ids(monkeypatch):
     """
     Without x-litellm-model header, create_batch should NOT encode batch IDs
     (falls through to Scenario 3 / custom_llm_provider fallback).
     """
     from litellm.proxy.batches_endpoints.endpoints import create_batch
 
+    monkeypatch.setenv("OPENAI_API_KEY", "sk-env-openai")
+
     raw_batch_id = "batch_abc123"
     mock_response = _make_batch_response(batch_id=raw_batch_id)
     mock_request = _make_mock_request(headers={})