diff --git a/tests/test_litellm/llms/bedrock/test_base_aws_llm.py b/tests/test_litellm/llms/bedrock/test_base_aws_llm.py
index a38e0c0b0ac..18fc7c6173e 100644
--- a/tests/test_litellm/llms/bedrock/test_base_aws_llm.py
+++ b/tests/test_litellm/llms/bedrock/test_base_aws_llm.py
@@ -555,9 +555,15 @@ def test_different_roles_without_session_names_should_not_share_cache():
 )
 def test_eks_irsa_ambient_credentials_used(role_kwargs, expected_client_kwargs):
     """
-    When only aws_role_name and aws_session_name are passed (no explicit creds),
-    boto3.client("sts", **expected) is called with no credential kwargs.
+    Test that in EKS/IRSA environments, ambient credentials are used when no explicit keys provided.
+    This allows web identity tokens to work automatically.
     """
+    # Isolate from ambient AWS_REGION/AWS_DEFAULT_REGION so no_region_or_endpoint is deterministic
+    env_without_aws_region = {
+        k: v
+        for k, v in os.environ.items()
+        if k not in ("AWS_REGION", "AWS_DEFAULT_REGION")
+    }
     base_aws_llm = BaseAWSLLM()
     mock_expiry = MagicMock()
     mock_expiry.tzinfo = timezone.utc
@@ -575,22 +581,25 @@ def test_eks_irsa_ambient_credentials_used(role_kwargs, expected_client_kwargs):
     mock_sts_client = MagicMock()
     mock_sts_client.assume_role.return_value = mock_sts_response
 
-    with patch("boto3.client", return_value=mock_sts_client) as mock_boto3_client:
-        credentials, ttl = base_aws_llm._auth_with_aws_role(
-            aws_access_key_id=None,
-            aws_secret_access_key=None,
-            aws_session_token=None,
-            aws_role_name="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
-            aws_session_name="test-session",
-            **role_kwargs,
-        )
-        mock_boto3_client.assert_called_once_with("sts", **expected_client_kwargs)
-        mock_sts_client.assume_role.assert_called_once_with(
-            RoleArn="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
-            RoleSessionName="test-session",
-        )
-        assert credentials.access_key == "assumed-access-key"
-        assert ttl is not None
+    with patch.dict(os.environ, env_without_aws_region, clear=True):
+        with patch("boto3.client", return_value=mock_sts_client) as mock_boto3_client:
+            credentials, ttl = base_aws_llm._auth_with_aws_role(
+                aws_access_key_id=None,
+                aws_secret_access_key=None,
+                aws_session_token=None,
+                aws_role_name="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
+                aws_session_name="test-session",
+                **role_kwargs,
+            )
+            mock_boto3_client.assert_called_once_with(
+                "sts", **expected_client_kwargs
+            )
+            mock_sts_client.assume_role.assert_called_once_with(
+                RoleArn="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
+                RoleSessionName="test-session",
+            )
+            assert credentials.access_key == "assumed-access-key"
+            assert ttl is not None
 
 
 @pytest.mark.parametrize(
@@ -632,9 +641,13 @@ def test_explicit_credentials_used_when_provided(role_kwargs, expected_client_kw
     """
     Test that explicit credentials are used when provided (non-EKS/IRSA scenario).
     """
+    # Isolate from ambient AWS_REGION/AWS_DEFAULT_REGION so no_region_or_endpoint is deterministic
+    env_without_aws_region = {
+        k: v
+        for k, v in os.environ.items()
+        if k not in ("AWS_REGION", "AWS_DEFAULT_REGION")
+    }
     base_aws_llm = BaseAWSLLM()
-        
-    # Mock the STS response with proper expiration handling
     mock_expiry = MagicMock()
     mock_expiry.tzinfo = timezone.utc
     # Create a timedelta object that returns 3600 when total_seconds() is called
@@ -652,24 +665,27 @@ def test_explicit_credentials_used_when_provided(role_kwargs, expected_client_kw
     mock_sts_client = MagicMock()
     mock_sts_client.assume_role.return_value = mock_sts_response
 
-    with patch("boto3.client", return_value=mock_sts_client) as mock_boto3_client:
-        credentials, ttl = base_aws_llm._auth_with_aws_role(
-            aws_access_key_id="explicit-access-key",
-            aws_secret_access_key="explicit-secret-key",
-            aws_session_token="assumed-session-token",
-            aws_role_name="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
-            aws_session_name="test-session",
-            **role_kwargs
-        )
-        mock_boto3_client.assert_called_once_with("sts", **expected_client_kwargs)
-        mock_sts_client.assume_role.assert_called_once_with(
-            RoleArn="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
-            RoleSessionName="test-session"
-        )
-        assert credentials.access_key == "assumed-access-key"
-        assert credentials.secret_key == "assumed-secret-key"
-        assert credentials.token == "assumed-session-token"
-        assert ttl is not None
+    with patch.dict(os.environ, env_without_aws_region, clear=True):
+        with patch("boto3.client", return_value=mock_sts_client) as mock_boto3_client:
+            credentials, ttl = base_aws_llm._auth_with_aws_role(
+                aws_access_key_id="explicit-access-key",
+                aws_secret_access_key="explicit-secret-key",
+                aws_session_token="assumed-session-token",
+                aws_role_name="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
+                aws_session_name="test-session",
+                **role_kwargs,
+            )
+            mock_boto3_client.assert_called_once_with(
+                "sts", **expected_client_kwargs
+            )
+            mock_sts_client.assume_role.assert_called_once_with(
+                RoleArn="arn:aws:iam::2222222222222:role/LitellmEvalBedrockRole",
+                RoleSessionName="test-session",
+            )
+            assert credentials.access_key == "assumed-access-key"
+            assert credentials.secret_key == "assumed-secret-key"
+            assert credentials.token == "assumed-session-token"
+            assert ttl is not None
 
 
 def test_partial_credentials_still_use_ambient():