From 98fa1a3b6cc8a5fbaa50f235e5fdc51193145395 Mon Sep 17 00:00:00 2001
From: WeAreResilience <286555414+WeAreResilience@users.noreply.github.com>
Date: Tue, 13 Oct 2026 22:05:09 -0500
Subject: [PATCH] fix: pass the configured session to Model.get in
 ModelBuilder.build

ModelBuilder created the model with self.sagemaker_session but reloaded
it with Model.get() using only the region, so the describe call went
through the default boto session. When that session points at a
different account, the describe fails because the model does not exist
there.

Fixes #6459
---
 .../src/sagemaker/serve/model_builder.py      |  6 ++-
 .../test_model_builder_model_get_session.py   | 47 +++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 sagemaker-serve/tests/unit/test_model_builder_model_get_session.py

diff --git a/sagemaker-serve/src/sagemaker/serve/model_builder.py b/sagemaker-serve/src/sagemaker/serve/model_builder.py
index 10a29fa5f8..960a006f39 100644
--- a/sagemaker-serve/src/sagemaker/serve/model_builder.py
+++ b/sagemaker-serve/src/sagemaker/serve/model_builder.py
@@ -3168,7 +3168,11 @@ def _create_sagemaker_model(self):
         self.sagemaker_session.create_model(**create_model_args)
         if isinstance(self.sagemaker_session, PipelineSession):
             return
-        return Model.get(model_name=self.model_name, region=self.region)
+        return Model.get(
+            model_name=self.model_name,
+            region=self.region,
+            session=self.sagemaker_session.boto_session,
+        )
 
     def _create_model(self):
         """Create a SageMaker Model instance from the current configuration."""
diff --git a/sagemaker-serve/tests/unit/test_model_builder_model_get_session.py b/sagemaker-serve/tests/unit/test_model_builder_model_get_session.py
new file mode 100644
index 0000000000..9e08390d0a
--- /dev/null
+++ b/sagemaker-serve/tests/unit/test_model_builder_model_get_session.py
@@ -0,0 +1,47 @@
+"""Unit tests for the session ModelBuilder uses to reload the created Model (issue #6459)."""
+
+import unittest
+from unittest.mock import Mock, patch
+
+from sagemaker.serve.model_builder import ModelBuilder
+
+ROLE_ARN = "arn:aws:iam::123456789012:role/TestRole"
+IMAGE_URI = "123456789012.dkr.ecr.us-west-2.amazonaws.com/my-image:latest"
+
+
+def _mock_session():
+    session = Mock()
+    session.boto_region_name = "us-west-2"
+    session.default_bucket.return_value = "test-bucket"
+    session.default_bucket_prefix = None
+    session.config = {}
+    session.sagemaker_config = {}
+    return session
+
+
+@patch("sagemaker.serve.model_builder.Model")
+@patch("sagemaker.serve.model_builder.resolve_nested_dict_value_from_config")
+@patch("sagemaker.serve.model_builder.resolve_value_from_config")
+@patch.object(ModelBuilder, "_init_sagemaker_session_if_does_not_exist")
+@patch.object(ModelBuilder, "_prepare_container_def")
+class TestCreateSageMakerModelSession(unittest.TestCase):
+    def test_model_get_uses_configured_boto_session(
+        self, mock_prepare, mock_init, mock_resolve, mock_resolve_nested, mock_model
+    ):
+        mock_prepare.return_value = {"Image": IMAGE_URI, "Environment": {}}
+        mock_resolve.side_effect = lambda value, *args, **kwargs: value
+        mock_resolve_nested.side_effect = lambda value, *args, **kwargs: value
+
+        session = _mock_session()
+        builder = ModelBuilder(image_uri=IMAGE_URI, role_arn=ROLE_ARN, sagemaker_session=session)
+        builder.model_name = "test-model"
+
+        result = builder._create_sagemaker_model()
+
+        session.create_model.assert_called_once()
+        mock_model.get.assert_called_once_with(
+            model_name="test-model",
+            region=builder.region,
+            session=session.boto_session,
+        )
+        self.assertIs(result, mock_model.get.return_value)