fix(code_executors): handle genai.ClientError 404 in sandbox recovery

sandboxes.get() raises google.genai.errors.ClientError (HTTP 404) when a
cached sandbox has been externally deleted, but the recovery path only catches
google.api_core.exceptions.NotFound. The two have no shared base class, so
the 404 slips past the except clause and the session becomes unrecoverable
instead of falling through to the sandbox recreate logic.

Added a second except for genai_errors.ClientError that treats e.code == 404
the same as NotFound, sets create_new_sandbox = True and continues normally.
Non-404 errors are still re-raised.

Also added two unit tests: one covering the 404 recovery path, and one
verifying that non-404 ClientErrors are not silently swallowed.

Fixes #5480

Author: alimuhammad-10P

src/google/adk/code_executors/agent_engine_sandbox_code_executor.py

@@ -131,6 +131,7 @@ def execute_code(
     sandbox_name = self.sandbox_resource_name
     if self.sandbox_resource_name is None:
       from google.api_core import exceptions
+      from google.genai import errors as genai_errors
       from vertexai import types
 
       # use sandbox name stored in session if available.
@@ -148,6 +149,11 @@ def execute_code(
             create_new_sandbox = True
         except exceptions.NotFound:
           create_new_sandbox = True
+        except genai_errors.ClientError as e:
+          if e.code == 404:
+            create_new_sandbox = True
+          else:
+            raise
 
       if create_new_sandbox:
         # Create a new sandbox and assign it to sandbox_name.

tests/unittests/code_executors/test_agent_engine_sandbox_code_executor.py

@@ -325,6 +325,95 @@ def test_execute_code_with_auto_create_agent_engine(
         == created_sandbox_name
     )
 
+  @patch("vertexai.Client")
+  def test_execute_code_recreates_sandbox_on_genai_404(
+      self,
+      mock_vertexai_client,
+      mock_invocation_context,
+  ):
+    """Tests sandbox recreation when sandboxes.get() raises genai ClientError 404."""
+    from google.genai.errors import ClientError
+
+    mock_api_client = MagicMock()
+    mock_vertexai_client.return_value = mock_api_client
+
+    existing_sandbox_name = "projects/123/locations/us-central1/reasoningEngines/456/sandboxEnvironments/old"
+    mock_invocation_context.session.state = {
+        "sandbox_name": existing_sandbox_name
+    }
+
+    # SDK raises genai ClientError(404), not api_core.NotFound
+    mock_api_client.agent_engines.sandboxes.get.side_effect = ClientError(
+        404,
+        {"error": {"code": 404, "message": "Not Found", "status": "NOT_FOUND"}},
+    )
+
+    operation_mock = MagicMock()
+    created_sandbox_name = "projects/123/locations/us-central1/reasoningEngines/456/sandboxEnvironments/789"
+    operation_mock.response.name = created_sandbox_name
+    mock_api_client.agent_engines.sandboxes.create.return_value = operation_mock
+
+    mock_response = MagicMock()
+    mock_json_output = MagicMock()
+    mock_json_output.mime_type = "application/json"
+    mock_json_output.data = json.dumps(
+        {"msg_out": "recreated", "msg_err": ""}
+    ).encode("utf-8")
+    mock_json_output.metadata = None
+    mock_response.outputs = [mock_json_output]
+    mock_api_client.agent_engines.sandboxes.execute_code.return_value = (
+        mock_response
+    )
+
+    executor = AgentEngineSandboxCodeExecutor(
+        agent_engine_resource_name=(
+            "projects/123/locations/us-central1/reasoningEngines/456"
+        )
+    )
+    result = executor.execute_code(
+        mock_invocation_context, CodeExecutionInput(code='print("hi")')
+    )
+
+    mock_api_client.agent_engines.sandboxes.create.assert_called_once()
+    assert (
+        mock_invocation_context.session.state["sandbox_name"]
+        == created_sandbox_name
+    )
+    assert result.stdout == "recreated"
+
+  @patch("vertexai.Client")
+  def test_execute_code_reraises_non_404_genai_client_error(
+      self,
+      mock_vertexai_client,
+      mock_invocation_context,
+  ):
+    """Tests that non-404 genai ClientErrors are re-raised."""
+    from google.genai.errors import ClientError
+
+    mock_api_client = MagicMock()
+    mock_vertexai_client.return_value = mock_api_client
+
+    mock_invocation_context.session.state = {
+        "sandbox_name": "projects/123/locations/us-central1/reasoningEngines/456/sandboxEnvironments/old"
+    }
+
+    mock_api_client.agent_engines.sandboxes.get.side_effect = ClientError(
+        500,
+        {"error": {"code": 500, "message": "Internal error", "status": "INTERNAL"}},
+    )
+
+    executor = AgentEngineSandboxCodeExecutor(
+        agent_engine_resource_name=(
+            "projects/123/locations/us-central1/reasoningEngines/456"
+        )
+    )
+    with pytest.raises(ClientError):
+      executor.execute_code(
+          mock_invocation_context, CodeExecutionInput(code='print("hi")')
+      )
+
+    mock_api_client.agent_engines.sandboxes.create.assert_not_called()
+
   @patch("vertexai.Client")
   @patch.dict(
       os.environ,