diff --git a/task-sdk/src/airflow/sdk/execution_time/task_runner.py b/task-sdk/src/airflow/sdk/execution_time/task_runner.py
index b90ec01e21e99..88fb19293d0c1 100644
--- a/task-sdk/src/airflow/sdk/execution_time/task_runner.py
+++ b/task-sdk/src/airflow/sdk/execution_time/task_runner.py
@@ -72,6 +72,7 @@
     AssetUniqueKey,
     AssetUriRef,
 )
+from airflow.sdk.definitions.context import render_template_to_string
 from airflow.sdk.definitions.mappedoperator import MappedOperator
 from airflow.sdk.definitions.param import process_params
 from airflow.sdk.definitions.xcom_arg import PlainXComArg
@@ -2334,8 +2335,8 @@ def _render_map_index(context: Context, ti: RuntimeTaskInstance, log: Logger) ->
     if (template := context.get("map_index_template")) is None:
         return None
     log.debug("Rendering map_index_template", template_length=len(template))
-    jinja_env = ti.task.dag.get_template_env()
-    rendered_map_index = jinja_env.from_string(template).render(context)
+    jinja_env = ti.task.dag.get_template_env(force_sandboxed=True)
+    rendered_map_index = render_template_to_string(jinja_env.from_string(template), context)
     log.debug("Map index rendered", length=len(rendered_map_index))
     return rendered_map_index
 
diff --git a/task-sdk/tests/task_sdk/execution_time/test_task_runner.py b/task-sdk/tests/task_sdk/execution_time/test_task_runner.py
index 2cd63cce594c7..8988428222178 100644
--- a/task-sdk/tests/task_sdk/execution_time/test_task_runner.py
+++ b/task-sdk/tests/task_sdk/execution_time/test_task_runner.py
@@ -2536,6 +2536,45 @@ def test_function():
     assert ti.rendered_map_index == "Hello! test_run"
 
 
+@pytest.mark.parametrize(
+    ("map_index_template", "expected"),
+    [
+        ("{{ ti.try_number }}", "1"),
+        ("index-{{ ti.try_number }}", "index-1"),
+        ("{{ '3.10' }}", "3.10"),
+    ],
+)
+@pytest.mark.parametrize("render_template_as_native_obj", [False, True])
+def test_execute_success_task_with_numeric_rendered_map_index(
+    create_runtime_ti,
+    mock_supervisor_comms,
+    map_index_template,
+    expected,
+    render_template_as_native_obj,
+):
+    """Test that numeric-looking map indices remain strings in both rendering modes."""
+
+    def test_function():
+        return "test function"
+
+    with DAG(
+        dag_id="dag_with_numeric_map_index_template",
+        schedule=None,
+        render_template_as_native_obj=render_template_as_native_obj,
+    ):
+        task = PythonOperator(
+            task_id="test_task",
+            python_callable=test_function,
+            map_index_template=map_index_template,
+        )
+
+    ti = create_runtime_ti(task)
+
+    run(ti, ti.get_template_context(), log=mock.MagicMock())
+
+    assert ti.rendered_map_index == expected
+
+
 def test_execute_failed_task_with_rendered_map_index(create_runtime_ti, mock_supervisor_comms):
     """Test that the map index is rendered in the task context."""