Raise when source_software_version is set without source_software

CHANGELOG.md

@@ -10,6 +10,9 @@
 - Set `num_samples` on the external `ImageSeries` objects used in the mocks, tests, and examples. pynwb 4.0
   requires `num_samples` when `format='external'` and timing is specified with `rate`, because the empty data
   array cannot be used to infer the number of frames. @rly (#62)
+- `PoseEstimation` now raises when `source_software_version` is set without `source_software`. The version is
+  stored as an attribute on the `source_software` dataset, so it was previously dropped silently on roundtrip.
+  @h-mayorquin (#63)
 
 ## ndx-pose 0.3.0 (June 2, 2026)
 

src/pynwb/ndx_pose/pose.py

@@ -319,6 +319,11 @@ def __init__(self, **kwargs):
         pose_estimation_series, description = popargs("pose_estimation_series", "description", kwargs)
         scorer = popargs("scorer", kwargs)
         source_software, source_software_version = popargs("source_software", "source_software_version", kwargs)
+        if source_software_version is not None and source_software is None:
+            raise ValueError(
+                "'source_software_version' was specified without 'source_software'. The version is stored as an "
+                "attribute on the 'source_software' dataset, so 'source_software' must be provided as well."
+            )
         super().__init__(**kwargs)
 
         self.pose_estimation_series = pose_estimation_series

src/pynwb/tests/unit/test_pose.py

@@ -182,6 +182,27 @@ def test_bad_device_link(self):
                 skeleton=skeleton,
             )
 
+    def test_source_software_version_without_source_software_raises(self):
+        """Test that setting source_software_version without source_software raises.
+
+        source_software_version is stored as the 'version' attribute on the 'source_software'
+        dataset, so it cannot be written without source_software and would otherwise be silently
+        dropped on roundtrip.
+        """
+        skeleton = mock_Skeleton()
+        pose_estimation_series = [mock_PoseEstimationSeries(name=name) for name in skeleton.nodes]
+
+        msg = (
+            "'source_software_version' was specified without 'source_software'. The version is stored as an "
+            "attribute on the 'source_software' dataset, so 'source_software' must be provided as well."
+        )
+        with self.assertRaisesWith(ValueError, msg):
+            PoseEstimation(
+                pose_estimation_series=pose_estimation_series,
+                skeleton=skeleton,
+                source_software_version="2.2b8",
+            )
+
     def test_constructor_nodes_edges(self):
         """Test the old constructor for PoseEstimation with nodes and edges."""
         front_left_paw = mock_PoseEstimationSeries(