diff --git a/NaviNIBS/Navigator/Model/Tools.py b/NaviNIBS/Navigator/Model/Tools.py
index ac74161..78a9149 100644
--- a/NaviNIBS/Navigator/Model/Tools.py
+++ b/NaviNIBS/Navigator/Model/Tools.py
@@ -28,6 +28,17 @@
 
 SurfMesh = pv.PolyData
 
+_sessionPathDependentAttribs = [
+    'romFilepath',
+    'toolStlFilepath',
+    'trackerStlFilepath',
+    'sessionPath',
+]
+"""
+Attribs signaled as changed when a tool's session path changes, since session-relative
+filepaths resolve differently afterward.
+"""
+
 
 @attrs.define
 class Tool(GenericCollectionDictItem[str]):
@@ -303,12 +314,7 @@ def sessionPath(self, newPath: tp.Optional[str]):
         if self._sessionPath == newPath:
             return
 
-        filepathAttribs = [
-            'romFilepath',
-            'toolStlFilepath',
-            'trackerStlFilepath'
-            'sessionPath'
-        ]
+        filepathAttribs = _sessionPathDependentAttribs
 
         if self._filepathsRelTo == '<session>':
             self.sigItemAboutToChange.emit(self.key, filepathAttribs)
@@ -656,13 +662,14 @@ def sessionPath(self, newPath: tp.Optional[str]):
         if self._sessionPath == newPath:
             return
 
-        changingKeys = [tool.key for tool in self.values() if tool.filepathsRelTo == '<session>']
-        self.sigItemsAboutToChange.emit(changingKeys)
+        changingKeys = [tool.key for tool in self.values() if tool.filepathsRelToKey == '<session>']
+        filepathAttribs = _sessionPathDependentAttribs
+        self.sigItemsAboutToChange.emit(changingKeys, filepathAttribs)
         self._sessionPath = newPath
         with self.sigItemsAboutToChange.blocked(), self.sigItemsChanged.blocked():
             for tool in self.values():
                 tool.sessionPath = self._sessionPath
-        self.sigItemsChanged.emit(changingKeys)
+        self.sigItemsChanged.emit(changingKeys, filepathAttribs)
 
     def asList(self) -> tp.List[tp.Dict[str, tp.Any]]:
         toolList = super().asList()
diff --git a/tests/test_Model/test_toolsSessionPath.py b/tests/test_Model/test_toolsSessionPath.py
new file mode 100644
index 0000000..c7d2f8a
--- /dev/null
+++ b/tests/test_Model/test_toolsSessionPath.py
@@ -0,0 +1,51 @@
+"""
+Regression tests for change signaling when a tool or tool collection's
+session path changes (e.g. after save-as / session move).
+"""
+
+from NaviNIBS.Navigator.Model.Tools import Tool, Tools
+
+
+def test_toolSessionPathChangeSignalsFilepathAttribs():
+    """
+    A missing comma previously merged 'trackerStlFilepath' and 'sessionPath'
+    into one bogus attrib name in the signaled attrib list.
+    """
+    tool = Tool(key='t1', usedFor='visualization',
+                filepathsRelTo='<session>', sessionPath='/tmp/sesA')
+    received = []
+    tool.sigItemAboutToChange.connect(lambda key, attribs=None: received.append(list(attribs)))
+    tool.sessionPath = '/tmp/sesB'
+
+    assert received, 'sessionPath change did not signal'
+    attribs = received[0]
+    assert 'trackerStlFilepathsessionPath' not in attribs
+    assert 'trackerStlFilepath' in attribs
+    assert 'sessionPath' in attribs
+
+
+def test_toolsCollectionSessionPathChangeSignalsSessionRelativeTools():
+    """
+    The collection-level setter previously compared the resolved
+    ``filepathsRelTo`` path against the literal token '<session>', so
+    session-relative tools were never included in the signaled keys.
+    """
+    tools = Tools(sessionPath='/tmp/sesA')
+    tools.addItem(Tool(key='rel', usedFor='visualization',
+                       filepathsRelTo='<session>', sessionPath='/tmp/sesA'))
+    tools.addItem(Tool(key='abs', usedFor='visualization',
+                       filepathsRelTo='<userDataDir>', sessionPath='/tmp/sesA'))
+
+    receivedAboutTo = []
+    receivedChanged = []
+    tools.sigItemsAboutToChange.connect(
+        lambda keys, attribs=None: receivedAboutTo.append((list(keys), attribs)))
+    tools.sigItemsChanged.connect(
+        lambda keys, attribs=None: receivedChanged.append((list(keys), attribs)))
+
+    tools.sessionPath = '/tmp/sesB'
+
+    assert receivedAboutTo and receivedChanged
+    assert receivedAboutTo[0][0] == ['rel']
+    assert receivedChanged[0][0] == ['rel']
+    assert 'sessionPath' in receivedChanged[0][1]