diff --git a/src/aiidalab_qe/app/result/__init__.py b/src/aiidalab_qe/app/result/__init__.py
index 81b0d250a..ce8d2be85 100644
--- a/src/aiidalab_qe/app/result/__init__.py
+++ b/src/aiidalab_qe/app/result/__init__.py
@@ -209,7 +209,7 @@ def _update_kill_button_layout(self):
             return
         process_node = self._model.fetch_process_node()
         if (
-            not self._model.has_process
+            not process_node
             or process_node.is_finished
             or process_node.is_excepted
             or self.state
@@ -236,7 +236,7 @@ def _update_status(self):
 
     def _update_state(self):
         process_node = self._model.fetch_process_node()
-        if not self._model.has_process:
+        if not process_node:
             self.state = self.State.INIT
         elif process_node.process_state in (
             ProcessState.CREATED,
diff --git a/src/aiidalab_qe/app/result/model.py b/src/aiidalab_qe/app/result/model.py
index 022dc5254..71b62da2f 100644
--- a/src/aiidalab_qe/app/result/model.py
+++ b/src/aiidalab_qe/app/result/model.py
@@ -18,13 +18,13 @@ def update(self):
         self._update_process_remote_folder_state()
 
     def kill_process(self):
-        if self.has_process:
-            control.kill_processes([self.process_node])
+        if process_node := self.fetch_process_node():
+            control.kill_processes([process_node])
 
     def clean_remote_data(self):
-        if not self.has_process:
+        if not (process_node := self.fetch_process_node()):
             return
-        for called_descendant in self.process_node.called_descendants:
+        for called_descendant in process_node.called_descendants:
             if isinstance(called_descendant, orm.CalcJobNode):
                 with contextlib.suppress(Exception):
                     called_descendant.outputs.remote_folder._clean()
@@ -35,10 +35,10 @@ def reset(self):
         self.process_info = ""
 
     def _update_process_remote_folder_state(self):
-        if not self.has_process:
+        if not (process_node := self.fetch_process_node()):
             return
         cleaned = []
-        for called_descendant in self.process_node.called_descendants:
+        for called_descendant in process_node.called_descendants:
             if isinstance(called_descendant, orm.CalcJobNode):
                 with contextlib.suppress(Exception):
                     cleaned.append(called_descendant.outputs.remote_folder.is_empty)
diff --git a/src/aiidalab_qe/app/result/summary/model.py b/src/aiidalab_qe/app/result/summary/model.py
index 881a3339c..d44f027b4 100644
--- a/src/aiidalab_qe/app/result/summary/model.py
+++ b/src/aiidalab_qe/app/result/summary/model.py
@@ -125,7 +125,8 @@ def _generate_report_parameters(self):
         """
         from aiida.orm.utils.serialize import deserialize_unsafe
 
-        qeapp_wc = self.process_node
+        if not (qeapp_wc := self.fetch_process_node()):
+            return {"error": "WorkChain not found."}
 
         ui_parameters = qeapp_wc.base.extras.get("ui_parameters", {})
         if isinstance(ui_parameters, str):
diff --git a/src/aiidalab_qe/app/result/viewer/viewer.py b/src/aiidalab_qe/app/result/viewer/viewer.py
index 3245ca777..0ab7e1138 100644
--- a/src/aiidalab_qe/app/result/viewer/viewer.py
+++ b/src/aiidalab_qe/app/result/viewer/viewer.py
@@ -49,14 +49,18 @@ def render(self):
         if self.rendered:
             return
 
-        node = self._model.process_node
+        node = self._model.fetch_process_node()
 
-        self.title = ipw.HTML(f"""
-            <hr style="height:2px;background-color:#2097F3;">
-            <h4>
-                QE App Workflow (pk: {node.pk}) &mdash; {node.inputs.structure.get_formula()}
-            </h4>
-        """)
+        self.title = ipw.HTML()
+
+        title = "<hr style='height:2px;background-color:#2097F3;'>"
+        if node:
+            formula = node.inputs.structure.get_formula()
+            title += f"\n<h4>QE App Workflow (pk: {node.pk}) &mdash; {formula}</h4>"
+        else:
+            title += "\n<h4>QE App Workflow</h4>"
+
+        self.title.value = title
 
         self.tabs = ipw.Tab(selected_index=None)
 
@@ -69,7 +73,7 @@ def render(self):
 
         self._update_tabs()
 
-        if node.is_finished:
+        if node and node.is_finished:
             self._add_workflow_output_widget()
 
     def _update_tabs(self):
@@ -87,7 +91,8 @@ def _update_tabs(self):
         self.summary.render()
 
     def _add_workflow_output_widget(self):
-        self.summary.children += (WorkChainOutputs(self._model.process_node),)
+        process_node = self._model.fetch_process_node()
+        self.summary.children += (WorkChainOutputs(node=process_node),)
 
     def _add_structure_panel(self):
         structure_model = StructureResultsModel()
diff --git a/src/aiidalab_qe/common/mixins.py b/src/aiidalab_qe/common/mixins.py
index bad2b2285..21421c233 100644
--- a/src/aiidalab_qe/common/mixins.py
+++ b/src/aiidalab_qe/common/mixins.py
@@ -49,25 +49,22 @@ def _link_model(self, model: T):
 
 class HasProcess(tl.HasTraits):
     process_uuid = tl.Unicode(allow_none=True)
-    monitor_counter = tl.Int(0)
-
-    process_node = None
-
-    @property
-    def has_process(self):
-        return self.process_node is not None
+    monitor_counter = tl.Int(0)  # used for continuous updates
 
     @property
     def inputs(self):
-        return self.process_node.inputs if self.has_process else []
+        process_node = self.fetch_process_node()
+        return process_node.inputs if process_node else []
 
     @property
     def properties(self):
-        return self.process_node.inputs.properties if self.has_process else []
+        process_node = self.fetch_process_node()
+        return process_node.inputs.properties if process_node else []
 
     @property
     def outputs(self):
-        return self.process_node.outputs if self.has_process else []
+        process_node = self.fetch_process_node()
+        return process_node.outputs if process_node else []
 
     def fetch_process_node(self):
         try:
@@ -75,10 +72,6 @@ def fetch_process_node(self):
         except NotExistent:
             return None
 
-    @tl.observe("process_uuid")
-    def _on_process_uuid_change(self, _):
-        self.process_node = self.fetch_process_node()
-
 
 class Confirmable(tl.HasTraits):
     confirmed = tl.Bool(False)
diff --git a/src/aiidalab_qe/common/panel.py b/src/aiidalab_qe/common/panel.py
index 3104379d2..c2cf8b256 100644
--- a/src/aiidalab_qe/common/panel.py
+++ b/src/aiidalab_qe/common/panel.py
@@ -231,7 +231,7 @@ def _get_child_outputs(self, child="this"):
         return AttributeDict({key: getattr(node.outputs, key) for key in node.outputs})
 
     def _fetch_child_process_node(self, child="this") -> orm.ProcessNode | None:
-        if not self.process_node:
+        if not self.process_uuid:
             return
         uuid = getattr(self, f"_{child}_process_uuid")
         label = getattr(self, f"_{child}_process_label")
@@ -240,7 +240,7 @@ def _fetch_child_process_node(self, child="this") -> orm.ProcessNode | None:
                 orm.QueryBuilder()
                 .append(
                     orm.WorkChainNode,
-                    filters={"uuid": self.process_node.uuid},
+                    filters={"uuid": self.process_uuid},
                     tag="root_process",
                 )
                 .append(
diff --git a/src/aiidalab_qe/plugins/xas/result/model.py b/src/aiidalab_qe/plugins/xas/result/model.py
index 92acc303c..ff607db2e 100644
--- a/src/aiidalab_qe/plugins/xas/result/model.py
+++ b/src/aiidalab_qe/plugins/xas/result/model.py
@@ -29,6 +29,8 @@ class XasResultsModel(ResultsModel):
     _this_process_label = "XspectraCrystalWorkChain"
 
     def update_spectrum_options(self):
+        if not (process_node := self.fetch_process_node()):
+            return
         outputs = self._get_child_outputs()
         (
             self.final_spectra,
@@ -36,7 +38,7 @@ def update_spectrum_options(self):
         ) = export_xas_data(outputs)
         xas_workchain = next(
             node
-            for node in self.process_node.called
+            for node in process_node.called
             if node.process_label == self._this_process_label
         )
         core_workchains = {
diff --git a/tests/test_plugins_bands.py b/tests/test_plugins_bands.py
index 98efdbbdc..15e038e65 100644
--- a/tests/test_plugins_bands.py
+++ b/tests/test_plugins_bands.py
@@ -6,7 +6,7 @@ def test_result(generate_qeapp_workchain):
 
     workchain = generate_qeapp_workchain()
     model = BandsResultsModel()
-    model.process_node = workchain.node
+    model.process_uuid = workchain.node.uuid
     result = BandsResults(model=model)
     result.render()
 
diff --git a/tests/test_plugins_electronic_structure.py b/tests/test_plugins_electronic_structure.py
index 81536f98d..307edcb43 100644
--- a/tests/test_plugins_electronic_structure.py
+++ b/tests/test_plugins_electronic_structure.py
@@ -9,7 +9,7 @@ def test_electronic_structure(generate_qeapp_workchain):
 
     workchain = generate_qeapp_workchain()
     model = ElectronicStructureResultsModel()
-    model.process_node = workchain.node
+    model.process_uuid = workchain.node.uuid
     result = ElectronicStructureResults(model=model)
     result.render()
 
diff --git a/tests/test_plugins_pdos.py b/tests/test_plugins_pdos.py
index ba2d27042..574c4a591 100644
--- a/tests/test_plugins_pdos.py
+++ b/tests/test_plugins_pdos.py
@@ -6,7 +6,7 @@ def test_result(generate_qeapp_workchain):
 
     workchain = generate_qeapp_workchain()
     model = PdosResultsModel()
-    model.process_node = workchain.node
+    model.process_uuid = workchain.node.uuid
     result = PdosResults(model=model)
     result.render()
 
diff --git a/tests/test_result.py b/tests/test_result.py
index ae6dd5bbc..0fd4c6796 100644
--- a/tests/test_result.py
+++ b/tests/test_result.py
@@ -43,7 +43,7 @@ def test_summary_report(data_regression, generate_qeapp_workchain):
     """Test the summary report can be properly generated."""
     workchain = generate_qeapp_workchain()
     model = WorkChainSummaryModel()
-    model.process_node = workchain.node
+    model.process_uuid = workchain.node.uuid
     report_parameters = model._generate_report_parameters()
     data_regression.check(report_parameters)
 
@@ -54,7 +54,7 @@ def test_summary_report_advanced_settings(data_regression, generate_qeapp_workch
         spin_type="collinear", electronic_type="metal", initial_magnetic_moments=0.1
     )
     model = WorkChainSummaryModel()
-    model.process_node = workchain.node
+    model.process_uuid = workchain.node.uuid
     report_parameters = model._generate_report_parameters()
     assert report_parameters["initial_magnetic_moments"]["Si"] == 0.1
 
@@ -63,7 +63,7 @@ def test_summary_view(generate_qeapp_workchain):
     """Test the report html can be properly generated."""
     workchain = generate_qeapp_workchain()
     model = WorkChainSummaryModel()
-    model.process_node = workchain.node
+    model.process_uuid = workchain.node.uuid
     report_html = model.generate_report_html()
     parsed = BeautifulSoup(report_html, "html.parser")
     # find the td with the text "Initial Magnetic Moments"