diff --git a/capsul/execution_context.py b/capsul/execution_context.py
index 82213e9ee..daf8c9863 100644
--- a/capsul/execution_context.py
+++ b/capsul/execution_context.py
@@ -94,7 +94,7 @@ def executable_requirements(self, executable):
 
 
 class CapsulWorkflow(Controller):
-    parameters: DictWithProxy
+    # parameters: DictWithProxy
     jobs: dict
 
     def __init__(self, executable, debug=False):
@@ -118,6 +118,7 @@ def __init__(self, executable, debug=False):
         top_parameters.content.update(job_parameters.content)
         self.parameters_values = top_parameters.proxy_values
         self.parameters_dict = top_parameters.content
+        # self.parameters = top_parameters
 
         # Set jobs chronology based on processes chronology
         for after_process, before_processes in process_chronology.items():
@@ -160,31 +161,33 @@ def __init__(self, executable, debug=False):
             job['wait_for'] = wait_for
             for waited in wait_for:
                 self.jobs[waited].setdefault('waited_by',[]).append(job_id)
-            
+
             parameters = top_parameters
             for index in job['parameters_location']:
                 if index.isnumeric():
                     index = int(index)
                 parameters = parameters[index]
-            def no_proxy(i):
-                if DictWithProxy.is_proxy(i):
-                    return no_proxy(i[1])
-                v = parameters.proxy_values[i]
-                if DictWithProxy.is_proxy(v):
-                    return no_proxy(v[1])
-                return i
             parameters_index = {}
             stack = list((k, v[1]) for k, v in parameters.content.items() if k != 'nodes')
             while stack:
                 k, i = stack.pop()
-                i = no_proxy(i)
+                i = self._no_proxy(parameters, i)
                 v = parameters.proxy_values[i]
                 if isinstance(v, list) and v and DictWithProxy.is_proxy(v[0]):
-                    parameters_index[k] = [no_proxy(i) for i in v]
+                    parameters_index[k] = [self._no_proxy(parameters, i)
+                                           for i in v]
                 else:
                     parameters_index[k] = i
             job['parameters_index'] = parameters_index
-    
+
+    @staticmethod
+    def _no_proxy(parameters, i):
+        if DictWithProxy.is_proxy(i):
+            return CapsulWorkflow._no_proxy(parameters, i[1])
+        v = parameters.proxy_values[i]
+        if DictWithProxy.is_proxy(v):
+            return CapsulWorkflow._no_proxy(parameters, v[1])
+        return i
 
     def _create_jobs(self,
                      top_parameters,
@@ -233,7 +236,13 @@ def _create_jobs(self,
                                                                         in_sub_pipelines=False):
                     if dest_node in disabled_nodes:
                         continue
-                    parameters.content[field.name] = nodes_dict.get(dest_node.name, {}).get(plug_name)
+                    if field.metadata('write', False) \
+                            and field.name in parameters.content:
+                        nodes_dict.get(dest_node.name, {})[plug_name] \
+                            = parameters.content[field.name]
+                    else:
+                        parameters.content[field.name] \
+                            = nodes_dict.get(dest_node.name, {}).get(plug_name)
                     break
                 if field.is_output():
                     for dest_node_name, dest_plug_name, dest_node, dest_plug, is_weak in process.plugs[field.name].links_to:
@@ -273,7 +282,14 @@ def _create_jobs(self,
                                 first = tmp
                                 first_index = first[1]
                                 second_index = second[1]
+                            v1 = parameters.proxy_values[
+                                self._no_proxy(parameters, first_index)]
+                            v2 = parameters.proxy_values[
+                                self._no_proxy(parameters, second_index)]
                             parameters.proxy_values[second_index] = first
+                            if v1 is None and v2 is not None:
+                                # move former dest value to source (temporary)
+                                parameters.proxy_values[first_index] = v2
         elif isinstance(process, ProcessIteration):
             parameters['_iterations'] = []
             iteration_index = 0
@@ -396,9 +412,9 @@ def find_temporary_to_generate(executable):
     for node in nodes:
         # print('!temporaries! initialize node', node.full_name)
         for field in node.user_fields():
-            if (field.output or 
-                not field.metadata('write', False) or
-                not node.plugs[field.name].activated):
+            if (field.output or
+                    not field.metadata('write', False) or
+                    not node.plugs[field.name].activated):
                 field.generate_temporary = False
             else:
                 field.generate_temporary = True