Header removals wait for the code editor to be left: autosave saves with drop=false, so follow_header adds and renames from the header but keeps a port or setting whose parameter is gone, and leaving the editor (blur or closing the panel) saves once more with removals; source saves of a flow run one at a time

backend/fluksio/flow/controller.py

@@ -1837,7 +1837,7 @@ def _signature_gap(
     )
 
 
-def follow_header(node: NodeDef, code: str) -> NodeDef:
+def follow_header(node: NodeDef, code: str, drop: bool = True) -> NodeDef:
     """The node with its input ports and settings read off ``def process(...)``.
 
     The inverse of the canvas's scaffold, which writes the input ports first,
@@ -1845,7 +1845,9 @@ def follow_header(node: NodeDef, code: str) -> NodeDef:
     keeps its kind. A new one is a setting when it has a default, which becomes
     its value, or when it follows a setting, and an input port otherwise. One
     name swapped for one other is a rename, so the port keeps its message and
-    the setting its value. A declared name the header no longer has is dropped.
+    the setting its value. A declared name the header no longer has is dropped,
+    unless ``drop`` is false: code saved while it is still being typed keeps
+    those, so a pause mid-edit does not cost a port its message.
 
     A header this cannot read for certain leaves the node as it is: a syntax
     error, no top-level ``def process``, a decorator, ``*args``, ``**kwargs``,
@@ -1907,6 +1909,13 @@ def follow_header(node: NodeDef, code: str) -> NodeDef:
             after_setting = True
         else:
             requires.append(MessageSpec(port=name))
+    if not drop:
+        kept = set(gone) - set(renamed.values())
+        # Where they were, so that typing the name back changes nothing.
+        for index, spec in enumerate(node.requires):
+            if spec.port in kept:
+                requires.insert(index, spec)
+        params |= {key: settings[key] for key in kept if key in settings}
     # Ports the header cannot name, such as a row not named yet, stay.
     requires += [spec for spec in node.requires if not written(spec.port)]
     return node.model_copy(update={"requires": requires, "params": params})