diff --git a/zxlive/custom_rule.py b/zxlive/custom_rule.py
index a19e37e..cff75f3 100644
--- a/zxlive/custom_rule.py
+++ b/zxlive/custom_rule.py
@@ -271,11 +271,8 @@ def filter_matchings_if_symbolic_compatible(matchings: list[Dict[VT, VT]], left:
     for matching in matchings:
         if len(matching) != len(left):
             continue
-        try:
-            match_symbolic_parameters(matching, left, right)
-            new_matchings.append(matching)
-        except ValueError:
-            pass
+        match_symbolic_parameters(matching, left, right)
+        new_matchings.append(matching)
     return new_matchings
 
 
diff --git a/zxlive/dialogs.py b/zxlive/dialogs.py
index a598fa5..6efb796 100644
--- a/zxlive/dialogs.py
+++ b/zxlive/dialogs.py
@@ -228,10 +228,7 @@ def save_diagram_dialog(graph: GraphT, parent: QWidget) -> Optional[tuple[str, F
     file_path, selected_format = file_path_and_format
 
     if selected_format in (FileFormat.QGraph, FileFormat.Json):
-        try:
-            graph.auto_detect_io()
-        except TypeError:
-            pass
+        graph.auto_detect_io()
         data = graph.to_json()
     elif selected_format == FileFormat.QASM:
         try:
diff --git a/zxlive/rewrite_action.py b/zxlive/rewrite_action.py
index 6b13517..762d5f9 100644
--- a/zxlive/rewrite_action.py
+++ b/zxlive/rewrite_action.py
@@ -79,6 +79,8 @@ def do_rewrite(self, panel: ProofPanel) -> None:
 
         try:
             g, rem_verts = self.apply_rewrite(g, matches)
+        except ValueError as ex:
+            raise ex
         except Exception as ex:
             show_error_msg('Error while applying rewrite rule', str(ex))
             return
diff --git a/zxlive/rewrite_data.py b/zxlive/rewrite_data.py
index bb31864..3c0cc9b 100644
--- a/zxlive/rewrite_data.py
+++ b/zxlive/rewrite_data.py
@@ -50,6 +50,24 @@ def read_custom_rules() -> list[RewriteData]:
                     custom_rules.append(rule)
     return custom_rules
 
+const_true = lambda graph, matches: matches
+
+
+def apply_simplification(simplification: Callable[[GraphT], Optional[int]]) -> Callable[
+    [GraphT, list], pyzx.rules.RewriteOutputType[VT, ET]]:
+    def rule(g: GraphT, matches: list) -> pyzx.rules.RewriteOutputType[VT, ET]:
+        simplification(g)
+        return ({}, [], [], True)
+
+    return rule
+
+
+def _extract_circuit(graph: GraphT, matches: list) -> GraphT:
+    graph.auto_detect_io()
+    simplify.full_reduce(graph)
+    return cast(GraphT, extract_circuit(graph).to_graph())
+
+
 # We want additional actions that are not part of the original PyZX editor
 # So we add them to operations
 
@@ -67,7 +85,7 @@ def read_custom_rules() -> list[RewriteData]:
         "text": "pivot",
         "tooltip": "Deletes a pair of spiders with 0/pi phases by performing a pivot",
         "matcher": lambda g, matchf: pyzx.rules.match_pivot_parallel(g, matchf, check_edge_types=True),
-        "rule": pyzx.rules.pivot,
+        "rule": apply_simplification(simplify.pivot_simp),
         "type": MATCHES_EDGES,
         "copy_first": True,
         "picture": "pivot_regular.png"
@@ -108,24 +126,6 @@ def read_custom_rules() -> list[RewriteData]:
     },
 }
 
-const_true = lambda graph, matches: matches
-
-
-def apply_simplification(simplification: Callable[[GraphT], Optional[int]]) -> Callable[
-    [GraphT, list], pyzx.rules.RewriteOutputType[VT, ET]]:
-    def rule(g: GraphT, matches: list) -> pyzx.rules.RewriteOutputType[VT, ET]:
-        simplification(g)
-        return ({}, [], [], True)
-
-    return rule
-
-
-def _extract_circuit(graph: GraphT, matches: list) -> GraphT:
-    graph.auto_detect_io()
-    simplify.full_reduce(graph)
-    return cast(GraphT, extract_circuit(graph).to_graph())
-
-
 # The OCM action simply saves the current graph without modifying anything.
 # This can be used to make repositioning the vertices an explicit proof step.
 def ocm_rule(_graph: GraphT, _matches: list) -> pyzx.rules.RewriteOutputType[VT, ET]:
diff --git a/zxlive/rule_panel.py b/zxlive/rule_panel.py
index d78c223..f295b7e 100644
--- a/zxlive/rule_panel.py
+++ b/zxlive/rule_panel.py
@@ -97,12 +97,9 @@ def add_edge(self, u: VT, v: VT, verts: list[VItem]) -> None:
         self.update_io_labels(self.graph_scene)
 
     def update_io_labels(self, scene: EditGraphScene) -> None:
-        try:
-            scene.g.auto_detect_io()
-            for v in scene.g.vertices():
-                if v in scene.g.inputs():
-                    scene.vertex_map[v].phase_item.setPlainText("in-" + str(scene.g.inputs().index(v)))
-                elif v in scene.g.outputs():
-                    scene.vertex_map[v].phase_item.setPlainText("out-" + str(scene.g.outputs().index(v)))
-        except TypeError:
-            return
+        scene.g.auto_detect_io()
+        for v in scene.g.vertices():
+            if v in scene.g.inputs():
+                scene.vertex_map[v].phase_item.setPlainText("in-" + str(scene.g.inputs().index(v)))
+            elif v in scene.g.outputs():
+                scene.vertex_map[v].phase_item.setPlainText("out-" + str(scene.g.outputs().index(v)))
diff --git a/zxlive/vitem.py b/zxlive/vitem.py
index 7e2dff7..8ac11c2 100644
--- a/zxlive/vitem.py
+++ b/zxlive/vitem.py
@@ -107,6 +107,7 @@ def g(self) -> GraphT:
 
     @property
     def ty(self) -> VertexType:
+        # https://github.com/zxcalc/zxlive/pull/281
         _ty: VertexType = self.g.type(self.v)
         return _ty