diff --git a/frontend/app.js b/frontend/app.js
index 4f32b18..4f4b54b 100644
--- a/frontend/app.js
+++ b/frontend/app.js
@@ -800,7 +800,8 @@ function renamePinAcrossSymbolInstances(symbolId, oldPinName, newPinName) {
   if (!state.model || !oldPinName || !newPinName || oldPinName === newPinName) {
     return;
   }
-  const refs = new Set((state.model.instances ?? []).filter((i) => i.symbol === symbolId).map((i) => i.ref));
+  const instances = (state.model.instances ?? []).filter((i) => i.symbol === symbolId);
+  const refs = new Set(instances.map((i) => i.ref));
   for (const net of state.model.nets ?? []) {
     for (const node of net.nodes ?? []) {
       if (refs.has(node.ref) && node.pin === oldPinName) {
@@ -808,6 +809,20 @@ function renamePinAcrossSymbolInstances(symbolId, oldPinName, newPinName) {
       }
     }
   }
+
+  for (const inst of instances) {
+    const pinUi = inst.properties?.pin_ui;
+    if (!pinUi || typeof pinUi !== "object" || Array.isArray(pinUi)) {
+      continue;
+    }
+    if (Object.prototype.hasOwnProperty.call(pinUi, oldPinName) && !Object.prototype.hasOwnProperty.call(pinUi, newPinName)) {
+      pinUi[newPinName] = pinUi[oldPinName];
+      delete pinUi[oldPinName];
+    } else if (Object.prototype.hasOwnProperty.call(pinUi, oldPinName) && Object.prototype.hasOwnProperty.call(pinUi, newPinName)) {
+      delete pinUi[oldPinName];
+    }
+  }
+
   if (state.selectedPin && refs.has(state.selectedPin.ref) && state.selectedPin.pin === oldPinName) {
     state.selectedPin.pin = newPinName;
   }
@@ -2256,6 +2271,7 @@ function setupEvents() {
     }
 
     pushHistory("symbol-edit");
+    const beforePins = new Set((sym.pins ?? []).map((p) => p.name));
     for (const entry of parsedPins) {
       if (entry.oldName && entry.oldName !== entry.pin.name) {
         renamePinAcrossSymbolInstances(inst.symbol, entry.oldName, entry.pin.name);
@@ -2270,6 +2286,20 @@ function setupEvents() {
     sym.pins = parsedPins.map((p) => p.pin);
     const allowedPins = new Set(sym.pins.map((p) => p.name));
     const refs = new Set((state.model.instances ?? []).filter((i) => i.symbol === inst.symbol).map((i) => i.ref));
+    for (const ii of state.model.instances ?? []) {
+      if (!refs.has(ii.ref)) {
+        continue;
+      }
+      const pinUi = ii.properties?.pin_ui;
+      if (!pinUi || typeof pinUi !== "object" || Array.isArray(pinUi)) {
+        continue;
+      }
+      for (const key of Object.keys(pinUi)) {
+        if (!allowedPins.has(key)) {
+          delete pinUi[key];
+        }
+      }
+    }
     for (const net of state.model.nets ?? []) {
       net.nodes = (net.nodes ?? []).filter((node) => !refs.has(node.ref) || allowedPins.has(node.pin));
     }
@@ -2278,7 +2308,10 @@ function setupEvents() {
     if (state.selectedPin && !pinExists(state.selectedPin.ref, state.selectedPin.pin)) {
       state.selectedPin = null;
     }
-    el.jsonFeedback.textContent = `Updated symbol ${inst.symbol}.`;
+    const removedPinCount = [...beforePins].filter((p) => !allowedPins.has(p)).length;
+    el.jsonFeedback.textContent = removedPinCount
+      ? `Updated symbol ${inst.symbol}. Removed ${removedPinCount} pin mappings from nets/UI metadata.`
+      : `Updated symbol ${inst.symbol}.`;
     queueCompile(true, "symbol-edit");
   });