diff --git a/src/frontend/components/circuit-tree-editor.tsx b/src/frontend/components/circuit-tree-editor.tsx
index f339c62..979f90f 100644
--- a/src/frontend/components/circuit-tree-editor.tsx
+++ b/src/frontend/components/circuit-tree-editor.tsx
@@ -30,8 +30,10 @@ import {
   formatPhaseTypeLabel,
   formatValue,
   getCircuitSectionLabel,
+  getLegacyProjectColumnLayoutStorageKey,
   getProjectColumnLayoutStorageKey,
   isGridEditorControlTarget,
+  migrateLegacyColumnLayout,
   normalizeColumnOrder,
   parseStoredColumnLayout,
 } from "../utils/circuit-grid-model";
@@ -374,14 +376,23 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
     setColumnOrder(allColumns.map((column) => column.key));
     setVisibleColumnKeys(defaultVisibleColumnKeys);
     try {
-      const parsed = parseStoredColumnLayout(
-        localStorage.getItem(
-          getProjectColumnLayoutStorageKey(projectId)
-        ) ??
-          localStorage.getItem(
-            LEGACY_COLUMN_LAYOUT_STORAGE_KEY
-          )
+      const currentLayout = parseStoredColumnLayout(
+        localStorage.getItem(getProjectColumnLayoutStorageKey(projectId))
       );
+      const legacyLayout =
+        parseStoredColumnLayout(
+          localStorage.getItem(
+            getLegacyProjectColumnLayoutStorageKey(projectId)
+          )
+        ) ??
+        parseStoredColumnLayout(
+          localStorage.getItem(LEGACY_COLUMN_LAYOUT_STORAGE_KEY)
+        );
+      const parsed =
+        currentLayout ??
+        (legacyLayout
+          ? migrateLegacyColumnLayout(legacyLayout)
+          : null);
       if (!parsed) {
         return;
       }
diff --git a/src/frontend/utils/circuit-grid-model.ts b/src/frontend/utils/circuit-grid-model.ts
index 49263b4..880dbe9 100644
--- a/src/frontend/utils/circuit-grid-model.ts
+++ b/src/frontend/utils/circuit-grid-model.ts
@@ -129,6 +129,8 @@ export const defaultVisibleColumnKeys = allColumns
   .map((column) => column.key);
 
 const projectColumnLayoutStoragePrefix =
+  "circuitTreeEditor.columnLayout.v3";
+const legacyProjectColumnLayoutStoragePrefix =
   "circuitTreeEditor.columnLayout.v2";
 
 export interface CircuitColumnLayout {
@@ -162,6 +164,12 @@ export function getProjectColumnLayoutStorageKey(
   return `${projectColumnLayoutStoragePrefix}.${projectId}`;
 }
 
+export function getLegacyProjectColumnLayoutStorageKey(
+  projectId: string
+): string {
+  return `${legacyProjectColumnLayoutStoragePrefix}.${projectId}`;
+}
+
 export function normalizeColumnOrder(keys: CellKey[]): CellKey[] {
   const unique = [...new Set(keys)];
   const allKeys = allColumns.map((column) => column.key);
@@ -225,6 +233,28 @@ export function parseStoredColumnLayout(
   }
 }
 
+export function migrateLegacyColumnLayout(
+  layout: CircuitColumnLayout
+): CircuitColumnLayout {
+  const newlyVisibleKey: CellKey = "protectionSummary";
+  const order = layout.order.filter(
+    (key) => key !== newlyVisibleKey
+  ) as CellKey[];
+  const totalPowerIndex = order.indexOf("rowTotalPower");
+  order.splice(
+    totalPowerIndex >= 0 ? totalPowerIndex + 1 : order.length,
+    0,
+    newlyVisibleKey
+  );
+
+  return {
+    order,
+    visible: layout.visible.includes(newlyVisibleKey)
+      ? layout.visible
+      : [...layout.visible, newlyVisibleKey],
+  };
+}
+
 const deviceOnlyColumns = new Set<CellKey>([
   "quantity",
   "powerPerUnit",
diff --git a/tests/circuit-grid-model.test.ts b/tests/circuit-grid-model.test.ts
index 5e045d9..b0472b8 100644
--- a/tests/circuit-grid-model.test.ts
+++ b/tests/circuit-grid-model.test.ts
@@ -6,12 +6,14 @@ import {
   buildDeviceRowEditPatch,
   formatValue,
   getCircuitSectionLabel,
+  getLegacyProjectColumnLayoutStorageKey,
   getProjectColumnLayoutStorageKey,
   isGridEditorControlTarget,
   getBlockSortValue,
   getCellKind,
   getCircuitValue,
   getDeviceValue,
+  migrateLegacyColumnLayout,
   parseStoredColumnLayout,
   parseNumeric,
 } from "../src/frontend/utils/circuit-grid-model.js";
@@ -79,6 +81,10 @@ describe("circuit grid model", () => {
   it("stores valid column layouts under a project-specific key", () => {
     assert.equal(
       getProjectColumnLayoutStorageKey("project-1"),
+      "circuitTreeEditor.columnLayout.v3.project-1"
+    );
+    assert.equal(
+      getLegacyProjectColumnLayoutStorageKey("project-1"),
       "circuitTreeEditor.columnLayout.v2.project-1"
     );
     const layout = parseStoredColumnLayout(
@@ -100,6 +106,39 @@ describe("circuit grid model", () => {
     assert.equal(parseStoredColumnLayout("{invalid"), null);
   });
 
+  it("adds the circuit protection column to legacy project layouts", () => {
+    const legacyLayout = parseStoredColumnLayout(
+      JSON.stringify({
+        order: [
+          "equipmentIdentifier",
+          "displayName",
+          "rowTotalPower",
+          "remark",
+        ],
+        visible: [
+          "equipmentIdentifier",
+          "displayName",
+          "rowTotalPower",
+          "remark",
+        ],
+      })
+    );
+    assert.ok(legacyLayout);
+
+    const migrated = migrateLegacyColumnLayout(legacyLayout);
+    assert.equal(
+      migrated.order.indexOf("protectionSummary"),
+      migrated.order.indexOf("rowTotalPower") + 1
+    );
+    assert.deepEqual(migrated.visible, [
+      "equipmentIdentifier",
+      "displayName",
+      "rowTotalPower",
+      "remark",
+      "protectionSummary",
+    ]);
+  });
+
   it("shows stable circuit sections with German labels", () => {
     assert.equal(
       getCircuitSectionLabel({