diff --git a/lib/storage/channel_order_store.dart b/lib/storage/channel_order_store.dart
index 88d3f7a..4e268b2 100644
--- a/lib/storage/channel_order_store.dart
+++ b/lib/storage/channel_order_store.dart
@@ -29,13 +29,15 @@ class ChannelOrderStore {
     String? jsonString = prefs.getString(keyFor);
     if (jsonString == null || jsonString.isEmpty) {
       // Attempt migration from legacy unscoped key on first load
+      // Only remove the legacy key when it actually exists: every prefs
+      // mutation rewrites the whole file on Windows.
       final legacyJsonString = prefs.getString(_keyPrefix);
-      prefs.remove(_keyPrefix);
       if (legacyJsonString != null && legacyJsonString.isNotEmpty) {
         appLogger.info(
           'Migrating channel order from legacy key $_keyPrefix to scoped key $keyFor',
         );
         await prefs.setString(keyFor, legacyJsonString);
+        await prefs.remove(_keyPrefix);
         jsonString = legacyJsonString;
       }
     }
diff --git a/lib/storage/channel_store.dart b/lib/storage/channel_store.dart
index 4f40482..b52b5b7 100644
--- a/lib/storage/channel_store.dart
+++ b/lib/storage/channel_store.dart
@@ -22,13 +22,15 @@ class ChannelStore {
     String? jsonString = prefs.getString(keyFor);
     if (jsonString == null || jsonString.isEmpty) {
       // Attempt migration from legacy unscoped key on first load
+      // Only remove the legacy key when it actually exists: every prefs
+      // mutation rewrites the whole file on Windows.
       final legacyJsonString = prefs.getString(_keyPrefix);
-      prefs.remove(_keyPrefix);
       if (legacyJsonString != null && legacyJsonString.isNotEmpty) {
         appLogger.info(
           'Migrating channel messages from legacy key $_keyPrefix to scoped key $keyFor',
         );
         await prefs.setString(keyFor, legacyJsonString);
+        await prefs.remove(_keyPrefix);
         jsonString = legacyJsonString;
       }
     }
diff --git a/lib/storage/community_store.dart b/lib/storage/community_store.dart
index c69d0b8..a8010a1 100644
--- a/lib/storage/community_store.dart
+++ b/lib/storage/community_store.dart
@@ -28,13 +28,15 @@ class CommunityStore {
     String? jsonString = prefs.getString(keyFor);
     if (jsonString == null || jsonString.isEmpty) {
       // Attempt migration from legacy unscoped key on first load
+      // Only remove the legacy key when it actually exists: every prefs
+      // mutation rewrites the whole file on Windows.
       final legacyJsonString = prefs.getString(_keyPrefix);
-      prefs.remove(_keyPrefix);
       if (legacyJsonString != null && legacyJsonString.isNotEmpty) {
         appLogger.info(
           'Migrating communities from legacy key $_keyPrefix to scoped key $keyFor',
         );
         await prefs.setString(keyFor, legacyJsonString);
+        await prefs.remove(_keyPrefix);
         jsonString = legacyJsonString;
       }
     }
diff --git a/lib/storage/contact_group_store.dart b/lib/storage/contact_group_store.dart
index ce6a0c6..0813274 100644
--- a/lib/storage/contact_group_store.dart
+++ b/lib/storage/contact_group_store.dart
@@ -21,13 +21,15 @@ class ContactGroupStore {
     String? jsonString = prefs.getString(keyFor);
     if (jsonString == null || jsonString.isEmpty) {
       // Attempt migration from legacy unscoped key on first load
+      // Only remove the legacy key when it actually exists: every prefs
+      // mutation rewrites the whole file on Windows.
       final legacyJsonString = prefs.getString(_keyPrefix);
-      prefs.remove(_keyPrefix);
       if (legacyJsonString != null && legacyJsonString.isNotEmpty) {
         appLogger.info(
           'Migrating channel messages from legacy key $_keyPrefix to scoped key $keyFor',
         );
         await prefs.setString(keyFor, legacyJsonString);
+        await prefs.remove(_keyPrefix);
         jsonString = legacyJsonString;
       }
     }
diff --git a/lib/storage/contact_store.dart b/lib/storage/contact_store.dart
index 5d1805d..9085d4e 100644
--- a/lib/storage/contact_store.dart
+++ b/lib/storage/contact_store.dart
@@ -23,13 +23,15 @@ class ContactStore {
     String? jsonString = prefs.getString(keyFor);
     if (jsonString == null || jsonString.isEmpty) {
       // Attempt migration from legacy unscoped key on first load
+      // Only remove the legacy key when it actually exists: every prefs
+      // mutation rewrites the whole file on Windows.
       final legacyJsonString = prefs.getString(_keyPrefix);
-      prefs.remove(_keyPrefix);
       if (legacyJsonString != null && legacyJsonString.isNotEmpty) {
         appLogger.info(
           'Migrating contacts from legacy key $_keyPrefix to scoped key $keyFor',
         );
         await prefs.setString(keyFor, legacyJsonString);
+        await prefs.remove(_keyPrefix);
         jsonString = legacyJsonString;
       }
     }
diff --git a/lib/storage/message_store.dart b/lib/storage/message_store.dart
index ccaf9ea..6045342 100644
--- a/lib/storage/message_store.dart
+++ b/lib/storage/message_store.dart
@@ -40,13 +40,18 @@ class MessageStore {
     String? jsonString = prefs.getString(key);
     if (jsonString == null || jsonString.isEmpty) {
       // Attempt migration from legacy unscoped key on first load
+      // Only touch storage when a legacy key actually exists. This ran
+      // unconditionally, and loadMessages is called once per contact during a
+      // contact pull. On Windows shared_preferences rewrites the WHOLE prefs
+      // file on every mutation, so each no-op remove cost a full multi-MB
+      // write - hundreds of them back to back on a large address book.
       final legacyJsonString = prefs.getString(oldKey);
-      prefs.remove(oldKey);
       if (legacyJsonString != null && legacyJsonString.isNotEmpty) {
         appLogger.info(
           'Migrating messages from legacy key $oldKey to scoped key $key',
         );
         await prefs.setString(key, legacyJsonString);
+        await prefs.remove(oldKey);
         jsonString = legacyJsonString;
       }
     }
diff --git a/lib/storage/unread_store.dart b/lib/storage/unread_store.dart
index 3b615b1..cc1f377 100644
--- a/lib/storage/unread_store.dart
+++ b/lib/storage/unread_store.dart
@@ -35,13 +35,15 @@ class UnreadStore {
     String? jsonString = prefs.getString(keyFor);
     if (jsonString == null || jsonString.isEmpty) {
       // Attempt migration from legacy unscoped key on first load
+      // Only remove the legacy key when it actually exists: every prefs
+      // mutation rewrites the whole file on Windows.
       final legacyJsonString = prefs.getString(_keyPrefix);
-      prefs.remove(_keyPrefix);
       if (legacyJsonString != null && legacyJsonString.isNotEmpty) {
         appLogger.info(
           'Migrating channel messages from legacy key $_keyPrefix to scoped key $keyFor',
         );
         await prefs.setString(keyFor, legacyJsonString);
+        await prefs.remove(_keyPrefix);
         jsonString = legacyJsonString;
       }
     }