diff --git a/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/LayoutParser.kt b/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/LayoutParser.kt
index 3164cc698..d2b51fb92 100644
--- a/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/LayoutParser.kt
+++ b/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/LayoutParser.kt
@@ -59,8 +59,7 @@ object LayoutParser {
 
     /** Parse simple layouts, defined only as rows of (normal) keys with popup keys. */
     fun parseSimpleString(layoutText: String): List<List<KeyData>> {
-        val rowStrings = layoutText.replace("\r\n", "\n").split("\\n\\s*\\n".toRegex()).filter { it.isNotBlank() }
-        return rowStrings.map { row ->
+        return LayoutUtils.getSimpleRowStrings(layoutText).map { row ->
             row.split("\n").mapNotNull { parseKey(it) }
         }
     }
diff --git a/app/src/main/java/helium314/keyboard/latin/App.kt b/app/src/main/java/helium314/keyboard/latin/App.kt
index 23308a14a..6172dac58 100644
--- a/app/src/main/java/helium314/keyboard/latin/App.kt
+++ b/app/src/main/java/helium314/keyboard/latin/App.kt
@@ -161,7 +161,7 @@ fun checkVersionUpgrade(context: Context) {
                 split[1] = newName
                 split.joinToString(":")
             }
-            Settings.writePrefAdditionalSubtypes(prefs, newSubtypeStrings.joinToString(";"))
+            prefs.edit().putString(Settings.PREF_ADDITIONAL_SUBTYPES, newSubtypeStrings.joinToString(";")).apply()
         }
         // rename other custom layouts
         LayoutUtilsCustom.onLayoutFileChanged()
@@ -630,7 +630,7 @@ private fun upgradesWhenComingFromOldAppName(context: Context) {
             val localeString = it.substringBefore(":")
             additionalSubtypes.add(it.replace(localeString, localeString.constructLocale().toLanguageTag()))
         }
-        Settings.writePrefAdditionalSubtypes(prefs, additionalSubtypes.joinToString(";"))
+        prefs.edit().putString(Settings.PREF_ADDITIONAL_SUBTYPES, additionalSubtypes.joinToString(";")).apply()
     }
     // move pinned clips to credential protected storage if device is not locked (should never happen)
     if (!prefs.contains(Settings.PREF_PINNED_CLIPS)) return
diff --git a/app/src/main/java/helium314/keyboard/latin/LatinIME.java b/app/src/main/java/helium314/keyboard/latin/LatinIME.java
index d2e75a457..f18c530e7 100644
--- a/app/src/main/java/helium314/keyboard/latin/LatinIME.java
+++ b/app/src/main/java/helium314/keyboard/latin/LatinIME.java
@@ -523,6 +523,11 @@ public class LatinIME extends InputMethodService implements
     }
 
     final class SubtypeState {
+        // When HintLocales causes a subtype override, we store
+        // the overridden subtype here in order to restore it when
+        // we switch to another input context that has no HintLocales.
+        private InputMethodSubtype mOverriddenByLocale;
+
         private InputMethodSubtype mLastActiveSubtype;
         private boolean mCurrentSubtypeHasBeenUsed = true; // starting with true avoids immediate switch
 
@@ -530,6 +535,70 @@ public class LatinIME extends InputMethodService implements
             mCurrentSubtypeHasBeenUsed = true;
         }
 
+        // TextFields can provide locale/language hints that the IME should use via 'hintLocales'.
+        // If a matching subtype is found, we temporarily switch to that subtype until
+        // we return to a context that does not provide any hints, or until the user
+        // explicitly changes the language/subtype in use.
+        public InputMethodSubtype getSubtypeForLocales(final RichInputMethodManager richImm, final Iterable<Locale> locales) {
+            final InputMethodSubtype overriddenByLocale = mOverriddenByLocale;
+            if (locales == null) {
+                if (overriddenByLocale != null) {
+                    // no locales provided, so switch back to
+                    // whatever subtype was used last time.
+                    mOverriddenByLocale = null;
+
+                    return overriddenByLocale;
+                }
+
+                return null;
+            }
+
+            final InputMethodSubtype currentSubtype = richImm.getCurrentSubtype().getRawSubtype();
+            final Locale currentSubtypeLocale = richImm.getCurrentSubtypeLocale();
+            final int minimumMatchLevel = 3; // LocaleUtils.LOCALE_LANGUAGE_MATCH_COUNTRY_DIFFER;
+
+            // Try finding a subtype matching the hint language.
+            for (final Locale hintLocale : locales) {
+                if (LocaleUtils.INSTANCE.getMatchLevel(hintLocale, currentSubtypeLocale) >= minimumMatchLevel
+                        || CollectionsKt.any(mSettings.getCurrent().mSecondaryLocales,
+                            (secLocale) -> LocaleUtils.INSTANCE.getMatchLevel(hintLocale, secLocale) >= minimumMatchLevel)) {
+                    // current locales are already a good match, and we want to avoid unnecessary layout switches.
+                    return null;
+                }
+
+                final InputMethodSubtype subtypeForHintLocale = richImm.findSubtypeForHintLocale(hintLocale);
+                if (subtypeForHintLocale == null) {
+                    continue;
+                }
+
+                if (subtypeForHintLocale.equals(currentSubtype)) {
+                    // no need to switch, we already use the correct locale.
+                    return null;
+                }
+
+                if (overriddenByLocale == null) {
+                    // auto-switching based on hint locale, so store
+                    // whatever subtype was in use so we can switch back
+                    // to it later when there are no hint locales.
+                    mOverriddenByLocale = currentSubtype;
+                }
+
+                return subtypeForHintLocale;
+            }
+
+            return null;
+        }
+
+        public void onSubtypeChanged(final InputMethodSubtype oldSubtype,
+                                     final InputMethodSubtype newSubtype) {
+            if (oldSubtype != mOverriddenByLocale) {
+                // Whenever the subtype is changed, clear tracking
+                // the subtype that is overridden by a HintLocale as
+                // we no longer have a subtype to automatically switch back to.
+                mOverriddenByLocale = null;
+            }
+        }
+
         public void switchSubtype(final RichInputMethodManager richImm) {
             final InputMethodSubtype currentSubtype = richImm.getCurrentSubtype().getRawSubtype();
             final InputMethodSubtype lastActiveSubtype = mLastActiveSubtype;
@@ -858,6 +927,8 @@ public class LatinIME extends InputMethodService implements
             return;
         }
         InputMethodSubtype oldSubtype = mRichImm.getCurrentSubtype().getRawSubtype();
+
+        mSubtypeState.onSubtypeChanged(oldSubtype, subtype);
         StatsUtils.onSubtypeChanged(oldSubtype, subtype);
         mRichImm.onSubtypeChanged(subtype);
         mInputLogic.onSubtypeChanged(SubtypeLocaleUtils.getCombiningRulesExtraValue(subtype),
@@ -876,20 +947,10 @@ public class LatinIME extends InputMethodService implements
         super.onStartInput(editorInfo, restarting);
 
         final List<Locale> hintLocales = EditorInfoCompatUtils.getHintLocales(editorInfo);
-        if (hintLocales == null) {
-            return;
-        }
-        // Try switching to a subtype matching the hint language.
-        for (final Locale hintLocale : hintLocales) {
-            if (LocaleUtils.INSTANCE.getMatchLevel(hintLocale, mRichImm.getCurrentSubtypeLocale()) >= 3
-                    || CollectionsKt.any(mSettings.getCurrent().mSecondaryLocales, (secLocale) -> LocaleUtils.INSTANCE.getMatchLevel(hintLocale, secLocale) >= 3))
-                return; // current locales are already a good match, and we want to avoid unnecessary layout switches
-            final InputMethodSubtype newSubtype = mRichImm.findSubtypeForHintLocale(hintLocale);
-            if (newSubtype == null) continue;
-            if (newSubtype.equals(mRichImm.getCurrentSubtype().getRawSubtype()))
-                return; // no need to switch, we already use the correct locale
-            mHandler.postSwitchLanguage(newSubtype);
-            break;
+        final InputMethodSubtype subtypeForLocales = mSubtypeState.getSubtypeForLocales(mRichImm, hintLocales);
+        if (subtypeForLocales != null) {
+            // found a better subtype using hint locales that we should switch to.
+            mHandler.postSwitchLanguage(subtypeForLocales);
         }
     }
 
diff --git a/app/src/main/java/helium314/keyboard/latin/settings/Defaults.kt b/app/src/main/java/helium314/keyboard/latin/settings/Defaults.kt
index 0301409ba..689087f9f 100644
--- a/app/src/main/java/helium314/keyboard/latin/settings/Defaults.kt
+++ b/app/src/main/java/helium314/keyboard/latin/settings/Defaults.kt
@@ -9,7 +9,6 @@ import helium314.keyboard.keyboard.KeyboardTheme
 import helium314.keyboard.latin.BuildConfig
 import helium314.keyboard.latin.common.Constants.Separators
 import helium314.keyboard.latin.common.Constants.Subtype.ExtraValue
-import helium314.keyboard.latin.utils.JniUtils
 import helium314.keyboard.latin.utils.LayoutType
 import helium314.keyboard.latin.utils.POPUP_KEYS_LABEL_DEFAULT
 import helium314.keyboard.latin.utils.POPUP_KEYS_ORDER_DEFAULT
@@ -74,9 +73,9 @@ object Defaults {
     const val PREF_LANGUAGE_SWITCH_KEY = "internal"
     const val PREF_SHOW_EMOJI_KEY = false
     const val PREF_VARIABLE_TOOLBAR_DIRECTION = true
-    const val PREF_ADDITIONAL_SUBTYPES = "de${Separators.SET}${ExtraValue.KEYBOARD_LAYOUT_SET}=qwerty${Separators.SETS}" +
-            "fr${Separators.SET}${ExtraValue.KEYBOARD_LAYOUT_SET}=qwertz${Separators.SETS}" +
-            "hu${Separators.SET}${ExtraValue.KEYBOARD_LAYOUT_SET}=qwerty"
+    const val PREF_ADDITIONAL_SUBTYPES = "de${Separators.SET}${ExtraValue.KEYBOARD_LAYOUT_SET}=MAIN:qwerty${Separators.SETS}" +
+            "fr${Separators.SET}${ExtraValue.KEYBOARD_LAYOUT_SET}=MAIN:qwertz${Separators.SETS}" +
+            "hu${Separators.SET}${ExtraValue.KEYBOARD_LAYOUT_SET}=MAIN:qwerty"
     const val PREF_ENABLE_SPLIT_KEYBOARD = false
     const val PREF_ENABLE_SPLIT_KEYBOARD_LANDSCAPE = false
     const val PREF_SPLIT_SPACER_SCALE = SettingsValues.DEFAULT_SIZE_SCALE
@@ -152,8 +151,6 @@ object Defaults {
     const val PREF_EMOJI_RECENT_KEYS = ""
     const val PREF_LAST_SHOWN_EMOJI_CATEGORY_PAGE_ID = 0
     const val PREF_PINNED_CLIPS = ""
-    @JvmField
-    val PREF_LIBRARY_CHECKSUM: String = JniUtils.expectedDefaultChecksum()
     const val PREF_SHOW_DEBUG_SETTINGS = false
     val PREF_DEBUG_MODE = BuildConfig.DEBUG
     const val PREF_SHOW_SUGGESTION_INFOS = false
diff --git a/app/src/main/java/helium314/keyboard/latin/settings/Settings.java b/app/src/main/java/helium314/keyboard/latin/settings/Settings.java
index 89e93e8dd..1510a65be 100644
--- a/app/src/main/java/helium314/keyboard/latin/settings/Settings.java
+++ b/app/src/main/java/helium314/keyboard/latin/settings/Settings.java
@@ -312,10 +312,6 @@ public final class Settings implements SharedPreferences.OnSharedPreferenceChang
         mPrefs.edit().putBoolean(Settings.PREF_ALWAYS_INCOGNITO_MODE, !oldValue).apply();
     }
 
-    public static void writePrefAdditionalSubtypes(final SharedPreferences prefs, final String prefSubtypes) {
-        prefs.edit().putString(PREF_ADDITIONAL_SUBTYPES, prefSubtypes).apply();
-    }
-
     public static int readHorizontalSpaceSwipe(final SharedPreferences prefs) {
         return switch (prefs.getString(PREF_SPACE_HORIZONTAL_SWIPE, Defaults.PREF_SPACE_HORIZONTAL_SWIPE)) {
             case "move_cursor" -> KeyboardActionListener.SWIPE_MOVE_CURSOR;
diff --git a/app/src/main/java/helium314/keyboard/latin/settings/SettingsSubtype.kt b/app/src/main/java/helium314/keyboard/latin/settings/SettingsSubtype.kt
index a5745295b..ca18b7fda 100644
--- a/app/src/main/java/helium314/keyboard/latin/settings/SettingsSubtype.kt
+++ b/app/src/main/java/helium314/keyboard/latin/settings/SettingsSubtype.kt
@@ -11,11 +11,9 @@ import helium314.keyboard.latin.common.LocaleUtils.constructLocale
 import helium314.keyboard.latin.define.DebugFlags
 import helium314.keyboard.latin.utils.LayoutType
 import helium314.keyboard.latin.utils.LayoutType.Companion.toExtraValue
-import helium314.keyboard.latin.utils.LayoutUtilsCustom
 import helium314.keyboard.latin.utils.Log
 import helium314.keyboard.latin.utils.ScriptUtils
 import helium314.keyboard.latin.utils.ScriptUtils.script
-import helium314.keyboard.latin.utils.SubtypeLocaleUtils
 import helium314.keyboard.latin.utils.SubtypeUtilsAdditional
 import helium314.keyboard.latin.utils.locale
 import java.util.Locale
@@ -27,23 +25,9 @@ data class SettingsSubtype(val locale: Locale, val extraValues: String) {
 
     /** Creates an additional subtype from the SettingsSubtype.
      *  Resulting InputMethodSubtypes are equal if SettingsSubtypes are equal */
-    fun toAdditionalSubtype(): InputMethodSubtype? {
+    fun toAdditionalSubtype(): InputMethodSubtype {
         val asciiCapable = locale.script() == ScriptUtils.SCRIPT_LATIN
-        val subtype = SubtypeUtilsAdditional.createAdditionalSubtype(locale, extraValues, asciiCapable, true)
-
-        // todo: this is returns null for all non-latin layouts
-        //  either fix it, or remove the check
-        //  if removed, removing a layout will result in fallback qwerty even for non-ascii, but this is better than the current alternative
-/*        if (subtype.nameResId == SubtypeLocaleUtils.UNKNOWN_KEYBOARD_LAYOUT
-            && mainLayoutName()?.endsWith("+") != true // "+" layouts and custom layouts are always "unknown"
-            && !LayoutUtilsCustom.isCustomLayout(mainLayoutName() ?: SubtypeLocaleUtils.QWERTY)
-        ) {
-            // Skip unknown keyboard layout subtype. This may happen when predefined keyboard
-            // layout has been removed.
-            Log.w(SettingsSubtype::class.simpleName, "unknown additional subtype $this")
-            return null
-        }*/
-        return subtype
+        return SubtypeUtilsAdditional.createAdditionalSubtype(locale, extraValues, asciiCapable, true)
     }
 
     fun mainLayoutName() = LayoutType.getMainLayoutFromExtraValue(extraValues)
@@ -54,7 +38,7 @@ data class SettingsSubtype(val locale: Locale, val extraValues: String) {
         val newList = extraValues.split(",")
             .filterNot { it.isBlank() || it.startsWith("$extraValueKey=") || it == extraValueKey }
         val newValue = if (extraValue == null) extraValueKey else "$extraValueKey=$extraValue"
-        val newValues = (newList + newValue).joinToString(",")
+        val newValues = (newList + newValue).sorted().joinToString(",")
         return copy(extraValues = newValues)
     }
 
diff --git a/app/src/main/java/helium314/keyboard/latin/utils/JniUtils.java b/app/src/main/java/helium314/keyboard/latin/utils/JniUtils.java
index 603e32ab6..6bae92d5e 100644
--- a/app/src/main/java/helium314/keyboard/latin/utils/JniUtils.java
+++ b/app/src/main/java/helium314/keyboard/latin/utils/JniUtils.java
@@ -13,7 +13,6 @@ import android.text.TextUtils;
 
 import helium314.keyboard.latin.App;
 import helium314.keyboard.latin.BuildConfig;
-import helium314.keyboard.latin.settings.Defaults;
 import helium314.keyboard.latin.settings.Settings;
 
 import java.io.File;
@@ -63,7 +62,7 @@ public final class JniUtils {
                     // we want the default preferences, because storing the checksum in device protected storage is discouraged
                     // see https://developer.android.com/reference/android/content/Context#createDeviceProtectedStorageContext()
                     // if device is locked, this will throw an IllegalStateException
-                    wantedChecksum = KtxKt.protectedPrefs(app).getString(Settings.PREF_LIBRARY_CHECKSUM, Defaults.PREF_LIBRARY_CHECKSUM);
+                    wantedChecksum = KtxKt.protectedPrefs(app).getString(Settings.PREF_LIBRARY_CHECKSUM, expectedDefaultChecksum());
                 }
                 final FileInputStream libStream = new FileInputStream(userSuppliedLibrary);
                 final String checksum = ChecksumCalculator.INSTANCE.checksum(libStream);
diff --git a/app/src/main/java/helium314/keyboard/latin/utils/LayoutUtils.kt b/app/src/main/java/helium314/keyboard/latin/utils/LayoutUtils.kt
index 56afe9ce9..68a99be99 100644
--- a/app/src/main/java/helium314/keyboard/latin/utils/LayoutUtils.kt
+++ b/app/src/main/java/helium314/keyboard/latin/utils/LayoutUtils.kt
@@ -1,6 +1,8 @@
 package helium314.keyboard.latin.utils
 
 import android.content.Context
+import helium314.keyboard.keyboard.internal.keyboard_parser.floris.SimplePopups
+import helium314.keyboard.keyboard.internal.keyboard_parser.getOrCreate
 import helium314.keyboard.latin.R
 import helium314.keyboard.latin.settings.Defaults.default
 import helium314.keyboard.latin.utils.LayoutType.Companion.folder
@@ -26,6 +28,7 @@ object LayoutUtils {
     fun getLMainLayoutsForLocales(locales: List<Locale>, context: Context): Collection<String> =
         locales.flatMapTo(HashSet()) { getAvailableLayouts(LayoutType.MAIN, context, it) }.sorted()
 
+    /** gets content for built-in (non-custom) layout [layoutName], with fallback to qwerty */
     fun getContent(layoutType: LayoutType, layoutName: String, context: Context): String {
         val layouts = context.assets.list(layoutType.folder)!!
         layouts.firstOrNull { it.startsWith("$layoutName.") }
@@ -33,4 +36,27 @@ object LayoutUtils {
         val fallback = layouts.first { it.startsWith(layoutType.default) } // must exist!
         return context.assets.open(layoutType.folder + File.separator + fallback).reader().readText()
     }
+
+    fun getContentWithPlus(mainLayoutName: String, locale: Locale, context: Context): String {
+        val content = getContent(LayoutType.MAIN, mainLayoutName, context)
+        if (!mainLayoutName.endsWith("+"))
+            return content
+        // the stuff below will not work if we add "+" layouts in json format
+        // ideally we should serialize keyData to json to solve this
+        val rows = getSimpleRowStrings(content)
+        val localeKeyboardInfos = getOrCreate(context, locale)
+        return rows.mapIndexed { i, row ->
+            val extraKeys = localeKeyboardInfos.getExtraKeys(i + 1) ?: return@mapIndexed row
+            val rowList = row.split("\n").filterNot { it.isEmpty() }.toMutableList()
+            extraKeys.forEach { key ->
+                val popups = (key.popup as? SimplePopups)?.popupKeys?.joinToString(" ")
+                    ?.takeIf { it.isNotEmpty() }?.let { " $it" } ?: ""
+                rowList.add(key.label + popups)
+            }
+            rowList.joinToString("\n")
+        }.joinToString("\n\n")
+    }
+
+    fun getSimpleRowStrings(layoutContent: String): List<String> =
+        layoutContent.replace("\r\n", "\n").split("\\n\\s*\\n".toRegex()).filter { it.isNotBlank() }
 }
diff --git a/app/src/main/java/helium314/keyboard/latin/utils/SubtypeSettings.kt b/app/src/main/java/helium314/keyboard/latin/utils/SubtypeSettings.kt
index 18739953b..f533223ec 100644
--- a/app/src/main/java/helium314/keyboard/latin/utils/SubtypeSettings.kt
+++ b/app/src/main/java/helium314/keyboard/latin/utils/SubtypeSettings.kt
@@ -52,9 +52,8 @@ object SubtypeSettings {
 
     fun addEnabledSubtype(prefs: SharedPreferences, newSubtype: InputMethodSubtype) {
         val subtype = newSubtype.toSettingsSubtype()
-        val subtypes = prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!
-            .split(Separators.SETS).filter { it.isNotBlank() }.map { it.toSettingsSubtype() } + subtype
-        val newString = subtypes.map { it.toPref() }.toSortedSet().joinToString(Separators.SETS)
+        val subtypes = createSettingsSubtypes(prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!) + subtype
+        val newString = createPrefSubtypes(subtypes)
         prefs.edit { putString(Settings.PREF_ENABLED_SUBTYPES, newString) }
 
         if (newSubtype !in enabledSubtypes) {
@@ -74,10 +73,8 @@ object SubtypeSettings {
 
     fun getSelectedSubtype(prefs: SharedPreferences): InputMethodSubtype {
         val selectedSubtype = prefs.getString(Settings.PREF_SELECTED_SUBTYPE, Defaults.PREF_SELECTED_SUBTYPE)!!.toSettingsSubtype()
-        if (selectedSubtype.isAdditionalSubtype(prefs)) {
-            val selectedAdditionalSubtype = selectedSubtype.toAdditionalSubtype()
-            if (selectedAdditionalSubtype != null) return selectedAdditionalSubtype
-        }
+        if (selectedSubtype.isAdditionalSubtype(prefs))
+            return selectedSubtype.toAdditionalSubtype()
         // no additional subtype, must be a resource subtype
 
         val subtype = enabledSubtypes.firstOrNull { it.toSettingsSubtype() == selectedSubtype }
@@ -157,6 +154,15 @@ object SubtypeSettings {
         RichInputMethodManager.getInstance().refreshSubtypeCaches()
     }
 
+    fun createSettingsSubtypes(prefSubtypes: String): List<SettingsSubtype> =
+        prefSubtypes.split(Separators.SETS).mapNotNull {
+            if (it.isEmpty()) null
+            else it.toSettingsSubtype()
+        }
+
+    fun createPrefSubtypes(subtypes: Collection<SettingsSubtype>): String =
+        subtypes.map { it.toPref() }.toSortedSet().joinToString(Separators.SETS)
+
     fun init(context: Context) {
         SubtypeLocaleUtils.init(context) // necessary to get the correct getKeyboardLayoutSetName
 
@@ -207,7 +213,8 @@ object SubtypeSettings {
         }
         if (subtypesToRemove.isEmpty()) return
         Log.w(TAG, "removing custom subtypes without main layout files: $subtypesToRemove")
-        Settings.writePrefAdditionalSubtypes(prefs, additionalSubtypes.filterNot { it in subtypesToRemove }.joinToString(Separators.SETS))
+        // todo: now we have a qwerty fallback anyway, consider removing this method (makes bugs more obvious to users)
+        prefs.edit().putString(Settings.PREF_ADDITIONAL_SUBTYPES, additionalSubtypes.filterNot { it in subtypesToRemove }.joinToString(Separators.SETS)).apply()
     }
 
     private fun loadAdditionalSubtypes(prefs: SharedPreferences) {
@@ -220,15 +227,11 @@ object SubtypeSettings {
     // requires loadResourceSubtypes to be called before
     private fun loadEnabledSubtypes(context: Context) {
         val prefs = context.prefs()
-        val settingsSubtypes = prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!
-            .split(Separators.SETS).filter { it.isNotEmpty() }.map { it.toSettingsSubtype() }
+        val settingsSubtypes = createSettingsSubtypes(prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!)
         for (settingsSubtype in settingsSubtypes) {
             if (settingsSubtype.isAdditionalSubtype(prefs)) {
-                val additionalSubtype = settingsSubtype.toAdditionalSubtype()
-                if (additionalSubtype != null) {
-                    enabledSubtypes.add(additionalSubtype)
-                    continue
-                }
+                enabledSubtypes.add(settingsSubtype.toAdditionalSubtype())
+                continue
             }
             val subtypesForLocale = resourceSubtypesByLocale[settingsSubtype.locale]
             if (subtypesForLocale == null) {
@@ -258,12 +261,11 @@ object SubtypeSettings {
 
     /** @return whether pref was changed */
     private fun removeEnabledSubtype(prefs: SharedPreferences, subtype: SettingsSubtype): Boolean {
-        val oldSubtypes = prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!
-            .split(Separators.SETS).filter { it.isNotEmpty() }.map { it.toSettingsSubtype() }
+        val oldSubtypes = createSettingsSubtypes(prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!)
         val newSubtypes = oldSubtypes - subtype
         if (oldSubtypes == newSubtypes)
             return false // already removed
-        prefs.edit { putString(Settings.PREF_ENABLED_SUBTYPES, newSubtypes.joinToString(Separators.SETS) { it.toPref() }) }
+        prefs.edit { putString(Settings.PREF_ENABLED_SUBTYPES, createPrefSubtypes(newSubtypes)) }
         if (subtype == prefs.getString(Settings.PREF_SELECTED_SUBTYPE, Defaults.PREF_SELECTED_SUBTYPE)!!.toSettingsSubtype()) {
             // switch subtype if the currently used one has been disabled
             try {
diff --git a/app/src/main/java/helium314/keyboard/latin/utils/SubtypeUtilsAdditional.kt b/app/src/main/java/helium314/keyboard/latin/utils/SubtypeUtilsAdditional.kt
index 048a7410b..b9bce10a9 100644
--- a/app/src/main/java/helium314/keyboard/latin/utils/SubtypeUtilsAdditional.kt
+++ b/app/src/main/java/helium314/keyboard/latin/utils/SubtypeUtilsAdditional.kt
@@ -53,10 +53,11 @@ object SubtypeUtilsAdditional {
         val prefs = context.prefs()
         SubtypeSettings.removeEnabledSubtype(context, subtype)
         val oldAdditionalSubtypesString = prefs.getString(Settings.PREF_ADDITIONAL_SUBTYPES, Defaults.PREF_ADDITIONAL_SUBTYPES)!!
-        val oldAdditionalSubtypes = createAdditionalSubtypes(oldAdditionalSubtypesString)
-        val newAdditionalSubtypes = oldAdditionalSubtypes.filter { it != subtype }
-        val newAdditionalSubtypesString = createPrefSubtypes(newAdditionalSubtypes)
-        Settings.writePrefAdditionalSubtypes(prefs, newAdditionalSubtypesString)
+        val oldAdditionalSubtypes = SubtypeSettings.createSettingsSubtypes(oldAdditionalSubtypesString)
+        val settingsSubtype = subtype.toSettingsSubtype()
+        val newAdditionalSubtypes = oldAdditionalSubtypes.filter { it != settingsSubtype }
+        val newAdditionalSubtypesString = SubtypeSettings.createPrefSubtypes(newAdditionalSubtypes)
+        prefs.edit().putString(Settings.PREF_ADDITIONAL_SUBTYPES, newAdditionalSubtypesString).apply()
     }
 
     // updates additional subtypes, enabled subtypes, and selected subtype
@@ -66,34 +67,37 @@ object SubtypeUtilsAdditional {
         val isSelected = prefs.getString(Settings.PREF_SELECTED_SUBTYPE, Defaults.PREF_SELECTED_SUBTYPE)!!.toSettingsSubtype() == from
         val isEnabled = prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!.split(Separators.SETS)
             .any { it.toSettingsSubtype() == from }
-        val new = prefs.getString(Settings.PREF_ADDITIONAL_SUBTYPES, Defaults.PREF_ADDITIONAL_SUBTYPES)!!
-            .split(Separators.SETS).mapNotNullTo(sortedSetOf()) {
-                if (it == from.toPref()) null else it
-            } + to.toPref()
-        prefs.edit().putString(Settings.PREF_ADDITIONAL_SUBTYPES, new.joinToString(Separators.SETS)).apply()
-
-        val fromSubtype = from.toAdditionalSubtype() // will be null if we edit a resource subtype
-        val toSubtype = to.toAdditionalSubtype() // should never be null
-        if (isSelected && toSubtype != null) {
-            SubtypeSettings.setSelectedSubtype(prefs, toSubtype)
+        val additionalSubtypes = SubtypeSettings.createSettingsSubtypes(prefs.getString(Settings.PREF_ADDITIONAL_SUBTYPES, Defaults.PREF_ADDITIONAL_SUBTYPES)!!)
+            .toMutableList()
+        additionalSubtypes.remove(from)
+        if (SubtypeSettings.getResourceSubtypesForLocale(to.locale).none { it.toSettingsSubtype() == to }) {
+            // We only add the "to" subtype if it's not equal to a resource subtype.
+            // This means we make additional subtype disappear as magically as it was added if all settings are default.
+            // If we don't do this, enabling the base subtype will result in the additional subtype being enabled,
+            // as both have the same settingsSubtype.
+            additionalSubtypes.add(to)
         }
-        if (fromSubtype != null && isEnabled && toSubtype != null) {
-            SubtypeSettings.removeEnabledSubtype(context, fromSubtype)
-            SubtypeSettings.addEnabledSubtype(prefs, toSubtype)
+        val editor = prefs.edit()
+        editor.putString(Settings.PREF_ADDITIONAL_SUBTYPES, SubtypeSettings.createPrefSubtypes(additionalSubtypes))
+        if (isSelected) {
+            editor.putString(Settings.PREF_SELECTED_SUBTYPE, to.toPref())
         }
+        if (isEnabled) {
+            val enabled = SubtypeSettings.createSettingsSubtypes(prefs.getString(Settings.PREF_ENABLED_SUBTYPES, Defaults.PREF_ENABLED_SUBTYPES)!!)
+                .toMutableList()
+            enabled.remove(from)
+            enabled.add(to)
+            editor.putString(Settings.PREF_ENABLED_SUBTYPES, SubtypeSettings.createPrefSubtypes(enabled))
+        }
+        editor.apply()
+        SubtypeSettings.reloadEnabledSubtypes(context)
     }
 
-    fun createAdditionalSubtypes(prefSubtypes: String): List<InputMethodSubtype> {
-        if (prefSubtypes.isEmpty())
-            return emptyList()
-        return prefSubtypes.split(Separators.SETS).mapNotNull { it.toSettingsSubtype().toAdditionalSubtype() }
-    }
-
-    fun createPrefSubtypes(subtypes: Collection<InputMethodSubtype>): String {
-        if (subtypes.isEmpty())
-            return ""
-        return subtypes.joinToString(Separators.SETS) { it.toSettingsSubtype().toPref() }
-    }
+    fun createAdditionalSubtypes(prefSubtypes: String): List<InputMethodSubtype> =
+        prefSubtypes.split(Separators.SETS).mapNotNull {
+            if (it.isEmpty()) null
+            else it.toSettingsSubtype().toAdditionalSubtype()
+        }
 
     private fun getNameResId(locale: Locale, mainLayoutName: String): Int {
         val nameId = SubtypeLocaleUtils.getSubtypeNameResId(locale, mainLayoutName)
diff --git a/app/src/main/java/helium314/keyboard/settings/dialogs/SubtypeDialog.kt b/app/src/main/java/helium314/keyboard/settings/dialogs/SubtypeDialog.kt
index 7da713ec3..7db7cadbf 100644
--- a/app/src/main/java/helium314/keyboard/settings/dialogs/SubtypeDialog.kt
+++ b/app/src/main/java/helium314/keyboard/settings/dialogs/SubtypeDialog.kt
@@ -125,8 +125,8 @@ fun SubtypeDialog(
         onConfirmed = { onConfirmed(currentSubtype) },
         neutralButtonText = if (initialSubtype.isAdditionalSubtype(prefs)) stringResource(R.string.delete) else null,
         onNeutral = {
-            SubtypeUtilsAdditional.removeAdditionalSubtype(ctx, initialSubtype.toAdditionalSubtype()!!)
-            SubtypeSettings.removeEnabledSubtype(ctx, initialSubtype.toAdditionalSubtype()!!)
+            SubtypeUtilsAdditional.removeAdditionalSubtype(ctx, initialSubtype.toAdditionalSubtype())
+            SubtypeSettings.removeEnabledSubtype(ctx, initialSubtype.toAdditionalSubtype())
             onDismissRequest()
         },
         title = {
@@ -393,7 +393,7 @@ private fun MainLayoutRow(
         if (showLayoutEditDialog != null) {
             val layoutName = showLayoutEditDialog!!.first
             val startContent = showLayoutEditDialog?.second
-                ?: if (layoutName in appLayouts) LayoutUtils.getContent(LayoutType.MAIN, layoutName, ctx)
+                ?: if (layoutName in appLayouts) LayoutUtils.getContentWithPlus(layoutName, currentSubtype.locale, ctx)
                 else null
             LayoutEditDialog(
                 onDismissRequest = { showLayoutEditDialog = null },
diff --git a/app/src/main/java/helium314/keyboard/settings/preferences/LoadGestureLibPreference.kt b/app/src/main/java/helium314/keyboard/settings/preferences/LoadGestureLibPreference.kt
index 591d4a5c7..5b51bdbe2 100644
--- a/app/src/main/java/helium314/keyboard/settings/preferences/LoadGestureLibPreference.kt
+++ b/app/src/main/java/helium314/keyboard/settings/preferences/LoadGestureLibPreference.kt
@@ -35,10 +35,13 @@ fun LoadGestureLibPreference(setting: Setting) {
     val abi = Build.SUPPORTED_ABIS[0]
     val libFile = File(ctx.filesDir?.absolutePath + File.separator + JniUtils.JNI_LIB_IMPORT_FILE_NAME)
     fun renameToLibFileAndRestart(file: File, checksum: String) {
+        libFile.setWritable(true)
         libFile.delete()
-        // store checksum in default preferences (soo JniUtils)
+        // store checksum in default preferences (see JniUtils)
         prefs.edit().putString(Settings.PREF_LIBRARY_CHECKSUM, checksum).commit()
-        file.renameTo(libFile)
+        file.copyTo(libFile)
+        libFile.setReadOnly()
+        file.delete()
         Runtime.getRuntime().exit(0) // exit will restart the app, so library will be loaded
     }
     var tempFilePath: String? by rememberSaveable { mutableStateOf(null) }
diff --git a/app/src/test/java/helium314/keyboard/SubtypeTest.kt b/app/src/test/java/helium314/keyboard/SubtypeTest.kt
new file mode 100644
index 000000000..a101c07d9
--- /dev/null
+++ b/app/src/test/java/helium314/keyboard/SubtypeTest.kt
@@ -0,0 +1,75 @@
+package helium314.keyboard
+
+import helium314.keyboard.keyboard.KeyboardId
+import helium314.keyboard.keyboard.KeyboardLayoutSet
+import helium314.keyboard.keyboard.internal.KeyboardParams
+import helium314.keyboard.keyboard.internal.keyboard_parser.POPUP_KEYS_NORMAL
+import helium314.keyboard.keyboard.internal.keyboard_parser.addLocaleKeyTextsToParams
+import helium314.keyboard.latin.LatinIME
+import helium314.keyboard.latin.common.LocaleUtils.constructLocale
+import helium314.keyboard.latin.settings.Settings
+import helium314.keyboard.latin.settings.SettingsSubtype.Companion.toSettingsSubtype
+import helium314.keyboard.latin.utils.LayoutType
+import helium314.keyboard.latin.utils.POPUP_KEYS_LAYOUT
+import helium314.keyboard.latin.utils.SubtypeSettings
+import helium314.keyboard.latin.utils.SubtypeUtilsAdditional
+import helium314.keyboard.latin.utils.prefs
+import org.junit.runner.RunWith
+import org.robolectric.Robolectric
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import org.robolectric.shadows.ShadowLog
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+@RunWith(RobolectricTestRunner::class)
+@Config(shadows = [
+    ShadowInputMethodManager2::class
+])
+class SubtypeTest {
+    private lateinit var latinIME: LatinIME
+    private lateinit var params: KeyboardParams
+
+    @BeforeTest fun setUp() {
+        latinIME = Robolectric.setupService(LatinIME::class.java)
+        ShadowLog.setupLogging()
+        ShadowLog.stream = System.out
+        params = KeyboardParams()
+        params.mId = KeyboardLayoutSet.getFakeKeyboardId(KeyboardId.ELEMENT_ALPHABET)
+        params.mPopupKeyTypes.add(POPUP_KEYS_LAYOUT)
+        addLocaleKeyTextsToParams(latinIME, params, POPUP_KEYS_NORMAL)
+    }
+
+    @Test fun emptyAdditionalSubtypesResultsInEmptyList() {
+        // avoid issues where empty string results in additional subtype for undefined locale
+        val prefs = latinIME.prefs()
+        prefs.edit().putString(Settings.PREF_ADDITIONAL_SUBTYPES, "").apply()
+        assertTrue(SubtypeSettings.getAdditionalSubtypes().isEmpty())
+        val from = SubtypeSettings.getResourceSubtypesForLocale("es".constructLocale()).first()
+
+        // no change, and "changed" subtype actually is resource subtype -> still expect empty list
+        SubtypeUtilsAdditional.changeAdditionalSubtype(from.toSettingsSubtype(), from.toSettingsSubtype(), latinIME)
+        assertEquals(emptyList(), SubtypeSettings.getAdditionalSubtypes().map { it.toSettingsSubtype() })
+    }
+
+    @Test fun subtypeStaysEnabledOnEdits() {
+        val prefs = latinIME.prefs()
+        prefs.edit().putString(Settings.PREF_ADDITIONAL_SUBTYPES, "").apply() // clear it for convenience
+
+        // edit enabled resource subtype
+        val from = SubtypeSettings.getResourceSubtypesForLocale("es".constructLocale()).first()
+        SubtypeSettings.addEnabledSubtype(prefs, from)
+        val to = from.toSettingsSubtype().withLayout(LayoutType.SYMBOLS, "symbols_arabic")
+        SubtypeUtilsAdditional.changeAdditionalSubtype(from.toSettingsSubtype(), to, latinIME)
+        assertEquals(to, SubtypeSettings.getEnabledSubtypes(false).single().toSettingsSubtype())
+
+        // change the new subtype to effectively be the same as original resource subtype
+        val toNew = to.withoutLayout(LayoutType.SYMBOLS)
+        assertEquals(from.toSettingsSubtype(), toNew)
+        SubtypeUtilsAdditional.changeAdditionalSubtype(to, toNew, latinIME)
+        assertEquals(emptyList(), SubtypeSettings.getAdditionalSubtypes().map { it.toSettingsSubtype() })
+        assertEquals(from.toSettingsSubtype(), SubtypeSettings.getEnabledSubtypes(false).single().toSettingsSubtype())
+    }
+}