diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/actions/MentionPreservingInputTransformation.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/actions/MentionPreservingInputTransformation.kt
new file mode 100644
index 000000000..a7c8cb073
--- /dev/null
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/actions/MentionPreservingInputTransformation.kt
@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.actions
+
+import androidx.compose.foundation.text.input.InputTransformation
+import androidx.compose.foundation.text.input.TextFieldBuffer
+
+/**
+ * Rejects any edit that partially modifies a previously-complete Nostr mention
+ * (`@npub1…`, `nostr:npub1…`, `@nprofile1…`, `nostr:nprofile1…`).
+ *
+ * Background: when an `OutputTransformation` collapses an underlying npub into a
+ * short `@DisplayName`, Compose's auto-derived offset mapping uses identity inside
+ * the wedge. Some IMEs — notably Microsoft SwiftKey — re-enter "word edit mode"
+ * over a previously-committed display token after autocorrect-on-space, then issue
+ * `setComposingText` with a shortened version. Because the mapping is identity
+ * inside the wedge, the IME's replacement only overwrites the leading characters
+ * of the underlying bech32, leaving an orphan tail that no longer matches the
+ * mention regex. The wedge collapses, the orphan bech32 becomes visible, and the
+ * cursor lands in the middle of it. Gboard never enters this state because it
+ * does not recompose previously-committed tokens.
+ *
+ * This guard runs on every input change. If the change's original-text range
+ * partially intersects a complete mention but does not fully cover it, the entire
+ * change is reverted. The mention stays atomic; the IME re-reads the unchanged
+ * buffer and moves on.
+ */
+object MentionPreservingInputTransformation : InputTransformation {
+    private val mentionRegex =
+        Regex("(?:@|nostr:)(?:npub1[a-z0-9]{58}|nprofile1[a-z0-9]+)")
+
+    override fun TextFieldBuffer.transformInput() {
+        val changeCount = changes.changeCount
+        if (changeCount == 0) return
+
+        val original = originalText.toString()
+        if (original.isEmpty()) return
+
+        val mentions = mentionRegex.findAll(original).toList()
+        if (mentions.isEmpty()) return
+
+        for (i in 0 until changeCount) {
+            val origRange = changes.getOriginalRange(i)
+            val origStart = origRange.min
+            val origEnd = origRange.max
+            for (mention in mentions) {
+                val mStart = mention.range.first
+                val mEndExclusive = mention.range.last + 1
+                val overlaps = origStart < mEndExclusive && origEnd > mStart
+                val fullyCovers = origStart <= mStart && origEnd >= mEndExclusive
+                if (overlaps && !fullyCovers) {
+                    revertAllChanges()
+                    return
+                }
+            }
+        }
+    }
+}
diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/creators/messagefield/MessageField.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/creators/messagefield/MessageField.kt
index 36cdecdcd..d25007493 100644
--- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/creators/messagefield/MessageField.kt
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/creators/messagefield/MessageField.kt
@@ -40,6 +40,7 @@ import androidx.compose.ui.platform.LocalSoftwareKeyboardController
 import androidx.compose.ui.text.input.KeyboardCapitalization
 import androidx.compose.ui.text.style.TextDirection
 import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.ui.actions.MentionPreservingInputTransformation
 import com.vitorpamplona.amethyst.ui.actions.UrlUserTagOutputTransformation
 import com.vitorpamplona.amethyst.ui.components.ThinPaddingTextField
 import com.vitorpamplona.amethyst.ui.stringRes
@@ -70,6 +71,7 @@ fun MessageField(
         state = viewModel.message,
         onTextChanged = viewModel::onMessageChanged,
         onContentReceived = onContentReceived,
+        inputTransformation = MentionPreservingInputTransformation,
         keyboardOptions =
             KeyboardOptions.Default.copy(
                 capitalization = KeyboardCapitalization.Sentences,
diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/NewGroupDMScreen.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/NewGroupDMScreen.kt
index 270113bd9..af68085c6 100644
--- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/NewGroupDMScreen.kt
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/NewGroupDMScreen.kt
@@ -77,6 +77,7 @@ import com.vitorpamplona.amethyst.commons.richtext.EncryptedMediaUrlVideo
 import com.vitorpamplona.amethyst.commons.richtext.MediaUrlImage
 import com.vitorpamplona.amethyst.commons.richtext.MediaUrlVideo
 import com.vitorpamplona.amethyst.commons.richtext.RichTextParser
+import com.vitorpamplona.amethyst.ui.actions.MentionPreservingInputTransformation
 import com.vitorpamplona.amethyst.ui.actions.UrlUserTagOutputTransformation
 import com.vitorpamplona.amethyst.ui.actions.uploads.SelectFromFiles
 import com.vitorpamplona.amethyst.ui.actions.uploads.SelectFromGallery
@@ -530,6 +531,7 @@ fun SendDirectMessageTo(
             ThinPaddingTextField(
                 state = postViewModel.toUsers,
                 onTextChanged = postViewModel::onToUsersChanged,
+                inputTransformation = MentionPreservingInputTransformation,
                 modifier =
                     Modifier
                         .weight(1f)
@@ -572,6 +574,7 @@ fun SendDirectMessageTo(
             ThinPaddingTextField(
                 state = postViewModel.subject,
                 onTextChanged = { postViewModel.onSubjectChanged() },
+                inputTransformation = MentionPreservingInputTransformation,
                 modifier = Modifier.fillMaxWidth(),
                 placeholder = {
                     Text(
diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/PrivateMessageEditFieldRow.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/PrivateMessageEditFieldRow.kt
index da9d8ed21..51b5bbd3d 100644
--- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/PrivateMessageEditFieldRow.kt
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/PrivateMessageEditFieldRow.kt
@@ -53,6 +53,7 @@ import androidx.lifecycle.viewmodel.compose.viewModel
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.model.LocalCache
 import com.vitorpamplona.amethyst.model.User
+import com.vitorpamplona.amethyst.ui.actions.MentionPreservingInputTransformation
 import com.vitorpamplona.amethyst.ui.actions.StrippingFailureDialog
 import com.vitorpamplona.amethyst.ui.actions.UrlUserTagOutputTransformation
 import com.vitorpamplona.amethyst.ui.actions.uploads.SelectFromGallery
@@ -203,6 +204,7 @@ fun EditField(
     ThinPaddingTextField(
         state = channelScreenModel.message,
         onTextChanged = { channelScreenModel.onMessageChanged() },
+        inputTransformation = MentionPreservingInputTransformation,
         keyboardOptions = PostKeyboard,
         shape = EditFieldBorder,
         modifier = Modifier.fillMaxWidth(),
diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/send/EditFieldRow.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/send/EditFieldRow.kt
index 1c2669b35..c9e63c90f 100644
--- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/send/EditFieldRow.kt
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/send/EditFieldRow.kt
@@ -37,6 +37,7 @@ import androidx.compose.ui.text.input.KeyboardCapitalization
 import androidx.compose.ui.text.style.TextDirection
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.ui.actions.MentionPreservingInputTransformation
 import com.vitorpamplona.amethyst.ui.actions.StrippingFailureDialog
 import com.vitorpamplona.amethyst.ui.actions.UrlUserTagOutputTransformation
 import com.vitorpamplona.amethyst.ui.actions.uploads.SelectFromGallery
@@ -116,6 +117,7 @@ fun EditFieldRow(
         ThinPaddingTextField(
             state = channelScreenModel.message,
             onTextChanged = { channelScreenModel.onMessageChanged() },
+            inputTransformation = MentionPreservingInputTransformation,
             keyboardOptions =
                 KeyboardOptions.Default.copy(
                     capitalization = KeyboardCapitalization.Sentences,
diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip23LongForm/LongFormPostScreen.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip23LongForm/LongFormPostScreen.kt
index 87977bdc4..2eb873924 100644
--- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip23LongForm/LongFormPostScreen.kt
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip23LongForm/LongFormPostScreen.kt
@@ -84,6 +84,7 @@ import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
 import com.vitorpamplona.amethyst.commons.model.EmptyTagList
 import com.vitorpamplona.amethyst.ui.actions.StrippingFailureDialog
+import com.vitorpamplona.amethyst.ui.actions.MentionPreservingInputTransformation
 import com.vitorpamplona.amethyst.ui.actions.UrlUserTagOutputTransformation
 import com.vitorpamplona.amethyst.ui.actions.uploads.GallerySelectSingle
 import com.vitorpamplona.amethyst.ui.actions.uploads.SelectFromFiles
@@ -381,6 +382,7 @@ private fun MarkdownPostScreenBody(
                     ThinPaddingTextField(
                         state = postViewModel.message,
                         onTextChanged = postViewModel::onMessageChanged,
+                        inputTransformation = MentionPreservingInputTransformation,
                         modifier =
                             Modifier
                                 .fillMaxWidth()
diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip99Classifieds/SellProduct.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip99Classifieds/SellProduct.kt
index c13346b81..52dfc08ac 100644
--- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip99Classifieds/SellProduct.kt
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip99Classifieds/SellProduct.kt
@@ -49,6 +49,7 @@ import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import coil3.compose.AsyncImage
 import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.ui.actions.MentionPreservingInputTransformation
 import com.vitorpamplona.amethyst.ui.actions.UrlUserTagOutputTransformation
 import com.vitorpamplona.amethyst.ui.components.TextSpinner
 import com.vitorpamplona.amethyst.ui.components.ThinPaddingTextField
@@ -111,6 +112,7 @@ fun SellProduct(postViewModel: NewProductViewModel) {
             ThinPaddingTextField(
                 state = postViewModel.title,
                 onTextChanged = { postViewModel.onTitleChanged() },
+                inputTransformation = MentionPreservingInputTransformation,
                 modifier = Modifier.fillMaxWidth(),
                 placeholder = {
                     Text(
@@ -311,6 +313,7 @@ fun SellProduct(postViewModel: NewProductViewModel) {
             ThinPaddingTextField(
                 state = postViewModel.locationText,
                 onTextChanged = { postViewModel.onLocationChanged() },
+                inputTransformation = MentionPreservingInputTransformation,
                 modifier = Modifier.fillMaxWidth(),
                 placeholder = {
                     Text(
diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/notifications/publicMessages/NewPublicMessageScreen.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/notifications/publicMessages/NewPublicMessageScreen.kt
index 1519ac398..9f284b4c9 100644
--- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/notifications/publicMessages/NewPublicMessageScreen.kt
+++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/notifications/publicMessages/NewPublicMessageScreen.kt
@@ -56,6 +56,7 @@ import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.ui.actions.StrippingFailureDialog
+import com.vitorpamplona.amethyst.ui.actions.MentionPreservingInputTransformation
 import com.vitorpamplona.amethyst.ui.actions.UrlUserTagOutputTransformation
 import com.vitorpamplona.amethyst.ui.actions.uploads.SelectFromFiles
 import com.vitorpamplona.amethyst.ui.actions.uploads.SelectFromGallery
@@ -417,6 +418,7 @@ fun SendDirectMessageTo(
             ThinPaddingTextField(
                 state = postViewModel.toUsers,
                 onTextChanged = postViewModel::onToUsersChanged,
+                inputTransformation = MentionPreservingInputTransformation,
                 modifier =
                     Modifier
                         .weight(1f)