diff --git a/CustomKeyboard/KeyboardViewController.m b/CustomKeyboard/KeyboardViewController.m
index 7e6d2c4..1be1c88 100644
--- a/CustomKeyboard/KeyboardViewController.m
+++ b/CustomKeyboard/KeyboardViewController.m
@@ -363,30 +363,33 @@ static void KBSkinInstallNotificationCallback(CFNotificationCenterRef center,
 
 // MARK: - KBKeyBoardMainViewDelegate
 - (void)keyBoardMainView:(KBKeyBoardMainView *)keyBoardMainView didTapKey:(KBKey *)key {
-    if (key.type != KBKeyTypeShift && key.type != KBKeyTypeModeChange) {
-        [[KBBackspaceUndoManager shared] registerNonClearAction];
-    }
     switch (key.type) {
         case KBKeyTypeCharacter: {
+            [[KBBackspaceUndoManager shared] registerNonClearAction];
             NSString *text = key.output ?: key.title ?: @"";
             [self.textDocumentProxy insertText:text];
             [self kb_updateCurrentWordWithInsertedText:text];
         } break;
         case KBKeyTypeBackspace:
+            [[KBBackspaceUndoManager shared] recordDeletionSnapshotBefore:self.textDocumentProxy.documentContextBeforeInput
+                                                                     after:self.textDocumentProxy.documentContextAfterInput];
             [self.textDocumentProxy deleteBackward];
             [self kb_scheduleContextRefreshResetSuppression:NO];
             break;
         case KBKeyTypeSpace:
+            [[KBBackspaceUndoManager shared] registerNonClearAction];
             [self.textDocumentProxy insertText:@" "];
             [self kb_clearCurrentWord];
             break;
         case KBKeyTypeReturn:
+            [[KBBackspaceUndoManager shared] registerNonClearAction];
             [self.textDocumentProxy insertText:@"\n"];
             [self kb_clearCurrentWord];
             break;
         case KBKeyTypeGlobe:
             [self advanceToNextInputMode]; break;
         case KBKeyTypeCustom:
+            [[KBBackspaceUndoManager shared] registerNonClearAction];
             // 点击自定义键切换到功能面板
             [self showFunctionPanel:YES];
             [self kb_clearCurrentWord];
diff --git a/CustomKeyboard/Utils/KBBackspaceLongPressHandler.m b/CustomKeyboard/Utils/KBBackspaceLongPressHandler.m
index ac3e3cd..0a34511 100644
--- a/CustomKeyboard/Utils/KBBackspaceLongPressHandler.m
+++ b/CustomKeyboard/Utils/KBBackspaceLongPressHandler.m
@@ -48,6 +48,8 @@ typedef NS_ENUM(NSInteger, KBBackspaceChunkClass) {
 @property (nonatomic, assign) CGPoint backspaceLastTouchPointInSelf;
 @property (nonatomic, assign) NSUInteger backspaceClearToken;
 @property (nonatomic, strong) UILabel *backspaceClearLabel;
+@property (nonatomic, copy) NSString *pendingClearBefore;
+@property (nonatomic, copy) NSString *pendingClearAfter;
 @end
 
 @implementation KBBackspaceLongPressHandler
@@ -73,6 +75,8 @@ typedef NS_ENUM(NSInteger, KBBackspaceChunkClass) {
     self.backspaceHasLastTouchPoint = NO;
     self.backspaceHoldToken += 1;
     [self kb_hideBackspaceClearLabel];
+    self.pendingClearBefore = nil;
+    self.pendingClearAfter = nil;
 
     if (!button) { return; }
 
@@ -99,7 +103,10 @@ typedef NS_ENUM(NSInteger, KBBackspaceChunkClass) {
     }
     switch (gr.state) {
         case UIGestureRecognizerStateBegan: {
-            [[KBBackspaceUndoManager shared] registerNonClearAction];
+            [self kb_captureDeletionSnapshotIfNeeded];
+            if (self.showClearLabelEnabled) {
+                [self kb_capturePendingClearSnapshotIfNeeded];
+            }
             self.backspaceHoldToken += 1;
             NSUInteger token = self.backspaceHoldToken;
             self.backspaceHoldActive = YES;
@@ -310,6 +317,9 @@ typedef NS_ENUM(NSInteger, KBBackspaceChunkClass) {
     [self kb_hideBackspaceClearLabel];
     if (shouldClear) {
         [self kb_clearAllInput];
+    } else {
+        self.pendingClearBefore = nil;
+        self.pendingClearAfter = nil;
     }
 }
 
@@ -421,9 +431,12 @@ typedef NS_ENUM(NSInteger, KBBackspaceChunkClass) {
     UIResponder *start = (UIResponder *)([self kb_hostView] ?: self.backspaceButton);
     UIInputViewController *ivc = KBFindInputViewController(start);
     if (ivc) {
-        NSString *before = ivc.textDocumentProxy.documentContextBeforeInput ?: @"";
-        [[KBBackspaceUndoManager shared] recordClearWithContext:before];
+        NSString *before = self.pendingClearBefore ?: (ivc.textDocumentProxy.documentContextBeforeInput ?: @"");
+        NSString *after = self.pendingClearAfter ?: (ivc.textDocumentProxy.documentContextAfterInput ?: @"");
+        [[KBBackspaceUndoManager shared] recordClearWithContextBefore:before after:after];
     }
+    self.pendingClearBefore = nil;
+    self.pendingClearAfter = nil;
     self.backspaceClearToken += 1;
     NSUInteger token = self.backspaceClearToken;
     [self kb_clearAllInputStepForToken:token guard:0 emptyRounds:0];
@@ -489,4 +502,25 @@ typedef NS_ENUM(NSInteger, KBBackspaceChunkClass) {
     return self.backspaceButton.superview;
 }
 
+- (void)kb_captureDeletionSnapshotIfNeeded {
+    if ([KBBackspaceUndoManager shared].hasUndo) { return; }
+    UIResponder *start = (UIResponder *)([self kb_hostView] ?: self.backspaceButton);
+    UIInputViewController *ivc = KBFindInputViewController(start);
+    if (!ivc) { return; }
+    id<UITextDocumentProxy> proxy = ivc.textDocumentProxy;
+    [[KBBackspaceUndoManager shared] recordDeletionSnapshotBefore:proxy.documentContextBeforeInput
+                                                             after:proxy.documentContextAfterInput];
+}
+
+- (void)kb_capturePendingClearSnapshotIfNeeded {
+    if ([KBBackspaceUndoManager shared].hasUndo) { return; }
+    if (self.pendingClearBefore.length > 0 || self.pendingClearAfter.length > 0) { return; }
+    UIResponder *start = (UIResponder *)([self kb_hostView] ?: self.backspaceButton);
+    UIInputViewController *ivc = KBFindInputViewController(start);
+    if (!ivc) { return; }
+    id<UITextDocumentProxy> proxy = ivc.textDocumentProxy;
+    self.pendingClearBefore = proxy.documentContextBeforeInput ?: @"";
+    self.pendingClearAfter = proxy.documentContextAfterInput ?: @"";
+}
+
 @end
diff --git a/CustomKeyboard/Utils/KBBackspaceUndoManager.h b/CustomKeyboard/Utils/KBBackspaceUndoManager.h
index 9b11946..573dd4d 100644
--- a/CustomKeyboard/Utils/KBBackspaceUndoManager.h
+++ b/CustomKeyboard/Utils/KBBackspaceUndoManager.h
@@ -15,13 +15,16 @@ extern NSNotificationName const KBBackspaceUndoStateDidChangeNotification;
 
 + (instancetype)shared;
 
-/// 记录一次“立刻清空”删除的内容（基于 documentContextBeforeInput）
-- (void)recordClearWithContext:(NSString *)context;
+/// 记录一次删除前的快照（不改变撤销按钮显示）。
+- (void)recordDeletionSnapshotBefore:(NSString *)before after:(NSString *)after;
+
+/// 记录一次“立刻清空”删除的内容（基于 documentContextBeforeInput/AfterInput）。
+- (void)recordClearWithContextBefore:(NSString *)before after:(NSString *)after;
 
 /// 在指定 responder 处执行撤销（向光标处插回删除的内容）
 - (void)performUndoFromResponder:(UIResponder *)responder;
 
-/// 非清空行为触发时，清理撤销状态
+/// 非删除行为触发时，清理撤销状态
 - (void)registerNonClearAction;
 
 @end
diff --git a/CustomKeyboard/Utils/KBBackspaceUndoManager.m b/CustomKeyboard/Utils/KBBackspaceUndoManager.m
index f6144a4..7cc4e3c 100644
--- a/CustomKeyboard/Utils/KBBackspaceUndoManager.m
+++ b/CustomKeyboard/Utils/KBBackspaceUndoManager.m
@@ -9,8 +9,8 @@
 NSNotificationName const KBBackspaceUndoStateDidChangeNotification = @"KBBackspaceUndoStateDidChangeNotification";
 
 @interface KBBackspaceUndoManager ()
-@property (nonatomic, strong) NSMutableArray<NSString *> *segments; // deletion order (last -> first)
-@property (nonatomic, assign) BOOL lastActionWasClear;
+@property (nonatomic, copy) NSString *undoText;
+@property (nonatomic, assign) NSInteger undoAfterLength;
 @property (nonatomic, assign) BOOL hasUndo;
 @end
 
@@ -27,42 +27,57 @@ NSNotificationName const KBBackspaceUndoStateDidChangeNotification = @"KBBackspa
 
 - (instancetype)init {
     if (self = [super init]) {
-        _segments = [NSMutableArray array];
+        _undoText = @"";
+        _undoAfterLength = 0;
     }
     return self;
 }
 
-- (void)recordClearWithContext:(NSString *)context {
-    if (context.length == 0) { return; }
-    NSString *segment = [self kb_segmentForClearFromContext:context];
-    if (segment.length == 0) { return; }
+- (void)recordDeletionSnapshotBefore:(NSString *)before after:(NSString *)after {
+    if (self.undoText.length > 0) { return; }
+    NSString *safeBefore = before ?: @"";
+    NSString *safeAfter = after ?: @"";
+    NSString *full = [safeBefore stringByAppendingString:safeAfter];
+    if (full.length == 0) { return; }
+    self.undoText = full;
+    self.undoAfterLength = (NSInteger)safeAfter.length;
+}
 
-    if (!self.lastActionWasClear) {
-        [self.segments removeAllObjects];
+- (void)recordClearWithContextBefore:(NSString *)before after:(NSString *)after {
+    if (self.undoText.length == 0) {
+        NSString *safeBefore = before ?: @"";
+        NSString *safeAfter = after ?: @"";
+        NSString *full = [safeBefore stringByAppendingString:safeAfter];
+        if (full.length > 0) {
+            self.undoText = full;
+            self.undoAfterLength = (NSInteger)safeAfter.length;
+        }
     }
-    [self.segments addObject:segment];
-    self.lastActionWasClear = YES;
+    if (self.undoText.length == 0) { return; }
     [self kb_updateHasUndo:YES];
 }
 
 - (void)performUndoFromResponder:(UIResponder *)responder {
-    if (self.segments.count == 0) { return; }
+    if (self.undoText.length == 0) { return; }
     UIInputViewController *ivc = KBFindInputViewController(responder);
     if (!ivc) { return; }
     id<UITextDocumentProxy> proxy = ivc.textDocumentProxy;
-    NSString *text = [self kb_buildUndoText];
-    if (text.length == 0) { return; }
-    [proxy insertText:text];
+    [self kb_clearAllTextForProxy:proxy];
+    [proxy insertText:self.undoText];
+    if (self.undoAfterLength > 0 &&
+        [proxy respondsToSelector:@selector(adjustTextPositionByCharacterOffset:)]) {
+        [proxy adjustTextPositionByCharacterOffset:-self.undoAfterLength];
+    }
 
-    [self.segments removeAllObjects];
-    self.lastActionWasClear = NO;
+    self.undoText = @"";
+    self.undoAfterLength = 0;
     [self kb_updateHasUndo:NO];
 }
 
 - (void)registerNonClearAction {
-    self.lastActionWasClear = NO;
-    if (self.segments.count == 0) { return; }
-    [self.segments removeAllObjects];
+    if (self.undoText.length == 0) { return; }
+    self.undoText = @"";
+    self.undoAfterLength = 0;
     [self kb_updateHasUndo:NO];
 }
 
@@ -74,97 +89,34 @@ NSNotificationName const KBBackspaceUndoStateDidChangeNotification = @"KBBackspa
     [[NSNotificationCenter defaultCenter] postNotificationName:KBBackspaceUndoStateDidChangeNotification object:self];
 }
 
-- (NSString *)kb_segmentForClearFromContext:(NSString *)context {
-    NSInteger length = context.length;
-    if (length == 0) { return @""; }
+static const NSInteger kKBUndoClearMaxRounds = 200;
 
-    static NSCharacterSet *sentenceBoundarySet = nil;
-    static NSCharacterSet *whitespaceSet = nil;
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-        sentenceBoundarySet = [NSCharacterSet characterSetWithCharactersInString:@".!?;。！？；…\n"];
-        whitespaceSet = [NSCharacterSet whitespaceAndNewlineCharacterSet];
-    });
+- (void)kb_clearAllTextForProxy:(id<UITextDocumentProxy>)proxy {
+    if (!proxy) { return; }
 
-    NSInteger end = length;
-    while (end > 0) {
-        unichar ch = [context characterAtIndex:end - 1];
-        if ([whitespaceSet characterIsMember:ch]) {
-            end -= 1;
-        } else {
-            break;
-        }
-    }
-    NSInteger searchEnd = end;
-    while (searchEnd > 0) {
-        unichar ch = [context characterAtIndex:searchEnd - 1];
-        if ([sentenceBoundarySet characterIsMember:ch]) {
-            searchEnd -= 1;
-        } else {
-            break;
+    if ([proxy respondsToSelector:@selector(adjustTextPositionByCharacterOffset:)]) {
+        NSInteger guard = 0;
+        NSString *contextAfter = proxy.documentContextAfterInput ?: @"";
+        while (contextAfter.length > 0 && guard < kKBUndoClearMaxRounds) {
+            NSInteger offset = (NSInteger)contextAfter.length;
+            [proxy adjustTextPositionByCharacterOffset:offset];
+            for (NSUInteger i = 0; i < contextAfter.length; i++) {
+                [proxy deleteBackward];
+            }
+            guard += 1;
+            contextAfter = proxy.documentContextAfterInput ?: @"";
         }
     }
 
-    NSInteger boundaryIndex = NSNotFound;
-    for (NSInteger i = searchEnd - 1; i >= 0; i--) {
-        unichar ch = [context characterAtIndex:i];
-        if ([sentenceBoundarySet characterIsMember:ch]) {
-            boundaryIndex = i;
-            break;
+    NSInteger guard = 0;
+    NSString *contextBefore = proxy.documentContextBeforeInput ?: @"";
+    while (contextBefore.length > 0 && guard < kKBUndoClearMaxRounds) {
+        for (NSUInteger i = 0; i < contextBefore.length; i++) {
+            [proxy deleteBackward];
         }
+        guard += 1;
+        contextBefore = proxy.documentContextBeforeInput ?: @"";
     }
-
-    NSInteger start = (boundaryIndex == NSNotFound) ? 0 : (boundaryIndex + 1);
-    if (start >= length) { return @""; }
-    return [context substringFromIndex:start];
-}
-
-- (NSString *)kb_buildUndoText {
-    if (self.segments.count == 0) { return @""; }
-    NSArray<NSString *> *ordered = [[self.segments reverseObjectEnumerator] allObjects];
-    NSMutableString *result = [NSMutableString string];
-    for (NSInteger i = 0; i < ordered.count; i++) {
-        NSString *segment = ordered[i] ?: @"";
-        if (segment.length == 0) { continue; }
-        if (i < ordered.count - 1) {
-            segment = [self kb_replaceTrailingBoundaryWithComma:segment];
-        }
-        [result appendString:segment];
-    }
-    return result;
-}
-
-- (NSString *)kb_replaceTrailingBoundaryWithComma:(NSString *)segment {
-    if (segment.length == 0) { return segment; }
-
-    static NSCharacterSet *boundarySet = nil;
-    static NSCharacterSet *englishBoundarySet = nil;
-    static NSCharacterSet *whitespaceSet = nil;
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-        boundarySet = [NSCharacterSet characterSetWithCharactersInString:@".!?;。！？；…\n"];
-        englishBoundarySet = [NSCharacterSet characterSetWithCharactersInString:@".!?;"];
-        whitespaceSet = [NSCharacterSet whitespaceAndNewlineCharacterSet];
-    });
-
-    NSInteger idx = segment.length - 1;
-    while (idx >= 0) {
-        unichar ch = [segment characterAtIndex:idx];
-        if ([whitespaceSet characterIsMember:ch]) {
-            idx -= 1;
-            continue;
-        }
-        if (![boundarySet characterIsMember:ch]) {
-            return segment;
-        }
-        NSString *comma = [englishBoundarySet characterIsMember:ch] ? @"," : @"，";
-        NSMutableString *mutable = [segment mutableCopy];
-        NSRange r = NSMakeRange(idx, 1);
-        [mutable replaceCharactersInRange:r withString:comma];
-        return mutable;
-    }
-
-    return segment;
 }
 
 @end
diff --git a/CustomKeyboard/View/KBFunctionView.m b/CustomKeyboard/View/KBFunctionView.m
index 6d74774..b058db0 100644
--- a/CustomKeyboard/View/KBFunctionView.m
+++ b/CustomKeyboard/View/KBFunctionView.m
@@ -770,18 +770,21 @@ static void KBULDarwinCallback(CFNotificationCenterRef center, void *observer, C
 - (void)kb_fullAccessChanged {
     dispatch_async(dispatch_get_main_queue(), ^{ [self kb_refreshPasteboardMonitor]; });
 }
-    - (void)onTapDelete {
+
+- (void)onTapDelete {
     NSLog(@"点击：删除");
-    [[KBBackspaceUndoManager shared] registerNonClearAction];
     UIInputViewController *ivc = KBFindInputViewController(self);
     id<UITextDocumentProxy> proxy = ivc.textDocumentProxy;
+    [[KBBackspaceUndoManager shared] recordDeletionSnapshotBefore:proxy.documentContextBeforeInput
+                                                             after:proxy.documentContextAfterInput];
     [proxy deleteBackward];
 }
 - (void)onTapClear {
     NSLog(@"点击：清空");
     [self.backspaceHandler performClearAction];
 }
-    - (void)onTapSend {
+
+- (void)onTapSend {
     NSLog(@"点击：发送");
     [[KBBackspaceUndoManager shared] registerNonClearAction];
     // 发送：插入换行。大多数聊天类 App 会把回车视为“发送”
diff --git a/CustomKeyboard/View/KBKeyBoardMainView.m b/CustomKeyboard/View/KBKeyBoardMainView.m
index a122dec..5a1528b 100644
--- a/CustomKeyboard/View/KBKeyBoardMainView.m
+++ b/CustomKeyboard/View/KBKeyBoardMainView.m
@@ -14,6 +14,7 @@
 #import "KBSuggestionBarView.h"
 #import "Masonry.h"
 #import "KBSkinManager.h"
+#import "KBBackspaceUndoManager.h"
 
 @interface KBKeyBoardMainView ()<KBToolBarDelegate, KBKeyboardViewDelegate, KBEmojiPanelViewDelegate, KBSuggestionBarViewDelegate>
 @property (nonatomic, strong) KBToolBar *topBar;
@@ -87,10 +88,18 @@
             make.top.equalTo(self.topBar.mas_bottom).offset(barSpacing);
         }];
         // 功能面板切换交由外部控制器处理；此处不直接创建/管理
+        [[NSNotificationCenter defaultCenter] addObserver:self
+                                                 selector:@selector(kb_undoStateChanged)
+                                                     name:KBBackspaceUndoStateDidChangeNotification
+                                                   object:nil];
     }
     return self;
 }
 
+- (void)dealloc {
+    [[NSNotificationCenter defaultCenter] removeObserver:self];
+}
+
 - (void)setEmojiPanelVisible:(BOOL)visible animated:(BOOL)animated {
     if (self.emojiPanelVisible == visible) return;
     self.emojiPanelVisible = visible;
@@ -108,7 +117,7 @@
         self.emojiView.alpha = visible ? 1.0 : 0.0;
         self.keyboardView.alpha = visible ? 0.0 : 1.0;
         self.topBar.alpha = visible ? 0.0 : 1.0;
-        self.suggestionBar.alpha = visible ? 0.0 : (self.suggestionBarHasItems ? 1.0 : 0.0);
+        self.suggestionBar.alpha = visible ? 0.0 : ([self kb_shouldShowSuggestions] ? 1.0 : 0.0);
     };
     void (^completion)(BOOL) = ^(BOOL finished) {
         self.emojiView.hidden = !visible;
@@ -117,7 +126,7 @@
         if (visible) {
             self.suggestionBar.hidden = YES;
         } else {
-            self.suggestionBar.hidden = !self.suggestionBarHasItems;
+            self.suggestionBar.hidden = ![self kb_shouldShowSuggestions];
         }
     };
 
@@ -258,14 +267,7 @@
 - (void)kb_setSuggestions:(NSArray<NSString *> *)suggestions {
     self.suggestionBarHasItems = (suggestions.count > 0);
     [self.suggestionBar updateSuggestions:suggestions];
-
-    if (self.emojiPanelVisible) {
-        self.suggestionBar.hidden = YES;
-        self.suggestionBar.alpha = 0.0;
-    } else {
-        self.suggestionBar.hidden = !self.suggestionBarHasItems;
-        self.suggestionBar.alpha = self.suggestionBarHasItems ? 1.0 : 0.0;
-    }
+    [self kb_applySuggestionVisibility];
 }
 
 #pragma mark - KBSuggestionBarViewDelegate
@@ -276,4 +278,22 @@
     }
 }
 
+- (void)kb_undoStateChanged {
+    [self kb_applySuggestionVisibility];
+}
+
+- (BOOL)kb_shouldShowSuggestions {
+    if (self.emojiPanelVisible) { return NO; }
+    if (![KBBackspaceUndoManager shared].hasUndo && self.suggestionBarHasItems) {
+        return YES;
+    }
+    return NO;
+}
+
+- (void)kb_applySuggestionVisibility {
+    BOOL shouldShow = [self kb_shouldShowSuggestions];
+    self.suggestionBar.hidden = !shouldShow;
+    self.suggestionBar.alpha = shouldShow ? 1.0 : 0.0;
+}
+
 @end