diff --git a/NEWS.md b/NEWS.md
index b2741da8..7abfd4ef 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -5,6 +5,7 @@ Red Panda C++ Version 3.2
   - fix: Don't auto scroll to the caret after undo/redo.
   - fix: "bits/stdc++" is not openned in readonly mode.
   - fix: astyle path error when reformat.
+  - fix: Slow when paste/replace bulk contents.
 
 Red Panda C++ Version 3.1
 
diff --git a/libs/qsynedit/qsynedit/document.cpp b/libs/qsynedit/qsynedit/document.cpp
index 9ebe2c47..f8e7f5b9 100644
--- a/libs/qsynedit/qsynedit/document.cpp
+++ b/libs/qsynedit/qsynedit/document.cpp
@@ -452,7 +452,8 @@ void Document::putLine(int index, const QString &s, bool notify) {
         if (index<0 || index>=mLines.count()) {
             listIndexOutOfBounds(index);
         }
-        beginUpdate();
+        if (notify)
+            beginUpdate();
         mLines[index]->setLineText(s);
         if (mIndexOfLongestLine == index) {
             // width is invalidated, so we must recalculate longest line
@@ -460,7 +461,8 @@ void Document::putLine(int index, const QString &s, bool notify) {
         }
         if (notify)
             emit putted(index);
-        endUpdate();
+        if (notify)
+            endUpdate();
     }
 }
 
diff --git a/libs/qsynedit/qsynedit/qsynedit.cpp b/libs/qsynedit/qsynedit/qsynedit.cpp
index 81e3746a..5cda9e4f 100644
--- a/libs/qsynedit/qsynedit/qsynedit.cpp
+++ b/libs/qsynedit/qsynedit/qsynedit.cpp
@@ -3246,12 +3246,15 @@ void QSynEdit::updateModifiedStatus()
         emit statusChanged(StatusChange::ModifyChanged);
 }
 
-int QSynEdit::reparseLines(int startLine, int endLine)
+int QSynEdit::reparseLines(int startLine, int endLine, bool needRescanFolds, bool toDocumentEnd)
 {
 
     SyntaxState state;
+    int maxLine = toDocumentEnd ? mDocument->count() : endLine+1;
     startLine = std::max(0,startLine);
     endLine = std::min(endLine, mDocument->count());
+    maxLine = std::min(maxLine, mDocument->count());
+
 
     if (startLine >= endLine)
         return startLine;
@@ -3271,7 +3274,7 @@ int QSynEdit::reparseLines(int startLine, int endLine)
         }
         mDocument->setSyntaxState(line,state);
         line++;
-    } while (line < mDocument->count());
+    } while (line < maxLine);
 
     //don't rescan folds if only currentLine is reparsed
     if (line-startLine==1)
@@ -3280,7 +3283,7 @@ int QSynEdit::reparseLines(int startLine, int endLine)
     if (mEditingCount>0)
         return line;
 
-    if (useCodeFolding())
+    if (needRescanFolds && useCodeFolding())
         rescanFolds();
     return line;
 }
@@ -5359,6 +5362,7 @@ int QSynEdit::doInsertTextByNormalMode(const BufferCoord& pos, const QStringList
     QString sLeftSide;
     QString sRightSide;
     QString str;
+    QElapsedTimer timer;
     bool bChangeScroll;
 //    int SpaceCount;
     int result = 0;
@@ -5382,13 +5386,14 @@ int QSynEdit::doInsertTextByNormalMode(const BufferCoord& pos, const QStringList
             str = sLeftSide + s;
         } else
             str = sLeftSide + text[0];
-        properSetLine(caretY - 1, str);
+        properSetLine(caretY - 1, str, false);
         mDocument->insertLines(caretY, text.length()-1);
     } else {
         str = sLeftSide + text[0] + sRightSide;
-        properSetLine(caretY - 1, str);
+        properSetLine(caretY - 1, str, false);
     }
-    reparseLines(caretY-1,caretY);
+    reparseLines(caretY-1,caretY, false, false);
+    timer.start();
     // step2: insert remaining lines of Value
     for (int i=1;i<text.length();i++) {
         bool notInComment = true;
@@ -5409,9 +5414,11 @@ int QSynEdit::doInsertTextByNormalMode(const BufferCoord& pos, const QStringList
             str = GetLeftSpacing(indentSpaces,true)+trimLeft(str);
         }
         properSetLine(caretY - 1, str,false);
-        reparseLines(caretY-1,caretY);
+        reparseLines(caretY-1,caretY, false, false);
         result++;
     }
+    if (useCodeFolding())
+        rescanFolds();
     bChangeScroll = !mOptions.testFlag(EditorOption::ScrollPastEol);
     mOptions.setFlag(EditorOption::ScrollPastEol);
     auto action = finally([&,this]{
diff --git a/libs/qsynedit/qsynedit/qsynedit.h b/libs/qsynedit/qsynedit/qsynedit.h
index f05daf14..bb6885f7 100644
--- a/libs/qsynedit/qsynedit/qsynedit.h
+++ b/libs/qsynedit/qsynedit/qsynedit.h
@@ -528,7 +528,7 @@ private:
     void updateCaret();
     void recalcCharExtent();
     void updateModifiedStatus();
-    int reparseLines(int startLine, int endLine);
+    int reparseLines(int startLine, int endLine, bool needRescanFolds = true,  bool toDocumentEnd = true);
     //void reparseLine(int line);
     void uncollapse(PCodeFoldingRange FoldRange);
     void collapse(PCodeFoldingRange FoldRange);