From eedf347866c24729c0b875af4b9f8b9c69bafe1d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Deniz=20=C5=9Eafak?= <denizsafak98@gmail.com>
Date: Mon, 27 Oct 2025 17:08:32 +0300
Subject: [PATCH] Upgraded Abogen's interface from PyQt5 to PyQt6, Added
 tooltip indicators in queue manager

---
 CHANGELOG.md                |   2 +
 abogen/Dockerfile           |   2 +-
 abogen/book_handler.py      | 252 +++++++++++++++++++-----------------
 abogen/constants.py         |   1 +
 abogen/conversion.py        |  12 +-
 abogen/gui.py               | 207 +++++++++++++++--------------
 abogen/main.py              |  30 +++--
 abogen/queue_manager_gui.py | 110 +++++++++-------
 abogen/queued_item.py       |   2 +
 abogen/voice_formula_gui.py | 126 +++++++++---------
 pyproject.toml              |   2 +-
 11 files changed, 406 insertions(+), 340 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cf96bd7..68ce173 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,6 @@
 # 1.2.1 (pre-release)
+- Upgraded Abogen's interface from PyQt5 to PyQt6 for better compatibility and long-term support.
+- Added tooltip indicators in queue manager to display book handler options (`Save chapters separately` and `Merge chapters at the end`) for queued items.
 - Added loading gif animation to book handler window.
 - Fixed subtitle word-count splitting logic for more accurate segmentation.
 
diff --git a/abogen/Dockerfile b/abogen/Dockerfile
index af76df7..f141c4f 100644
--- a/abogen/Dockerfile
+++ b/abogen/Dockerfile
@@ -12,7 +12,7 @@ RUN apt-get update \
         python3 \
         python3-venv \
         python3-pip \
-        python3-pyqt5 \
+        python3-pyqt6 \
         espeak-ng \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/*
diff --git a/abogen/book_handler.py b/abogen/book_handler.py
index 4d7ca8e..67ac0cd 100644
--- a/abogen/book_handler.py
+++ b/abogen/book_handler.py
@@ -4,24 +4,34 @@ import base64
 import fitz  # PyMuPDF for PDF support
 from ebooklib import epub
 from bs4 import BeautifulSoup, NavigableString
-from PyQt5.QtWidgets import (
+from PyQt6.QtGui import QAction, QMovie, QFont
+from PyQt6.QtWidgets import (
+    QApplication,
     QDialog,
     QTreeWidget,
     QTreeWidgetItem,
-    QDialogButtonBox,
+    QTextEdit,
+    QPushButton,
     QVBoxLayout,
     QHBoxLayout,
-    QTextEdit,
-    QTreeWidgetItemIterator,
+    QDialogButtonBox,
     QSplitter,
     QWidget,
-    QPushButton,
     QCheckBox,
-    QMenu,
+    QTreeWidgetItemIterator,
     QLabel,
+    QMenu,
+)
+from PyQt6.QtCore import (
+    Qt,
+    QThread,
+    pyqtSignal,
+    QObject,
+    QSize,
+    QEvent,
+    QPoint,
+    QRect,
 )
-from PyQt5.QtCore import Qt, QThread, pyqtSignal, QSize
-from PyQt5.QtGui import QMovie
 from abogen.utils import clean_text, calculate_text_length, detect_encoding, get_resource_path
 import os
 import logging  # Add logging
@@ -97,9 +107,9 @@ class HandlerDialog(QDialog):
         self._block_signals = False  # Flag to prevent recursive signals
         # Configure window: remove help button and allow resizing
         self.setWindowFlags(
-            Qt.Window | Qt.WindowCloseButtonHint | Qt.WindowMaximizeButtonHint
+            Qt.WindowType.Window | Qt.WindowType.WindowCloseButtonHint | Qt.WindowType.WindowMaximizeButtonHint
         )
-        self.setWindowModality(Qt.NonModal)
+        self.setWindowModality(Qt.WindowModality.NonModal)
         # Initialize save chapters flags from class variables
         self.save_chapters_separately = HandlerDialog._save_chapters_separately
         self.merge_chapters_at_end = HandlerDialog._merge_chapters_at_end
@@ -164,8 +174,8 @@ class HandlerDialog(QDialog):
         # Build treeview
         self.treeWidget = QTreeWidget(self)
         self.treeWidget.setHeaderHidden(True)
-        self.treeWidget.setSelectionMode(QTreeWidget.ExtendedSelection)
-        self.treeWidget.setContextMenuPolicy(Qt.CustomContextMenu)
+        self.treeWidget.setSelectionMode(QTreeWidget.SelectionMode.ExtendedSelection)
+        self.treeWidget.setContextMenuPolicy(Qt.ContextMenuPolicy.CustomContextMenu)
         self.treeWidget.customContextMenuRequested.connect(self.on_tree_context_menu)
 
         # Initialize checked_chapters set
@@ -177,8 +187,8 @@ class HandlerDialog(QDialog):
 
         # Add a placeholder "Information" item so the tree isn't empty immediately
         info_item = QTreeWidgetItem(self.treeWidget, ["Information"])
-        info_item.setData(0, Qt.UserRole, "info:bookinfo")
-        info_item.setFlags(info_item.flags() & ~Qt.ItemIsUserCheckable)
+        info_item.setData(0, Qt.ItemDataRole.UserRole, "info:bookinfo")
+        info_item.setFlags(info_item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
         font = info_item.font(0)
         font.setBold(True)
         info_item.setFont(0, font)
@@ -243,8 +253,8 @@ class HandlerDialog(QDialog):
 
             # Add stretches to center the content horizontally
             h.addStretch(1)
-            h.addWidget(gif_label, 0, Qt.AlignVCenter)
-            h.addWidget(text_label, 0, Qt.AlignVCenter)
+            h.addWidget(gif_label, 0, Qt.AlignmentFlag.AlignVCenter)
+            h.addWidget(text_label, 0, Qt.AlignmentFlag.AlignVCenter)
             h.addStretch(1)
 
             # Insert at top of main layout if present, otherwise keep as child
@@ -1148,8 +1158,8 @@ class HandlerDialog(QDialog):
         self.treeWidget.clear()
 
         info_item = QTreeWidgetItem(self.treeWidget, ["Information"])
-        info_item.setData(0, Qt.UserRole, "info:bookinfo")
-        info_item.setFlags(info_item.flags() & ~Qt.ItemIsUserCheckable)
+        info_item.setData(0, Qt.ItemDataRole.UserRole, "info:bookinfo")
+        info_item.setFlags(info_item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
         font = info_item.font(0)
         font.setBold(True)
         info_item.setFont(0, font)
@@ -1172,7 +1182,7 @@ class HandlerDialog(QDialog):
 
         has_parents = False
         iterator = QTreeWidgetItemIterator(
-            self.treeWidget, QTreeWidgetItemIterator.HasChildren
+            self.treeWidget, QTreeWidgetItemIterator.IteratorFlag.HasChildren
         )
         if iterator.value():
             has_parents = True
@@ -1195,7 +1205,7 @@ class HandlerDialog(QDialog):
             children = node.get("children", [])
 
             item = QTreeWidgetItem(parent_item, [title])
-            item.setData(0, Qt.UserRole, src)
+            item.setData(0, Qt.ItemDataRole.UserRole, src)
 
             is_empty = (
                     src
@@ -1211,18 +1221,18 @@ class HandlerDialog(QDialog):
                     seen_content_hashes.add(content_hash)
 
             if src and not is_empty and not is_duplicate:
-                item.setFlags(item.flags() | Qt.ItemIsUserCheckable)
+                item.setFlags(item.flags() | Qt.ItemFlag.ItemIsUserCheckable)
                 is_checked = src in self.checked_chapters
-                item.setCheckState(0, Qt.Checked if is_checked else Qt.Unchecked)
+                item.setCheckState(0, Qt.CheckState.Checked if is_checked else Qt.CheckState.Unchecked)
             elif is_duplicate:
                 # Mark as duplicate and remove checkbox
                 item.setText(0, f"{title} (Duplicate)")
-                item.setFlags(item.flags() & ~Qt.ItemIsUserCheckable)
+                item.setFlags(item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
             elif children:
-                item.setFlags(item.flags() | Qt.ItemIsUserCheckable)
-                item.setCheckState(0, Qt.Unchecked)
+                item.setFlags(item.flags() | Qt.ItemFlag.ItemIsUserCheckable)
+                item.setCheckState(0, Qt.CheckState.Unchecked)
             else:
-                item.setFlags(item.flags() & ~Qt.ItemIsUserCheckable)
+                item.setFlags(item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
 
             if children:
                 self._build_epub_tree_from_nav(children, item, seen_content_hashes)
@@ -1252,18 +1262,18 @@ class HandlerDialog(QDialog):
                 continue
 
             item = QTreeWidgetItem(parent_item, [title])
-            item.setData(0, Qt.UserRole, href)
+            item.setData(0, Qt.ItemDataRole.UserRole, href)
 
             has_content = (
                     href and href in self.content_texts and self.content_texts[href].strip()
             )
 
             if has_content or children:
-                item.setFlags(item.flags() | Qt.ItemIsUserCheckable)
+                item.setFlags(item.flags() | Qt.ItemFlag.ItemIsUserCheckable)
                 is_checked = href and href in self.checked_chapters
-                item.setCheckState(0, Qt.Checked if is_checked else Qt.Unchecked)
+                item.setCheckState(0, Qt.CheckState.Checked if is_checked else Qt.CheckState.Unchecked)
             else:
-                item.setFlags(item.flags() & ~Qt.ItemIsUserCheckable)
+                item.setFlags(item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
 
             if children:
                 self._build_epub_tree_fallback(children, item)
@@ -1318,27 +1328,27 @@ class HandlerDialog(QDialog):
                     if page_num in self.bookmark_items_map:
                         orig = self.bookmark_items_map[page_num]
                         child = QTreeWidgetItem(orig, [f"{title} (Same page)"])
-                        child.setData(0, Qt.UserRole, page_id)
-                        child.setFlags(child.flags() & ~Qt.ItemIsUserCheckable)
+                        child.setData(0, Qt.ItemDataRole.UserRole, page_id)
+                        child.setFlags(child.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
                         continue
                     bookmark_item = QTreeWidgetItem(parent_item, [title])
-                    bookmark_item.setData(0, Qt.UserRole, page_id)
+                    bookmark_item.setData(0, Qt.ItemDataRole.UserRole, page_id)
                     # only allow checking if this chapter has content
                     if self.content_lengths.get(page_id, 0) > 0:
                         bookmark_item.setFlags(
-                            bookmark_item.flags() | Qt.ItemIsUserCheckable
+                            bookmark_item.flags() | Qt.ItemFlag.ItemIsUserCheckable
                         )
                         bookmark_item.setCheckState(
                             0,
                             (
-                                Qt.Checked
+                                Qt.CheckState.Checked
                                 if page_id in self.checked_chapters
-                                else Qt.Unchecked
+                                else Qt.CheckState.Unchecked
                             ),
                         )
                     else:
                         bookmark_item.setFlags(
-                            bookmark_item.flags() & ~Qt.ItemIsUserCheckable
+                            bookmark_item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable
                         )
                     # map for uncategorized pages
                     self.bookmark_items_map[page_num] = bookmark_item
@@ -1363,23 +1373,23 @@ class HandlerDialog(QDialog):
                                 page_title += f" - {first_line}"
 
                         page_item = QTreeWidgetItem(bookmark_item, [page_title])
-                        page_item.setData(0, Qt.UserRole, page_id)
+                        page_item.setData(0, Qt.ItemDataRole.UserRole, page_id)
                         # only allow checking if this sub-page has content
                         if self.content_lengths.get(page_id, 0) > 0:
                             page_item.setFlags(
-                                page_item.flags() | Qt.ItemIsUserCheckable
+                                page_item.flags() | Qt.ItemFlag.ItemIsUserCheckable
                             )
                             page_item.setCheckState(
                                 0,
                                 (
-                                    Qt.Checked
+                                    Qt.CheckState.Checked
                                     if page_id in self.checked_chapters
-                                    else Qt.Unchecked
+                                    else Qt.CheckState.Unchecked
                                 ),
                             )
                         else:
                             page_item.setFlags(
-                                page_item.flags() & ~Qt.ItemIsUserCheckable
+                                page_item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable
                             )
 
                         added_pages.add(sub_page_num)
@@ -1405,15 +1415,15 @@ class HandlerDialog(QDialog):
                 if first and len(first) < 100:
                     title += f" - {first}"
             page_item = QTreeWidgetItem(parent_item, [title])
-            page_item.setData(0, Qt.UserRole, page_id)
+            page_item.setData(0, Qt.ItemDataRole.UserRole, page_id)
             # only allow checking if uncategorized page has content
             if self.content_lengths.get(page_id, 0) > 0:
-                page_item.setFlags(page_item.flags() | Qt.ItemIsUserCheckable)
+                page_item.setFlags(page_item.flags() | Qt.ItemFlag.ItemIsUserCheckable)
                 page_item.setCheckState(
-                    0, Qt.Checked if page_id in self.checked_chapters else Qt.Unchecked
+                    0, Qt.CheckState.Checked if page_id in self.checked_chapters else Qt.CheckState.Unchecked
                 )
             else:
-                page_item.setFlags(page_item.flags() & ~Qt.ItemIsUserCheckable)
+                page_item.setFlags(page_item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
 
     def _build_markdown_tree(self):
         """Build tree structure for markdown file based on parsed TOC."""
@@ -1426,13 +1436,13 @@ class HandlerDialog(QDialog):
                 chapter_id = list(self.content_texts.keys())[0]
                 title = "Content"
                 item = QTreeWidgetItem(self.treeWidget, [title])
-                item.setData(0, Qt.UserRole, chapter_id)
+                item.setData(0, Qt.ItemDataRole.UserRole, chapter_id)
                 if self.content_lengths.get(chapter_id, 0) > 0:
-                    item.setFlags(item.flags() | Qt.ItemIsUserCheckable)
+                    item.setFlags(item.flags() | Qt.ItemFlag.ItemIsUserCheckable)
                     is_checked = chapter_id in self.checked_chapters
-                    item.setCheckState(0, Qt.Checked if is_checked else Qt.Unchecked)
+                    item.setCheckState(0, Qt.CheckState.Checked if is_checked else Qt.CheckState.Unchecked)
                 else:
-                    item.setFlags(item.flags() & ~Qt.ItemIsUserCheckable)
+                    item.setFlags(item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
             return
 
         def build_from_toc(toc_list, parent_item):
@@ -1441,17 +1451,17 @@ class HandlerDialog(QDialog):
                 chapter_id = header['id']
 
                 item = QTreeWidgetItem(parent_item, [title])
-                item.setData(0, Qt.UserRole, chapter_id)
+                item.setData(0, Qt.ItemDataRole.UserRole, chapter_id)
 
                 has_content = self.content_lengths.get(chapter_id, 0) > 0
                 has_children = bool(header.get('children'))
 
                 if has_content or has_children:
-                    item.setFlags(item.flags() | Qt.ItemIsUserCheckable)
+                    item.setFlags(item.flags() | Qt.ItemFlag.ItemIsUserCheckable)
                     is_checked = chapter_id in self.checked_chapters
-                    item.setCheckState(0, Qt.Checked if is_checked else Qt.Unchecked)
+                    item.setCheckState(0, Qt.CheckState.Checked if is_checked else Qt.CheckState.Unchecked)
                 else:
-                    item.setFlags(item.flags() & ~Qt.ItemIsUserCheckable)
+                    item.setFlags(item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
 
                 if has_children:
                     build_from_toc(header['children'], item)
@@ -1460,7 +1470,7 @@ class HandlerDialog(QDialog):
 
     def _build_pdf_pages_tree(self):
         pages_item = QTreeWidgetItem(self.treeWidget, ["Pages"])
-        pages_item.setFlags(pages_item.flags() & ~Qt.ItemIsUserCheckable)
+        pages_item.setFlags(pages_item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
         font = pages_item.font(0)
         font.setBold(True)
         pages_item.setFont(0, font)
@@ -1476,15 +1486,15 @@ class HandlerDialog(QDialog):
                     page_title += f" - {first_line}"
 
             page_item = QTreeWidgetItem(pages_item, [page_title])
-            page_item.setData(0, Qt.UserRole, page_id)
+            page_item.setData(0, Qt.ItemDataRole.UserRole, page_id)
             # only allow checking if standalone page has content
             if self.content_lengths.get(page_id, 0) > 0:
-                page_item.setFlags(page_item.flags() | Qt.ItemIsUserCheckable)
+                page_item.setFlags(page_item.flags() | Qt.ItemFlag.ItemIsUserCheckable)
                 page_item.setCheckState(
-                    0, Qt.Checked if page_id in self.checked_chapters else Qt.Unchecked
+                    0, Qt.CheckState.Checked if page_id in self.checked_chapters else Qt.CheckState.Unchecked
                 )
             else:
-                page_item.setFlags(page_item.flags() & ~Qt.ItemIsUserCheckable)
+                page_item.setFlags(page_item.flags() & ~Qt.ItemFlag.ItemIsUserCheckable)
 
     def _are_provided_checks_relevant(self):
         if not self.checked_chapters:
@@ -1494,8 +1504,8 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if item.flags() & Qt.ItemIsUserCheckable:
-                identifier = item.data(0, Qt.UserRole)
+            if item.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                identifier = item.data(0, Qt.ItemDataRole.UserRole)
                 if identifier:
                     all_identifiers.add(identifier)
             iterator += 1
@@ -1525,7 +1535,7 @@ class HandlerDialog(QDialog):
         rightWidget = QWidget()
         rightWidget.setLayout(previewLayout)
 
-        buttons = QDialogButtonBox(QDialogButtonBox.Ok | QDialogButtonBox.Cancel, self)
+        buttons = QDialogButtonBox(QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel, self)
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)
 
@@ -1611,7 +1621,7 @@ class HandlerDialog(QDialog):
         leftWidget = QWidget()
         leftWidget.setLayout(leftLayout)
 
-        self.splitter = QSplitter(Qt.Horizontal)
+        self.splitter = QSplitter(Qt.Orientation.Horizontal)
         self.splitter.addWidget(leftWidget)
         self.splitter.addWidget(rightWidget)
         self.splitter.setSizes([280, 420])
@@ -1643,8 +1653,8 @@ class HandlerDialog(QDialog):
             while iterator.value():
                 item = iterator.value()
                 if (
-                        item.flags() & Qt.ItemIsUserCheckable
-                        and item.checkState(0) == Qt.Checked
+                        item.flags() & Qt.ItemFlag.ItemIsUserCheckable
+                        and item.checkState(0) == Qt.CheckState.Checked
                 ):
                     checked_count += 1
                     if checked_count >= 2:
@@ -1658,8 +1668,8 @@ class HandlerDialog(QDialog):
             while iterator.value():
                 item = iterator.value()
                 if (
-                        item.flags() & Qt.ItemIsUserCheckable
-                        and item.checkState(0) == Qt.Checked
+                        item.flags() & Qt.ItemFlag.ItemIsUserCheckable
+                        and item.checkState(0) == Qt.CheckState.Checked
                 ):
                     parent = item.parent()
                     if parent and parent != self.treeWidget.invisibleRootItem():
@@ -1683,8 +1693,8 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if item.flags() & Qt.ItemIsUserCheckable:
-                item.setCheckState(0, Qt.Checked)
+            if item.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                item.setCheckState(0, Qt.CheckState.Checked)
             iterator += 1
         self._block_signals = False
         self._update_checked_set_from_tree()
@@ -1694,8 +1704,8 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if item.flags() & Qt.ItemIsUserCheckable:
-                item.setCheckState(0, Qt.Unchecked)
+            if item.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                item.setCheckState(0, Qt.CheckState.Unchecked)
             iterator += 1
         self._block_signals = False
         self._update_checked_set_from_tree()
@@ -1705,8 +1715,8 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if item.flags() & Qt.ItemIsUserCheckable and item.childCount() > 0:
-                item.setCheckState(0, Qt.Checked)
+            if item.flags() & Qt.ItemFlag.ItemIsUserCheckable and item.childCount() > 0:
+                item.setCheckState(0, Qt.CheckState.Checked)
             iterator += 1
         self._block_signals = False
         self._update_checked_set_from_tree()
@@ -1716,8 +1726,8 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if item.flags() & Qt.ItemIsUserCheckable and item.childCount() > 0:
-                item.setCheckState(0, Qt.Unchecked)
+            if item.flags() & Qt.ItemFlag.ItemIsUserCheckable and item.childCount() > 0:
+                item.setCheckState(0, Qt.CheckState.Unchecked)
             iterator += 1
         self._block_signals = False
         self._update_checked_set_from_tree()
@@ -1742,30 +1752,30 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if not (item.flags() & Qt.ItemIsUserCheckable):
+            if not (item.flags() & Qt.ItemFlag.ItemIsUserCheckable):
                 iterator += 1
                 continue
 
-            src = item.data(0, Qt.UserRole)
+            src = item.data(0, Qt.ItemDataRole.UserRole)
 
             has_significant_content = src and self.content_lengths.get(src, 0) > 1000
             is_parent = item.childCount() > 0
 
             if has_significant_content or is_parent:
-                item.setCheckState(0, Qt.Checked)
+                item.setCheckState(0, Qt.CheckState.Checked)
                 if is_parent:
                     for i in range(item.childCount()):
                         child = item.child(i)
-                        if child.flags() & Qt.ItemIsUserCheckable:
-                            child_src = child.data(0, Qt.UserRole)
+                        if child.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                            child_src = child.data(0, Qt.ItemDataRole.UserRole)
                             child_has_content = (
                                     child_src and self.content_lengths.get(child_src, 0) > 0
                             )
                             child_is_parent = child.childCount() > 0
                             if child_has_content or child_is_parent:
-                                child.setCheckState(0, Qt.Checked)
+                                child.setCheckState(0, Qt.CheckState.Checked)
             else:
-                item.setCheckState(0, Qt.Unchecked)
+                item.setCheckState(0, Qt.CheckState.Unchecked)
 
             iterator += 1
 
@@ -1774,32 +1784,32 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if not (item.flags() & Qt.ItemIsUserCheckable):
+            if not (item.flags() & Qt.ItemFlag.ItemIsUserCheckable):
                 iterator += 1
                 continue
 
-            identifier = item.data(0, Qt.UserRole)
+            identifier = item.data(0, Qt.ItemDataRole.UserRole)
 
             # Select chapters with content > 500 characters or parent items
             has_significant_content = identifier and self.content_lengths.get(identifier, 0) > 500
             is_parent = item.childCount() > 0
 
             if has_significant_content or is_parent:
-                item.setCheckState(0, Qt.Checked)
+                item.setCheckState(0, Qt.CheckState.Checked)
                 # Also check children if this is a parent
                 if is_parent:
                     for i in range(item.childCount()):
                         child = item.child(i)
-                        if child.flags() & Qt.ItemIsUserCheckable:
-                            child_identifier = child.data(0, Qt.UserRole)
+                        if child.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                            child_identifier = child.data(0, Qt.ItemDataRole.UserRole)
                             child_has_content = (
                                     child_identifier and self.content_lengths.get(child_identifier, 0) > 0
                             )
                             child_is_parent = child.childCount() > 0
                             if child_has_content or child_is_parent:
-                                child.setCheckState(0, Qt.Checked)
+                                child.setCheckState(0, Qt.CheckState.Checked)
             else:
-                item.setCheckState(0, Qt.Unchecked)
+                item.setCheckState(0, Qt.CheckState.Unchecked)
 
             iterator += 1
 
@@ -1808,19 +1818,19 @@ class HandlerDialog(QDialog):
             iterator = QTreeWidgetItemIterator(self.treeWidget)
             while iterator.value():
                 item = iterator.value()
-                if item.flags() & Qt.ItemIsUserCheckable:
-                    item.setCheckState(0, Qt.Checked)
+                if item.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                    item.setCheckState(0, Qt.CheckState.Checked)
                 iterator += 1
             return
 
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if not (item.flags() & Qt.ItemIsUserCheckable):
+            if not (item.flags() & Qt.ItemFlag.ItemIsUserCheckable):
                 iterator += 1
                 continue
 
-            identifier = item.data(0, Qt.UserRole)
+            identifier = item.data(0, Qt.ItemDataRole.UserRole)
 
             if not identifier:
                 iterator += 1
@@ -1830,7 +1840,7 @@ class HandlerDialog(QDialog):
                     not identifier.startswith("page_")
                     or self.content_lengths.get(identifier, 0) > 0
             ):
-                item.setCheckState(0, Qt.Checked)
+                item.setCheckState(0, Qt.CheckState.Checked)
 
             iterator += 1
 
@@ -1839,8 +1849,8 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if item.checkState(0) == Qt.Checked:
-                identifier = item.data(0, Qt.UserRole)
+            if item.checkState(0) == Qt.CheckState.Checked:
+                identifier = item.data(0, Qt.ItemDataRole.UserRole)
                 if identifier:
                     self.checked_chapters.add(identifier)
             iterator += 1
@@ -1853,17 +1863,17 @@ class HandlerDialog(QDialog):
 
         self._block_signals = True
 
-        if item.flags() & Qt.ItemIsUserCheckable:
+        if item.flags() & Qt.ItemFlag.ItemIsUserCheckable:
             for i in range(item.childCount()):
                 child = item.child(i)
-                if child.flags() & Qt.ItemIsUserCheckable:
+                if child.flags() & Qt.ItemFlag.ItemIsUserCheckable:
                     child.setCheckState(0, item.checkState(0))
 
         self._block_signals = False
         self._update_checked_set_from_tree()
 
     def handle_item_double_click(self, item, column=0):
-        if item.flags() & Qt.ItemIsUserCheckable and item.childCount() == 0:
+        if item.flags() & Qt.ItemFlag.ItemIsUserCheckable and item.childCount() == 0:
             rect = self.treeWidget.visualItemRect(item)
             checkbox_width = 20
 
@@ -1871,7 +1881,7 @@ class HandlerDialog(QDialog):
 
             if mouse_pos.x() > rect.x() + checkbox_width:
                 new_state = (
-                    Qt.Unchecked if item.checkState(0) == Qt.Checked else Qt.Checked
+                    Qt.CheckState.Unchecked if item.checkState(0) == Qt.CheckState.Checked else Qt.CheckState.Checked
                 )
                 item.setCheckState(0, new_state)
 
@@ -1880,7 +1890,7 @@ class HandlerDialog(QDialog):
             self.previewEdit.clear()
             return
 
-        identifier = current.data(0, Qt.UserRole)
+        identifier = current.data(0, Qt.ItemDataRole.UserRole)
 
         if identifier == "info:bookinfo":
             self._display_book_info()
@@ -2172,8 +2182,8 @@ class HandlerDialog(QDialog):
         while iterator.value():
             item = iterator.value()
             item_order_counter += 1
-            if item.checkState(0) == Qt.Checked:
-                identifier = item.data(0, Qt.UserRole)
+            if item.checkState(0) == Qt.CheckState.Checked:
+                identifier = item.data(0, Qt.ItemDataRole.UserRole)
 
                 if identifier and identifier != "info:bookinfo":
                     all_checked_identifiers.add(identifier)
@@ -2208,8 +2218,8 @@ class HandlerDialog(QDialog):
         while iterator.value():
             item = iterator.value()
             item_order_counter += 1
-            if item.checkState(0) == Qt.Checked:
-                identifier = item.data(0, Qt.UserRole)
+            if item.checkState(0) == Qt.CheckState.Checked:
+                identifier = item.data(0, Qt.ItemDataRole.UserRole)
                 if identifier and identifier != "info:bookinfo":
                     all_checked_identifiers.add(identifier)
                     ordered_checked_items.append((item_order_counter, item, identifier))
@@ -2244,8 +2254,8 @@ class HandlerDialog(QDialog):
         iterator = QTreeWidgetItemIterator(self.treeWidget)
         while iterator.value():
             item = iterator.value()
-            if item.checkState(0) == Qt.Checked:
-                identifier = item.data(0, Qt.UserRole)
+            if item.checkState(0) == Qt.CheckState.Checked:
+                identifier = item.data(0, Qt.ItemDataRole.UserRole)
                 if identifier:
                     all_checked_identifiers.add(identifier)
             iterator += 1
@@ -2270,15 +2280,15 @@ class HandlerDialog(QDialog):
         while iterator.value():
             item = iterator.value()
             if item.childCount() > 0:
-                parent_checked = item.checkState(0) == Qt.Checked
-                parent_id = item.data(0, Qt.UserRole)
+                parent_checked = item.checkState(0) == Qt.CheckState.Checked
+                parent_id = item.data(0, Qt.ItemDataRole.UserRole)
                 parent_title = item.text(0)
                 checked_children = []
                 for i in range(item.childCount()):
                     child = item.child(i)
-                    child_id = child.data(0, Qt.UserRole)
+                    child_id = child.data(0, Qt.ItemDataRole.UserRole)
                     if (
-                            child.checkState(0) == Qt.Checked
+                            child.checkState(0) == Qt.CheckState.Checked
                             and child_id
                             and child_id not in included_text_ids
                     ):
@@ -2306,12 +2316,12 @@ class HandlerDialog(QDialog):
                             else:
                                 section_titles.append((title, text))
                         included_text_ids.add(child_id)
-            elif item.flags() & Qt.ItemIsUserCheckable:
-                identifier = item.data(0, Qt.UserRole)
+            elif item.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                identifier = item.data(0, Qt.ItemDataRole.UserRole)
                 if (
                         identifier
                         and identifier not in included_text_ids
-                        and item.checkState(0) == Qt.Checked
+                        and item.checkState(0) == Qt.CheckState.Checked
                 ):
                     text = self.content_texts.get(identifier, "")
                     if text:
@@ -2363,8 +2373,8 @@ class HandlerDialog(QDialog):
         print(f"Checking selected items: {state}")
         self.treeWidget.blockSignals(True)
         for item in self.treeWidget.selectedItems():
-            if item.flags() & Qt.ItemIsUserCheckable:
-                item.setCheckState(0, Qt.Checked if state else Qt.Unchecked)
+            if item.flags() & Qt.ItemFlag.ItemIsUserCheckable:
+                item.setCheckState(0, Qt.CheckState.Checked if state else Qt.CheckState.Unchecked)
         self.treeWidget.blockSignals(False)
         self._update_checked_set_from_tree()
 
@@ -2377,30 +2387,30 @@ class HandlerDialog(QDialog):
             action.triggered.connect(self.check_selected_items)
             action = menu.addAction("Clear")
             action.triggered.connect(self.uncheck_selected_items)
-            menu.exec_(self.treeWidget.mapToGlobal(pos))
+            menu.exec(self.treeWidget.mapToGlobal(pos))
             return
 
         if (
                 not item
                 or item.childCount() == 0
-                or not (item.flags() & Qt.ItemIsUserCheckable)
+                or not (item.flags() & Qt.ItemFlag.ItemIsUserCheckable)
         ):
             return
 
         menu = QMenu(self)
-        checked = item.checkState(0) == Qt.Checked
+        checked = item.checkState(0) == Qt.CheckState.Checked
         text = "Unselect only this" if checked else "Select only this"
         action = menu.addAction(text)
 
         def do_toggle():
             self.treeWidget.blockSignals(True)
-            new_state = Qt.Unchecked if checked else Qt.Checked
+            new_state = Qt.CheckState.Unchecked if checked else Qt.CheckState.Checked
             item.setCheckState(0, new_state)
             self.treeWidget.blockSignals(False)
             self._update_checked_set_from_tree()
 
         action.triggered.connect(do_toggle)
-        menu.exec_(self.treeWidget.mapToGlobal(pos))
+        menu.exec(self.treeWidget.mapToGlobal(pos))
 
     def closeEvent(self, event):
         if self.pdf_doc is not None:
diff --git a/abogen/constants.py b/abogen/constants.py
index fa88ee7..7092686 100644
--- a/abogen/constants.py
+++ b/abogen/constants.py
@@ -148,6 +148,7 @@ COLORS = {
     "BLUE_BORDER_HOVER": "#6ab0de",
     "YELLOW_BACKGROUND": "rgba(255, 221, 51, 0.40)",
     "GREY_BACKGROUND": "rgba(128, 128, 128, 0.15)",
+    "GREY_BORDER": "#808080",
     "RED_BACKGROUND": "rgba(232, 78, 60, 0.15)",
     "RED_BG": "rgba(232, 78, 60, 0.10)",
     "RED_BG_HOVER": "rgba(232, 78, 60, 0.15)",
diff --git a/abogen/conversion.py b/abogen/conversion.py
index b937b5a..5be2c9f 100644
--- a/abogen/conversion.py
+++ b/abogen/conversion.py
@@ -3,8 +3,8 @@ import re
 import time
 import hashlib  # For generating unique cache filenames
 from platformdirs import user_desktop_dir
-from PyQt5.QtCore import QThread, pyqtSignal, Qt, QTimer
-from PyQt5.QtWidgets import QCheckBox, QVBoxLayout, QDialog, QLabel, QDialogButtonBox
+from PyQt6.QtCore import QThread, pyqtSignal, Qt, QTimer
+from PyQt6.QtWidgets import QCheckBox, QVBoxLayout, QDialog, QLabel, QDialogButtonBox
 import soundfile as sf
 from abogen.utils import clean_text, create_process, get_user_cache_path, detect_encoding
 from abogen.constants import (
@@ -96,8 +96,8 @@ class ChapterOptionsDialog(QDialog):
         # Prevent closing with the X button and remove the help button
         self.setWindowFlags(
             self.windowFlags()
-            & ~Qt.WindowCloseButtonHint
-            & ~Qt.WindowContextHelpButtonHint
+            & ~Qt.WindowType.WindowCloseButtonHint
+            & ~Qt.WindowType.WindowContextHelpButtonHint
         )
 
         layout = QVBoxLayout(self)
@@ -131,7 +131,7 @@ class ChapterOptionsDialog(QDialog):
         layout.addWidget(self.countdown_label)
 
         # Add OK button
-        button_box = QDialogButtonBox(QDialogButtonBox.Ok)
+        button_box = QDialogButtonBox(QDialogButtonBox.StandardButton.Ok)
         button_box.accepted.connect(self.accept)
         layout.addWidget(button_box)
 
@@ -180,7 +180,7 @@ class ChapterOptionsDialog(QDialog):
 
     # Prevent escape key from closing the dialog
     def keyPressEvent(self, event):
-        if event.key() == Qt.Key_Escape:
+        if event.key() == Qt.Key.Key_Escape:
             event.ignore()
         else:
             super().keyPressEvent(event)
diff --git a/abogen/gui.py b/abogen/gui.py
index f742ca3..229b2c6 100644
--- a/abogen/gui.py
+++ b/abogen/gui.py
@@ -8,28 +8,31 @@ from abogen.queue_manager_gui import QueueManager
 from abogen.queued_item import QueuedItem
 import abogen.hf_tracker as hf_tracker
 import hashlib  # Added for cache path generation
-from PyQt5.QtWidgets import (
+from PyQt6.QtWidgets import (
     QApplication,
+    QMainWindow,
     QWidget,
     QVBoxLayout,
     QHBoxLayout,
     QPushButton,
-    QFileDialog,
-    QLabel,
-    QProgressBar,
-    QSlider,
     QComboBox,
-    QSizePolicy,
     QTextEdit,
-    QFileIconProvider,
+    QLabel,
+    QSlider,
     QMessageBox,
+    QFileDialog,
+    QProgressBar,
+    QFrame,
+    QStyleFactory,
+    QInputDialog,
+    QFileIconProvider,
+    QSizePolicy,
     QDialog,
     QCheckBox,
     QMenu,
-    QAction,
-    QActionGroup,
 )
-from PyQt5.QtCore import (
+from PyQt6.QtGui import QAction, QActionGroup
+from PyQt6.QtCore import (
     Qt,
     QUrl,
     QPoint,
@@ -42,8 +45,9 @@ from PyQt5.QtCore import (
     QSize,
     QTimer,
     QEvent,
+    QProcess,
 )
-from PyQt5.QtGui import (
+from PyQt6.QtGui import (
     QTextCursor,
     QDesktopServices,
     QIcon,
@@ -52,6 +56,7 @@ from PyQt5.QtGui import (
     QPolygon,
     QColor,
     QMovie,
+    QPalette,
 )
 from abogen.utils import (
     load_config,
@@ -95,12 +100,12 @@ class DarkTitleBarEventFilter(QObject):
         self.set_title_bar_dark_mode = set_title_bar_dark_mode_func
 
     def eventFilter(self, obj, event):
-        if event.type() == QEvent.Show:
+        if event.type() == QEvent.Type.Show:
             # Only apply to QWidget windows
             if isinstance(obj, QWidget) and obj.isWindow():
                 if self.is_windows and self.get_dark_mode():
                     self.set_title_bar_dark_mode(obj, True)
-        return False
+        return super().eventFilter(obj, event)
 
 
 class ShowWarningSignalEmitter(QObject):  # New class to handle signal emission
@@ -154,7 +159,7 @@ class InputBox(QLabel):
 
     def __init__(self, parent=None):
         super().__init__(parent)
-        self.setAlignment(Qt.AlignCenter)
+        self.setAlignment(Qt.AlignmentFlag.AlignCenter)
         self.setAcceptDrops(True)
         self.setText(
             "Drag and drop your file here or click to browse.\n(.txt, .epub, .pdf, .md)"
@@ -162,8 +167,8 @@ class InputBox(QLabel):
         self.setStyleSheet(
             f"QLabel {{ {self.STYLE_DEFAULT} }} QLabel:hover {{ {self.STYLE_DEFAULT_HOVER} }}"
         )
-        self.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
-        self.setCursor(Qt.PointingHandCursor)
+        self.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding)
+        self.setCursor(Qt.CursorShape.PointingHandCursor)
 
         # Add clear button
         self.clear_btn = QPushButton("✕", self)
@@ -223,7 +228,7 @@ class InputBox(QLabel):
         pixmap = qicon.pixmap(size)
         # convert to base64 PNG
         buffer = QBuffer()
-        buffer.open(QIODevice.WriteOnly)
+        buffer.open(QIODevice.OpenModeFlag.WriteOnly)
         pixmap.save(buffer, "PNG")
         img_data = base64.b64encode(buffer.data()).decode()
 
@@ -356,6 +361,9 @@ class InputBox(QLabel):
         self.window().displayed_file_path = (
             None  # Reset the displayed file path when clearing input
         )
+        # Reset book handler attributes
+        self.window().save_chapters_separately = None
+        self.window().merge_chapters_at_end = None
         self.setText(
             "Drag and drop your file here or click to browse.\n(.txt, .epub, .pdf, .md)"
         )
@@ -384,7 +392,7 @@ class InputBox(QLabel):
         return f"{size:.{decimal_places}f} PB"
 
     def mousePressEvent(self, event):
-        if event.button() == Qt.LeftButton:
+        if event.button() == Qt.MouseButton.LeftButton:
             self.window().open_file_dialog()
 
     def dragEnterEvent(self, event):
@@ -542,7 +550,7 @@ class InputBox(QLabel):
 
             menu.addAction(act_input)
             # Show the menu anchored to the button
-            menu.exec_(self.go_to_folder_btn.mapToGlobal(QPoint(0, self.go_to_folder_btn.height())))
+            menu.exec(self.go_to_folder_btn.mapToGlobal(QPoint(0, self.go_to_folder_btn.height())))
         else:
             if (
                     file_to_check
@@ -560,7 +568,7 @@ class TextboxDialog(QDialog):
         super().__init__(parent)
         self.setWindowTitle("Enter Text")
         self.setWindowFlags(
-            Qt.Window | Qt.WindowCloseButtonHint | Qt.WindowMaximizeButtonHint
+            Qt.WindowType.Window | Qt.WindowType.WindowCloseButtonHint | Qt.WindowType.WindowMaximizeButtonHint
         )
         self.resize(700, 500)
 
@@ -634,16 +642,16 @@ class TextboxDialog(QDialog):
             # Check if we need to warn about overwriting a non-temporary file
             if hasattr(self, "is_non_cache_file") and self.is_non_cache_file:
                 msg_box = QMessageBox(self)
-                msg_box.setIcon(QMessageBox.Warning)
+                msg_box.setIcon(QMessageBox.Icon.Warning)
                 msg_box.setWindowTitle("File Overwrite Warning")
                 msg_box.setText(
                     f"You are about to overwrite the original file:\n{self.non_cache_file_path}"
                 )
                 msg_box.setInformativeText("Do you want to continue?")
-                msg_box.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
-                msg_box.setDefaultButton(QMessageBox.No)
+                msg_box.setStandardButtons(QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No)
+                msg_box.setDefaultButton(QMessageBox.StandardButton.No)
 
-                if msg_box.exec_() != QMessageBox.Yes:
+                if msg_box.exec() != QMessageBox.StandardButton.Yes:
                     # User canceled, don't close the dialog
                     return
 
@@ -873,7 +881,7 @@ class abogen(QWidget):
         self.log_text = QTextEdit(self)
         self.log_text.setReadOnly(True)
         self.log_text.setUndoRedoEnabled(False)
-        self.log_text.setFrameStyle(QTextEdit.NoFrame)
+        self.log_text.setFrameStyle(QFrame.Shape.NoFrame)
         self.log_text.setStyleSheet("QTextEdit { border: none; }")
         self.log_text.hide()
         container_layout.addWidget(self.log_text, 1)
@@ -884,11 +892,11 @@ class abogen(QWidget):
         speed_layout = QVBoxLayout()
         speed_layout.setSpacing(2)
         speed_layout.addWidget(QLabel("Speed:", self))
-        self.speed_slider = QSlider(Qt.Horizontal, self)
+        self.speed_slider = QSlider(Qt.Orientation.Horizontal, self)
         self.speed_slider.setMinimum(10)
         self.speed_slider.setMaximum(200)
         self.speed_slider.setValue(100)
-        self.speed_slider.setTickPosition(QSlider.TicksBelow)
+        self.speed_slider.setTickPosition(QSlider.TickPosition.TicksBelow)
         self.speed_slider.setTickInterval(5)
         self.speed_slider.setSingleStep(5)
         speed_layout.addWidget(self.speed_slider)
@@ -910,7 +918,7 @@ class abogen(QWidget):
             "The first character represents the language:\n"
             '"a" => American English\n"b" => British English\n"e" => Spanish\n"f" => French\n"h" => Hindi\n"i" => Italian\n"j" => Japanese\n"p" => Brazilian Portuguese\n"z" => Mandarin Chinese\nThe second character represents the gender:\n"m" => Male\n"f" => Female'
         )
-        self.voice_combo.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed)
+        self.voice_combo.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed)
         voice_layout.addWidget(self.voice_combo)
         # Voice formula button
         self.btn_voice_formula_mixer = QPushButton(self)
@@ -925,11 +933,11 @@ class abogen(QWidget):
         # Play/Stop icons
         def make_icon(color, shape):
             pix = QPixmap(20, 20)
-            pix.fill(Qt.transparent)
+            pix.fill(Qt.GlobalColor.transparent)
             p = QPainter(pix)
-            p.setRenderHint(QPainter.Antialiasing)
+            p.setRenderHint(QPainter.RenderHint.Antialiasing)
             p.setBrush(QColor(*color))
-            p.setPen(Qt.NoPen)
+            p.setPen(Qt.PenStyle.NoPen)
             if shape == "play":
                 pts = [
                     pix.rect().topLeft() + QPoint(4, 2),
@@ -983,7 +991,7 @@ class abogen(QWidget):
         self.subtitle_combo.setStyleSheet(
             "QComboBox { min-height: 20px; padding: 6px 12px; }"
         )
-        self.subtitle_combo.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed)
+        self.subtitle_combo.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed)
         self.subtitle_combo.setCurrentText(self.subtitle_mode)
         self.subtitle_combo.currentTextChanged.connect(self.on_subtitle_mode_changed)
         # Enable/disable subtitle options based on selected language (profile or voice)
@@ -1001,7 +1009,7 @@ class abogen(QWidget):
         self.format_combo.setStyleSheet(
             "QComboBox { min-height: 20px; padding: 6px 12px; }"
         )
-        self.format_combo.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed)
+        self.format_combo.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed)
         # Add items with display labels and underlying keys
         for key, label in [
             ("wav", "wav"),
@@ -1032,7 +1040,7 @@ class abogen(QWidget):
             "QComboBox { min-height: 20px; padding: 6px 12px; }"
         )
         self.subtitle_format_combo.setSizePolicy(
-            QSizePolicy.Expanding, QSizePolicy.Fixed
+            QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed
         )
         for value, text in SUBTITLE_FORMATS:
             self.subtitle_format_combo.addItem(text, value)
@@ -1079,7 +1087,7 @@ class abogen(QWidget):
             "QComboBox { min-height: 20px; padding: 6px 12px; }"
         )
         self.replace_newlines_combo.setSizePolicy(
-            QSizePolicy.Expanding, QSizePolicy.Fixed
+            QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed
         )
         # Set initial value based on config
         self.replace_newlines_combo.setCurrentIndex(
@@ -1106,7 +1114,7 @@ class abogen(QWidget):
         self.save_combo.setStyleSheet(
             "QComboBox { min-height: 20px; padding: 6px 12px; }"
         )
-        self.save_combo.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed)
+        self.save_combo.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Fixed)
         self.save_combo.setCurrentText(self.save_option)
         self.save_combo.currentTextChanged.connect(self.on_save_option_changed)
         save_layout.addWidget(self.save_combo)
@@ -1121,7 +1129,7 @@ class abogen(QWidget):
         save_path_row.addWidget(selected_folder_label)
         self.save_path_label = QLabel("", self.save_path_row_widget)
         self.save_path_label.setStyleSheet(f"QLabel {{ color: {COLORS['GREEN']}; }}")
-        self.save_path_label.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Preferred)
+        self.save_path_label.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Preferred)
         save_path_row.addWidget(self.save_path_label)
         self.save_path_row_widget.hide()  # Hide the whole row by default
         controls_layout.addWidget(self.save_path_row_widget)
@@ -1164,9 +1172,10 @@ class abogen(QWidget):
         self.btn_start.setFixedHeight(60)
         self.btn_start.clicked.connect(self.start_conversion)
         controls_layout.addWidget(self.btn_start)
+        # Add controls to a container widget
         self.controls_widget = QWidget()
         self.controls_widget.setLayout(controls_layout)
-        self.controls_widget.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Fixed)
+        self.controls_widget.setSizePolicy(QSizePolicy.Policy.Preferred, QSizePolicy.Policy.Fixed)
         container_layout.addWidget(self.controls_widget)
         # Progress bar
         self.progress_bar = QProgressBar(self)
@@ -1175,7 +1184,7 @@ class abogen(QWidget):
         container_layout.addWidget(self.progress_bar)
         # ETR Label
         self.etr_label = QLabel("Estimated time remaining: Calculating...", self)
-        self.etr_label.setAlignment(Qt.AlignCenter)
+        self.etr_label.setAlignment(Qt.AlignmentFlag.AlignCenter)
         self.etr_label.hide()
         container_layout.addWidget(self.etr_label)
         # Cancel button
@@ -1274,12 +1283,12 @@ class abogen(QWidget):
             checked_chapters=self.selected_chapters,
             parent=self
         )
-        dialog.setWindowModality(Qt.NonModal)
+        dialog.setWindowModality(Qt.WindowModality.NonModal)
         dialog.setModal(False)
         dialog.show()  # We'll handle the dialog result asynchronously
 
         def on_dialog_finished(result):
-            if result != QDialog.Accepted:
+            if result != QDialog.DialogCode.Accepted:
                 return False
             chapters_text, all_checked_hrefs = dialog.get_selected_text()
             if not all_checked_hrefs:
@@ -1319,7 +1328,7 @@ class abogen(QWidget):
             if self.save_as_project:
                 # Get project directory from user
                 project_dir = QFileDialog.getExistingDirectory(
-                    self, "Select Project Folder", "", QFileDialog.ShowDirsOnly
+                    self, "Select Project Folder", "", QFileDialog.Option.ShowDirsOnly
                 )
                 if not project_dir:
                     # User cancelled, fallback to cache
@@ -1445,7 +1454,7 @@ class abogen(QWidget):
                     dialog.non_cache_file_path = edit_file
             except Exception:
                 pass
-        if dialog.exec_() == QDialog.Accepted:
+        if dialog.exec() == QDialog.DialogCode.Accepted:
             text = dialog.get_text()
             if not text.strip():
                 self._show_error_message_box("Textbox Error", "Text cannot be empty.")
@@ -1605,7 +1614,7 @@ class abogen(QWidget):
         at_bottom = sb.value() == sb.maximum()
 
         cursor = txt.textCursor()
-        cursor.movePosition(QTextCursor.End)
+        cursor.movePosition(QTextCursor.MoveOperation.End)
 
         fmt = cursor.charFormat()
         if isinstance(message, tuple):
@@ -1624,7 +1633,7 @@ class abogen(QWidget):
             end = doc.findBlockByNumber(excess).position()
             trim_cursor = QTextCursor(doc)
             trim_cursor.setPosition(start)
-            trim_cursor.setPosition(end, QTextCursor.KeepAnchor)
+            trim_cursor.setPosition(end, QTextCursor.MoveMode.KeepAnchor)
             trim_cursor.removeSelectedText()
 
         if at_bottom:
@@ -1743,6 +1752,8 @@ class abogen(QWidget):
             total_char_count=self.char_count,
             replace_single_newlines=self.replace_single_newlines,
             save_base_path=save_base_path,
+            save_chapters_separately=getattr(self, "save_chapters_separately", None),
+            merge_chapters_at_end=getattr(self, "merge_chapters_at_end", None),
         )
 
         # Prevent adding duplicate items to the queue
@@ -1760,6 +1771,10 @@ class abogen(QWidget):
                     == item_queue.replace_single_newlines
                     and getattr(queued_item, "save_base_path", None)
                     == item_queue.save_base_path
+                    and getattr(queued_item, "save_chapters_separately", None)
+                    == item_queue.save_chapters_separately
+                    and getattr(queued_item, "merge_chapters_at_end", None)
+                    == item_queue.merge_chapters_at_end
             ):
                 QMessageBox.warning(
                     self, "Duplicate Item", "This item is already in the queue."
@@ -1779,10 +1794,10 @@ class abogen(QWidget):
                 self,
                 "Confirm Clear Queue",
                 f"Are you sure you want to clear {len(self.queued_items)} items from the queue?",
-                QMessageBox.Yes | QMessageBox.No,
-                QMessageBox.No,
+                QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
+                QMessageBox.StandardButton.No,
             )
-            if reply != QMessageBox.Yes:
+            if reply != QMessageBox.StandardButton.Yes:
                 return
         self.queued_items = []
         self.enable_disable_queue_buttons()
@@ -1790,7 +1805,7 @@ class abogen(QWidget):
     def manage_queue(self):
         # show a dialog to manage the queue
         dialog = QueueManager(self, self.queued_items)
-        if dialog.exec_() == QDialog.Accepted:
+        if dialog.exec() == QDialog.DialogCode.Accepted:
             self.queued_items = dialog.get_queue()
             # re-enable/disable buttons based on queue state
             self.enable_disable_queue_buttons()
@@ -2057,7 +2072,7 @@ class abogen(QWidget):
         dialog.setLayout(layout)
         dialog.setMinimumSize(400, 300)
         dialog.setSizeGripEnabled(True)  # Allow resizing
-        dialog.exec_()
+        dialog.exec()
 
     def on_conversion_finished(self, message, output_path):
         prevent_sleep_end()
@@ -2516,14 +2531,14 @@ class abogen(QWidget):
 
     def _show_error_message_box(self, title, message):
         box = QMessageBox(self)
-        box.setIcon(QMessageBox.Critical)
+        box.setIcon(QMessageBox.Icon.Critical)
         box.setWindowTitle(title)
         box.setText(message)
         copy_btn = QPushButton("Copy")
-        box.addButton(copy_btn, QMessageBox.ActionRole)
-        box.addButton(QMessageBox.Ok)
+        box.addButton(copy_btn, QMessageBox.ButtonRole.ActionRole)
+        box.addButton(QMessageBox.StandardButton.Ok)
         copy_btn.clicked.connect(lambda: QApplication.clipboard().setText(message))
-        box.exec_()
+        box.exec()
 
     def _show_preview_error_box(self, msg):
         self._show_error_message_box("Preview Error", f"Preview error: {msg}")
@@ -2551,14 +2566,14 @@ class abogen(QWidget):
     def cancel_conversion(self):
         if self.is_converting:
             box = QMessageBox(self)
-            box.setIcon(QMessageBox.Warning)
+            box.setIcon(QMessageBox.Icon.Warning)
             box.setWindowTitle("Cancel Conversion")
             box.setText(
                 "A conversion is currently running. Are you sure you want to cancel?"
             )
-            box.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
-            box.setDefaultButton(QMessageBox.No)
-            if box.exec_() != QMessageBox.Yes:
+            box.setStandardButtons(QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No)
+            box.setDefaultButton(QMessageBox.StandardButton.No)
+            if box.exec() != QMessageBox.StandardButton.Yes:
                 return
         try:
             if (
@@ -2643,7 +2658,7 @@ class abogen(QWidget):
         save_config(self.config)
 
     def on_gpu_setting_changed(self, state):
-        self.use_gpu = state == Qt.Checked
+        self.use_gpu = state == Qt.CheckState.Checked.value
         self.config["use_gpu"] = self.use_gpu
         save_config(self.config)
 
@@ -2660,14 +2675,14 @@ class abogen(QWidget):
     def closeEvent(self, event):
         if self.is_converting:
             box = QMessageBox(self)
-            box.setIcon(QMessageBox.Warning)
+            box.setIcon(QMessageBox.Icon.Warning)
             box.setWindowTitle("Conversion in Progress")
             box.setText(
                 "A conversion is currently running. Are you sure you want to exit?"
             )
-            box.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
-            box.setDefaultButton(QMessageBox.No)
-            if box.exec_() == QMessageBox.Yes:
+            box.setStandardButtons(QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No)
+            box.setDefaultButton(QMessageBox.StandardButton.No)
+            if box.exec() == QMessageBox.StandardButton.Yes:
                 self.cleanup_conversion_thread()
                 event.accept()
             else:
@@ -2681,10 +2696,10 @@ class abogen(QWidget):
         from abogen.conversion import ChapterOptionsDialog
 
         dialog = ChapterOptionsDialog(chapter_count, parent=self)
-        dialog.setWindowModality(Qt.ApplicationModal)
+        dialog.setWindowModality(Qt.WindowModality.ApplicationModal)
 
         # If dialog is accepted, pass the options to the conversion thread
-        if dialog.exec_() == QDialog.Accepted:
+        if dialog.exec() == QDialog.DialogCode.Accepted:
             options = dialog.get_options()
             if (
                     hasattr(self, "conversion_thread")
@@ -2696,8 +2711,7 @@ class abogen(QWidget):
             self.cancel_conversion()
 
     def apply_theme(self, theme):
-        from PyQt5.QtGui import QPalette, QColor
-        from PyQt5.QtWidgets import QStyleFactory
+
 
         app = QApplication.instance()
         is_windows = platform.system() == "Windows"
@@ -2981,7 +2995,7 @@ class abogen(QWidget):
         about_action.triggered.connect(self.show_about_dialog)
         menu.addAction(about_action)
 
-        menu.exec_(self.settings_btn.mapToGlobal(QPoint(0, self.settings_btn.height())))
+        menu.exec(self.settings_btn.mapToGlobal(QPoint(0, self.settings_btn.height())))
 
     def toggle_replace_single_newlines(self, enabled):
         self.replace_single_newlines = enabled
@@ -2989,7 +3003,7 @@ class abogen(QWidget):
         save_config(self.config)
 
     def restart_app(self):
-        from PyQt5.QtCore import QProcess
+
         import sys
 
         exe = sys.executable
@@ -3022,10 +3036,10 @@ class abogen(QWidget):
             self,
             "Restart Required",
             message,
-            QMessageBox.Yes | QMessageBox.No,
-            QMessageBox.No,
+            QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
+            QMessageBox.StandardButton.No,
         )
-        if reply == QMessageBox.Yes:
+        if reply == QMessageBox.StandardButton.Yes:
             self.config["disable_kokoro_internet"] = disabled
             save_config(self.config)
             try:
@@ -3040,10 +3054,10 @@ class abogen(QWidget):
             self,
             "Reset Settings",
             "This will reset all settings to their default values and restart the application.\n\nDo you want to continue?",
-            QMessageBox.Yes | QMessageBox.No,
-            QMessageBox.No,
+            QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
+            QMessageBox.StandardButton.No,
         )
-        if reply == QMessageBox.Yes:
+        if reply == QMessageBox.StandardButton.Yes:
             from abogen.utils import get_user_config_path
 
             config_path = get_user_config_path()
@@ -3204,9 +3218,9 @@ Categories=AudioVideo;Audio;Utility;
                     self,
                     "Install Application Entry",
                     "Install application entry for current user?",
-                    QMessageBox.Yes | QMessageBox.No,
+                    QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
                 )
-                if reply == QMessageBox.Yes:
+                if reply == QMessageBox.StandardButton.Yes:
                     import shutil
 
                     user_app_dir = os.path.expanduser("~/.local/share/applications")
@@ -3266,12 +3280,11 @@ Categories=AudioVideo;Audio;Utility;
                     initial_state = entry.get("voices", [])
                 else:
                     initial_state = entry
-            else:
-                initial_state = []
+                    self.selected_lang = entry[0][0] if entry and entry[0] else None
         dialog = VoiceFormulaDialog(
             self, initial_state=initial_state, selected_profile=selected_profile
         )
-        if dialog.exec_() == QDialog.Accepted:
+        if dialog.exec() == QDialog.DialogCode.Accepted:
             if dialog.current_profile:
                 self.selected_profile_name = dialog.current_profile
                 self.config["selected_profile_name"] = dialog.current_profile
@@ -3292,7 +3305,7 @@ Categories=AudioVideo;Audio;Utility;
         # Create custom dialog
         dialog = QDialog(self)
         dialog.setWindowTitle(f"About {PROGRAM_NAME}")
-        dialog.setWindowFlags(dialog.windowFlags() & ~Qt.WindowContextHelpButtonHint)
+        dialog.setWindowFlags(dialog.windowFlags() & ~Qt.WindowType.WindowContextHelpButtonHint)
         dialog.setFixedSize(400, 320)  # Increased height for new button
 
         layout = QVBoxLayout(dialog)
@@ -3314,7 +3327,7 @@ Categories=AudioVideo;Audio;Utility;
         title_label = QLabel(
             f"<h1 style='margin-bottom: 0;'>{PROGRAM_NAME} <span style='font-size: 12px; font-weight: normal; color: #666;'>v{VERSION}</span></h1><h3 style='margin-top: 5px;'>Audiobook Generator</h3>"
         )
-        title_label.setTextFormat(Qt.RichText)
+        title_label.setTextFormat(Qt.TextFormat.RichText)
         header_layout.addWidget(title_label, 1)
         layout.addLayout(header_layout)
 
@@ -3323,7 +3336,7 @@ Categories=AudioVideo;Audio;Utility;
             f"<p>{PROGRAM_DESCRIPTION}</p>"
             "<p>Visit the GitHub repository for updates, documentation, and to report issues.</p>"
         )
-        desc_label.setTextFormat(Qt.RichText)
+        desc_label.setTextFormat(Qt.TextFormat.RichText)
         desc_label.setWordWrap(True)
         layout.addWidget(desc_label)
 
@@ -3346,7 +3359,7 @@ Categories=AudioVideo;Audio;Utility;
         close_btn.setFixedHeight(32)
         layout.addWidget(close_btn)
 
-        dialog.exec_()
+        dialog.exec()
 
     def manual_check_for_updates(self):
         """Manually check for updates and always show result"""
@@ -3359,7 +3372,7 @@ Categories=AudioVideo;Audio;Utility;
 
         def show_update_message(remote_version, local_version):
             msg_box = QMessageBox(self)
-            msg_box.setIcon(QMessageBox.Information)
+            msg_box.setIcon(QMessageBox.Icon.Information)
             msg_box.setWindowTitle("Update Available")
             msg_box.setText(
                 f"A new version of {PROGRAM_NAME} is available! ({local_version} > {remote_version})"
@@ -3371,9 +3384,9 @@ Categories=AudioVideo;Audio;Utility;
                 "Alternatively, visit the GitHub repository for more information. "
                 "Would you like to view the changelog?"
             )
-            msg_box.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
-            msg_box.setDefaultButton(QMessageBox.Yes)
-            if msg_box.exec_() == QMessageBox.Yes:
+            msg_box.setStandardButtons(QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No)
+            msg_box.setDefaultButton(QMessageBox.StandardButton.Yes)
+            if msg_box.exec() == QMessageBox.StandardButton.Yes:
                 try:
                     QDesktopServices.openUrl(QUrl(GITHUB_URL + "/releases/latest"))
                 except Exception:
@@ -3455,7 +3468,7 @@ Categories=AudioVideo;Audio;Utility;
 
             # Create a custom message box with checkbox
             msg_box = QMessageBox(self)
-            msg_box.setIcon(QMessageBox.Question)
+            msg_box.setIcon(QMessageBox.Icon.Question)
             msg_box.setWindowTitle("Clear Cache Files")
 
             msg_text = f"Found {file_count} cache file{'s' if file_count != 1 else ''} in the {PROGRAM_NAME} cache folder."
@@ -3474,10 +3487,10 @@ Categories=AudioVideo;Audio;Utility;
             msg_box.setCheckBox(preview_cache_checkbox)
 
             # Add buttons
-            msg_box.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
-            msg_box.setDefaultButton(QMessageBox.Yes)
+            msg_box.setStandardButtons(QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No)
+            msg_box.setDefaultButton(QMessageBox.StandardButton.Yes)
 
-            if msg_box.exec_() != QMessageBox.Yes:
+            if msg_box.exec() != QMessageBox.StandardButton.Yes:
                 return
 
             # Delete the text files
@@ -3522,7 +3535,7 @@ Categories=AudioVideo;Audio;Utility;
 
     def set_max_log_lines(self):
         """Open a dialog to set the maximum lines in the log window."""
-        from PyQt5.QtWidgets import QInputDialog
+        from PyQt6.QtWidgets import QInputDialog
 
         value, ok = QInputDialog.getInt(
             self,
@@ -3545,7 +3558,7 @@ Categories=AudioVideo;Audio;Utility;
 
     def set_max_subtitle_words(self):
         """Open a dialog to set the maximum words per subtitle"""
-        from PyQt5.QtWidgets import QInputDialog
+        from PyQt6.QtWidgets import QInputDialog
 
         current_value = self.config.get("max_subtitle_words", 50)
 
@@ -3574,7 +3587,7 @@ Categories=AudioVideo;Audio;Utility;
 
     def set_silence_between_chapters(self):
         """Open a dialog to set the silence duration between chapters"""
-        from PyQt5.QtWidgets import QInputDialog, QDialog
+
 
         current_value = self.config.get("silence_duration", 2.0)
 
@@ -3583,14 +3596,14 @@ Categories=AudioVideo;Audio;Utility;
         dlg.setLabelText(
             "Enter the duration of silence\nbetween chapters (in seconds):"
         )
-        dlg.setInputMode(QInputDialog.DoubleInput)
+        dlg.setInputMode(QInputDialog.InputMode.DoubleInput)
         dlg.setDoubleDecimals(1)
         dlg.setDoubleMinimum(0.0)
         dlg.setDoubleMaximum(60.0)
         dlg.setDoubleValue(current_value)
         dlg.setDoubleStep(0.1)  # <-- set step to 0.1
 
-        if dlg.exec_() == QDialog.Accepted:
+        if dlg.exec() == QDialog.DialogCode.Accepted:
             value = dlg.doubleValue()
             # Round to one decimal to avoid floating-point representation noise
             value = round(value, 1)
diff --git a/abogen/main.py b/abogen/main.py
index 8838ac3..ac4a2c6 100644
--- a/abogen/main.py
+++ b/abogen/main.py
@@ -7,19 +7,24 @@ import signal
 
 # Qt platform plugin detection (fixes #59)
 try:
-    from PyQt5.QtCore import QLibraryInfo
-    plugins = QLibraryInfo.location(QLibraryInfo.PluginsPath)
+    from PyQt6.QtCore import QLibraryInfo
+    
+    # Get the path to the plugins directory
+    plugins = QLibraryInfo.path(QLibraryInfo.LibraryPath.PluginsPath)
+    
     # Normalize path to use the OS-native separators and absolute path
     platform_dir = os.path.normpath(os.path.join(plugins, "platforms"))
+    
     # Ensure we work with an absolute path for clarity
     platform_dir = os.path.abspath(platform_dir)
+    
     if os.path.isdir(platform_dir):
         os.environ["QT_QPA_PLATFORM_PLUGIN_PATH"] = platform_dir
         print("QT_QPA_PLATFORM_PLUGIN_PATH set to:", platform_dir)
     else:
-        print("PyQt5 platform plugins not found at", platform_dir)
+        print("PyQt6 platform plugins not found at", platform_dir)
 except ImportError:
-    print("PyQt5 not installed.")
+    print("PyQt6 not installed.")
 
 # Set application ID for Windows taskbar icon
 if platform.system() == "Windows":
@@ -31,9 +36,16 @@ if platform.system() == "Windows":
     except Exception as e:
         print("Warning: failed to set AppUserModelID:", e)
 
-from PyQt5.QtWidgets import QApplication
-from PyQt5.QtGui import QIcon
-from PyQt5.QtCore import qInstallMessageHandler, QtMsgType
+from PyQt6.QtWidgets import QApplication
+from PyQt6.QtGui import QIcon
+from PyQt6.QtCore import (
+    Qt,
+    QLibraryInfo,
+    qInstallMessageHandler,
+    QStandardPaths,
+    QSettings,
+    QtMsgType,
+)
 
 # Add the directory to Python path
 sys.path.insert(0, os.path.join(os.path.dirname(__file__)))
@@ -82,10 +94,12 @@ if platform.system() == "Darwin" and platform.processor() == "arm":
 
 # Custom message handler to filter out specific Qt warnings
 def qt_message_handler(mode, context, message):
+    # In PyQt6, the mode is an enum, so we compare with the enum members
     if "Wayland does not support QWindow::requestActivate()" in message:
         return  # Suppress this specific message
     if "setGrabPopup called with a parent, QtWaylandClient" in message:
         return
+
     if mode == QtMsgType.QtWarningMsg:
         print(f"Qt Warning: {message}")
     elif mode == QtMsgType.QtCriticalMsg:
@@ -129,7 +143,7 @@ def main():
 
     ex = abogen()
     ex.show()
-    sys.exit(app.exec_())
+    sys.exit(app.exec())
 
 
 if __name__ == "__main__":
diff --git a/abogen/queue_manager_gui.py b/abogen/queue_manager_gui.py
index 1a5d2ee..a8ff439 100644
--- a/abogen/queue_manager_gui.py
+++ b/abogen/queue_manager_gui.py
@@ -2,7 +2,7 @@
 # button to remove an item from the queue
 # button to clear the queue
 
-from PyQt5.QtWidgets import (
+from PyQt6.QtWidgets import (
     QDialog,
     QVBoxLayout,
     QHBoxLayout,
@@ -14,18 +14,20 @@ from PyQt5.QtWidgets import (
     QLabel,
     QWidget,
     QSizePolicy,
+    QAbstractItemView,
 )
-from PyQt5.QtCore import QFileInfo, Qt
+from PyQt6.QtCore import QFileInfo, Qt
 from abogen.constants import COLORS
 from copy import deepcopy
-from PyQt5.QtGui import QFontMetrics
+from PyQt6.QtGui import QFontMetrics
 
 
 class ElidedLabel(QLabel):
-    def __init__(self, text, parent=None):
-        super().__init__(text, parent)
+    def __init__(self, text):
+        super().__init__(text)
         self._full_text = text
-        self.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Preferred)
+        self.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Preferred)
+        self.setTextFormat(Qt.TextFormat.PlainText)
 
     def setText(self, text):
         self._full_text = text
@@ -34,7 +36,7 @@ class ElidedLabel(QLabel):
 
     def resizeEvent(self, event):
         metrics = QFontMetrics(self.font())
-        elided = metrics.elidedText(self._full_text, Qt.ElideRight, self.width())
+        elided = metrics.elidedText(self._full_text, Qt.TextElideMode.ElideRight, self.width())
         super().setText(elided)
         super().resizeEvent(event)
 
@@ -53,8 +55,8 @@ class QueueListItemWidget(QWidget):
         name_label = ElidedLabel(os.path.basename(file_name))
         char_label = QLabel(f"Chars: {char_count}")
         char_label.setStyleSheet(f"color: {COLORS['LIGHT_DISABLED']};")
-        char_label.setAlignment(Qt.AlignRight | Qt.AlignVCenter)
-        char_label.setSizePolicy(QSizePolicy.Minimum, QSizePolicy.Preferred)
+        char_label.setAlignment(Qt.AlignmentFlag.AlignRight | Qt.AlignmentFlag.AlignVCenter)
+        char_label.setSizePolicy(QSizePolicy.Policy.Minimum, QSizePolicy.Policy.Preferred)
         layout.addWidget(name_label, 1)
         layout.addWidget(char_label, 0)
         self.setLayout(layout)
@@ -67,12 +69,12 @@ class DroppableQueueListWidget(QListWidget):
         self.setAcceptDrops(True)
         # Overlay for drag hover
         self.drag_overlay = QLabel("", self)
-        self.drag_overlay.setAlignment(Qt.AlignCenter)
+        self.drag_overlay.setAlignment(Qt.AlignmentFlag.AlignCenter)
         self.drag_overlay.setStyleSheet(
             f"border:2px dashed {COLORS['BLUE_BORDER_HOVER']}; border-radius:5px; padding:20px; background:{COLORS['BLUE_BG_HOVER']};"
         )
         self.drag_overlay.setVisible(False)
-        self.drag_overlay.setAttribute(Qt.WA_TransparentForMouseEvents, True)
+        self.drag_overlay.setAttribute(Qt.WidgetAttribute.WA_TransparentForMouseEvents, True)
 
     def dragEnterEvent(self, event):
         if event.mimeData().hasUrls():
@@ -132,9 +134,9 @@ class QueueManager(QDialog):
         layout.setSpacing(12)  # set spacing between widgets in main layout
         # list of queued items
         self.listwidget = DroppableQueueListWidget(self)
-        self.listwidget.setSelectionMode(QListWidget.ExtendedSelection)
+        self.listwidget.setSelectionMode(QAbstractItemView.SelectionMode.ExtendedSelection)
         self.listwidget.setAlternatingRowColors(True)
-        self.listwidget.setContextMenuPolicy(Qt.CustomContextMenu)
+        self.listwidget.setContextMenuPolicy(Qt.ContextMenuPolicy.CustomContextMenu)
         self.listwidget.customContextMenuRequested.connect(self.show_context_menu)
         # Add informative instructions at the top
         instructions = QLabel(
@@ -145,7 +147,7 @@ class QueueManager(QDialog):
             "Changing the main window configuration afterward <b>does not</b> affect files already in the queue. "
             "You can view each file's configuration by hovering over them."
         )
-        instructions.setAlignment(Qt.AlignLeft)
+        instructions.setAlignment(Qt.AlignmentFlag.AlignLeft)
         instructions.setWordWrap(True)
         instructions.setStyleSheet("margin-bottom: 8px;")
         layout.addWidget(instructions)
@@ -154,12 +156,12 @@ class QueueManager(QDialog):
             "Drag and drop your text files here or use the 'Add files' button.",
             self.listwidget,
         )
-        self.empty_overlay.setAlignment(Qt.AlignCenter)
+        self.empty_overlay.setAlignment(Qt.AlignmentFlag.AlignCenter)
         self.empty_overlay.setStyleSheet(
             f"color: {COLORS['LIGHT_DISABLED']}; background: transparent; padding: 20px;"
         )
         self.empty_overlay.setWordWrap(True)
-        self.empty_overlay.setAttribute(Qt.WA_TransparentForMouseEvents, True)
+        self.empty_overlay.setAttribute(Qt.WidgetAttribute.WA_TransparentForMouseEvents, True)
         self.empty_overlay.hide()
         # add queue items to the list
         self.process_queue()
@@ -192,7 +194,7 @@ class QueueManager(QDialog):
         self.listwidget.currentItemChanged.connect(self.update_button_states)
         self.listwidget.itemSelectionChanged.connect(self.update_button_states)
 
-        buttons = QDialogButtonBox(QDialogButtonBox.Ok | QDialogButtonBox.Cancel, self)
+        buttons = QDialogButtonBox(QDialogButtonBox.StandardButton.Ok | QDialogButtonBox.StandardButton.Cancel, self)
         buttons.accepted.connect(self.accept)
         buttons.rejected.connect(self.reject)
 
@@ -211,7 +213,6 @@ class QueueManager(QDialog):
         
         self.listwidget.clear()
         if not self.queue:
-            self.empty_overlay.resize(self.listwidget.size())
             self.empty_overlay.show()
             self.update_button_states()
             return
@@ -262,10 +263,18 @@ class QueueManager(QDialog):
                 f"<b>Characters:</b> {getattr(item, 'total_char_count', '')}<br>"
                 f"<b>Replace Single Newlines:</b> {getattr(item, 'replace_single_newlines', False)}"
             )
+            # Add book handler options if present
+            save_chapters_separately = getattr(item, 'save_chapters_separately', None)
+            merge_chapters_at_end = getattr(item, 'merge_chapters_at_end', None)
+            if save_chapters_separately is not None:
+                tooltip += f"<br><b>Save chapters separately:</b> {'Yes' if save_chapters_separately else 'No'}"
+                # Only show merge option if saving chapters separately
+                if save_chapters_separately and merge_chapters_at_end is not None:
+                    tooltip += f"<br><b>Merge chapters at the end:</b> {'Yes' if merge_chapters_at_end else 'No'}"
             list_item.setToolTip(tooltip)
             list_item.setIcon(icon)
             # Store both paths for context menu
-            list_item.setData(Qt.UserRole, {
+            list_item.setData(Qt.ItemDataRole.UserRole, {
                 'display_path': display_file_path,
                 'processing_path': processing_file_path
             })
@@ -280,7 +289,7 @@ class QueueManager(QDialog):
         items = self.listwidget.selectedItems()
         if not items:
             return
-        from PyQt5.QtWidgets import QMessageBox
+        from PyQt6.QtWidgets import QMessageBox
 
         # Remove by index to ensure correct mapping
         rows = sorted([self.listwidget.row(item) for item in items], reverse=True)
@@ -290,10 +299,10 @@ class QueueManager(QDialog):
                 self,
                 "Confirm Remove",
                 f"Are you sure you want to remove {len(rows)} selected items from the queue?",
-                QMessageBox.Yes | QMessageBox.No,
-                QMessageBox.No,
+                QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
+                QMessageBox.StandardButton.No,
             )
-            if reply != QMessageBox.Yes:
+            if reply != QMessageBox.StandardButton.Yes:
                 return
         for row in rows:
             if 0 <= row < len(self.queue):
@@ -302,17 +311,17 @@ class QueueManager(QDialog):
         self.update_button_states()
 
     def clear_queue(self):
-        from PyQt5.QtWidgets import QMessageBox
+        from PyQt6.QtWidgets import QMessageBox
 
         if len(self.queue) > 1:
             reply = QMessageBox.question(
                 self,
                 "Confirm Clear Queue",
                 f"Are you sure you want to clear {len(self.queue)} items from the queue?",
-                QMessageBox.Yes | QMessageBox.No,
-                QMessageBox.No,
+                QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
+                QMessageBox.StandardButton.No,
             )
-            if reply != QMessageBox.Yes:
+            if reply != QMessageBox.StandardButton.Yes:
                 return
         self.queue.clear()
         self.listwidget.clear()
@@ -362,6 +371,13 @@ class QueueManager(QDialog):
             attrs["replace_single_newlines"] = getattr(
                 parent, "replace_single_newlines", False
             )
+            # book handler options
+            attrs["save_chapters_separately"] = getattr(
+                parent, "save_chapters_separately", None
+            )
+            attrs["merge_chapters_at_end"] = getattr(
+                parent, "merge_chapters_at_end", None
+            )
         else:
             # fallback: empty values
             attrs = {
@@ -378,11 +394,13 @@ class QueueManager(QDialog):
                     "replace_single_newlines",
                 ]
             }
+            attrs["save_chapters_separately"] = None
+            attrs["merge_chapters_at_end"] = None
         return attrs
 
     def add_files_from_paths(self, file_paths):
         from abogen.utils import calculate_text_length
-        from PyQt5.QtWidgets import QMessageBox
+        from PyQt6.QtWidgets import QMessageBox
         import os
 
         current_attrs = self.get_current_attributes()
@@ -430,6 +448,10 @@ class QueueManager(QDialog):
                     == getattr(item, "replace_single_newlines", False)
                     and getattr(queued_item, "save_base_path", None)
                     == getattr(item, "save_base_path", None)
+                    and getattr(queued_item, "save_chapters_separately", None)
+                    == getattr(item, "save_chapters_separately", None)
+                    and getattr(queued_item, "merge_chapters_at_end", None)
+                    == getattr(item, "merge_chapters_at_end", None)
                 ):
                     is_duplicate = True
                     break
@@ -447,7 +469,7 @@ class QueueManager(QDialog):
         self.update_button_states()
 
     def add_more_files(self):
-        from PyQt5.QtWidgets import QFileDialog
+        from PyQt6.QtWidgets import QFileDialog
         from abogen.utils import calculate_text_length  # import the function
 
         # Only allow .txt files
@@ -477,9 +499,9 @@ class QueueManager(QDialog):
             self.clear_button.setEnabled(bool(self.queue))
 
     def show_context_menu(self, pos):
-        from PyQt5.QtWidgets import QMenu, QAction
-        from PyQt5.QtGui import QDesktopServices
-        from PyQt5.QtCore import QUrl
+        from PyQt6.QtWidgets import QMenu
+        from PyQt6.QtGui import QAction, QDesktopServices
+        from PyQt6.QtCore import QUrl
         import os
 
         global_pos = self.listwidget.viewport().mapToGlobal(pos)
@@ -495,10 +517,10 @@ class QueueManager(QDialog):
             open_file_action = QAction("Open file", self)
 
             def open_file():
-                from PyQt5.QtWidgets import QMessageBox
+                from PyQt6.QtWidgets import QMessageBox
 
                 item = selected_items[0]
-                paths = item.data(Qt.UserRole)
+                paths = item.data(Qt.ItemDataRole.UserRole)
                 if isinstance(paths, dict):
                     file_path = paths.get('display_path', paths.get('processing_path', ''))
                 else:
@@ -524,7 +546,7 @@ class QueueManager(QDialog):
             # If the queued item represents a converted document (markdown, pdf, epub)
             # show two actions: Go to processed file (the cached .txt) and Go to input file (original source)
             item = selected_items[0]
-            paths = item.data(Qt.UserRole)
+            paths = item.data(Qt.ItemDataRole.UserRole)
             if isinstance(paths, dict):
                 display_path = paths.get('display_path', '')
                 processing_path = paths.get('processing_path', '')
@@ -539,7 +561,7 @@ class QueueManager(QDialog):
                 isinstance(processing_path, str) and processing_path.lower().endswith(doc_exts)
             )
 
-            from PyQt5.QtWidgets import QMessageBox
+            from PyQt6.QtWidgets import QMessageBox
 
             def open_folder_for(path_label: str):
                 # path_label should be either 'display' or 'processing'
@@ -588,7 +610,7 @@ class QueueManager(QDialog):
 
                 def go_to_folder():
                     item = selected_items[0]
-                    paths = item.data(Qt.UserRole)
+                    paths = item.data(Qt.ItemDataRole.UserRole)
                     if isinstance(paths, dict):
                         file_path = paths.get('display_path', paths.get('processing_path', ''))
                     else:
@@ -618,7 +640,7 @@ class QueueManager(QDialog):
         clear_action = QAction("Clear Queue", self)
         clear_action.triggered.connect(self.clear_queue)
         menu.addAction(clear_action)
-        menu.exec_(global_pos)
+        menu.exec(global_pos)
 
     def accept(self):
         # Accept: keep changes
@@ -626,7 +648,7 @@ class QueueManager(QDialog):
 
     def reject(self):
         # Cancel: restore original queue
-        from PyQt5.QtWidgets import QMessageBox
+        from PyQt6.QtWidgets import QMessageBox
 
         # Warn if user changed a lot (e.g., more than 1 items difference)
         original_count = len(self._original_queue)
@@ -636,19 +658,19 @@ class QueueManager(QDialog):
                 self,
                 "Confirm Cancel",
                 f"Are you sure you want to cancel and discard all changes?",
-                QMessageBox.Yes | QMessageBox.No,
-                QMessageBox.No,
+                QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
+                QMessageBox.StandardButton.No,
             )
-            if reply != QMessageBox.Yes:
+            if reply != QMessageBox.StandardButton.Yes:
                 return
         self.queue.clear()
         self.queue.extend(deepcopy(self._original_queue))
         super().reject()
 
     def keyPressEvent(self, event):
-        from PyQt5.QtCore import Qt
+        from PyQt6.QtCore import Qt
 
-        if event.key() == Qt.Key_Delete:
+        if event.key() == Qt.Key.Key_Delete:
             self.remove_item()
         else:
             super().keyPressEvent(event)
diff --git a/abogen/queued_item.py b/abogen/queued_item.py
index f8c9ece..17f26d5 100644
--- a/abogen/queued_item.py
+++ b/abogen/queued_item.py
@@ -15,3 +15,5 @@ class QueuedItem:
     total_char_count: int
     replace_single_newlines: bool = False
     save_base_path: str = None
+    save_chapters_separately: bool = None
+    merge_chapters_at_end: bool = None
diff --git a/abogen/voice_formula_gui.py b/abogen/voice_formula_gui.py
index ae361a3..0bd0bfc 100644
--- a/abogen/voice_formula_gui.py
+++ b/abogen/voice_formula_gui.py
@@ -1,6 +1,6 @@
 import json
 import os
-from PyQt5.QtWidgets import (
+from PyQt6.QtWidgets import (
     QDialog,
     QVBoxLayout,
     QCheckBox,
@@ -22,12 +22,11 @@ from PyQt5.QtWidgets import (
     QFileDialog,
     QSplitter,
     QMenu,
-    QAction,
-    QComboBox,
     QApplication,
+    QComboBox,
 )
-from PyQt5.QtCore import Qt, QTimer, QPoint, QRect, QSize
-from PyQt5.QtGui import QPixmap, QIcon
+from PyQt6.QtCore import Qt, QTimer, QPoint, QRect, QSize
+from PyQt6.QtGui import QPixmap, QIcon, QAction
 from abogen.constants import (
     VOICES_INTERNAL,
     SUPPORTED_LANGUAGES_FOR_SUBTITLE_GENERATION,
@@ -91,7 +90,7 @@ class FlowLayout(QLayout):
         return len(self._item_list)
 
     def expandingDirections(self):
-        return Qt.Orientations(Qt.Orientation(0))
+        return Qt.Orientation(0)
 
     def hasHeightForWidth(self):
         return True
@@ -132,10 +131,10 @@ class FlowLayout(QLayout):
         for item in self._item_list:
             style = self.parentWidget().style() if self.parentWidget() else QStyle()
             layout_spacing_x = style.layoutSpacing(
-                QSizePolicy.PushButton, QSizePolicy.PushButton, Qt.Horizontal
+                QSizePolicy.ControlType.PushButton, QSizePolicy.ControlType.PushButton, Qt.Orientation.Horizontal
             )
             layout_spacing_y = style.layoutSpacing(
-                QSizePolicy.PushButton, QSizePolicy.PushButton, Qt.Vertical
+                QSizePolicy.ControlType.PushButton, QSizePolicy.ControlType.PushButton, Qt.Orientation.Vertical
             )
             space_x = spacing if spacing >= 0 else layout_spacing_x
             space_y = spacing if spacing >= 0 else layout_spacing_y
@@ -163,7 +162,7 @@ class VoiceMixer(QWidget):
         super().__init__()
         self.voice_name = voice_name
         self.setFixedWidth(VOICE_MIXER_WIDTH)
-        self.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
+        self.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding)
 
         # TODO Set CSS for rounded corners
         # self.setObjectName("VoiceMixer")
@@ -173,7 +172,7 @@ class VoiceMixer(QWidget):
 
         # Name label at the top
         name = voice_name
-        layout.addWidget(QLabel(name), alignment=Qt.AlignCenter)
+        layout.addWidget(QLabel(name), alignment=Qt.AlignmentFlag.AlignCenter)
 
         # Voice name label with gender icon
         is_female = self.voice_name in VOICES_INTERNAL and self.voice_name[1] == "f"
@@ -181,7 +180,7 @@ class VoiceMixer(QWidget):
         # Icons layout (flag and gender)
         icons_layout = QHBoxLayout()
         icons_layout.setSpacing(3)
-        icons_layout.setAlignment(Qt.AlignCenter)  # Center the icons horizontally
+        icons_layout.setAlignment(Qt.AlignmentFlag.AlignCenter)  # Center the icons horizontally
 
         # Flag icon
         flag_icon_path = get_resource_path(
@@ -194,11 +193,11 @@ class VoiceMixer(QWidget):
         gender_label = QLabel()
         flag_pixmap = QPixmap(flag_icon_path)
         flag_label.setPixmap(
-            flag_pixmap.scaled(16, 16, Qt.KeepAspectRatio, Qt.SmoothTransformation)
+            flag_pixmap.scaled(16, 16, Qt.AspectRatioMode.KeepAspectRatio, Qt.TransformationMode.SmoothTransformation)
         )
         gender_pixmap = QPixmap(gender_icon_path)
         gender_label.setPixmap(
-            gender_pixmap.scaled(16, 16, Qt.KeepAspectRatio, Qt.SmoothTransformation)
+            gender_pixmap.scaled(16, 16, Qt.AspectRatioMode.KeepAspectRatio, Qt.TransformationMode.SmoothTransformation)
         )
         icons_layout.addWidget(flag_label)
         icons_layout.addWidget(gender_label)
@@ -210,7 +209,7 @@ class VoiceMixer(QWidget):
         self.checkbox = QCheckBox()
         self.checkbox.setChecked(initial_status)
         self.checkbox.stateChanged.connect(self.toggle_inputs)
-        layout.addWidget(self.checkbox, alignment=Qt.AlignCenter)
+        layout.addWidget(self.checkbox, alignment=Qt.AlignmentFlag.AlignCenter)
 
         # Spinbox and slider
         self.spin_box = QDoubleSpinBox()
@@ -219,10 +218,10 @@ class VoiceMixer(QWidget):
         self.spin_box.setDecimals(2)
         self.spin_box.setValue(initial_weight)
 
-        self.slider = QSlider(Qt.Vertical)
+        self.slider = QSlider(Qt.Orientation.Vertical)
         self.slider.setRange(0, 100)
         self.slider.setValue(int(initial_weight * 100))
-        self.slider.setSizePolicy(QSizePolicy.Fixed, QSizePolicy.Expanding)
+        self.slider.setSizePolicy(QSizePolicy.Policy.Fixed, QSizePolicy.Policy.Expanding)
         self.slider.setFixedWidth(SLIDER_WIDTH)
 
         # Fix slider in Windows
@@ -249,17 +248,17 @@ class VoiceMixer(QWidget):
         # Layout for slider and labels
         slider_layout = QVBoxLayout()
         slider_layout.addWidget(self.spin_box)
-        slider_layout.addWidget(QLabel("1", alignment=Qt.AlignCenter))
+        slider_layout.addWidget(QLabel("1", alignment=Qt.AlignmentFlag.AlignCenter))
 
         slider_center_layout = QHBoxLayout()
-        slider_center_layout.addWidget(self.slider, alignment=Qt.AlignHCenter)
+        slider_center_layout.addWidget(self.slider, alignment=Qt.AlignmentFlag.AlignHCenter)
         slider_center_layout.setContentsMargins(0, 0, 0, 0)
 
         slider_center_widget = QWidget()
         slider_center_widget.setLayout(slider_center_layout)
 
         slider_layout.addWidget(slider_center_widget, stretch=1)
-        slider_layout.addWidget(QLabel("0", alignment=Qt.AlignCenter))
+        slider_layout.addWidget(QLabel("0", alignment=Qt.AlignmentFlag.AlignCenter))
         slider_layout.setStretch(2, 1)
 
         layout.addLayout(slider_layout, stretch=1)
@@ -307,9 +306,9 @@ class HoverLabel(QLabel):
             """
         )
         # Make sure the entire button is clickable, not just the text
-        self.delete_button.setFocusPolicy(Qt.NoFocus)
-        self.delete_button.setAttribute(Qt.WA_TransparentForMouseEvents, False)
-        self.delete_button.setCursor(Qt.PointingHandCursor)
+        self.delete_button.setFocusPolicy(Qt.FocusPolicy.NoFocus)
+        self.delete_button.setAttribute(Qt.WidgetAttribute.WA_TransparentForMouseEvents, False)
+        self.delete_button.setCursor(Qt.CursorShape.PointingHandCursor)
         self.delete_button.hide()
 
     def resizeEvent(self, event):
@@ -357,7 +356,7 @@ class VoiceFormulaDialog(QDialog):
         if parent is not None and hasattr(parent, "subtitle_combo"):
             self.subtitle_combo = parent.subtitle_combo
         # Create main container layout with profile section and mixer section
-        splitter = QSplitter(Qt.Horizontal)
+        splitter = QSplitter(Qt.Orientation.Horizontal)
         # Profile section
         profile_widget = QWidget()
         profile_layout = QVBoxLayout(profile_widget)
@@ -371,8 +370,8 @@ class VoiceFormulaDialog(QDialog):
         profile_layout.addLayout(header_layout)
         # Profile list
         self.profile_list = QListWidget()
-        self.profile_list.setSelectionMode(QListWidget.SingleSelection)
-        self.profile_list.setSelectionBehavior(QListWidget.SelectRows)
+        self.profile_list.setSelectionMode(QListWidget.SelectionMode.SingleSelection)
+        self.profile_list.setSelectionBehavior(QListWidget.SelectionBehavior.SelectRows)
         self.profile_list.setStyleSheet(
             "QListWidget::item:selected { background: palette(highlight); color: palette(highlighted-text); }"
         )
@@ -388,7 +387,7 @@ class VoiceFormulaDialog(QDialog):
             idx = list(profiles.keys()).index(self.current_profile)
             self.profile_list.setCurrentRow(idx)
         profile_layout.addWidget(self.profile_list)
-        self.profile_list.setContextMenuPolicy(Qt.CustomContextMenu)
+        self.profile_list.setContextMenuPolicy(Qt.ContextMenuPolicy.CustomContextMenu)
         self.profile_list.customContextMenuRequested.connect(
             self.show_profile_context_menu
         )
@@ -409,7 +408,7 @@ class VoiceFormulaDialog(QDialog):
 
         self.setWindowTitle("Voice Mixer")
         self.setWindowFlags(
-            Qt.Window | Qt.WindowCloseButtonHint | Qt.WindowMaximizeButtonHint
+            Qt.WindowType.Window | Qt.WindowType.WindowCloseButtonHint | Qt.WindowType.WindowMaximizeButtonHint
         )
         self.setMinimumSize(MIN_WINDOW_WIDTH, MIN_WINDOW_HEIGHT)
         self.resize(INITIAL_WINDOW_WIDTH, INITIAL_WINDOW_HEIGHT)
@@ -468,21 +467,21 @@ class VoiceFormulaDialog(QDialog):
 
         # Separator
         separator = QFrame()
-        separator.setFrameShadow(QFrame.Sunken)
+        separator.setFrameShadow(QFrame.Shadow.Sunken)
         mixer_layout.addWidget(separator)
 
         # Voice list scroll area
         self.scroll_area = QScrollArea()
         self.scroll_area.setWidgetResizable(True)
-        self.scroll_area.setHorizontalScrollBarPolicy(Qt.ScrollBarAsNeeded)
-        self.scroll_area.setVerticalScrollBarPolicy(Qt.ScrollBarAsNeeded)
+        self.scroll_area.setHorizontalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAsNeeded)
+        self.scroll_area.setVerticalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAsNeeded)
         self.scroll_area.viewport().installEventFilter(self)
 
         self.voice_list_widget = QWidget()
         self.voice_list_layout = QHBoxLayout()
         self.voice_list_widget.setLayout(self.voice_list_layout)
         self.voice_list_widget.setSizePolicy(
-            QSizePolicy.Expanding, QSizePolicy.Expanding
+            QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding
         )
         self.scroll_area.setWidget(self.voice_list_widget)
         mixer_layout.addWidget(self.scroll_area, stretch=1)
@@ -497,6 +496,9 @@ class VoiceFormulaDialog(QDialog):
         ok_button.setDefault(True)
         ok_button.setFocus()
 
+        # Connect buttons
+        clear_all_button.clicked.connect(self.clear_all_voices)
+        ok_button.clicked.connect(self.accept)
         # Connect buttons
         clear_all_button.clicked.connect(self.clear_all_voices)
         ok_button.clicked.connect(self.accept)
@@ -533,7 +535,7 @@ class VoiceFormulaDialog(QDialog):
 
     def keyPressEvent(self, event):
         # Bind Delete key to delete_profile when a profile is selected
-        if event.key() == Qt.Key_Delete and self.profile_list.hasFocus():
+        if event.key() == Qt.Key.Key_Delete and self.profile_list.hasFocus():
             item = self.profile_list.currentItem()
             if item:
                 self.delete_profile(item)
@@ -562,10 +564,10 @@ class VoiceFormulaDialog(QDialog):
                 self,
                 "Unsaved Changes",
                 msg,
-                QMessageBox.Save | QMessageBox.Discard | QMessageBox.Cancel,
-                QMessageBox.Save,
+                QMessageBox.StandardButton.Save | QMessageBox.StandardButton.Discard | QMessageBox.StandardButton.Cancel,
+                QMessageBox.StandardButton.Save,
             )
-            if ret == QMessageBox.Save:
+            if ret == QMessageBox.StandardButton.Save:
                 # Save all using stored states
                 profiles = load_profiles()
                 for i in dirty_indices:
@@ -590,7 +592,7 @@ class VoiceFormulaDialog(QDialog):
                 self.update_profile_save_buttons()
                 self.update_profile_list_colors()
                 return True
-            elif ret == QMessageBox.Discard:
+            elif ret == QMessageBox.StandardButton.Discard:
                 # Discard all modifications
                 self._profile_states.clear()
                 for i in dirty_indices:
@@ -612,17 +614,17 @@ class VoiceFormulaDialog(QDialog):
         else:
             # Fallback to original logic for 0 or 1 dirty profile
             box = QMessageBox(self)
-            box.setIcon(QMessageBox.Warning)
+            box.setIcon(QMessageBox.Icon.Warning)
             box.setWindowTitle("Unsaved Changes")
             box.setText(
                 "You have unsaved changes in your profile. Do you want to save the changes?"
             )
             box.setStandardButtons(
-                QMessageBox.Save | QMessageBox.Discard | QMessageBox.Cancel
+                QMessageBox.StandardButton.Save | QMessageBox.StandardButton.Discard | QMessageBox.StandardButton.Cancel
             )
-            box.setDefaultButton(QMessageBox.Save)
-            ret = box.exec_()
-            if ret == QMessageBox.Save:
+            box.setDefaultButton(QMessageBox.StandardButton.Save)
+            ret = box.exec()
+            if ret == QMessageBox.StandardButton.Save:
                 for i in range(self.profile_list.count()):
                     item = self.profile_list.item(i)
                     name = item.text().lstrip("*")
@@ -636,7 +638,7 @@ class VoiceFormulaDialog(QDialog):
                 if hasattr(parent, "populate_profiles_in_voice_combo"):
                     parent.populate_profiles_in_voice_combo()
                 return True
-            elif ret == QMessageBox.Discard:
+            elif ret == QMessageBox.StandardButton.Discard:
                 profiles = load_profiles()
                 for i in range(self.profile_list.count()):
                     item = self.profile_list.item(i)
@@ -717,7 +719,7 @@ class VoiceFormulaDialog(QDialog):
         return voice_mixer
 
     def handle_voice_checkbox(self, voice_mixer, state):
-        if state == Qt.Checked:
+        if state == Qt.CheckState.Checked.value:
             self.last_enabled_voice = voice_mixer.voice_name
         self.update_weighted_sums()
 
@@ -767,7 +769,7 @@ class VoiceFormulaDialog(QDialog):
                     f'<b><span style="color:{COLORS.get("BLUE")}">{name}: {percentage:.1f}%</span></b>',
                     name,
                 )
-                voice_label.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Preferred)
+                voice_label.setSizePolicy(QSizePolicy.Policy.Preferred, QSizePolicy.Policy.Preferred)
                 voice_label.delete_button.clicked.connect(
                     lambda _, vn=name: self.disable_voice_by_name(vn)
                 )
@@ -787,7 +789,7 @@ class VoiceFormulaDialog(QDialog):
             mixer.checkbox.setChecked(False)
 
     def eventFilter(self, source, event):
-        if source is self.scroll_area.viewport() and event.type() == event.Wheel:
+        if source is self.scroll_area.viewport() and event.type() == event.Type.Wheel:
             # Skip if over an enabled slider
             if any(
                 mixer.slider.underMouse() and mixer.slider.isEnabled()
@@ -890,10 +892,10 @@ class VoiceFormulaDialog(QDialog):
             self,
             "Invalid Profiles",
             msg,
-            QMessageBox.Yes | QMessageBox.Cancel,
-            QMessageBox.Yes,
+            QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.Cancel,
+            QMessageBox.StandardButton.Yes,
         )
-        if reply == QMessageBox.Yes:
+        if reply == QMessageBox.StandardButton.Yes:
             for i, name in reversed(zero):
                 self.profile_list.takeItem(i)
                 delete_profile(name)
@@ -980,8 +982,8 @@ class VoiceFormulaDialog(QDialog):
         super().closeEvent(event)
 
     def _parse_rgba_to_qcolor(self, rgba_str):
-        from PyQt5.QtCore import Qt
-        from PyQt5.QtGui import QColor
+        from PyQt6.QtCore import Qt
+        from PyQt6.QtGui import QColor
 
         """Helper to convert 'rgba(R,G,B,A_float)' string to QColor."""
         match = re.match(r"rgba\((\d+),\s*(\d+),\s*(\d+),\s*([\d.]+)\)", rgba_str)
@@ -1136,9 +1138,9 @@ class VoiceFormulaDialog(QDialog):
                     msg += f"\nThis will overwrite an existing profile."
                 msg += "\nContinue?"
                 reply = QMessageBox.question(
-                    self, "Import Profile", msg, QMessageBox.Yes | QMessageBox.No
+                    self, "Import Profile", msg, QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No
                 )
-                if reply != QMessageBox.Yes:
+                if reply != QMessageBox.StandardButton.Yes:
                     return
                 profiles.update(imported_profiles)
                 save_profiles(profiles)
@@ -1153,9 +1155,9 @@ class VoiceFormulaDialog(QDialog):
                     msg += f"\n{len(collisions)} profile(s) will be overwritten."
                 msg += "\nContinue?"
                 reply = QMessageBox.question(
-                    self, "Import Profiles", msg, QMessageBox.Yes | QMessageBox.No
+                    self, "Import Profiles", msg, QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No
                 )
-                if reply != QMessageBox.Yes:
+                if reply != QMessageBox.StandardButton.Yes:
                     return
                 profiles.update(imported_profiles)
                 save_profiles(profiles)
@@ -1196,7 +1198,7 @@ class VoiceFormulaDialog(QDialog):
         menu.addAction(dup_act)
         menu.addAction(export_act)
         menu.addAction(delete_act)
-        act = menu.exec_(self.profile_list.viewport().mapToGlobal(pos))
+        act = menu.exec(self.profile_list.viewport().mapToGlobal(pos))
         if act == rename_act:
             self.rename_profile(item)
         elif act == delete_act:
@@ -1323,9 +1325,9 @@ class VoiceFormulaDialog(QDialog):
             self,
             "Delete Profile",
             f"Delete profile '{name}'?",
-            QMessageBox.Yes | QMessageBox.No,
+            QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No,
         )
-        if reply == QMessageBox.Yes:
+        if reply == QMessageBox.StandardButton.Yes:
             delete_profile(name)
             row = self.profile_list.row(item)
             self.profile_list.takeItem(row)
@@ -1378,7 +1380,7 @@ class VoiceFormulaDialog(QDialog):
                 self.profile_list.setItemWidget(item, widget)
 
     def update_profile_list_colors(self):
-        from PyQt5.QtCore import Qt
+        from PyQt6.QtCore import Qt
 
         profiles = load_profiles()
         for i in range(self.profile_list.count()):
@@ -1386,13 +1388,13 @@ class VoiceFormulaDialog(QDialog):
             name = item.text().lstrip("*")
             if self._virtual_new_profile and name == "New profile":
                 color = self._parse_rgba_to_qcolor(COLORS.get("YELLOW_BACKGROUND"))
-                item.setData(Qt.BackgroundRole, color)
+                item.setData(Qt.ItemDataRole.BackgroundRole, color)
             elif item.text().startswith("*"):
                 color = self._parse_rgba_to_qcolor(COLORS.get("YELLOW_BACKGROUND"))
-                item.setData(Qt.BackgroundRole, color)
+                item.setData(Qt.ItemDataRole.BackgroundRole, color)
             else:
                 item.setData(
-                    Qt.BackgroundRole, self.profile_list.palette().base().color()
+                    Qt.ItemDataRole.BackgroundRole, self.profile_list.palette().base().color()
                 )
                 weights = profiles.get(name, {}).get("voices", [])
                 total = 0
@@ -1406,7 +1408,7 @@ class VoiceFormulaDialog(QDialog):
                             total += entry[1]
                 if total == 0:
                     color = self._parse_rgba_to_qcolor(COLORS.get("RED_BACKGROUND"))
-                    item.setData(Qt.BackgroundRole, color)
+                    item.setData(Qt.ItemDataRole.BackgroundRole, color)
         self.update_profile_save_buttons()
 
     def preview_current_mix(self):
diff --git a/pyproject.toml b/pyproject.toml
index b668986..a167281 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -13,7 +13,7 @@ license = "MIT"
 requires-python = ">=3.10, <3.13"
 keywords = ["audiobook", "epub", "pdf", "text-to-speech", "subtitle", "tts", "kokoro", "accessibility", "book-converter", "voice-synthesis", "multilingual", "chapter-management", "subtitles", "content-creation", "media-generation"]
 dependencies = [
-    "PyQt5>=5.15.11",
+    "PyQt6>=6.10.0",
     "kokoro>=0.9.4",
     "misaki[zh]>=0.9.4",
     "ebooklib>=0.19",