diff --git a/examples/corelib/time/calendarbackendplugin/application/main.cpp b/examples/corelib/time/calendarbackendplugin/application/main.cpp
index e270bb194b2..0aa35451829 100644
--- a/examples/corelib/time/calendarbackendplugin/application/main.cpp
+++ b/examples/corelib/time/calendarbackendplugin/application/main.cpp
@@ -7,6 +7,7 @@
 #include <QCalendar>
 #include <QCalendarWidget>
 #include <QCommandLineParser>
+#include <QDebug>
 #include <QPluginLoader>
 
 int main(int argc, char *argv[])
diff --git a/examples/qtconcurrent/wordcount/main.cpp b/examples/qtconcurrent/wordcount/main.cpp
index 4175641ce93..b157aabe47c 100644
--- a/examples/qtconcurrent/wordcount/main.cpp
+++ b/examples/qtconcurrent/wordcount/main.cpp
@@ -3,9 +3,11 @@
 
 #include <QtWidgets/qfiledialog.h>
 #include <QtWidgets/qapplication.h>
+#include <QtCore/qdebug.h>
 #include <QtCore/qmimedatabase.h>
 #include <QtCore/qelapsedtimer.h>
 #include <QtConcurrent/qtconcurrentmap.h>
+#include <QtCore/qtextstream.h>
 
 typedef QMap<QString, int> WordCount;
 
diff --git a/examples/sql/sqlbrowser/main.cpp b/examples/sql/sqlbrowser/main.cpp
index b3fa8af1429..4cfd5db44db 100644
--- a/examples/sql/sqlbrowser/main.cpp
+++ b/examples/sql/sqlbrowser/main.cpp
@@ -4,6 +4,7 @@
 #include "browser.h"
 
 #include <QApplication>
+#include <QDebug>
 #include <QMainWindow>
 #include <QMenu>
 #include <QMenuBar>
diff --git a/examples/widgets/graphicsview/chip/chip.cpp b/examples/widgets/graphicsview/chip/chip.cpp
index c1a539eddba..c67c5beb2e4 100644
--- a/examples/widgets/graphicsview/chip/chip.cpp
+++ b/examples/widgets/graphicsview/chip/chip.cpp
@@ -6,6 +6,7 @@
 #include <QGraphicsSceneMouseEvent>
 #include <QPainter>
 #include <QStyleOptionGraphicsItem>
+#include <QVarLengthArray>
 
 Chip::Chip(const QColor &color, int x, int y)
 {
diff --git a/examples/widgets/itemviews/editabletreemodel/mainwindow.cpp b/examples/widgets/itemviews/editabletreemodel/mainwindow.cpp
index cf88932cdb0..75d7eb7e73c 100644
--- a/examples/widgets/itemviews/editabletreemodel/mainwindow.cpp
+++ b/examples/widgets/itemviews/editabletreemodel/mainwindow.cpp
@@ -4,6 +4,7 @@
 #include "mainwindow.h"
 #include "treemodel.h"
 
+#include <QDebug>
 #include <QFile>
 
 using namespace Qt::StringLiterals;
diff --git a/examples/xml/dombookmarks/xbeltree.cpp b/examples/xml/dombookmarks/xbeltree.cpp
index eff2fea8f04..ab158e2c3fd 100644
--- a/examples/xml/dombookmarks/xbeltree.cpp
+++ b/examples/xml/dombookmarks/xbeltree.cpp
@@ -14,6 +14,7 @@
 #  include <QContextMenuEvent>
 #endif
 
+#include <QTextStream>
 #include <QUrl>
 
 using namespace Qt::StringLiterals;
diff --git a/src/corelib/io/qdebug.h b/src/corelib/io/qdebug.h
index 9cfd461870b..4af152440c7 100644
--- a/src/corelib/io/qdebug.h
+++ b/src/corelib/io/qdebug.h
@@ -11,6 +11,7 @@
 
 #include <QtCore/qcompare.h>
 #include <QtCore/qcontainerfwd.h>
+#include <QtCore/qfloat16.h>
 #include <QtCore/qtextstream.h>
 #include <QtCore/qttypetraits.h>
 #include <QtCore/qtypes.h>
diff --git a/src/corelib/kernel/qcoreapplication.h b/src/corelib/kernel/qcoreapplication.h
index 65eaf50e8b3..e0253afa645 100644
--- a/src/corelib/kernel/qcoreapplication.h
+++ b/src/corelib/kernel/qcoreapplication.h
@@ -15,9 +15,6 @@
 #include <QtCore/qscopedpointer.h>
 #endif
 #include <QtCore/qnativeinterface.h>
-#ifndef QT_NO_DEBUGSTREAM
-#include <QtCore/qdebug.h>
-#endif
 
 #ifndef QT_NO_QOBJECT
 #if defined(Q_OS_WIN) && !defined(tagMSG)
@@ -29,6 +26,7 @@ QT_BEGIN_NAMESPACE
 
 
 class QCoreApplicationPrivate;
+class QDebug;
 class QTranslator;
 #if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
 class QPostEventList;
diff --git a/src/corelib/serialization/qcborcommon.h b/src/corelib/serialization/qcborcommon.h
index bd7a93dfe70..202bc49278d 100644
--- a/src/corelib/serialization/qcborcommon.h
+++ b/src/corelib/serialization/qcborcommon.h
@@ -6,7 +6,6 @@
 
 #include <QtCore/qobjectdefs.h>
 #include <QtCore/qmetatype.h>
-#include <QtCore/qdebug.h>
 
 #if 0
 #pragma qt_class(QtCborCommon)
@@ -20,6 +19,8 @@
 
 QT_BEGIN_NAMESPACE
 
+class QDebug;
+
 enum class QCborSimpleType : quint8 {
     False = 20,
     True = 21,
diff --git a/src/corelib/serialization/qcborvalue.cpp b/src/corelib/serialization/qcborvalue.cpp
index 9581015dc11..e9b7d5b71b6 100644
--- a/src/corelib/serialization/qcborvalue.cpp
+++ b/src/corelib/serialization/qcborvalue.cpp
@@ -15,6 +15,7 @@
 #include "qcborstreamwriter.h"
 #endif
 
+#include <QtCore/qdebug.h>
 #include <qendian.h>
 #include <qlocale.h>
 #include <qdatetime.h>
diff --git a/src/corelib/thread/qfutureinterface.cpp b/src/corelib/thread/qfutureinterface.cpp
index 280615bf76a..7f1b2bef154 100644
--- a/src/corelib/thread/qfutureinterface.cpp
+++ b/src/corelib/thread/qfutureinterface.cpp
@@ -897,8 +897,8 @@ void QFutureInterfaceBase::setContinuation(std::function<void(const QFutureInter
     // future's data stays alive.
     if (d->continuationState != QFutureInterfaceBasePrivate::Cleaned) {
         if (d->continuation) {
-            qWarning() << "Adding a continuation to a future which already has a continuation. "
-                          "The existing continuation is overwritten.";
+            qWarning("Adding a continuation to a future which already has a continuation. "
+                     "The existing continuation is overwritten.");
         }
         d->continuation = std::move(func);
         d->continuationData = continuationFutureData;
diff --git a/src/corelib/time/qtimezonelocale.cpp b/src/corelib/time/qtimezonelocale.cpp
index 21002373d7a..1ea1f40b701 100644
--- a/src/corelib/time/qtimezonelocale.cpp
+++ b/src/corelib/time/qtimezonelocale.cpp
@@ -245,8 +245,9 @@ const MetaZoneData *metaZoneDataFor(const MetaZoneData *from, QLocale::Territory
         // Fall back to World (if territory itself isn't World).
     } while (std::exchange(land, QLocale::World) != QLocale::World);
 
-    qWarning() << "Metazone" << from->metaZoneId() << "lacks World data for"
-               << QLocale::territoryToString(territory);
+    qWarning("Metazone %s lacks World data for %ls",
+             from->metaZoneId().constData(),
+             qUtf16Printable(QLocale::territoryToString(territory)));
     return nullptr;
 }
 
diff --git a/src/gui/accessible/qaccessible.h b/src/gui/accessible/qaccessible.h
index 9986689ffed..b552914ee6f 100644
--- a/src/gui/accessible/qaccessible.h
+++ b/src/gui/accessible/qaccessible.h
@@ -15,7 +15,6 @@
 #if QT_CONFIG(accessibility)
 
 #include <QtCore/qcoreapplication.h>
-#include <QtCore/qdebug.h>
 #include <QtCore/qglobal.h>
 #include <QtCore/qlist.h>
 #include <QtCore/qobject.h>
@@ -28,6 +27,7 @@
 
 QT_BEGIN_NAMESPACE
 
+class QDebug;
 class QAccessibleInterface;
 class QAccessibleEvent;
 class QWindow;
diff --git a/src/gui/vulkan/qvulkaninstance.h b/src/gui/vulkan/qvulkaninstance.h
index 221f605fa2a..819751025be 100644
--- a/src/gui/vulkan/qvulkaninstance.h
+++ b/src/gui/vulkan/qvulkaninstance.h
@@ -48,7 +48,6 @@ typedef int VkDebugReportObjectTypeEXT;
 #if __has_include(<vulkan/vulkan.h>) || defined(Q_QDOC)
 
 #include <QtCore/qbytearraylist.h>
-#include <QtCore/qdebug.h>
 #include <QtCore/qhashfunctions.h>
 #include <QtCore/qlist.h>
 #include <QtCore/qscopedpointer.h>
@@ -56,6 +55,8 @@ typedef int VkDebugReportObjectTypeEXT;
 
 QT_BEGIN_NAMESPACE
 
+class QDebug;
+
 class QVulkanInstancePrivate;
 class QPlatformVulkanInstance;
 class QVulkanFunctions;
diff --git a/src/network/access/qhttpmultipart.cpp b/src/network/access/qhttpmultipart.cpp
index 2249dbc05ce..f5b9745c3f3 100644
--- a/src/network/access/qhttpmultipart.cpp
+++ b/src/network/access/qhttpmultipart.cpp
@@ -4,6 +4,7 @@
 #include "qhttpmultipart.h"
 #include "qhttpmultipart_p.h"
 #include "QtCore/qdatetime.h" // for initializing the random number generator with QTime
+#include <QtCore/qdebug.h>
 #include "QtCore/qmutex.h"
 #include "QtCore/qrandom.h"
 
diff --git a/src/network/access/qnetworkrequest.h b/src/network/access/qnetworkrequest.h
index fa312bfe6f7..5b687785593 100644
--- a/src/network/access/qnetworkrequest.h
+++ b/src/network/access/qnetworkrequest.h
@@ -13,6 +13,8 @@
 
 #include <QtCore/q26numeric.h>
 
+#include <chrono>
+
 QT_BEGIN_NAMESPACE
 
 class QSslConfiguration;
diff --git a/src/network/socket/qabstractsocket.cpp b/src/network/socket/qabstractsocket.cpp
index e456d00713b..9976a9c1260 100644
--- a/src/network/socket/qabstractsocket.cpp
+++ b/src/network/socket/qabstractsocket.cpp
@@ -435,6 +435,7 @@
 #include "private/qhostinfo_p.h"
 
 #include <qabstracteventdispatcher.h>
+#include <QtCore/qdebug.h>
 #include <qhostaddress.h>
 #include <qhostinfo.h>
 #include <qmetaobject.h>
diff --git a/src/network/socket/qabstractsocket.h b/src/network/socket/qabstractsocket.h
index 1d5d45096ab..75e35e6de3f 100644
--- a/src/network/socket/qabstractsocket.h
+++ b/src/network/socket/qabstractsocket.h
@@ -13,12 +13,10 @@
 #endif
 #include <QtCore/qiodevice.h>
 #include <QtCore/qobject.h>
-#ifndef QT_NO_DEBUG_STREAM
-#include <QtCore/qdebug.h>
-#endif
 
 QT_BEGIN_NAMESPACE
 
+class QDebug;
 
 class QHostAddress;
 #ifndef QT_NO_NETWORKPROXY
diff --git a/src/network/socket/qlocalsocket.cpp b/src/network/socket/qlocalsocket.cpp
index dff7e428495..39178b42aab 100644
--- a/src/network/socket/qlocalsocket.cpp
+++ b/src/network/socket/qlocalsocket.cpp
@@ -6,6 +6,8 @@
 #include "qlocalsocket.h"
 #include "qlocalsocket_p.h"
 
+#include <QtCore/qdebug.h>
+
 QT_BEGIN_NAMESPACE
 
 /*!
diff --git a/src/network/socket/qlocalsocket.h b/src/network/socket/qlocalsocket.h
index 2bd9689a052..3187bb43b1b 100644
--- a/src/network/socket/qlocalsocket.h
+++ b/src/network/socket/qlocalsocket.h
@@ -8,14 +8,11 @@
 #include <QtCore/qiodevice.h>
 #include <QtNetwork/qabstractsocket.h>
 
-#ifndef QT_NO_DEBUG_STREAM
-#include <QtCore/qdebug.h>
-#endif
-
 QT_REQUIRE_CONFIG(localserver);
 
 QT_BEGIN_NAMESPACE
 
+class QDebug;
 class QLocalSocketPrivate;
 
 class Q_NETWORK_EXPORT QLocalSocket : public QIODevice
diff --git a/src/network/ssl/qsslerror.h b/src/network/ssl/qsslerror.h
index 1f461bf26d7..7103a68df23 100644
--- a/src/network/ssl/qsslerror.h
+++ b/src/network/ssl/qsslerror.h
@@ -6,6 +6,7 @@
 #define QSSLERROR_H
 
 #include <QtNetwork/qtnetworkglobal.h>
+#include <QtCore/qdebug.h>
 #include <QtCore/qvariant.h>
 #include <QtNetwork/qsslcertificate.h>
 
diff --git a/src/opengl/qopengldebug.h b/src/opengl/qopengldebug.h
index 843ab7212ae..f9a40313ad8 100644
--- a/src/opengl/qopengldebug.h
+++ b/src/opengl/qopengldebug.h
@@ -12,7 +12,6 @@
 #include <QtCore/qflags.h>
 #include <QtCore/qlist.h>
 #include <QtCore/qmetatype.h>
-#include <QtCore/qdebug.h>
 #include <QtGui/qopenglcontext.h>
 
 #if defined(Q_QDOC)
@@ -22,6 +21,7 @@ typedef unsigned int GLuint;
 
 QT_BEGIN_NAMESPACE
 
+class QDebug;
 class QOpenGLDebugLogger;
 class QOpenGLDebugLoggerPrivate;
 class QOpenGLDebugMessagePrivate;
diff --git a/src/plugins/platforms/qnx/qqnxkeytranslator.h b/src/plugins/platforms/qnx/qqnxkeytranslator.h
index 5e0dd56e2e3..d48792c10ec 100644
--- a/src/plugins/platforms/qnx/qqnxkeytranslator.h
+++ b/src/plugins/platforms/qnx/qqnxkeytranslator.h
@@ -6,10 +6,6 @@
 
 #include <sys/keycodes.h>
 
-#if defined(QQNXEVENTTHREAD_DEBUG)
-#include <QtCore/QDebug>
-#endif
-
 QT_BEGIN_NAMESPACE
 
 int qtKeyForPrivateUseQnxKey( int key )
@@ -79,7 +75,7 @@ int qtKeyForPrivateUseQnxKey( int key )
 
     default:
 #if defined(QQNXEVENTTHREAD_DEBUG)
-        qDebug() << "QQNX: unknown key for translation:" << key;
+        qDebug("QQNX: unknown key for translation: %d", key);
 #endif
         break;
     }
diff --git a/src/plugins/platforms/wasm/qwasmdom.cpp b/src/plugins/platforms/wasm/qwasmdom.cpp
index b6f6be898ec..71efcee7887 100644
--- a/src/plugins/platforms/wasm/qwasmdom.cpp
+++ b/src/plugins/platforms/wasm/qwasmdom.cpp
@@ -3,6 +3,7 @@
 
 #include "qwasmdom.h"
 
+#include <QtCore/qdebug.h>
 #include <QtCore/qdir.h>
 #include <QtCore/qfile.h>
 #include <QtCore/qpoint.h>
diff --git a/src/testlib/qtesttostring.h b/src/testlib/qtesttostring.h
index e8ada71f9ea..8ea899323f6 100644
--- a/src/testlib/qtesttostring.h
+++ b/src/testlib/qtesttostring.h
@@ -18,6 +18,7 @@
 #include <QtCore/qcborcommon.h>
 #include <QtCore/qcbormap.h>
 #include <QtCore/qcborvalue.h>
+#include <QtCore/qdebug.h>
 #include <QtCore/qdatetime.h>
 #include <QtCore/qmetaobject.h>
 #include <QtCore/qmetatype.h>
diff --git a/src/tools/androidtestrunner/main.cpp b/src/tools/androidtestrunner/main.cpp
index 228aa676f5b..8dd2d550705 100644
--- a/src/tools/androidtestrunner/main.cpp
+++ b/src/tools/androidtestrunner/main.cpp
@@ -4,6 +4,7 @@
 
 #include <QtCore/QCoreApplication>
 #include <QtCore/QDeadlineTimer>
+#include <QtCore/qdebug.h>
 #include <QtCore/QDir>
 #include <QtCore/QHash>
 #include <QtCore/QProcess>