diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index a22408c..2dadc1f 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -173,3 +173,33 @@ jobs:
           files: Reclass-x86_64.AppImage
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  linux-qt5:
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Install Qt5
+        uses: jurplel/install-qt-action@v4
+        with:
+          version: '5.15.2'
+          cache: true
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y ninja-build libgl1-mesa-dev
+
+      - name: Configure
+        run: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
+
+      - name: Build
+        run: cmake --build build
+
+      - name: Test
+        run: xvfb-run ctest --test-dir build --output-on-failure --exclude-regex "test_editor"
+        env:
+          QT_QPA_PLATFORM: offscreen
diff --git a/src/main.cpp b/src/main.cpp
index b01e3c9..33c1df7 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,4 +1,5 @@
 #include "mainwindow.h"
+#include "qt5compat.h"
 #include "generator.h"
 #include "mcp/mcp_bridge.h"
 #include <QApplication>
@@ -359,14 +360,14 @@ QIcon MainWindow::makeIcon(const QString& svgPath) {
 void MainWindow::createMenus() {
     // File
     auto* file = m_titleBar->menuBar()->addMenu("&File");
-    file->addAction("&New", QKeySequence::New, this, &MainWindow::newDocument);
-    file->addAction("New &Tab", QKeySequence(Qt::CTRL | Qt::Key_T), this, &MainWindow::newFile);
-    file->addAction(makeIcon(":/vsicons/folder-opened.svg"), "&Open...", QKeySequence::Open, this, &MainWindow::openFile);
+    rcx::compat::addAction(file, "&New", QKeySequence::New, this, &MainWindow::newDocument);
+    rcx::compat::addAction(file, "New &Tab", QKeySequence(Qt::CTRL | Qt::Key_T), this, &MainWindow::newFile);
+    rcx::compat::addAction(file, makeIcon(":/vsicons/folder-opened.svg"), "&Open...", QKeySequence::Open, this, &MainWindow::openFile);
     file->addSeparator();
-    file->addAction(makeIcon(":/vsicons/save.svg"), "&Save", QKeySequence::Save, this, &MainWindow::saveFile);
-    file->addAction(makeIcon(":/vsicons/save-as.svg"), "Save &As...", QKeySequence::SaveAs, this, &MainWindow::saveFileAs);
+    rcx::compat::addAction(file, makeIcon(":/vsicons/save.svg"), "&Save", QKeySequence::Save, this, &MainWindow::saveFile);
+    rcx::compat::addAction(file, makeIcon(":/vsicons/save-as.svg"), "Save &As...", QKeySequence::SaveAs, this, &MainWindow::saveFileAs);
     file->addSeparator();
-    file->addAction("&Unload Project", QKeySequence(Qt::CTRL | Qt::Key_W), this, &MainWindow::closeFile);
+    rcx::compat::addAction(file, "&Unload Project", QKeySequence(Qt::CTRL | Qt::Key_W), this, &MainWindow::closeFile);
     file->addSeparator();
     file->addAction(makeIcon(":/vsicons/export.svg"), "Export &C++ Header...", this, &MainWindow::exportCpp);
     file->addSeparator();
@@ -374,12 +375,12 @@ void MainWindow::createMenus() {
     file->addSeparator();
     file->addAction(makeIcon(":/vsicons/settings-gear.svg"), "&Options...", this, &MainWindow::showOptionsDialog);
     file->addSeparator();
-    file->addAction(makeIcon(":/vsicons/close.svg"), "E&xit", QKeySequence(Qt::Key_Close), this, &QMainWindow::close);
+    rcx::compat::addAction(file, makeIcon(":/vsicons/close.svg"), "E&xit", QKeySequence(Qt::Key_Close), this, &QMainWindow::close);
 
     // Edit
     auto* edit = m_titleBar->menuBar()->addMenu("&Edit");
-    edit->addAction(makeIcon(":/vsicons/arrow-left.svg"), "&Undo", QKeySequence::Undo, this, &MainWindow::undo);
-    edit->addAction(makeIcon(":/vsicons/arrow-right.svg"), "&Redo", QKeySequence::Redo, this, &MainWindow::redo);
+    rcx::compat::addAction(edit, makeIcon(":/vsicons/arrow-left.svg"), "&Undo", QKeySequence::Undo, this, &MainWindow::undo);
+    rcx::compat::addAction(edit, makeIcon(":/vsicons/arrow-right.svg"), "&Redo", QKeySequence::Redo, this, &MainWindow::redo);
     edit->addSeparator();
     edit->addAction("&Type Aliases...", this, &MainWindow::showTypeAliasesDialog);
 
diff --git a/src/qt5compat.h b/src/qt5compat.h
new file mode 100644
index 0000000..89dbc30
--- /dev/null
+++ b/src/qt5compat.h
@@ -0,0 +1,37 @@
+#pragma once
+#include <QtGlobal>
+#include <QMenu>
+#include <QAction>
+#include <QKeySequence>
+#include <QIcon>
+
+namespace rcx { namespace compat {
+
+// QMenu::addAction with shortcut — Qt6 puts shortcut before receiver,
+// Qt5 puts it after.  These normalize to the Qt6 argument order.
+
+template<typename Obj, typename Func>
+inline QAction* addAction(QMenu* menu, const QString& text,
+                          const QKeySequence& shortcut,
+                          const Obj* receiver, Func slot)
+{
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    return menu->addAction(text, shortcut, receiver, slot);
+#else
+    return menu->addAction(text, receiver, slot, shortcut);
+#endif
+}
+
+template<typename Obj, typename Func>
+inline QAction* addAction(QMenu* menu, const QIcon& icon, const QString& text,
+                          const QKeySequence& shortcut,
+                          const Obj* receiver, Func slot)
+{
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    return menu->addAction(icon, text, shortcut, receiver, slot);
+#else
+    return menu->addAction(icon, text, receiver, slot, shortcut);
+#endif
+}
+
+}} // namespace rcx::compat