NOISSUE Refactor UpdateChecker and add standalone updater

- Removed unused member variables and methods from UpdateChecker.
- Improved update checking logic by parsing both RSS feed and GitHub releases.
- Introduced Installer class for handling update downloads and installations.
- Added support for various archive formats (.zip, .tar.gz) in Installer.
- Created meshmc-updater executable for standalone update operations.
- Updated CMake configuration to include new updater components.

Signed-off-by: Mehmet Samet Duman <yongdohyun@projecttick.org>

20 files changed, 1017 insertions, 1061 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index cb61eca58c..4abba22dac 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -202,8 +202,14 @@ set(MeshMC_BUILD_ARTIFACT "" CACHE STRING "Artifact name to help the updater ide
 # Build platform.
 set(MeshMC_BUILD_PLATFORM "" CACHE STRING "A short string identifying the platform that this build was built for. Only used by the notification system and to display in the about dialog.")
 
-# Channel list URL
-set(MeshMC_UPDATER_BASE "" CACHE STRING "Base URL for the updater.")
+# Channel list URL (legacy - kept for compatibility)
+set(MeshMC_UPDATER_BASE "" CACHE STRING "Base URL for the legacy GoUpdate system (unused).")
+
+# New updater: RSS feed URL (projt: namespace)
+set(MeshMC_UPDATER_FEED_URL "" CACHE STRING "RSS feed URL for the updater (projt: namespace, e.g. https://projecttick.org/product/meshmc/feed.xml).")
+
+# New updater: GitHub releases API URL
+set(MeshMC_UPDATER_GITHUB_API_URL "" CACHE STRING "GitHub Releases API URL for update verification (e.g. https://api.github.com/repos/Project-Tick/MeshMC/releases/latest).")
 
 # Notification URL
 set(MeshMC_NOTIFICATION_URL "https://projecttick.org/" CACHE STRING "URL for checking for notifications.")
@@ -401,6 +407,7 @@ add_subdirectory(libraries/katabasis) # An OAuth2 library that tried to do too m
 ############################### Built Artifacts ###############################
 
 add_subdirectory(buildconfig)
+add_subdirectory(updater)
 
 # NOTE: this must always be last to appease the CMake deity of quirky install command evaluation order.
 add_subdirectory(launcher)
diff --git a/buildconfig/BuildConfig.cpp.in b/buildconfig/BuildConfig.cpp.in
index e368dc2ffa..e639997526 100644
--- a/buildconfig/BuildConfig.cpp.in
+++ b/buildconfig/BuildConfig.cpp.in
@@ -52,6 +52,8 @@ Config::Config()
     COMPILER_TARGET_SYSTEM_VERSION = "@MeshMC_COMPILER_TARGET_SYSTEM_VERSION@";
     COMPILER_TARGET_SYSTEM_PROCESSOR = "@MeshMC_COMPILER_TARGET_PROCESSOR@";
     UPDATER_BASE = "@MeshMC_UPDATER_BASE@";
+    UPDATER_FEED_URL = "@MeshMC_UPDATER_FEED_URL@";
+    UPDATER_GITHUB_API_URL = "@MeshMC_UPDATER_GITHUB_API_URL@";
     ANALYTICS_ID = "@MeshMC_ANALYTICS_ID@";
     NOTIFICATION_URL = "@MeshMC_NOTIFICATION_URL@";
     FULL_VERSION_STR = "@MeshMC_VERSION_MAJOR@.@MeshMC_VERSION_MINOR@.@MeshMC_VERSION_BUILD@";
@@ -59,11 +61,19 @@ Config::Config()
     GIT_COMMIT = "@MeshMC_GIT_COMMIT@";
     GIT_REFSPEC = "@MeshMC_GIT_REFSPEC@";
     GIT_TAG = "@MeshMC_GIT_TAG@";
-    if(GIT_REFSPEC.startsWith("refs/heads/") && !UPDATER_BASE.isEmpty() && !BUILD_PLATFORM.isEmpty() && VERSION_BUILD >= 0)
+
+    // New updater: enabled when both feed and GitHub API URLs are configured and
+    // a build artifact name is provided for platform-specific asset matching.
+    if (!UPDATER_FEED_URL.isEmpty() && !UPDATER_GITHUB_API_URL.isEmpty() && !BUILD_ARTIFACT.isEmpty())
+    {
+        UPDATER_ENABLED = true;
+    }
+
+    // VERSION_CHANNEL is still populated from the git branch for informational use.
+    if (GIT_REFSPEC.startsWith("refs/heads/"))
     {
         VERSION_CHANNEL = GIT_REFSPEC;
         VERSION_CHANNEL.remove("refs/heads/");
-        UPDATER_ENABLED = true;
     }
     else
     {
diff --git a/buildconfig/BuildConfig.h b/buildconfig/BuildConfig.h
index d96ccaab36..535d9a0502 100644
--- a/buildconfig/BuildConfig.h
+++ b/buildconfig/BuildConfig.h
@@ -56,9 +56,15 @@ public:
     /// A short string identifying this build's platform. For example, "lin64" or "win32".
     QString BUILD_PLATFORM;
 
-    /// URL for the updater's channel
+    /// URL for the updater's channel (legacy, unused)
     QString UPDATER_BASE;
 
+    /// RSS feed URL for the new updater (projt: namespace).
+    QString UPDATER_FEED_URL;
+
+    /// GitHub releases API URL for update verification.
+    QString UPDATER_GITHUB_API_URL;
+
     /// A string containing the build timestamp
     QString BUILD_DATE;
 
diff --git a/launcher/Application.cpp b/launcher/Application.cpp
index 892fb2c14c..874b6ae996 100644
--- a/launcher/Application.cpp
+++ b/launcher/Application.cpp
@@ -937,16 +937,15 @@ void Application::initSubsystems()
     }
 
     // initialize the updater
-    if(BuildConfig.UPDATER_ENABLED)
-    {
-        auto platform = getIdealPlatform(BuildConfig.BUILD_PLATFORM);
-        auto channelUrl = BuildConfig.UPDATER_BASE + platform + "/channels.json";
-        qDebug() << "Initializing updater with platform: " << platform << " -- " << channelUrl;
-        m_updateChecker.reset(new UpdateChecker(
-            m_network, channelUrl,
-            BuildConfig.VERSION_CHANNEL,
-            BuildConfig.VERSION_BUILD));
-        qDebug() << "<> Updater started.";
+    if(BuildConfig.UPDATER_ENABLED && UpdateChecker::isUpdaterSupported())
+    {
+        m_updateChecker.reset(new UpdateChecker(m_network));
+        qDebug() << "<> Updater initialized (feed:" << BuildConfig.UPDATER_FEED_URL
+                 << "| github:" << BuildConfig.UPDATER_GITHUB_API_URL << ").";
+    }
+    else if(BuildConfig.UPDATER_ENABLED)
+    {
+        qDebug() << "<> Updater disabled on this platform/mode.";
     }
 
     // Instance icons
diff --git a/launcher/Application.h b/launcher/Application.h
index 43cc0c25a9..8cd15c02eb 100644
--- a/launcher/Application.h
+++ b/launcher/Application.h
@@ -29,7 +29,7 @@
 #include <QDateTime>
 #include <QUrl>
 #include <QHash>
-#include <updater/GoUpdate.h>
+#include <updater/UpdateChecker.h>
 
 #include <BaseInstance.h>
 
@@ -49,7 +49,6 @@ class AccountList;
 class IconList;
 class QNetworkAccessManager;
 class JavaInstallList;
-class UpdateChecker;
 class BaseProfilerFactory;
 class BaseDetachedToolFactory;
 class TranslationsModel;
diff --git a/launcher/CMakeLists.txt b/launcher/CMakeLists.txt
index c1c0a65507..00b5b6f909 100644
--- a/launcher/CMakeLists.txt
+++ b/launcher/CMakeLists.txt
@@ -148,28 +148,12 @@ set(LAUNCH_SOURCES
     launch/LogModel.h
 )
 
-# Old update system
+# New updater system (replaces the old GoUpdate-based system)
 set(UPDATE_SOURCES
-    updater/GoUpdate.h
-    updater/GoUpdate.cpp
     updater/UpdateChecker.h
     updater/UpdateChecker.cpp
-    updater/DownloadTask.h
-    updater/DownloadTask.cpp
 )
 
-add_unit_test(UpdateChecker
-    SOURCES updater/UpdateChecker_test.cpp
-    LIBS MeshMC_logic
-    DATA updater/testdata
-    )
-
-add_unit_test(DownloadTask
-    SOURCES updater/DownloadTask_test.cpp
-    LIBS MeshMC_logic
-    DATA updater/testdata
-    )
-
 # Rarely used notifications
 set(NOTIFICATIONS_SOURCES
     # Notifications - short warning messages
diff --git a/launcher/UpdateController.cpp b/launcher/UpdateController.cpp
index bb2bd36176..8ab57c5804 100644
--- a/launcher/UpdateController.cpp
+++ b/launcher/UpdateController.cpp
@@ -19,409 +19,60 @@
  *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-#include <QFile>
-#include <QMessageBox>
-#include <FileSystem.h>
-#include <updater/GoUpdate.h>
 #include "UpdateController.h"
+
 #include <QApplication>
-#include <thread>
-#include <chrono>
-#include <LocalPeer.h>
+#include <QDebug>
+#include <QDir>
+#include <QMessageBox>
+#include <QProcess>
 
 #include "BuildConfig.h"
+#include "FileSystem.h"
 
-
-// from <sys/stat.h>
-#ifndef S_IRUSR
-#define __S_IREAD 0400         /* Read by owner.  */
-#define __S_IWRITE 0200        /* Write by owner.  */
-#define __S_IEXEC 0100         /* Execute by owner.  */
-#define S_IRUSR __S_IREAD      /* Read by owner.  */
-#define S_IWUSR __S_IWRITE     /* Write by owner.  */
-#define S_IXUSR __S_IEXEC      /* Execute by owner.  */
-
-#define S_IRGRP (S_IRUSR >> 3) /* Read by group.  */
-#define S_IWGRP (S_IWUSR >> 3) /* Write by group.  */
-#define S_IXGRP (S_IXUSR >> 3) /* Execute by group.  */
-
-#define S_IROTH (S_IRGRP >> 3) /* Read by others.  */
-#define S_IWOTH (S_IWGRP >> 3) /* Write by others.  */
-#define S_IXOTH (S_IXGRP >> 3) /* Execute by others.  */
-#endif
-static QFile::Permissions unixModeToPermissions(const int mode)
+UpdateController::UpdateController(QWidget *parent, const QString &root, const QString &downloadUrl)
+    : m_parent(parent), m_root(root), m_downloadUrl(downloadUrl)
 {
-    QFile::Permissions perms;
-
-    if (mode & S_IRUSR)
-    {
-        perms |= QFile::ReadUser;
-    }
-    if (mode & S_IWUSR)
-    {
-        perms |= QFile::WriteUser;
-    }
-    if (mode & S_IXUSR)
-    {
-        perms |= QFile::ExeUser;
-    }
-
-    if (mode & S_IRGRP)
-    {
-        perms |= QFile::ReadGroup;
-    }
-    if (mode & S_IWGRP)
-    {
-        perms |= QFile::WriteGroup;
-    }
-    if (mode & S_IXGRP)
-    {
-        perms |= QFile::ExeGroup;
-    }
-
-    if (mode & S_IROTH)
-    {
-        perms |= QFile::ReadOther;
-    }
-    if (mode & S_IWOTH)
-    {
-        perms |= QFile::WriteOther;
-    }
-    if (mode & S_IXOTH)
-    {
-        perms |= QFile::ExeOther;
-    }
-    return perms;
-}
-
-static const QLatin1String liveCheckFile("live.check");
-
-UpdateController::UpdateController(QWidget * parent, const QString& root, const QString updateFilesDir, GoUpdate::OperationList operations)
-{
-    m_parent = parent;
-    m_root = root;
-    m_updateFilesDir = updateFilesDir;
-    m_operations = operations;
 }
 
-
-void UpdateController::installUpdates()
+bool UpdateController::startUpdate()
 {
-    qint64 pid = -1;
-    QStringList args;
-    bool started = false;
-
-    qDebug() << "Installing updates.";
+    // Locate the updater binary next to ourselves.
+    QString updaterName = BuildConfig.MESHMC_NAME + "-updater";
 #ifdef Q_OS_WIN
-    QString finishCmd = QApplication::applicationFilePath();
-#elif defined(Q_OS_LINUX) || defined(Q_OS_FREEBSD)
-    QString finishCmd = FS::PathCombine(m_root, BuildConfig.MESHMC_NAME);
-#elif defined Q_OS_MAC
-    QString finishCmd = QApplication::applicationFilePath();
-#else
-#error Unsupported operating system.
+    updaterName += ".exe";
 #endif
-
-    QString backupPath = FS::PathCombine(m_root, "update", "backup");
-    QDir origin(m_root);
-
-    // clean up the backup folder. it should be empty before we start
-    if(!FS::deletePath(backupPath))
-    {
-        qWarning() << "couldn't remove previous backup folder" << backupPath;
-    }
-    // and it should exist.
-    if(!FS::ensureFolderPathExists(backupPath))
-    {
-        qWarning() << "couldn't create folder" << backupPath;
-        return;
-    }
-
-    // perform the update operations
-    for(auto op: m_operations)
-    {
-        switch(op.type)
-        {
-            // replace = move original out to backup, if it exists, move the new file in its place
-            case GoUpdate::Operation::OP_REPLACE:
-            {
-#ifdef Q_OS_WIN32
-                QString windowsExeName = BuildConfig.MESHMC_NAME + ".exe";
-                // hack for people renaming the .exe because ... reasons :)
-                if(op.destination == windowsExeName)
-                {
-                    op.destination = QFileInfo(QApplication::applicationFilePath()).fileName();
-                }
-#endif
-                QFileInfo destination (FS::PathCombine(m_root, op.destination));
-                if(destination.exists())
-                {
-                    QString backupName = op.destination;
-                    backupName.replace('/', '_');
-                    QString backupFilePath = FS::PathCombine(backupPath, backupName);
-                    if(!QFile::rename(destination.absoluteFilePath(), backupFilePath))
-                    {
-                        qWarning() << "Couldn't move:" << destination.absoluteFilePath() << "to" << backupFilePath;
-                        m_failedOperationType = Replace;
-                        m_failedFile = op.destination;
-                        fail();
-                        return;
-                    }
-                    BackupEntry be;
-                    be.original = destination.absoluteFilePath();
-                    be.backup = backupFilePath;
-                    be.update = op.source;
-                    m_replace_backups.append(be);
-                }
-                // make sure the folder we are putting this into exists
-                if(!FS::ensureFilePathExists(destination.absoluteFilePath()))
-                {
-                    qWarning() << "REPLACE: Couldn't create folder:" << destination.absoluteFilePath();
-                    m_failedOperationType = Replace;
-                    m_failedFile = op.destination;
-                    fail();
-                    return;
-                }
-                // now move the new file in
-                if(!QFile::rename(op.source, destination.absoluteFilePath()))
-                {
-                    qWarning() << "REPLACE: Couldn't move:" << op.source << "to" << destination.absoluteFilePath();
-                    m_failedOperationType = Replace;
-                    m_failedFile = op.destination;
-                    fail();
-                    return;
-                }
-                QFile::setPermissions(destination.absoluteFilePath(), unixModeToPermissions(op.destinationMode));
-            }
-            break;
-            // delete = move original to backup
-            case GoUpdate::Operation::OP_DELETE:
-            {
-                QString destFilePath = FS::PathCombine(m_root, op.destination);
-                if(QFile::exists(destFilePath))
-                {
-                    QString backupName = op.destination;
-                    backupName.replace('/', '_');
-                    QString trashFilePath = FS::PathCombine(backupPath, backupName);
-
-                    if(!QFile::rename(destFilePath, trashFilePath))
-                    {
-                        qWarning() << "DELETE: Couldn't move:" << op.destination << "to" << trashFilePath;
-                        m_failedFile = op.destination;
-                        m_failedOperationType = Delete;
-                        fail();
-                        return;
-                    }
-                    BackupEntry be;
-                    be.original = destFilePath;
-                    be.backup = trashFilePath;
-                    m_delete_backups.append(be);
-                }
-            }
-            break;
-        }
-    }
-
-    // try to start the new binary
-    args = qApp->arguments();
-    args.removeFirst();
-
-    bool doLiveCheck = true;
-    bool startFailed = false;
-
-    // remove live check file, if any
-    if(QFile::exists(liveCheckFile))
-    {
-        if(!QFile::remove(liveCheckFile))
-        {
-            qWarning() << "Couldn't remove the" << liveCheckFile << "file! We will proceed without :(";
-            doLiveCheck = false;
-        }
-    }
-
-    if(doLiveCheck)
-    {
-        if(!args.contains("--alive"))
-        {
-            args.append("--alive");
-        }
-    }
-
-    // FIXME: reparse args and construct a safe variant from scratch. This is a workaround for GH-1874:
-    QStringList realargs;
-    int skip = 0;
-    for(auto & arg: args)
-    {
-        if(skip)
-        {
-            skip--;
-            continue;
-        }
-        if(arg == "-l")
-        {
-            skip = 1;
-            continue;
-        }
-        realargs.append(arg);
-    }
-
-    // start the updated application
-    started = QProcess::startDetached(finishCmd, realargs, QDir::currentPath(), &pid);
-    // much dumber check - just find out if the call
-    if(!started || pid == -1)
-    {
-        qWarning() << "Couldn't start new process properly!";
-        startFailed = true;
-    }
-    if(!startFailed && doLiveCheck)
-    {
-        int attempts = 0;
-        while(attempts < 10)
-        {
-            attempts++;
-            QString key;
-            std::this_thread::sleep_for(std::chrono::milliseconds(250));
-            if(!QFile::exists(liveCheckFile))
-            {
-                qWarning() << "Couldn't find the" << liveCheckFile << "file!";
-                startFailed = true;
-                continue;
-            }
-            try
-            {
-                key = QString::fromUtf8(FS::read(liveCheckFile));
-                auto id = ApplicationId::fromRawString(key);
-                LocalPeer peer(nullptr, id);
-                if(peer.isClient())
-                {
-                    startFailed = false;
-                    qDebug() << "Found process started with key " << key;
-                    break;
-                }
-                else
-                {
-                    startFailed = true;
-                    qDebug() << "Process started with key " << key << "apparently died or is not reponding...";
-                    break;
-                }
-            }
-            catch (const Exception &e)
-            {
-                qWarning() << "Couldn't read the" << liveCheckFile << "file!";
-                startFailed = true;
-                continue;
-            }
-        }
-    }
-    if(startFailed)
-    {
-        m_failedOperationType = Start;
-        fail();
-        return;
-    }
-    else
-    {
-        origin.rmdir(m_updateFilesDir);
-        qApp->quit();
-        return;
-    }
-}
-
-void UpdateController::fail()
-{
-    qWarning() << "Update failed!";
-
-    QString msg;
-    bool doRollback = false;
-    QString failTitle = QObject::tr("Update failed!");
-    QString rollFailTitle = QObject::tr("Rollback failed!");
-    switch (m_failedOperationType)
-    {
-        case Replace:
-        {
-            msg = QObject::tr(
-                "Couldn't replace file %1. Changes will be reverted.\n"
-                "See the %2 log file for details."
-            ).arg(m_failedFile, BuildConfig.MESHMC_NAME);
-            doRollback = true;
-            QMessageBox::critical(m_parent, failTitle, msg);
-            break;
-        }
-        case Delete:
-        {
-            msg = QObject::tr(
-                "Couldn't remove file %1. Changes will be reverted.\n"
-                "See the %2 log file for details."
-            ).arg(m_failedFile, BuildConfig.MESHMC_NAME);
-            doRollback = true;
-            QMessageBox::critical(m_parent, failTitle, msg);
-            break;
-        }
-        case Start:
-        {
-            msg = QObject::tr("The new version didn't start or is too old and doesn't respond to startup checks.\n"
-                "\n"
-                "Roll back to previous version?");
-            auto result = QMessageBox::critical(
-                m_parent,
-                failTitle,
-                msg,
-                QMessageBox::Yes | QMessageBox::No,
-                QMessageBox::Yes
-            );
-            doRollback = (result == QMessageBox::Yes);
-            break;
-        }
-        case Nothing:
-        default:
-            return;
-    }
-    if(doRollback)
-    {
-        auto rollbackOK = rollback();
-        if(!rollbackOK)
-        {
-            msg = QObject::tr("The rollback failed too.\n"
-                "You will have to repair %1 manually.\n"
-                "Please let us know why and how this happened.").arg(BuildConfig.MESHMC_NAME);
-            QMessageBox::critical(m_parent, rollFailTitle, msg);
-            qApp->quit();
-        }
-    }
-    else
-    {
-        qApp->quit();
-    }
+    const QString updaterPath = FS::PathCombine(m_root, updaterName);
+
+    if (!QFile::exists(updaterPath)) {
+        qCritical() << "UpdateController: updater binary not found at" << updaterPath;
+        QMessageBox::critical(
+            m_parent,
+            QCoreApplication::translate("UpdateController", "Updater Not Found"),
+            QCoreApplication::translate("UpdateController", "The updater binary could not be found at:\n%1\n\nPlease reinstall %2.")
+                .arg(updaterPath, BuildConfig.MESHMC_DISPLAYNAME));
+        return false;
+    }
+
+    const QStringList args = {
+        "--url",  m_downloadUrl,
+        "--root", m_root,
+        "--exec", QApplication::applicationFilePath()
+    };
+
+    qDebug() << "UpdateController: launching" << updaterPath << "with args" << args;
+    const bool ok = QProcess::startDetached(updaterPath, args);
+    if (!ok) {
+        qCritical() << "UpdateController: failed to start updater binary.";
+        QMessageBox::critical(
+            m_parent,
+            QCoreApplication::translate("UpdateController", "Update Failed"),
+            QCoreApplication::translate("UpdateController", "Could not launch the updater binary.\nPlease update %1 manually.")
+                .arg(BuildConfig.MESHMC_DISPLAYNAME));
+        return false;
+    }
+
+    return true;
 }
 
-bool UpdateController::rollback()
-{
-    bool revertOK = true;
-    // if the above failed, roll back changes
-    for(auto backup:m_replace_backups)
-    {
-        qWarning() << "restoring" << backup.original << "from" << backup.backup;
-        if(!QFile::rename(backup.original, backup.update))
-        {
-            revertOK = false;
-            qWarning() << "moving new" << backup.original << "back to" << backup.update << "failed!";
-            continue;
-        }
 
-        if(!QFile::rename(backup.backup, backup.original))
-        {
-            revertOK = false;
-            qWarning() << "restoring" << backup.original << "failed!";
-        }
-    }
-    for(auto backup:m_delete_backups)
-    {
-        qWarning() << "restoring" << backup.original << "from" << backup.backup;
-        if(!QFile::rename(backup.backup, backup.original))
-        {
-            revertOK = false;
-            qWarning() << "restoring" << backup.original << "failed!";
-        }
-    }
-    return revertOK;
-}
diff --git a/launcher/UpdateController.h b/launcher/UpdateController.h
index 0188df32ab..a57636c746 100644
--- a/launcher/UpdateController.h
+++ b/launcher/UpdateController.h
@@ -22,44 +22,33 @@
 #pragma once
 
 #include <QString>
-#include <QList>
-#include <updater/GoUpdate.h>
 
 class QWidget;
 
+/*!
+ * UpdateController launches the separate meshmc-updater binary and then
+ * requests the main application to quit so the updater can proceed.
+ *
+ * The updater binary receives:
+ *   --url  <download_url>   - artifact to download and install
+ *   --root <root_path>      - installation root (directory of the binary)
+ *   --exec <app_binary>     - path to re-launch after the update completes
+ */
 class UpdateController
 {
 public:
-    UpdateController(QWidget * parent, const QString &root, const QString updateFilesDir, GoUpdate::OperationList operations);
-    void installUpdates();
+    UpdateController(QWidget *parent, const QString &root, const QString &downloadUrl);
 
-private:
-    void fail();
-    bool rollback();
+    /*!
+     * Locates the meshmc-updater binary next to the running executable,
+     * launches it with the required arguments, and returns true on success.
+     * The caller is responsible for quitting the main application afterwards.
+     */
+    bool startUpdate();
 
 private:
-    QString m_root;
-    QString m_updateFilesDir;
-    GoUpdate::OperationList m_operations;
-    QWidget * m_parent;
-
-    struct BackupEntry
-    {
-        // path where we got the new file from
-        QString update;
-        // path of what is being actually updated
-        QString original;
-        // path where the backup of the updated file was placed
-        QString backup;
-    };
-    QList <BackupEntry> m_replace_backups;
-    QList <BackupEntry> m_delete_backups;
-    enum Failure
-    {
-        Replace,
-        Delete,
-        Start,
-        Nothing
-    } m_failedOperationType = Nothing;
-    QString m_failedFile;
+    QWidget  *m_parent;
+    QString   m_root;
+    QString   m_downloadUrl;
 };
+
diff --git a/launcher/ui/MainWindow.cpp b/launcher/ui/MainWindow.cpp
index c69b0bab08..e8d0e3414d 100644
--- a/launcher/ui/MainWindow.cpp
+++ b/launcher/ui/MainWindow.cpp
@@ -842,7 +842,7 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new MainWindow
     }
 
 
-    if(BuildConfig.UPDATER_ENABLED)
+    if(BuildConfig.UPDATER_ENABLED && UpdateChecker::isUpdaterSupported())
     {
         bool updatesAllowed = APPLICATION->updatesAreAllowed();
         updatesAllowedChanged(updatesAllowed);
@@ -857,7 +857,7 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new MainWindow
         // if automatic update checks are allowed, start one.
         if (APPLICATION->settings()->get("AutoUpdate").toBool() && updatesAllowed)
         {
-            updater->checkForUpdate(APPLICATION->settings()->get("UpdateChannel").toString(), false);
+            updater->checkForUpdate(false);
         }
     }
 
@@ -1127,7 +1127,7 @@ void MainWindow::repopulateAccountsMenu()
 
 void MainWindow::updatesAllowedChanged(bool allowed)
 {
-    if(!BuildConfig.UPDATER_ENABLED)
+    if(!BuildConfig.UPDATER_ENABLED || !UpdateChecker::isUpdaterSupported())
     {
         return;
     }
@@ -1238,14 +1238,14 @@ void MainWindow::updateNewsLabel()
     }
 }
 
-void MainWindow::updateAvailable(GoUpdate::Status status)
+void MainWindow::updateAvailable(UpdateAvailableStatus status)
 {
     if(!APPLICATION->updatesAreAllowed())
     {
         updateNotAvailable();
         return;
     }
-    UpdateDialog dlg(true, this);
+    UpdateDialog dlg(true, status, this);
     UpdateAction action = (UpdateAction)dlg.exec();
     switch (action)
     {
@@ -1253,14 +1253,36 @@ void MainWindow::updateAvailable(GoUpdate::Status status)
         qDebug() << "Update will be installed later.";
         break;
     case UPDATE_NOW:
-        downloadUpdates(status);
+        if(!status.downloadUrl.isEmpty())
+        {
+            APPLICATION->updateIsRunning(true);
+            UpdateController controller(this, APPLICATION->root(), status.downloadUrl);
+            if(controller.startUpdate())
+            {
+                // The updater binary has been launched; quit the main app so
+                // the updater can overwrite its files.
+                QCoreApplication::quit();
+            }
+            APPLICATION->updateIsRunning(false);
+        }
+        else
+        {
+            CustomMessageBox::selectable(
+                this,
+                tr("No Download URL"),
+                tr("An update to version %1 is available, but no download URL "
+                   "was found for your platform (%2).\n"
+                   "Please visit the project website to download it manually.")
+                    .arg(status.version, BuildConfig.BUILD_ARTIFACT),
+                QMessageBox::Information)->show();
+        }
         break;
     }
 }
 
 void MainWindow::updateNotAvailable()
 {
-    UpdateDialog dlg(false, this);
+    UpdateDialog dlg(false, {}, this);
     dlg.exec();
 }
 
@@ -1302,38 +1324,11 @@ void MainWindow::notificationsChanged()
     APPLICATION->settings()->set("ShownNotifications", intListToString(shownNotifications));
 }
 
-void MainWindow::downloadUpdates(GoUpdate::Status status)
+void MainWindow::downloadUpdates(UpdateAvailableStatus status)
 {
-    if(!APPLICATION->updatesAreAllowed())
-    {
-        return;
-    }
-    qDebug() << "Downloading updates.";
-    ProgressDialog updateDlg(this);
-    status.rootPath = APPLICATION->root();
-
-    auto dlPath = FS::PathCombine(APPLICATION->root(), "update", "XXXXXX");
-    if (!FS::ensureFilePathExists(dlPath))
-    {
-        CustomMessageBox::selectable(this, tr("Error"), tr("Couldn't create folder for update downloads:\n%1").arg(dlPath), QMessageBox::Warning)->show();
-    }
-    GoUpdate::DownloadTask updateTask(APPLICATION->network(), status, dlPath, &updateDlg);
-    // If the task succeeds, install the updates.
-    if (updateDlg.execWithTask(&updateTask))
-    {
-        /**
-         * NOTE: This disables launching instances until the update either succeeds (and this process exits)
-         * or the update fails (and the control leaves this scope).
-         */
-        APPLICATION->updateIsRunning(true);
-        UpdateController update(this, APPLICATION->root(), updateTask.updateFilesDir(), updateTask.operations());
-        update.installUpdates();
-        APPLICATION->updateIsRunning(false);
-    }
-    else
-    {
-        CustomMessageBox::selectable(this, tr("Error"), updateTask.failReason(), QMessageBox::Warning)->show();
-    }
+    // Kept as a stub — actual update installation is now done by the separate
+    // meshmc-updater binary launched from updateAvailable().
+    Q_UNUSED(status)
 }
 
 void MainWindow::onCatToggled(bool state)
@@ -1622,14 +1617,14 @@ void MainWindow::on_actionConfig_Folder_triggered()
 
 void MainWindow::checkForUpdates()
 {
-    if(BuildConfig.UPDATER_ENABLED)
+    if(BuildConfig.UPDATER_ENABLED && UpdateChecker::isUpdaterSupported())
     {
         auto updater = APPLICATION->updateChecker();
-        updater->checkForUpdate(APPLICATION->settings()->get("UpdateChannel").toString(), true);
+        updater->checkForUpdate(true);
     }
     else
     {
-        qWarning() << "Updater not set up. Cannot check for updates.";
+        qWarning() << "Updater not set up or not supported on this platform. Cannot check for updates.";
     }
 }
 
diff --git a/launcher/ui/MainWindow.h b/launcher/ui/MainWindow.h
index b8005d3243..51026560cd 100644
--- a/launcher/ui/MainWindow.h
+++ b/launcher/ui/MainWindow.h
@@ -47,7 +47,7 @@
 #include "BaseInstance.h"
 #include "minecraft/auth/MinecraftAccount.h"
 #include "net/NetJob.h"
-#include "updater/GoUpdate.h"
+#include "updater/UpdateChecker.h"
 
 class LaunchController;
 class NewsChecker;
@@ -185,7 +185,7 @@ private slots:
 
     void startTask(Task *task);
 
-    void updateAvailable(GoUpdate::Status status);
+    void updateAvailable(UpdateAvailableStatus status);
 
     void updateNotAvailable();
 
@@ -200,9 +200,10 @@ private slots:
     void updateNewsLabel();
 
     /*!
-     * Runs the DownloadTask and installs updates.
+     * Stub kept for source compatibility; actual installation is delegated to
+     * the meshmc-updater binary via UpdateController.
      */
-    void downloadUpdates(GoUpdate::Status status);
+    void downloadUpdates(UpdateAvailableStatus status);
 
     void konamiTriggered();
 
diff --git a/launcher/ui/dialogs/UpdateDialog.cpp b/launcher/ui/dialogs/UpdateDialog.cpp
index d8a2df670c..75f3c395c8 100644
--- a/launcher/ui/dialogs/UpdateDialog.cpp
+++ b/launcher/ui/dialogs/UpdateDialog.cpp
@@ -21,170 +21,40 @@
 
 #include "UpdateDialog.h"
 #include "ui_UpdateDialog.h"
-#include <QDebug>
-#include <QRegularExpression>
 #include "Application.h"
-#include <settings/SettingsObject.h>
-#include <Json.h>
-
 #include "BuildConfig.h"
-#include "HoeDown.h"
 
-UpdateDialog::UpdateDialog(bool hasUpdate, QWidget *parent) : QDialog(parent), ui(new Ui::UpdateDialog)
+UpdateDialog::UpdateDialog(bool hasUpdate, const UpdateAvailableStatus &status, QWidget *parent)
+    : QDialog(parent), ui(new Ui::UpdateDialog)
 {
     ui->setupUi(this);
-    auto channel = APPLICATION->settings()->get("UpdateChannel").toString();
-    if(hasUpdate)
-    {
-        ui->label->setText(tr("A new %1 update is available!").arg(channel));
-    }
-    else
-    {
-        ui->label->setText(tr("No %1 updates found. You are running the latest version.").arg(channel));
-        ui->btnUpdateNow->setHidden(true);
-        ui->btnUpdateLater->setText(tr("Close"));
-    }
-    ui->changelogBrowser->setHtml(tr("<center><h1>Loading changelog...</h1></center>"));
-    loadChangelog();
-    restoreGeometry(QByteArray::fromBase64(APPLICATION->settings()->get("UpdateDialogGeometry").toByteArray()));
-}
-
-UpdateDialog::~UpdateDialog()
-{
-}
-
-void UpdateDialog::loadChangelog()
-{
-    auto channel = APPLICATION->settings()->get("UpdateChannel").toString();
-    dljob = new NetJob("Changelog", APPLICATION->network());
-    QString url;
-    if(channel == "stable")
-    {
-        url = QString("https://raw.githubusercontent.com/Project-Tick/MeshMC/%1/changelog.md").arg(channel);
-        m_changelogType = CHANGELOG_MARKDOWN;
-    }
-    else
-    {
-        url = QString("https://api.github.com/repos/Project-Tick/MeshMC/compare/%1...%2").arg(BuildConfig.GIT_COMMIT, channel);
-        m_changelogType = CHANGELOG_COMMITS;
-    }
-    dljob->addNetAction(Net::Download::makeByteArray(QUrl(url), &changelogData));
-    connect(dljob.get(), &NetJob::succeeded, this, &UpdateDialog::changelogLoaded);
-    connect(dljob.get(), &NetJob::failed, this, &UpdateDialog::changelogFailed);
-    dljob->start();
-}
 
-QString reprocessMarkdown(QByteArray markdown)
-{
-    HoeDown hoedown;
-    QString output = hoedown.process(markdown);
-
-    // HACK: easier than customizing hoedown
-    output.replace(QRegularExpression("GH-([0-9]+)"), "<a href=\"https://github.com/Project-Tick/MeshMC/issues/\\1\">GH-\\1</a>");
-    qDebug() << output;
-    return output;
-}
-
-QString reprocessCommits(QByteArray json)
-{
-    auto channel = APPLICATION->settings()->get("UpdateChannel").toString();
-    try
-    {
-        QString result;
-        auto document = Json::requireDocument(json);
-        auto rootobject = Json::requireObject(document);
-        auto status = Json::requireString(rootobject, "status");
-        auto diff_url = Json::requireString(rootobject, "html_url");
-
-        auto print_commits = [&]()
-        {
-            result += "<table cellspacing=0 cellpadding=2 style='border-width: 1px; border-style: solid'>";
-            auto commitarray = Json::requireArray(rootobject, "commits");
-            for(int i = commitarray.size() - 1; i >= 0; i--)
-            {
-                const auto & commitval = commitarray[i];
-                auto commitobj = Json::requireObject(commitval);
-                auto parents_info = Json::ensureArray(commitobj, "parents");
-                // NOTE: this ignores merge commits, because they have more than one parent
-                if(parents_info.size() > 1)
-                {
-                    continue;
-                }
-                auto commit_url = Json::requireString(commitobj, "html_url");
-                auto commit_info = Json::requireObject(commitobj, "commit");
-                auto commit_message = Json::requireString(commit_info, "message");
-                auto lines = commit_message.split('\n');
-                QRegularExpression regexp("(?<prefix>(GH-(?<issuenr>[0-9]+))|(NOISSUE)|(SCRATCH))? *(?<rest>.*) *");
-                auto match = regexp.match(lines.takeFirst(), 0, QRegularExpression::NormalMatch);
-                auto issuenr = match.captured("issuenr");
-                auto prefix = match.captured("prefix");
-                auto rest = match.captured("rest");
-                result += "<tr><td>";
-                if(issuenr.length())
-                {
-                    result += QString("<a href=\"https://github.com/Project-Tick/MeshMC/issues/%1\">GH-%2</a>").arg(issuenr, issuenr);
-                }
-                else if(prefix.length())
-                {
-                    result += QString("<a href=\"%1\">%2</a>").arg(commit_url, prefix);
-                }
-                else
-                {
-                    result += QString("<a href=\"%1\">NOISSUE</a>").arg(commit_url);
-                }
-                result += "</td>";
-                lines.prepend(rest);
-                result += "<td><p>" + lines.join("<br />") + "</p></td></tr>";
-            }
-            result += "</table>";
-        };
+    if (hasUpdate) {
+        ui->label->setText(tr("<b>%1 %2</b> is available!").arg(
+            BuildConfig.MESHMC_DISPLAYNAME, status.version));
 
-        if(status == "identical")
-        {
-            return QObject::tr("<p>There are no code changes between your current version and latest %1.</p>").arg(channel);
-        }
-        else if(status == "ahead")
-        {
-            result += QObject::tr("<p>Following commits were added since last update:</p>");
-            print_commits();
-        }
-        else if(status == "diverged")
-        {
-            auto commit_ahead = Json::requireInteger(rootobject, "ahead_by");
-            auto commit_behind = Json::requireInteger(rootobject, "behind_by");
-            result += QObject::tr("<p>The update removes %1 commits and adds the following %2:</p>").arg(commit_behind).arg(commit_ahead);
-            print_commits();
+        if (!status.releaseNotes.isEmpty()) {
+            ui->changelogBrowser->setHtml(status.releaseNotes);
+        } else {
+            ui->changelogBrowser->setHtml(
+                tr("<center><p>No release notes available.</p></center>"));
         }
-        result += QObject::tr("<p>You can <a href=\"%1\">look at the changes on github</a>.</p>").arg(diff_url);
-        return result;
-    }
-    catch (const JSONValidationError &e)
-    {
-        qWarning() << "Got an unparseable commit log from github:" << e.what();
-        qDebug() << json;
+    } else {
+        ui->label->setText(tr("You are running the latest version of %1.").arg(
+            BuildConfig.MESHMC_DISPLAYNAME));
+        ui->changelogBrowser->setHtml(
+            tr("<center><p>No updates found.</p></center>"));
+        ui->btnUpdateNow->setHidden(true);
+        ui->btnUpdateLater->setText(tr("Close"));
     }
-    return QString();
-}
 
-void UpdateDialog::changelogLoaded()
-{
-    QString result;
-    switch(m_changelogType)
-    {
-        case CHANGELOG_COMMITS:
-            result = reprocessCommits(changelogData);
-            break;
-        case CHANGELOG_MARKDOWN:
-            result = reprocessMarkdown(changelogData);
-            break;
-    }
-    changelogData.clear();
-    ui->changelogBrowser->setHtml(result);
+    restoreGeometry(QByteArray::fromBase64(
+        APPLICATION->settings()->get("UpdateDialogGeometry").toByteArray()));
 }
 
-void UpdateDialog::changelogFailed(QString reason)
+UpdateDialog::~UpdateDialog()
 {
-    ui->changelogBrowser->setHtml(tr("<p align=\"center\" <span style=\"font-size:22pt;\">Failed to fetch changelog... Error: %1</span></p>").arg(reason));
+    delete ui;
 }
 
 void UpdateDialog::on_btnUpdateLater_clicked()
@@ -197,7 +67,7 @@ void UpdateDialog::on_btnUpdateNow_clicked()
     done(UPDATE_NOW);
 }
 
-void UpdateDialog::closeEvent(QCloseEvent* evt)
+void UpdateDialog::closeEvent(QCloseEvent *evt)
 {
     APPLICATION->settings()->set("UpdateDialogGeometry", saveGeometry().toBase64());
     QDialog::closeEvent(evt);
diff --git a/launcher/ui/dialogs/UpdateDialog.h b/launcher/ui/dialogs/UpdateDialog.h
index a4b846242a..ca3011a184 100644
--- a/launcher/ui/dialogs/UpdateDialog.h
+++ b/launcher/ui/dialogs/UpdateDialog.h
@@ -39,7 +39,7 @@
 #pragma once
 
 #include <QDialog>
-#include "net/NetJob.h"
+#include "updater/UpdateChecker.h"
 
 namespace Ui
 {
@@ -52,39 +52,26 @@ enum UpdateAction
     UPDATE_NOW = QDialog::Accepted,
 };
 
-enum ChangelogType
-{
-    CHANGELOG_MARKDOWN,
-    CHANGELOG_COMMITS
-};
-
 class UpdateDialog : public QDialog
 {
     Q_OBJECT
 
 public:
-    explicit UpdateDialog(bool hasUpdate = true, QWidget *parent = 0);
+    /*!
+     * Constructs the update dialog.
+     * \a hasUpdate    - true when an update is available (shows "Update now" button).
+     * \a status       - update information (version, release notes); ignored when hasUpdate is false.
+     */
+    explicit UpdateDialog(bool hasUpdate, const UpdateAvailableStatus &status = {}, QWidget *parent = nullptr);
     ~UpdateDialog();
 
 public slots:
     void on_btnUpdateNow_clicked();
     void on_btnUpdateLater_clicked();
 
-    /// Starts loading the changelog
-    void loadChangelog();
-
-    /// Slot for when the chengelog loads successfully.
-    void changelogLoaded();
-
-    /// Slot for when the chengelog fails to load...
-    void changelogFailed(QString reason);
-
 protected:
     void closeEvent(QCloseEvent * ) override;
 
 private:
     Ui::UpdateDialog *ui;
-    QByteArray changelogData;
-    NetJob::Ptr dljob;
-    ChangelogType m_changelogType = CHANGELOG_MARKDOWN;
 };
diff --git a/launcher/ui/pages/global/MeshMCPage.cpp b/launcher/ui/pages/global/MeshMCPage.cpp
index 159d8cec40..032d631d61 100644
--- a/launcher/ui/pages/global/MeshMCPage.cpp
+++ b/launcher/ui/pages/global/MeshMCPage.cpp
@@ -78,18 +78,12 @@ MeshMCPage::MeshMCPage(QWidget *parent) : QWidget(parent), ui(new Ui::MeshMCPage
     m_languageModel = APPLICATION->translations();
     loadSettings();
 
-    if(BuildConfig.UPDATER_ENABLED)
+    if(BuildConfig.UPDATER_ENABLED && UpdateChecker::isUpdaterSupported())
     {
-        QObject::connect(APPLICATION->updateChecker().get(), &UpdateChecker::channelListLoaded, this, &MeshMCPage::refreshUpdateChannelList);
-
-        if (APPLICATION->updateChecker()->hasChannels())
-        {
-            refreshUpdateChannelList();
-        }
-        else
-        {
-            APPLICATION->updateChecker()->updateChanList(false);
-        }
+        // New updater: hide the legacy channel selector (no channel selection in the new system).
+        ui->updateChannelComboBox->setVisible(false);
+        ui->updateChannelLabel->setVisible(false);
+        ui->updateChannelDescLabel->setVisible(false);
     }
     else
     {
@@ -187,74 +181,17 @@ void MeshMCPage::on_migrateDataFolderMacBtn_clicked()
 
 void MeshMCPage::refreshUpdateChannelList()
 {
-    // Stop listening for selection changes. It's going to change a lot while we update it and
-    // we don't need to update the
-    // description label constantly.
-    QObject::disconnect(ui->updateChannelComboBox, SIGNAL(currentIndexChanged(int)), this,
-                        SLOT(updateChannelSelectionChanged(int)));
-
-    QList<UpdateChecker::ChannelListEntry> channelList = APPLICATION->updateChecker()->getChannelList();
-    ui->updateChannelComboBox->clear();
-    int selection = -1;
-    for (int i = 0; i < channelList.count(); i++)
-    {
-        UpdateChecker::ChannelListEntry entry = channelList.at(i);
-
-        // When it comes to selection, we'll rely on the indexes of a channel entry being the
-        // same in the
-        // combo box as it is in the update checker's channel list.
-        // This probably isn't very safe, but the channel list doesn't change often enough (or
-        // at all) for
-        // this to be a big deal. Hope it doesn't break...
-        ui->updateChannelComboBox->addItem(entry.name);
-
-        // If the update channel we just added was the selected one, set the current index in
-        // the combo box to it.
-        if (entry.id == m_currentUpdateChannel)
-        {
-            qDebug() << "Selected index" << i << "channel id" << m_currentUpdateChannel;
-            selection = i;
-        }
-    }
-
-    ui->updateChannelComboBox->setCurrentIndex(selection);
-
-    // Start listening for selection changes again and update the description label.
-    QObject::connect(ui->updateChannelComboBox, SIGNAL(currentIndexChanged(int)), this,
-                     SLOT(updateChannelSelectionChanged(int)));
-    refreshUpdateChannelDesc();
-
-    // Now that we've updated the channel list, we can enable the combo box.
-    // It starts off disabled so that if the channel list hasn't been loaded, it will be
-    // disabled.
-    ui->updateChannelComboBox->setEnabled(true);
+    // No-op: the new updater does not use named channels.
 }
 
-void MeshMCPage::updateChannelSelectionChanged(int index)
+void MeshMCPage::updateChannelSelectionChanged(int)
 {
-    refreshUpdateChannelDesc();
+    // No-op.
 }
 
 void MeshMCPage::refreshUpdateChannelDesc()
 {
-    // Get the channel list.
-    QList<UpdateChecker::ChannelListEntry> channelList = APPLICATION->updateChecker()->getChannelList();
-    int selectedIndex = ui->updateChannelComboBox->currentIndex();
-    if (selectedIndex < 0)
-    {
-        return;
-    }
-    if (selectedIndex < channelList.count())
-    {
-        // Find the channel list entry with the given index.
-        UpdateChecker::ChannelListEntry selected = channelList.at(selectedIndex);
-
-        // Set the description text.
-        ui->updateChannelDescLabel->setText(selected.description);
-
-        // Set the currently selected channel ID.
-        m_currentUpdateChannel = selected.id;
-    }
+    // No-op.
 }
 
 void MeshMCPage::applySettings()
@@ -268,7 +205,7 @@ void MeshMCPage::applySettings()
 
     // Updates
     s->set("AutoUpdate", ui->autoUpdateCheckBox->isChecked());
-    s->set("UpdateChannel", m_currentUpdateChannel);
+    // (UpdateChannel setting removed - the new updater always checks the stable feed)
 
     // Console settings
     s->set("ShowConsole", ui->showConsoleCheck->isChecked());
@@ -309,7 +246,7 @@ void MeshMCPage::loadSettings()
     auto s = APPLICATION->settings();
     // Updates
     ui->autoUpdateCheckBox->setChecked(s->get("AutoUpdate").toBool());
-    m_currentUpdateChannel = s->get("UpdateChannel").toString();
+    // (no channel to read in the new updater system)
 
     // Console settings
     ui->showConsoleCheck->setChecked(s->get("ShowConsole").toBool());
diff --git a/launcher/ui/pages/global/MeshMCPage.h b/launcher/ui/pages/global/MeshMCPage.h
index c35a838385..255b200d1c 100644
--- a/launcher/ui/pages/global/MeshMCPage.h
+++ b/launcher/ui/pages/global/MeshMCPage.h
@@ -112,11 +112,6 @@ slots:
 private:
     Ui::MeshMCPage *ui;
 
-    /*!
-     * Stores the currently selected update channel.
-     */
-    QString m_currentUpdateChannel;
-
     // default format for the font preview...
     QTextCharFormat *defaultFormat;
 
diff --git a/launcher/updater/UpdateChecker.cpp b/launcher/updater/UpdateChecker.cpp
index 00d0d71c83..f218ca29c3 100644
--- a/launcher/updater/UpdateChecker.cpp
+++ b/launcher/updater/UpdateChecker.cpp
@@ -17,277 +17,266 @@
  *
  *   You should have received a copy of the GNU General Public License
  *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
- *  
- *  This file incorporates work covered by the following copyright and
- *  permission notice:
- *
- * Copyright 2013-2021 MultiMC Contributors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
  */
 
 #include "UpdateChecker.h"
 
-#include <QJsonObject>
-#include <QJsonArray>
-#include <QJsonValue>
 #include <QDebug>
-
-#define API_VERSION 0
-#define CHANLIST_FORMAT 0
+#include <QDir>
+#include <QJsonDocument>
+#include <QJsonObject>
+#include <QXmlStreamReader>
 
 #include "BuildConfig.h"
-#include "sys.h"
+#include "FileSystem.h"
+#include "net/Download.h"
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
 
-UpdateChecker::UpdateChecker(shared_qobject_ptr<QNetworkAccessManager> nam, QString channelUrl, QString currentChannel, int currentBuild)
+bool UpdateChecker::isPortableMode()
 {
-    m_network = nam;
-    m_channelUrl = channelUrl;
-    m_currentChannel = currentChannel;
-    m_currentBuild = currentBuild;
+    // portable.txt lives next to the application binary.
+    return QFile::exists(FS::PathCombine(QCoreApplication::applicationDirPath(), "portable.txt"));
 }
 
-QList<UpdateChecker::ChannelListEntry> UpdateChecker::getChannelList() const
+bool UpdateChecker::isAppImage()
 {
-    return m_channels;
+    return !qEnvironmentVariable("APPIMAGE").isEmpty();
 }
 
-bool UpdateChecker::hasChannels() const
+QString UpdateChecker::currentVersion()
 {
-    return !m_channels.isEmpty();
+    return QString("%1.%2.%3")
+        .arg(BuildConfig.VERSION_MAJOR)
+        .arg(BuildConfig.VERSION_MINOR)
+        .arg(BuildConfig.VERSION_HOTFIX);
 }
 
-void UpdateChecker::checkForUpdate(QString updateChannel, bool notifyNoUpdate)
+QString UpdateChecker::normalizeVersion(const QString &v)
 {
-    qDebug() << "Checking for updates.";
+    QString out = v.trimmed();
+    if (out.startsWith('v', Qt::CaseInsensitive))
+        out.remove(0, 1);
+    return out;
+}
 
-    // If the channel list hasn't loaded yet, load it and defer checking for updates until
-    // later.
-    if (!m_chanListLoaded)
-    {
-        qDebug() << "Channel list isn't loaded yet. Loading channel list and deferring update check.";
-        m_checkUpdateWaiting = true;
-        m_deferredUpdateChannel = updateChannel;
-        updateChanList(notifyNoUpdate);
-        return;
+int UpdateChecker::compareVersions(const QString &v1, const QString &v2)
+{
+    const QStringList parts1 = v1.split('.');
+    const QStringList parts2 = v2.split('.');
+    const int len = std::max(parts1.size(), parts2.size());
+    for (int i = 0; i < len; ++i) {
+        const int a = (i < parts1.size()) ? parts1.at(i).toInt() : 0;
+        const int b = (i < parts2.size()) ? parts2.at(i).toInt() : 0;
+        if (a != b)
+            return a - b;
     }
+    return 0;
+}
 
-    if (m_updateChecking)
-    {
-        qDebug() << "Ignoring update check request. Already checking for updates.";
-        return;
-    }
+// ---------------------------------------------------------------------------
+// Public
+// ---------------------------------------------------------------------------
 
-    // Find the desired channel within the channel list and get its repo URL. If if cannot be
-    // found, error.
-    QString stableUrl;
-    m_newRepoUrl = "";
-    for (ChannelListEntry entry : m_channels)
-    {
-        qDebug() << "channelEntry = " << entry.id;
-        if(entry.id == "stable") {
-            stableUrl = entry.url;
-        }
-        if (entry.id == updateChannel) {
-            m_newRepoUrl = entry.url;
-            qDebug() << "is intended update channel: " << entry.id;
-        }
-        if (entry.id == m_currentChannel) {
-            m_currentRepoUrl = entry.url;
-            qDebug() << "is current update channel: " << entry.id;
-        }
-    }
+UpdateChecker::UpdateChecker(shared_qobject_ptr<QNetworkAccessManager> nam, QObject *parent)
+    : QObject(parent), m_network(nam)
+{
+}
 
-    qDebug() << "m_repoUrl = " << m_newRepoUrl;
+bool UpdateChecker::isUpdaterSupported()
+{
+    if (!BuildConfig.UPDATER_ENABLED)
+        return false;
+
+#if defined(Q_OS_LINUX) || defined(Q_OS_FREEBSD)
+    // On Linux/BSD: disable unless this is a portable install and not an AppImage.
+    if (isAppImage())
+        return false;
+    if (!isPortableMode())
+        return false;
+#endif
+
+    return true;
+}
 
-    if (m_newRepoUrl.isEmpty()) {
-        qWarning() << "m_repoUrl was empty. defaulting to 'stable': " << stableUrl;
-        m_newRepoUrl = stableUrl;
+void UpdateChecker::checkForUpdate(bool notifyNoUpdate)
+{
+    if (!isUpdaterSupported()) {
+        qDebug() << "UpdateChecker: updater not supported on this platform/mode. Skipping.";
+        return;
     }
 
-    // If nothing applies, error
-    if (m_newRepoUrl.isEmpty())
-    {
-        qCritical() << "failed to select any update repository for: " << updateChannel;
-        emit updateCheckFailed();
+    if (m_checking) {
+        qDebug() << "UpdateChecker: check already in progress, ignoring.";
         return;
     }
 
-    m_updateChecking = true;
+    qDebug() << "UpdateChecker: starting dual-source update check.";
+    m_checking = true;
+    m_feedData.clear();
+    m_githubData.clear();
 
-    QUrl indexUrl = QUrl(m_newRepoUrl).resolved(QUrl("index.json"));
+    m_checkJob.reset(new NetJob("Update Check", m_network));
+    m_checkJob->addNetAction(Net::Download::makeByteArray(QUrl(BuildConfig.UPDATER_FEED_URL), &m_feedData));
+    m_checkJob->addNetAction(Net::Download::makeByteArray(QUrl(BuildConfig.UPDATER_GITHUB_API_URL), &m_githubData));
 
-    indexJob = new NetJob("GoUpdate Repository Index", m_network);
-    indexJob->addNetAction(Net::Download::makeByteArray(indexUrl, &indexData));
-    connect(indexJob.get(), &NetJob::succeeded, [this, notifyNoUpdate](){ updateCheckFinished(notifyNoUpdate); });
-    connect(indexJob.get(), &NetJob::failed, this, &UpdateChecker::updateCheckFailed);
-    indexJob->start();
-}
+    connect(m_checkJob.get(), &NetJob::succeeded,
+            [this, notifyNoUpdate]() { onDownloadsFinished(notifyNoUpdate); });
+    connect(m_checkJob.get(), &NetJob::failed,
+            this, &UpdateChecker::onDownloadsFailed);
 
-void UpdateChecker::updateCheckFinished(bool notifyNoUpdate)
-{
-    qDebug() << "Finished downloading repo index. Checking for new versions.";
+    m_checkJob->start();
+}
 
-    QJsonParseError jsonError;
-    indexJob.reset();
+// ---------------------------------------------------------------------------
+// Private slots
+// ---------------------------------------------------------------------------
 
-    QJsonDocument jsonDoc = QJsonDocument::fromJson(indexData, &jsonError);
-    indexData.clear();
-    if (jsonError.error != QJsonParseError::NoError || !jsonDoc.isObject())
-    {
-        qCritical() << "Failed to parse GoUpdate repository index. JSON error"
-                     << jsonError.errorString() << "at offset" << jsonError.offset;
-        m_updateChecking = false;
-        return;
-    }
+void UpdateChecker::onDownloadsFinished(bool notifyNoUpdate)
+{
+    m_checking = false;
+    m_checkJob.reset();
 
-    QJsonObject object = jsonDoc.object();
+    // ---- Parse the RSS feed -----------------------------------------------
+    // We look for the first <item> whose <projt:channel> == "stable".
+    // From that item we read <projt:version> and the <projt:asset> whose
+    // name attribute contains BuildConfig.BUILD_ARTIFACT.
 
-    bool success = false;
-    int apiVersion = object.value("ApiVersion").toVariant().toInt(&success);
-    if (apiVersion != API_VERSION || !success)
-    {
-        qCritical() << "Failed to check for updates. API version mismatch. We're using"
-                     << API_VERSION << "server has" << apiVersion;
-        m_updateChecking = false;
-        return;
-    }
+    QString feedVersion;
+    QString downloadUrl;
+    QString releaseNotes;
 
-    qDebug() << "Processing repository version list.";
-    QJsonObject newestVersion;
-    QJsonArray versions = object.value("Versions").toArray();
-    for (QJsonValue versionVal : versions)
     {
-        QJsonObject version = versionVal.toObject();
-        if (newestVersion.value("Id").toVariant().toInt() <
-            version.value("Id").toVariant().toInt())
-        {
-            newestVersion = version;
+        QXmlStreamReader xml(m_feedData);
+        m_feedData.clear();
+
+        bool insideItem = false;
+        bool isStable   = false;
+        QString itemVersion;
+        QString itemUrl;
+        QString itemNotes;
+
+        // We iterate forward and take the FIRST stable item we encounter
+        // (the feed lists newest first).
+        while (!xml.atEnd() && !xml.hasError()) {
+            xml.readNext();
+
+            if (xml.isStartElement()) {
+                const QStringView name = xml.name();
+
+                if (name == u"item") {
+                    insideItem = true;
+                    isStable   = false;
+                    itemVersion.clear();
+                    itemUrl.clear();
+                    itemNotes.clear();
+                } else if (insideItem) {
+                    if (xml.namespaceUri() == u"https://projecttick.org/ns/projt-launcher/feed") {
+                        if (name == u"version") {
+                            itemVersion = xml.readElementText().trimmed();
+                        } else if (name == u"channel") {
+                            isStable = (xml.readElementText().trimmed() == "stable");
+                        } else if (name == u"asset") {
+                            const QString assetName = xml.attributes().value("name").toString();
+                            const QString assetUrl  = xml.attributes().value("url").toString();
+                            if (!BuildConfig.BUILD_ARTIFACT.isEmpty()
+                                    && assetName.contains(BuildConfig.BUILD_ARTIFACT, Qt::CaseInsensitive)) {
+                                itemUrl = assetUrl;
+                            }
+                        }
+                    } else if (name == u"description" && xml.namespaceUri().isEmpty()) {
+                        itemNotes = xml.readElementText(QXmlStreamReader::IncludeChildElements).trimmed();
+                    }
+                }
+            } else if (xml.isEndElement() && xml.name() == u"item" && insideItem) {
+                insideItem = false;
+                if (isStable && !itemVersion.isEmpty()) {
+                    // First stable item wins.
+                    feedVersion  = normalizeVersion(itemVersion);
+                    downloadUrl  = itemUrl;
+                    releaseNotes = itemNotes;
+                    break;
+                }
+            }
         }
-    }
 
-    // We've got the version with the greatest ID number. Now compare it to our current build
-    // number and update if they're different.
-    int newBuildNumber = newestVersion.value("Id").toVariant().toInt();
-    if (newBuildNumber != m_currentBuild)
-    {
-        qDebug() << "Found newer version with ID" << newBuildNumber;
-        // Update!
-        GoUpdate::Status updateStatus;
-        updateStatus.updateAvailable = true;
-        updateStatus.currentVersionId = m_currentBuild;
-        updateStatus.currentRepoUrl = m_currentRepoUrl;
-        updateStatus.newVersionId = newBuildNumber;
-        updateStatus.newRepoUrl = m_newRepoUrl;
-        emit updateAvailable(updateStatus);
-    }
-    else if (notifyNoUpdate)
-    {
-        emit noUpdateFound();
+        if (xml.hasError()) {
+            emit checkFailed(tr("Failed to parse update feed: %1").arg(xml.errorString()));
+            return;
+        }
     }
-    m_updateChecking = false;
-}
-
-void UpdateChecker::updateCheckFailed()
-{
-    qCritical() << "Update check failed for reasons unknown.";
-}
-
-void UpdateChecker::updateChanList(bool notifyNoUpdate)
-{
-    qDebug() << "Loading the channel list.";
 
-    if (m_chanListLoading)
-    {
-        qDebug() << "Ignoring channel list update request. Already grabbing channel list.";
+    if (feedVersion.isEmpty()) {
+        emit checkFailed(tr("No stable release entry found in the update feed."));
         return;
     }
 
-    m_chanListLoading = true;
-    chanListJob = new NetJob("Update System Channel List", m_network);
-    chanListJob->addNetAction(Net::Download::makeByteArray(QUrl(m_channelUrl), &chanlistData));
-    connect(chanListJob.get(), &NetJob::succeeded, [this, notifyNoUpdate]() { chanListDownloadFinished(notifyNoUpdate); });
-    connect(chanListJob.get(), &NetJob::failed, this, &UpdateChecker::chanListDownloadFailed);
-    chanListJob->start();
-}
-
-void UpdateChecker::chanListDownloadFinished(bool notifyNoUpdate)
-{
-    chanListJob.reset();
-
-    QJsonParseError jsonError;
-    QJsonDocument jsonDoc = QJsonDocument::fromJson(chanlistData, &jsonError);
-    chanlistData.clear();
-    if (jsonError.error != QJsonParseError::NoError)
-    {
-        // TODO: Report errors to the user.
-        qCritical() << "Failed to parse channel list JSON:" << jsonError.errorString() << "at" << jsonError.offset;
-        m_chanListLoading = false;
-        return;
+    if (downloadUrl.isEmpty()) {
+        qWarning() << "UpdateChecker: feed has version" << feedVersion
+                   << "but no asset matching BUILD_ARTIFACT '" << BuildConfig.BUILD_ARTIFACT << "'";
+        // We can still report an update even without a direct URL —
+        // the UpdateDialog will inform the user.
     }
 
-    QJsonObject object = jsonDoc.object();
+    // ---- Parse the GitHub releases JSON -----------------------------------
+    // Expect the GitHub REST API format: { "tag_name": "vX.Y.Z", ... }
 
-    bool success = false;
-    int formatVersion = object.value("format_version").toVariant().toInt(&success);
-    if (formatVersion != CHANLIST_FORMAT || !success)
+    QString githubVersion;
     {
-        qCritical()
-            << "Failed to check for updates. Channel list format version mismatch. We're using"
-            << CHANLIST_FORMAT << "server has" << formatVersion;
-        m_chanListLoading = false;
-        return;
-    }
+        QJsonParseError jsonError;
+        const QJsonDocument doc = QJsonDocument::fromJson(m_githubData, &jsonError);
+        m_githubData.clear();
 
-    // Load channels into a temporary array.
-    QList<ChannelListEntry> loadedChannels;
-    QJsonArray channelArray = object.value("channels").toArray();
-    for (QJsonValue chanVal : channelArray)
-    {
-        QJsonObject channelObj = chanVal.toObject();
-        ChannelListEntry entry {
-            channelObj.value("id").toVariant().toString(),
-            channelObj.value("name").toVariant().toString(),
-            channelObj.value("description").toVariant().toString(),
-            channelObj.value("url").toVariant().toString()
-        };
-        if (entry.id.isEmpty() || entry.name.isEmpty() || entry.url.isEmpty())
-        {
-            qCritical() << "Channel list entry with empty ID, name, or URL. Skipping.";
-            continue;
+        if (jsonError.error != QJsonParseError::NoError || !doc.isObject()) {
+            emit checkFailed(tr("Failed to parse GitHub releases response: %1").arg(jsonError.errorString()));
+            return;
+        }
+
+        const QString tag = doc.object().value("tag_name").toString().trimmed();
+        if (tag.isEmpty()) {
+            emit checkFailed(tr("GitHub releases response contained no tag_name field."));
+            return;
         }
-        loadedChannels.append(entry);
+        githubVersion = normalizeVersion(tag);
     }
 
-    // Swap  the channel list we just loaded into the object's channel list.
-    m_channels.swap(loadedChannels);
+    qDebug() << "UpdateChecker: feed version =" << feedVersion
+             << "| github version =" << githubVersion
+             << "| current =" << currentVersion();
 
-    m_chanListLoading = false;
-    m_chanListLoaded = true;
-    qDebug() << "Successfully loaded UpdateChecker channel list.";
+    // ---- Cross-check both sources -----------------------------------------
+    if (feedVersion != githubVersion) {
+        qDebug() << "UpdateChecker: feed and GitHub disagree on version — no update reported.";
+        if (notifyNoUpdate)
+            emit noUpdateFound();
+        return;
+    }
 
-    // If we're waiting to check for updates, do that now.
-    if (m_checkUpdateWaiting) {
-        checkForUpdate(m_deferredUpdateChannel, notifyNoUpdate);
+    // ---- Compare against the running version ------------------------------
+    if (compareVersions(feedVersion, currentVersion()) <= 0) {
+        qDebug() << "UpdateChecker: already up to date.";
+        if (notifyNoUpdate)
+            emit noUpdateFound();
+        return;
     }
 
-    emit channelListLoaded();
+    qDebug() << "UpdateChecker: update available:" << feedVersion;
+    UpdateAvailableStatus status;
+    status.version      = feedVersion;
+    status.downloadUrl  = downloadUrl;
+    status.releaseNotes = releaseNotes;
+    emit updateAvailable(status);
 }
 
-void UpdateChecker::chanListDownloadFailed(QString reason)
+void UpdateChecker::onDownloadsFailed(QString reason)
 {
-    m_chanListLoading = false;
-    qCritical() << QString("Failed to download channel list: %1").arg(reason);
-    emit channelListLoaded();
+    m_checking = false;
+    m_checkJob.reset();
+    m_feedData.clear();
+    m_githubData.clear();
+    qCritical() << "UpdateChecker: download failed:" << reason;
+    emit checkFailed(reason);
 }
 
diff --git a/launcher/updater/UpdateChecker.h b/launcher/updater/UpdateChecker.h
index 19b020d262..d253d2fbbc 100644
--- a/launcher/updater/UpdateChecker.h
+++ b/launcher/updater/UpdateChecker.h
@@ -17,128 +17,96 @@
  *
  *   You should have received a copy of the GNU General Public License
  *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
- *  
- *  This file incorporates work covered by the following copyright and
- *  permission notice:
- *
- * Copyright 2013-2021 MultiMC Contributors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
  */
 
 #pragma once
 
+#include <QObject>
+#include <QString>
 #include "net/NetJob.h"
-#include "GoUpdate.h"
 
+/*!
+ * Carries all information about an available update that is needed by the
+ * UpdateController and the UpdateDialog.
+ */
+struct UpdateAvailableStatus
+{
+    /// Normalized version string, e.g. "7.1.0"
+    QString version;
+    /// Direct download URL for this platform's artifact (from the feed).
+    QString downloadUrl;
+    /// HTML release notes extracted from the feed's <description> element.
+    QString releaseNotes;
+};
+Q_DECLARE_METATYPE(UpdateAvailableStatus)
+
+/*!
+ * UpdateChecker performs the two-source update check used by MeshMC.
+ *
+ * Algorithm:
+ *   1. Download the RSS feed at BuildConfig.UPDATER_FEED_URL in parallel with
+ *      the GitHub releases JSON at BuildConfig.UPDATER_GITHUB_API_URL.
+ *   2. Parse the latest stable <item> from the feed → extract <projt:version>
+ *      and the <projt:asset> URL whose name contains BuildConfig.BUILD_ARTIFACT.
+ *   3. Parse the GitHub JSON → strip leading "v" from tag_name.
+ *   4. Both versions must match and be greater than the running version;
+ *      otherwise the check is considered a no-update or failure.
+ *
+ * Platform / mode gating (runtime):
+ *   - Linux + APPIMAGE env variable set  → updater disabled.
+ *   - Linux + no portable.txt in app dir → updater disabled.
+ *   - Windows / macOS / Linux-portable   → updater active.
+ */
 class UpdateChecker : public QObject
 {
     Q_OBJECT
 
 public:
-    UpdateChecker(shared_qobject_ptr<QNetworkAccessManager> nam, QString channelUrl, QString currentChannel, int currentBuild);
-    void checkForUpdate(QString updateChannel, bool notifyNoUpdate);
-
-    /*!
-     * Causes the update checker to download the channel list from the URL specified in config.h (generated by CMake).
-     * If this isn't called before checkForUpdate(), it will automatically be called.
-     */
-    void updateChanList(bool notifyNoUpdate);
-
-    /*!
-     * An entry in the channel list.
-     */
-    struct ChannelListEntry
-    {
-        QString id;
-        QString name;
-        QString description;
-        QString url;
-    };
+    explicit UpdateChecker(shared_qobject_ptr<QNetworkAccessManager> nam, QObject* parent = nullptr);
 
     /*!
-     * Returns a the current channel list.
-     * If the channel list hasn't been loaded, this list will be empty.
+     * Starts an asynchronous two-source update check.
+     * If \a notifyNoUpdate is true, noUpdateFound() is emitted when the running
+     * version is already the latest; otherwise the signal is suppressed.
+     * Repeated calls while a check is in progress are silently ignored.
      */
-    QList<ChannelListEntry> getChannelList() const;
+    void checkForUpdate(bool notifyNoUpdate);
 
     /*!
-     * Returns false if the channel list is empty.
+     * Returns true if the updater may run on this platform / installation mode.
+     * Evaluated at runtime: AppImage detection, portable.txt presence, OS.
+     * Also checks that BuildConfig.UPDATER_ENABLED is true.
      */
-    bool hasChannels() const;
+    static bool isUpdaterSupported();
 
 signals:
-    //! Signal emitted when an update is available. Passes the URL for the repo and the ID and name for the version.
-    void updateAvailable(GoUpdate::Status status);
-
-    //! Signal emitted when the channel list finishes loading or fails to load.
-    void channelListLoaded();
+    //! Emitted when both sources agree that a newer version is available.
+    void updateAvailable(UpdateAvailableStatus status);
 
+    //! Emitted when the check completes but the running version is current.
     void noUpdateFound();
 
-private slots:
-    void updateCheckFinished(bool notifyNoUpdate);
-    void updateCheckFailed();
+    //! Emitted on any network or parse failure.
+    void checkFailed(QString reason);
 
-    void chanListDownloadFinished(bool notifyNoUpdate);
-    void chanListDownloadFailed(QString reason);
+private slots:
+    void onDownloadsFinished(bool notifyNoUpdate);
+    void onDownloadsFailed(QString reason);
 
 private:
-    friend class UpdateCheckerTest;
+    static bool isPortableMode();
+    static bool isAppImage();
+    /// Returns current version as "MAJOR.MINOR.HOTFIX".
+    static QString currentVersion();
+    /// Strips a leading 'v' and returns a clean X.Y.Z string.
+    static QString normalizeVersion(const QString &v);
+    /// Compares two "X.Y.Z" strings numerically. Returns >0 if v1 > v2.
+    static int compareVersions(const QString &v1, const QString &v2);
 
     shared_qobject_ptr<QNetworkAccessManager> m_network;
-
-    NetJob::Ptr indexJob;
-    QByteArray indexData;
-    NetJob::Ptr chanListJob;
-    QByteArray chanlistData;
-
-    QString m_channelUrl;
-
-    QList<ChannelListEntry> m_channels;
-
-    /*!
-     * True while the system is checking for updates.
-     * If checkForUpdate is called while this is true, it will be ignored.
-     */
-    bool m_updateChecking = false;
-
-    /*!
-     * True if the channel list has loaded.
-     * If this is false, trying to check for updates will call updateChanList first.
-     */
-    bool m_chanListLoaded = false;
-
-    /*!
-     * Set to true while the channel list is currently loading.
-     */
-    bool m_chanListLoading = false;
-
-    /*!
-     * Set to true when checkForUpdate is called while the channel list isn't loaded.
-     * When the channel list finishes loading, if this is true, the update checker will check for updates.
-     */
-    bool m_checkUpdateWaiting = false;
-
-    /*!
-     * if m_checkUpdateWaiting, this is the last used update channel
-     */
-    QString m_deferredUpdateChannel;
-
-    int m_currentBuild = -1;
-    QString m_currentChannel;
-    QString m_currentRepoUrl;
-
-    QString m_newRepoUrl;
+    NetJob::Ptr m_checkJob;
+    QByteArray m_feedData;
+    QByteArray m_githubData;
+    bool m_checking = false;
 };
 
diff --git a/updater/CMakeLists.txt b/updater/CMakeLists.txt
new file mode 100644
index 0000000000..b65709fa90
--- /dev/null
+++ b/updater/CMakeLists.txt
@@ -0,0 +1,40 @@
+# SPDX-FileCopyrightText: 2026 Project Tick
+# SPDX-FileContributor: Project Tick
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+cmake_minimum_required(VERSION 3.28)
+
+project(meshmc-updater)
+
+set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+find_package(Qt6 REQUIRED COMPONENTS Core Network)
+find_package(LibArchive REQUIRED)
+
+# On Windows: use Win32 subsystem so no console window appears.
+if(WIN32)
+    set(UPDATER_WIN32_FLAG WIN32)
+else()
+    set(UPDATER_WIN32_FLAG "")
+endif()
+
+add_executable(meshmc-updater ${UPDATER_WIN32_FLAG}
+    main.cpp
+    Installer.h
+    Installer.cpp
+)
+
+target_link_libraries(meshmc-updater
+    PRIVATE
+        Qt6::Core
+        Qt6::Network
+        LibArchive::LibArchive
+)
+
+# Install alongside the main binary so UpdateController can find it.
+install(TARGETS meshmc-updater
+    RUNTIME DESTINATION "${BINARY_DEST_DIR}"
+)
diff --git a/updater/Installer.cpp b/updater/Installer.cpp
new file mode 100644
index 0000000000..4f4b249dad
--- /dev/null
+++ b/updater/Installer.cpp
@@ -0,0 +1,346 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "Installer.h"
+
+#include <QCoreApplication>
+#include <QDebug>
+#include <QDir>
+#include <QDirIterator>
+#include <QFileInfo>
+#include <QNetworkReply>
+#include <QNetworkRequest>
+#include <QProcess>
+#include <QSaveFile>
+#include <QTemporaryDir>
+#include <QThread>
+
+// LibArchive is used for zip and tar.gz extraction.
+#include <archive.h>
+#include <archive_entry.h>
+
+// ---------------------------------------------------------------------------
+// Construction
+// ---------------------------------------------------------------------------
+
+Installer::Installer(QObject *parent) : QObject(parent)
+{
+    m_nam = new QNetworkAccessManager(this);
+}
+
+// ---------------------------------------------------------------------------
+// Public
+// ---------------------------------------------------------------------------
+
+void Installer::start()
+{
+    emit progressMessage(tr("Downloading update from %1 …").arg(m_url));
+    qDebug() << "Installer: downloading" << m_url;
+
+    // Determine a temp file name from the URL.
+    const QFileInfo urlInfo(QUrl(m_url).path());
+    m_tempFile = QDir::tempPath() + "/meshmc-update-" + urlInfo.fileName();
+
+    QNetworkRequest req{QUrl{m_url}};
+    req.setAttribute(QNetworkRequest::RedirectPolicyAttribute, QNetworkRequest::NoLessSafeRedirectPolicy);
+    QNetworkReply *reply = m_nam->get(req);
+    connect(reply, &QNetworkReply::downloadProgress, this, &Installer::onDownloadProgress);
+    connect(reply, &QNetworkReply::finished,         this, &Installer::onDownloadFinished);
+}
+
+// ---------------------------------------------------------------------------
+// Private slots
+// ---------------------------------------------------------------------------
+
+void Installer::onDownloadProgress(qint64 received, qint64 total)
+{
+    if (total > 0) {
+        const int pct = static_cast<int>((received * 100) / total);
+        emit progressMessage(tr("Downloading … %1%").arg(pct));
+    }
+}
+
+void Installer::onDownloadFinished()
+{
+    auto *reply = qobject_cast<QNetworkReply *>(sender());
+    if (!reply) return;
+    reply->deleteLater();
+
+    if (reply->error() != QNetworkReply::NoError) {
+        emit finished(false, tr("Download failed: %1").arg(reply->errorString()));
+        return;
+    }
+
+    // Write to temp file.
+    QSaveFile file(m_tempFile);
+    if (!file.open(QIODevice::WriteOnly)) {
+        emit finished(false, tr("Cannot write temp file: %1").arg(file.errorString()));
+        return;
+    }
+    file.write(reply->readAll());
+    if (!file.commit()) {
+        emit finished(false, tr("Cannot commit temp file: %1").arg(file.errorString()));
+        return;
+    }
+
+    emit progressMessage(tr("Download complete. Installing …"));
+    qDebug() << "Installer: saved to" << m_tempFile;
+
+    const bool ok = installArchive(m_tempFile);
+
+    if (!ok) {
+        QFile::remove(m_tempFile);
+        return; // finished() already emitted inside installArchive / installExe
+    }
+
+    QFile::remove(m_tempFile);
+    relaunch();
+    emit finished(true, QString());
+}
+
+// ---------------------------------------------------------------------------
+// Private helpers
+// ---------------------------------------------------------------------------
+
+bool Installer::installArchive(const QString &filePath)
+{
+    const QString lower = filePath.toLower();
+
+    if (lower.endsWith(".exe")) {
+        return installExe(filePath);
+    }
+
+    if (lower.endsWith(".zip") || lower.endsWith(".tar.gz") || lower.endsWith(".tgz")) {
+        // Extract into a temp directory, then copy over root.
+        QTemporaryDir tempDir;
+        if (!tempDir.isValid()) {
+            emit finished(false, tr("Cannot create temporary directory for extraction."));
+            return false;
+        }
+
+        emit progressMessage(tr("Extracting archive …"));
+
+        bool extractOk = false;
+        if (lower.endsWith(".zip")) {
+            extractOk = extractZip(filePath, tempDir.path());
+        } else {
+            extractOk = extractTarGz(filePath, tempDir.path());
+        }
+
+        if (!extractOk) {
+            return false; // finished() already emitted
+        }
+
+        // Copy all extracted files into the root, skipping the updater binary itself.
+        emit progressMessage(tr("Installing files …"));
+
+        const QString updaterName =
+#ifdef Q_OS_WIN
+            "meshmc-updater.exe";
+#else
+            "meshmc-updater";
+#endif
+
+        QDir src(tempDir.path());
+        // If the archive has a single top-level directory, descend into it.
+        const QStringList topEntries = src.entryList(QDir::Dirs | QDir::NoDotAndDotDot);
+        if (topEntries.size() == 1 &&
+            src.entryList(QDir::Files | QDir::NoDotAndDotDot).isEmpty()) {
+            src.cd(topEntries.first());
+        }
+
+        const QDir dest(m_root);
+        QDirIterator it(src.absolutePath(), QDir::Files | QDir::NoDotAndDotDot, QDirIterator::Subdirectories);
+        while (it.hasNext()) {
+            it.next();
+            const QFileInfo &fi = it.fileInfo();
+
+            const QString relPath = src.relativeFilePath(fi.absoluteFilePath());
+            // Don't replace ourselves while running.
+            if (relPath == updaterName)
+                continue;
+
+            const QString destPath = dest.filePath(relPath);
+            QFileInfo destInfo(destPath);
+            if (!QDir().mkpath(destInfo.absolutePath())) {
+                emit finished(false, tr("Cannot create directory: %1").arg(destInfo.absolutePath()));
+                return false;
+            }
+            if (destInfo.exists())
+                QFile::remove(destPath);
+
+            if (!QFile::copy(fi.absoluteFilePath(), destPath)) {
+                emit finished(false, tr("Cannot copy %1 to %2.").arg(relPath, destPath));
+                return false;
+            }
+
+            // Preserve executable bit on Unix.
+#ifndef Q_OS_WIN
+            if (fi.isExecutable()) {
+                QFile(destPath).setPermissions(
+                    QFile::ReadOwner | QFile::WriteOwner | QFile::ExeOwner |
+                    QFile::ReadGroup | QFile::ExeGroup |
+                    QFile::ReadOther | QFile::ExeOther);
+            }
+#endif
+        }
+
+        return true;
+    }
+
+    emit finished(false, tr("Unknown archive format: %1").arg(QFileInfo(filePath).suffix()));
+    return false;
+}
+
+bool Installer::installExe(const QString &filePath)
+{
+    // For Windows NSIS / Inno Setup installers, just run the installer directly.
+    // It handles file replacement and relaunching.
+#ifdef Q_OS_WIN
+    emit progressMessage(tr("Launching installer …"));
+    const bool ok = QProcess::startDetached(filePath, QStringList());
+    if (!ok) {
+        emit finished(false, tr("Failed to launch installer: %1").arg(filePath));
+        return false;
+    }
+    // The installer will take care of everything; exit after launching.
+    QCoreApplication::quit();
+    return true;
+#else
+    Q_UNUSED(filePath)
+    emit finished(false, tr(".exe installers are only supported on Windows."));
+    return false;
+#endif
+}
+
+bool Installer::extractZip(const QString &zipPath, const QString &destDir)
+{
+    archive *a = archive_read_new();
+    archive_read_support_format_zip(a);
+    archive_read_support_filter_all(a);
+
+    if (archive_read_open_filename(a, zipPath.toLocal8Bit().constData(), 10240) != ARCHIVE_OK) {
+        const QString err = QString::fromLocal8Bit(archive_error_string(a));
+        archive_read_free(a);
+        emit finished(false, tr("Cannot open zip archive: %1").arg(err));
+        return false;
+    }
+
+    archive *ext = archive_write_disk_new();
+    archive_write_disk_set_options(ext,
+        ARCHIVE_EXTRACT_TIME | ARCHIVE_EXTRACT_PERM | ARCHIVE_EXTRACT_ACL | ARCHIVE_EXTRACT_FFLAGS);
+    archive_write_disk_set_standard_lookup(ext);
+
+    archive_entry *entry = nullptr;
+    bool ok = true;
+    while (archive_read_next_header(a, &entry) == ARCHIVE_OK) {
+        const QString entryPath = destDir + "/" + QString::fromLocal8Bit(archive_entry_pathname(entry));
+        archive_entry_set_pathname(entry, entryPath.toLocal8Bit().constData());
+
+        if (archive_write_header(ext, entry) != ARCHIVE_OK) {
+            ok = false;
+            break;
+        }
+        if (archive_entry_size(entry) > 0) {
+            const void *buf;
+            size_t size;
+            la_int64_t offset;
+            while (archive_read_data_block(a, &buf, &size, &offset) == ARCHIVE_OK) {
+                archive_write_data_block(ext, buf, size, offset);
+            }
+        }
+        archive_write_finish_entry(ext);
+    }
+
+    archive_read_close(a);
+    archive_read_free(a);
+    archive_write_close(ext);
+    archive_write_free(ext);
+
+    if (!ok) {
+        emit finished(false, tr("Failed to extract zip archive."));
+        return false;
+    }
+    return true;
+}
+
+bool Installer::extractTarGz(const QString &tarPath, const QString &destDir)
+{
+    archive *a = archive_read_new();
+    archive_read_support_format_tar(a);
+    archive_read_support_format_gnutar(a);
+    archive_read_support_filter_gzip(a);
+    archive_read_support_filter_bzip2(a);
+    archive_read_support_filter_xz(a);
+
+    if (archive_read_open_filename(a, tarPath.toLocal8Bit().constData(), 10240) != ARCHIVE_OK) {
+        const QString err = QString::fromLocal8Bit(archive_error_string(a));
+        archive_read_free(a);
+        emit finished(false, tr("Cannot open tar archive: %1").arg(err));
+        return false;
+    }
+
+    archive *ext = archive_write_disk_new();
+    archive_write_disk_set_options(ext,
+        ARCHIVE_EXTRACT_TIME | ARCHIVE_EXTRACT_PERM | ARCHIVE_EXTRACT_ACL | ARCHIVE_EXTRACT_FFLAGS);
+    archive_write_disk_set_standard_lookup(ext);
+
+    archive_entry *entry = nullptr;
+    bool ok = true;
+    while (archive_read_next_header(a, &entry) == ARCHIVE_OK) {
+        const QString entryPath = destDir + "/" + QString::fromLocal8Bit(archive_entry_pathname(entry));
+        archive_entry_set_pathname(entry, entryPath.toLocal8Bit().constData());
+
+        if (archive_write_header(ext, entry) != ARCHIVE_OK) {
+            ok = false;
+            break;
+        }
+        if (archive_entry_size(entry) > 0) {
+            const void *buf;
+            size_t size;
+            la_int64_t offset;
+            while (archive_read_data_block(a, &buf, &size, &offset) == ARCHIVE_OK) {
+                archive_write_data_block(ext, buf, size, offset);
+            }
+        }
+        archive_write_finish_entry(ext);
+    }
+
+    archive_read_close(a);
+    archive_read_free(a);
+    archive_write_close(ext);
+    archive_write_free(ext);
+
+    if (!ok) {
+        emit finished(false, tr("Failed to extract tar archive."));
+        return false;
+    }
+    return true;
+}
+
+void Installer::relaunch()
+{
+    if (m_exec.isEmpty())
+        return;
+
+    qDebug() << "Installer: relaunching" << m_exec;
+    QProcess::startDetached(m_exec, QStringList());
+}
diff --git a/updater/Installer.h b/updater/Installer.h
new file mode 100644
index 0000000000..2f56315a07
--- /dev/null
+++ b/updater/Installer.h
@@ -0,0 +1,78 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <QObject>
+#include <QString>
+#include <QNetworkAccessManager>
+
+/*!
+ * Installer downloads an update artifact and installs it.
+ *
+ * Supported artifact types (determined by file extension):
+ *   .exe   - Windows NSIS/Inno installer: run directly, installer handles everything.
+ *   .zip   - Portable zip archive: extract over the root directory.
+ *   .tar.gz / .tgz - Portable tarball: extract over the root directory.
+ *   .dmg   - macOS disk image: mount, copy .app bundle, unmount. (planned)
+ *
+ * After a successful archive extraction the application binary given by
+ * \c setRelaunchPath() is started and the updater exits.
+ */
+class Installer : public QObject
+{
+    Q_OBJECT
+
+public:
+    explicit Installer(QObject *parent = nullptr);
+
+    void setDownloadUrl(const QString &url)   { m_url       = url;   }
+    void setRootPath(const QString &root)     { m_root      = root;  }
+    void setRelaunchPath(const QString &exec) { m_exec      = exec;  }
+
+    /*!
+     * Start the install process asynchronously.
+     * The object emits \c finished() with a success flag when done.
+     */
+    void start();
+
+signals:
+    void progressMessage(const QString &msg);
+    void finished(bool success, const QString &errorMessage);
+
+private slots:
+    void onDownloadProgress(qint64 received, qint64 total);
+    void onDownloadFinished();
+
+private:
+    bool installArchive(const QString &filePath);
+    bool installExe(const QString &filePath);
+    bool extractZip(const QString &zipPath, const QString &destDir);
+    bool extractTarGz(const QString &tarPath, const QString &destDir);
+    void relaunch();
+
+    QString  m_url;
+    QString  m_root;
+    QString  m_exec;
+    QString  m_tempFile;
+
+    QNetworkAccessManager *m_nam = nullptr;
+};
diff --git a/updater/main.cpp b/updater/main.cpp
new file mode 100644
index 0000000000..158cbed597
--- /dev/null
+++ b/updater/main.cpp
@@ -0,0 +1,105 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*
+ * meshmc-updater — standalone updater binary for MeshMC.
+ *
+ * Usage:
+ *   meshmc-updater --url <download_url>
+ *                  --root <install_root>
+ *                  --exec <relaunch_path>
+ *
+ *   --url   : Full URL of the artifact to download and install.
+ *   --root  : Installation root directory (where meshmc binary lives).
+ *   --exec  : Path to the main MeshMC binary to relaunch after update.
+ *
+ * The binary waits a short time after launch to let the main application
+ * exit cleanly before overwriting its files.
+ */
+
+#include <QCoreApplication>
+#include <QCommandLineOption>
+#include <QCommandLineParser>
+#include <QDebug>
+#include <QThread>
+#include <QTimer>
+
+#include "Installer.h"
+
+int main(int argc, char *argv[])
+{
+    QCoreApplication app(argc, argv);
+    app.setApplicationName("meshmc-updater");
+    app.setOrganizationName("Project Tick");
+
+    QCommandLineParser parser;
+    parser.setApplicationDescription("MeshMC Updater");
+    parser.addHelpOption();
+
+    QCommandLineOption urlOpt("url",     "URL of the update artifact to download.", "url");
+    QCommandLineOption rootOpt("root",   "Installation root directory.",            "root");
+    QCommandLineOption execOpt("exec",   "Path to relaunch after update.",          "exec");
+
+    parser.addOption(urlOpt);
+    parser.addOption(rootOpt);
+    parser.addOption(execOpt);
+    parser.process(app);
+
+    const QString url  = parser.value(urlOpt).trimmed();
+    const QString root = parser.value(rootOpt).trimmed();
+    const QString exec = parser.value(execOpt).trimmed();
+
+    if (url.isEmpty() || root.isEmpty()) {
+        fprintf(stderr, "meshmc-updater: --url and --root are required.\n");
+        return 1;
+    }
+
+    qDebug() << "meshmc-updater: url =" << url
+             << "| root =" << root
+             << "| exec =" << exec;
+
+    // Give the main application 2 seconds to exit before we start overwriting files.
+    auto *installer = new Installer(&app);
+    installer->setDownloadUrl(url);
+    installer->setRootPath(root);
+    installer->setRelaunchPath(exec);
+
+    QObject::connect(installer, &Installer::progressMessage,
+                     [](const QString &msg) { qDebug() << "updater:" << msg; });
+
+    QObject::connect(installer, &Installer::finished,
+                     [](bool success, const QString &errorMsg) {
+                         if (!success) {
+                             qCritical() << "meshmc-updater: installation failed:" << errorMsg;
+                             QCoreApplication::exit(1);
+                         } else {
+                             qDebug() << "meshmc-updater: update installed successfully.";
+                             QCoreApplication::exit(0);
+                         }
+                     });
+
+    // Delay start to give the parent process time to close.
+    QTimer::singleShot(2000, &app, [installer]() {
+        installer->start();
+    });
+
+    return app.exec();
+}