.gitignore

@@ -20,3 +20,4 @@ packs/
 .__pycache__
 .pytest_cache
 .venvtodo.txt
+*.bak

launcher/bootstrap/src/main/java/me/sashegdev/zernmc/launcher/Bootstrap.java

@@ -78,6 +78,19 @@ public class Bootstrap {
         log("Server version: " + serverVersion);
         setVersionInfo(currentVersion, serverVersion);
 
+        if ("unknown".equals(serverVersion)) {
+            boolean ranDiagnostics = runDiagnosticsIfPossible();
+            if (ranDiagnostics) {
+                serverVersion = getServerVersion();
+                log("Server version after diagnostics: " + serverVersion);
+                setVersionInfo(currentVersion, serverVersion);
+            }
+            if ("unknown".equals(serverVersion) && !argList.contains("--offline")) {
+                log("Server still unreachable. Launcher will start in offline mode.");
+                argList.add("--offline");
+            }
+        }
+        
         loadMirrors();
         log("Primary server: " + BASE_URL);
         log("Mirrors available: " + (MIRRORS.size() + 1));
@@ -125,6 +138,119 @@ public class Bootstrap {
         }
     }
 
+    private static boolean runDiagnosticsIfPossible() {
+        Path diagJar = binDir.resolve("zernmcdiag.jar");
+        if (!Files.exists(diagJar)) {
+            log("Diagnostics tool not found: bin/zernmcdiag.jar is missing.");
+            log("Please download the latest launcher manually from the ZernMC website.");
+            showMessageUi("ZernMC — нет связи с сервером",
+                    "Не удалось связаться с серверами Zern.\n\n"
+                            + "Файл диагностики (bin/zernmcdiag.jar) отсутствует.\n"
+                            + "Скачайте свежий лаунчер вручную с официального сайта ZernMC.");
+            return false;
+        }
+
+        boolean confirmed;
+        if (isCliMode) {
+            confirmed = askCliConfirm();
+        } else {
+            confirmed = confirmUi("ZernMC — нет связи с сервером",
+                    "Не удалось связаться с серверами Zern.\nПровести диагностику сети?");
+        }
+        if (!confirmed) {
+            log("Diagnostics declined by user.");
+            return false;
+        }
+
+        try {
+            launchDiag(diagJar);
+            return true;
+        } catch (Exception e) {
+            log("Failed to launch diagnostics: " + e.getMessage());
+            return false;
+        }
+    }
+
+    private static void launchDiag(Path diagJar) throws Exception {
+        String os = System.getProperty("os.name").toLowerCase();
+        Path javaBin = findJava(false);
+        if (os.contains("windows")) {
+            Path javawPath = javaBin.resolveSibling("javaw.exe");
+            if (Files.exists(javawPath)) {
+                javaBin = javawPath;
+            }
+        }
+
+        List<String> cmd = new ArrayList<>();
+        cmd.add(javaBin.toAbsolutePath().toString());
+        cmd.add("-Dfile.encoding=UTF-8");
+        cmd.add("-jar");
+        cmd.add(diagJar.toAbsolutePath().toString());
+        if (isCliMode) {
+            cmd.add("--cli");
+        }
+
+        log("Starting diagnostics: " + String.join(" ", cmd));
+
+        ProcessBuilder pb = new ProcessBuilder(cmd);
+        pb.directory(baseDir.toFile());
+        pb.redirectErrorStream(false);
+
+        Process p = pb.start();
+        drainOutput(p.getInputStream(), "diag");
+        drainOutput(p.getErrorStream(), "diag-err");
+        int exit = p.waitFor();
+        log("Diagnostics finished, exit code: " + exit);
+    }
+
+    private static void drainOutput(InputStream stream, String tag) {
+        Thread t = new Thread(() -> {
+            try (BufferedReader reader = new BufferedReader(new InputStreamReader(stream, StandardCharsets.UTF_8))) {
+                String line;
+                while ((line = reader.readLine()) != null) {
+                    log("[" + tag + "] " + line);
+                }
+            } catch (IOException ignored) {
+            }
+        }, "diag-drain-" + tag);
+        t.setDaemon(true);
+        t.start();
+    }
+
+    private static boolean askCliConfirm() {
+        System.out.println("Server unreachable. Run network diagnostics? [y/N]");
+        try {
+            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in, StandardCharsets.UTF_8));
+            String line = reader.readLine();
+            return line != null && (line.equalsIgnoreCase("y") || line.equalsIgnoreCase("yes"));
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
+    private static boolean confirmUi(String title, String message) {
+        final boolean[] result = new boolean[1];
+        try {
+            SwingUtilities.invokeAndWait(() -> {
+                int choice = JOptionPane.showConfirmDialog(null, message, title,
+                        JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
+                result[0] = choice == JOptionPane.YES_OPTION;
+            });
+        } catch (Exception e) {
+            log("UI confirm error: " + e.getMessage());
+        }
+        return result[0];
+    }
+
+    private static void showMessageUi(String title, String message) {
+        try {
+            SwingUtilities.invokeAndWait(() ->
+                    JOptionPane.showMessageDialog(null, message, title, JOptionPane.INFORMATION_MESSAGE));
+        } catch (Exception e) {
+            log("UI message error: " + e.getMessage());
+        }
+    }
+    
     private static void launchInProcess(String[] args) throws Exception {
         ClassLoader parent = Bootstrap.class.getClassLoader();
         URL[] urls = { getLauncherJar().toUri().toURL() };
@@ -172,6 +298,12 @@ public class Bootstrap {
         cmd.add(getLauncherJar().toAbsolutePath().toString());
         cmd.add("--jfx");
 
+        for (String arg : args) {
+            if (!"--jfx".equals(arg) && !"--cli".equals(arg) && !cmd.contains(arg)) {
+                cmd.add(arg);
+            }
+        }
+        
         ProcessBuilder pb = new ProcessBuilder(cmd);
         pb.directory(baseDir.toFile());
         pb.redirectErrorStream(false);

launcher/diag/pom.xml

@@ -0,0 +1,75 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>me.sashegdev</groupId>
+        <artifactId>ZernMCLauncher</artifactId>
+        <version>${revision}</version>
+    </parent>
+
+    <artifactId>zernmc-diag</artifactId>
+    <packaging>jar</packaging>
+
+    <name>ZernMC Network Diagnostics</name>
+    <description>Standalone network diagnostics utility (DNS, connectivity, report upload)</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>dnsjava</groupId>
+            <artifactId>dnsjava</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.json</groupId>
+            <artifactId>json</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.10.1</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>3.5.0</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <outputFile>../../server/builds/bin/zernmcdiag.jar</outputFile>
+                            <filters>
+                                <filter>
+                                    <artifact>dnsjava:dnsjava</artifact>
+                                    <excludes>
+                                        <exclude>META-INF/services/java.net.spi.InetAddressResolverProvider</exclude>
+                                        <exclude>META-INF/services/sun.net.spi.nameservice.NameServiceDescriptor</exclude>
+                                    </excludes>
+                                </filter>
+                            </filters>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>me.sashegdev.zernmc.launcher.diag.DiagMain</mainClass>
+                                    <manifestEntries>
+                                        <Implementation-Version>${project.version}.${hotfix}</Implementation-Version>
+                                        <Implementation-Title>ZernMC Network Diagnostics</Implementation-Title>
+                                        <Implementation-Vendor>SashegDev</Implementation-Vendor>
+                                    </manifestEntries>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/DiagCheck.java

@@ -0,0 +1,29 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.nio.file.Path;
+
+public record DiagCheck(String category, String name, String status, String detail, long latencyMs) {
+
+    public boolean ok() {
+        return "OK".equals(status);
+    }
+
+    public String renderLine() {
+        StringBuilder sb = new StringBuilder();
+        if ("OK".equals(status)) {
+            sb.append("  [OK]  ");
+        } else if ("FAIL".equals(status)) {
+            sb.append("  [FAIL]");
+        } else {
+            sb.append("  [SKIP]");
+        }
+        sb.append(' ').append(category).append(" / ").append(name);
+        if (latencyMs >= 0) {
+            sb.append(" (").append(latencyMs).append(" ms)");
+        }
+        if (detail != null && !detail.isEmpty()) {
+            sb.append(" -> ").append(detail);
+        }
+        return sb.toString();
+    }
+}

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/DiagConstants.java

@@ -0,0 +1,55 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.util.List;
+import java.util.Map;
+
+public final class DiagConstants {
+
+    public static final String HOST_API = "api.zern.cc";
+
+    public static final List<String> HOSTS = List.of(
+            HOST_API,
+            "api.zernmc.ru",
+            "api.zernmc.online",
+            "api.pl.zern.cc",
+            "api.swe.zern.cc",
+            "api.ru.zern.cc"
+    );
+
+    public static final List<String> KNOWN_SERVER_IPS = List.of(
+            "87.120.187.36",   // main (Frankfurt)
+            "212.22.82.243",   // ru geo (Moscow)
+            "2.26.5.202",      // pl geo (Warsaw)
+            "2.26.55.218"      // swe geo (Stockholm)
+    );
+
+    public static final String PRIMARY_API = "https://" + HOST_API;
+    public static final String DIRECT_API = "http://87.120.187.36:1582";
+
+    public static final List<Integer> TLS_PORTS = List.of(443, 80);
+    public static final int DIRECT_PORT = 1582;
+
+    public static final String VERSION_PATH = "/launcher/version";
+    public static final String CLIENT_IP_PATH = "/launcher/ip";
+    public static final String DIAG_UPLOAD_PATH = "/diag/upload";
+
+    public static final String DOH_GOOGLE_URL = "https://dns.google/resolve?name=%s&type=A";
+    public static final String DOH_CLOUDFLARE_URL = "https://cloudflare-dns.com/dns-query?name=%s&type=A";
+
+    public static final Map<String, String> DNS_PROVIDERS = Map.ofEntries(
+            Map.entry("Google 8.8.8.8", "8.8.8.8"),
+            Map.entry("Google 8.8.4.4", "8.8.4.4"),
+            Map.entry("Cloudflare 1.1.1.1", "1.1.1.1"),
+            Map.entry("Cloudflare 1.0.0.1", "1.0.0.1"),
+            Map.entry("Yandex 77.88.8.8", "77.88.8.8"),
+            Map.entry("Yandex 77.88.8.1", "77.88.8.1"),
+            Map.entry("OpenDNS 208.67.222.222", "208.67.222.222"),
+            Map.entry("Quad9 9.9.9.9", "9.9.9.9")
+    );
+
+    public static final int CONNECT_TIMEOUT_MS = 8000;
+    public static final int READ_TIMEOUT_MS = 8000;
+
+    private DiagConstants() {
+    }
+}

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/DiagMain.java

@@ -0,0 +1,79 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.List;
+
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+
+public final class DiagMain {
+
+    public static void main(String[] args) {
+        List<String> argList = Arrays.asList(args);
+        boolean cliMode = argList.contains("--cli");
+        Path baseDir = baseDirFromArgs(argList);
+
+        if (cliMode) {
+            runCli(baseDir);
+            return;
+        }
+
+        SwingUtilities.invokeLater(() -> {
+            try {
+                UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
+            } catch (Exception ignored) {
+            }
+            DiagnosticsUI ui = new DiagnosticsUI(baseDir);
+            ui.addWindowListener(new WindowAdapter() {
+                @Override
+                public void windowClosed(WindowEvent e) {
+                    System.exit(0);
+                }
+            });
+            ui.setVisible(true);
+            ui.start();
+        });
+    }
+
+    private static Path baseDirFromArgs(List<String> args) {
+        int idx = args.indexOf("--dir");
+        if (idx >= 0 && idx + 1 < args.size()) {
+            return Path.of(args.get(idx + 1)).toAbsolutePath();
+        }
+        return Path.of("").toAbsolutePath();
+    }
+
+    private static void runCli(Path baseDir) {
+        NetworkDiagnostics diag = new NetworkDiagnostics(baseDir, System.out::println, null);
+        Path log = diag.run();
+        System.out.println("Diagnostics log: " + (log != null ? log.toAbsolutePath() : "n/a"));
+        System.out.println("Client IP: " + diag.getClientIp());
+        if (log != null) {
+            System.out.print("Send report to the Zern server? [y/N]: ");
+            System.out.flush();
+            try {
+                BufferedReader reader = new BufferedReader(new InputStreamReader(System.in, StandardCharsets.UTF_8));
+                String line = reader.readLine();
+                if (line != null && (line.equalsIgnoreCase("y") || line.equalsIgnoreCase("yes"))) {
+                    ReportSender.SendResult r = ReportSender.send(log, diag.getClientIp());
+                    System.out.println("Send result: " + (r.ok() ? "OK via " + r.endpoint() : "FAILED (" + r.detail() + ")"));
+                }
+            } catch (Exception e) {
+                System.out.println("Send skipped: " + e.getMessage());
+            }
+        }
+        int exitCode = 0;
+        for (DiagCheck c : diag.getChecks()) {
+            if ("FAIL".equals(c.status()) && c.category().equals("HTTP")) {
+                exitCode = 1;
+            }
+        }
+        System.exit(exitCode);
+    }
+}

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/DiagnosticsUI.java

@@ -0,0 +1,194 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.awt.BorderLayout;
+import java.awt.Color;
+import java.awt.Desktop;
+import java.awt.Dimension;
+import java.awt.FlowLayout;
+import java.awt.Font;
+import java.awt.GridLayout;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import javax.swing.BorderFactory;
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.JOptionPane;
+import javax.swing.JPanel;
+import javax.swing.JScrollPane;
+import javax.swing.JTextArea;
+import javax.swing.SwingWorker;
+import javax.swing.border.EmptyBorder;
+
+public final class DiagnosticsUI extends JFrame {
+
+    private static final Color BG = new Color(0x15151a);
+    private static final Color PANEL = new Color(0x1e1e24);
+    private static final Color TEXT = new Color(0xe8e8ea);
+    private static final Color ACCENT = new Color(0x5dade2);
+
+    private final Path baseDir;
+    private final JTextArea output = new JTextArea();
+    private final JButton sendButton = new JButton("Отправить на сервер");
+    private final JLabel statusLabel = new JLabel("Запуск диагностики...");
+    private volatile Path diagLog;
+    private volatile String clientIp = "unknown";
+
+    public DiagnosticsUI(Path baseDir) {
+        this.baseDir = baseDir;
+        setTitle("ZernMC — Диагностика сети");
+        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
+        setSize(760, 560);
+        setMinimumSize(new Dimension(600, 420));
+        setLocationRelativeTo(null);
+
+        getContentPane().setBackground(BG);
+        ((JPanel) getContentPane()).setBorder(new EmptyBorder(16, 16, 16, 16));
+
+        JLabel header = new JLabel("Проверка связи с серверами Zern");
+        header.setFont(new Font("Segoe UI", Font.BOLD, 17));
+        header.setForeground(ACCENT);
+        header.setBorder(new EmptyBorder(0, 0, 10, 0));
+
+        output.setEditable(false);
+        output.setFont(new Font("Consolas", Font.PLAIN, 12));
+        output.setBackground(PANEL);
+        output.setForeground(TEXT);
+        output.setBorder(BorderFactory.createEmptyBorder(8, 8, 8, 8));
+        JScrollPane scroll = new JScrollPane(output);
+        scroll.setBorder(BorderFactory.createLineBorder(PANEL));
+
+        statusLabel.setForeground(TEXT);
+        statusLabel.setBorder(new EmptyBorder(8, 0, 0, 0));
+
+        JButton openButton = new JButton("Открыть папку с логом");
+        JButton closeButton = new JButton("Закрыть");
+        sendButton.setEnabled(false);
+
+        JPanel buttons = new JPanel(new FlowLayout(FlowLayout.RIGHT, 8, 0));
+        buttons.setOpaque(false);
+        buttons.add(openButton);
+        buttons.add(sendButton);
+        buttons.add(closeButton);
+
+        JPanel south = new JPanel(new BorderLayout());
+        south.setOpaque(false);
+        south.add(statusLabel, BorderLayout.NORTH);
+        south.add(buttons, BorderLayout.SOUTH);
+
+        setLayout(new BorderLayout());
+        add(header, BorderLayout.NORTH);
+        add(scroll, BorderLayout.CENTER);
+        add(south, BorderLayout.SOUTH);
+
+        openButton.addActionListener(e -> openFolder());
+        closeButton.addActionListener(e -> dispose());
+        sendButton.addActionListener(e -> sendReport());
+    }
+
+    public void start() {
+        SwingWorker<Void, String> worker = new SwingWorker<>() {
+            @Override
+            protected Void doInBackground() {
+                publish("\u2014 Сервер Zern недоступен, выполняем диагностику \u2014");
+                NetworkDiagnostics diag = new NetworkDiagnostics(baseDir,
+                        this::publish,
+                        c -> publish(renderCheck(c)));
+                diagLog = diag.run();
+                clientIp = diag.getClientIp();
+                publish("Диагностика завершена. Лог: " + (diagLog != null ? diagLog.toAbsolutePath() : "n/a"));
+                return null;
+            }
+
+            @Override
+            protected void process(java.util.List<String> chunks) {
+                for (String line : chunks) {
+                    appendLine(line);
+                }
+            }
+
+            @Override
+            protected void done() {
+                sendButton.setEnabled(diagLog != null);
+                statusLabel.setText("Готово. Можете отправить лог на сервер или сохранить его.");
+            }
+        };
+        worker.execute();
+    }
+
+    private static String renderCheck(DiagCheck c) {
+        String prefix = switch (c.status()) {
+            case "OK" -> "[OK]  ";
+            case "FAIL" -> "[FAIL]";
+            default -> "[SKIP]";
+        };
+        StringBuilder sb = new StringBuilder(prefix).append(' ').append(c.category()).append(" / ").append(c.name());
+        if (c.latencyMs() >= 0) {
+            sb.append(" (").append(c.latencyMs()).append(" ms)");
+        }
+        if (c.detail() != null && !c.detail().isEmpty()) {
+            sb.append(" -> ").append(c.detail());
+        }
+        return sb.toString();
+    }
+
+    private void appendLine(String line) {
+        output.append(line);
+        if (!line.endsWith("\n")) {
+            output.append("\n");
+        }
+        output.setCaretPosition(output.getDocument().getLength());
+    }
+
+    private void openFolder() {
+        try {
+            Path dir = diagLog != null ? diagLog.getParent() : baseDir;
+            if (dir != null && Files.exists(dir)) {
+                Desktop.getDesktop().open(dir.toFile());
+            } else {
+                JOptionPane.showMessageDialog(this, "Папка ещё не создана.");
+            }
+        } catch (Exception e) {
+            JOptionPane.showMessageDialog(this, "Не удалось открыть папку: " + e.getMessage());
+        }
+    }
+
+    private void sendReport() {
+        if (diagLog == null) {
+            return;
+        }
+        sendButton.setEnabled(false);
+        statusLabel.setText("Отправка отчёта на сервер...");
+        SwingWorker<ReportSender.SendResult, Void> worker = new SwingWorker<>() {
+            @Override
+            protected ReportSender.SendResult doInBackground() throws Exception {
+                return ReportSender.send(diagLog, clientIp);
+            }
+
+            @Override
+            protected void done() {
+                sendButton.setEnabled(true);
+                try {
+                    ReportSender.SendResult r = get();
+                    if (r.ok()) {
+                        statusLabel.setText("Отчёт отправлен: " + r.endpoint());
+                        JOptionPane.showMessageDialog(DiagnosticsUI.this,
+                                "Отчёт успешно отправлен на сервер Zern.",
+                                "Отправлено", JOptionPane.INFORMATION_MESSAGE);
+                    } else {
+                        statusLabel.setText("Не удалось отправить отчёт.");
+                        JOptionPane.showMessageDialog(DiagnosticsUI.this,
+                                "Не удалось отправить отчёт на сервер.\n"
+                                        + "Сохраните лог и отправьте его вручную:\n" + diagLog.toAbsolutePath()
+                                        + "\n\nОшибка: " + r.detail(),
+                                "Ошибка отправки", JOptionPane.WARNING_MESSAGE);
+                    }
+                } catch (Exception e) {
+                    statusLabel.setText("Ошибка отправки: " + e.getMessage());
+                }
+            }
+        };
+        worker.execute();
+    }
+}

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/DnsResolver.java

@@ -0,0 +1,128 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.net.InetAddress;
+import java.net.URL;
+import java.net.URLConnection;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.json.JSONArray;
+import org.json.JSONObject;
+import org.xbill.DNS.ARecord;
+import org.xbill.DNS.Lookup;
+import org.xbill.DNS.Record;
+import org.xbill.DNS.SimpleResolver;
+import org.xbill.DNS.Type;
+
+public final class DnsResolver {
+
+    private DnsResolver() {
+    }
+
+    public static List<String> resolveSystem(String host) {
+        try {
+            InetAddress[] addrs = InetAddress.getAllByName(host);
+            List<String> ips = new ArrayList<>();
+            for (InetAddress a : addrs) {
+                String ip = a.getHostAddress();
+                if (ip != null && !ips.contains(ip)) {
+                    ips.add(ip);
+                }
+            }
+            return ips;
+        } catch (Exception e) {
+            return List.of();
+        }
+    }
+
+    public static List<String> resolveDoHGoogle(String host) {
+        try {
+            String url = String.format(DiagConstants.DOH_GOOGLE_URL, host);
+            String body = doGet(url, "application/json");
+            JSONObject json = new JSONObject(body);
+            JSONArray answers = json.optJSONArray("Answer");
+            if (answers == null) {
+                return List.of();
+            }
+            List<String> ips = new ArrayList<>();
+            for (int i = 0; i < answers.length(); i++) {
+                JSONObject a = answers.optJSONObject(i);
+                if (a != null && a.optInt("type", 0) == 1) {
+                    String data = a.optString("data", null);
+                    if (data != null && !ips.contains(data)) {
+                        ips.add(data);
+                    }
+                }
+            }
+            return ips;
+        } catch (Exception e) {
+            return List.of();
+        }
+    }
+
+    public static List<String> resolveDoHCloudflare(String host) {
+        try {
+            String url = String.format(DiagConstants.DOH_CLOUDFLARE_URL, host);
+            String body = doGet(url, "application/dns-json");
+            JSONObject json = new JSONObject(body);
+            JSONArray answers = json.optJSONArray("Answer");
+            if (answers == null) {
+                return List.of();
+            }
+            List<String> ips = new ArrayList<>();
+            for (int i = 0; i < answers.length(); i++) {
+                JSONObject a = answers.optJSONObject(i);
+                if (a != null && a.optInt("type", 0) == 1) {
+                    String data = a.optString("data", null);
+                    if (data != null && !ips.contains(data)) {
+                        ips.add(data);
+                    }
+                }
+            }
+            return ips;
+        } catch (Exception e) {
+            return List.of();
+        }
+    }
+
+    public static List<String> resolveUdp(String providerIp, String host) {
+        try {
+            SimpleResolver resolver = new SimpleResolver(providerIp);
+            resolver.setTimeout(Duration.ofSeconds(5));
+            Lookup lookup = new Lookup(org.xbill.DNS.Name.fromString(host + "."), Type.A);
+            lookup.setResolver(resolver);
+            lookup.setCache(null);
+            Record[] records = lookup.run();
+            if (records == null) {
+                return List.of();
+            }
+            List<String> ips = new ArrayList<>();
+            for (Record r : records) {
+                if (r instanceof ARecord a) {
+                    String ip = a.getAddress().getHostAddress();
+                    if (ip != null && !ips.contains(ip)) {
+                        ips.add(ip);
+                    }
+                }
+            }
+            return ips;
+        } catch (Exception e) {
+            return List.of();
+        }
+    }
+
+    private static String doGet(String url, String accept) throws Exception {
+        URLConnection conn = new URL(url).openConnection();
+        conn.setConnectTimeout(DiagConstants.CONNECT_TIMEOUT_MS);
+        conn.setReadTimeout(DiagConstants.READ_TIMEOUT_MS);
+        conn.setRequestProperty("Accept", accept);
+        conn.setRequestProperty("User-Agent", "ZernMC-Diag");
+        conn.connect();
+        byte[] buf;
+        try (var in = conn.getInputStream()) {
+            buf = in.readAllBytes();
+        }
+        return new String(buf, java.nio.charset.StandardCharsets.UTF_8);
+    }
+}

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/NetProbe.java

@@ -0,0 +1,58 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+
+public final class NetProbe {
+
+    public record TcpResult(boolean ok, long latencyMs, String detail) {
+    }
+
+    public record HttpResult(boolean ok, int status, long latencyMs, String bodySnippet, String detail) {
+    }
+
+    private NetProbe() {
+    }
+
+    public static TcpResult tcpConnect(String host, int port, int timeoutMs) {
+        long t0 = System.currentTimeMillis();
+        try (Socket socket = new Socket()) {
+            socket.connect(new InetSocketAddress(host, port), timeoutMs);
+            return new TcpResult(true, System.currentTimeMillis() - t0, host + ":" + port);
+        } catch (Exception e) {
+            return new TcpResult(false, System.currentTimeMillis() - t0, host + ":" + port + " -> " + e.getMessage());
+        }
+    }
+
+    public static HttpResult httpGet(String url, int timeoutMs) {
+        long t0 = System.currentTimeMillis();
+        HttpURLConnection conn = null;
+        try {
+            conn = (HttpURLConnection) URI.create(url).toURL().openConnection();
+            conn.setConnectTimeout(timeoutMs);
+            conn.setReadTimeout(timeoutMs);
+            conn.setRequestProperty("User-Agent", "ZernMC-Diag/1.0");
+            conn.setInstanceFollowRedirects(false);
+            int status = conn.getResponseCode();
+            InputStream in = status >= 400 ? conn.getErrorStream() : conn.getInputStream();
+            String snippet = "";
+            if (in != null) {
+                byte[] bytes = in.readAllBytes();
+                String body = new String(bytes, StandardCharsets.UTF_8).trim();
+                snippet = body.length() > 200 ? body.substring(0, 200) + "..." : body;
+            }
+            boolean ok = status >= 200 && status < 400;
+            return new HttpResult(ok, status, System.currentTimeMillis() - t0, snippet, "HTTP " + status);
+        } catch (Exception e) {
+            return new HttpResult(false, 0, System.currentTimeMillis() - t0, "", e.getMessage());
+        } finally {
+            if (conn != null) {
+                conn.disconnect();
+            }
+        }
+    }
+}

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/NetworkDiagnostics.java

@@ -0,0 +1,263 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.text.SimpleDateFormat;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.Date;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+
+import org.json.JSONObject;
+
+public final class NetworkDiagnostics {
+
+    private final Path baseDir;
+    private final Consumer<String> onLine;
+    private final Consumer<DiagCheck> onCheck;
+    private final List<DiagCheck> checks = new CopyOnWriteArrayList<>();
+    private final StringBuilder report = new StringBuilder();
+    private String clientIp = "unknown";
+
+    public NetworkDiagnostics(Path baseDir, Consumer<String> onLine, Consumer<DiagCheck> onCheck) {
+        this.baseDir = baseDir;
+        this.onLine = onLine;
+        this.onCheck = onCheck;
+    }
+
+    public List<DiagCheck> getChecks() {
+        return checks;
+    }
+
+    public String getClientIp() {
+        return clientIp;
+    }
+
+    public Path run() {
+        checks.clear();
+        report.setLength(0);
+
+        report.append("=== ZernMC Network Diagnostics Report ===\n");
+        report.append("Timestamp: ").append(timestamp()).append('\n');
+        report.append("Base dir: ").append(baseDir.toAbsolutePath()).append('\n');
+        report.append("Zern server known IP(s): ").append(String.join(", ", DiagConstants.KNOWN_SERVER_IPS)).append('\n');
+        report.append("Primary API: ").append(DiagConstants.PRIMARY_API).append('\n');
+        report.append("Direct API: ").append(DiagConstants.DIRECT_API).append('\n');
+
+        runDnsChecks();
+        runConnectivityChecks();
+        runHttpChecks();
+        clientIp = determineClientIp();
+
+        int ok = 0, fail = 0, skip = 0;
+        for (DiagCheck c : checks) {
+            switch (c.status()) {
+                case "OK" -> ok++;
+                case "FAIL" -> fail++;
+                default -> skip++;
+            }
+        }
+        report.append("=== Summary ===\n");
+        report.append("OK: ").append(ok).append(", FAIL: ").append(fail).append(", SKIP: ").append(skip).append('\n');
+
+        report.append("--- JSON ---\n");
+        JSONObject json = new JSONObject();
+        json.put("client_ip", clientIp);
+        json.put("timestamp", timestamp());
+        JSONObject jsonChecks = new JSONObject();
+        for (DiagCheck c : checks) {
+            JSONObject j = new JSONObject();
+            j.put("status", c.status());
+            j.put("detail", c.detail() == null ? "" : c.detail());
+            j.put("latency_ms", c.latencyMs());
+            jsonChecks.put(c.category() + "/" + c.name(), j);
+        }
+        json.put("checks", jsonChecks);
+        report.append(json.toString(2)).append('\n');
+
+        return writeLog();
+    }
+
+    private Path writeLog() {
+        try {
+            Files.createDirectories(baseDir);
+            Path log = baseDir.resolve("diag.log");
+            Files.writeString(log, report.toString(), StandardCharsets.UTF_8);
+            if (onLine != null) {
+                onLine.accept("\nDiagnostic log written to: " + log.toAbsolutePath());
+            }
+            return log;
+        } catch (IOException e) {
+            if (onLine != null) {
+                onLine.accept("Failed to write diag.log: " + e.getMessage());
+            }
+            return null;
+        }
+    }
+
+    private void runDnsChecks() {
+        report.append("\n=== DNS resolution ===\n");
+        for (String host : DiagConstants.HOSTS) {
+            report.append("Host: ").append(host).append('\n');
+            submit(resolveToCheck(host, "system", DnsResolver.resolveSystem(host)));
+        }
+
+        List<Callable<DiagCheck>> tasks = new ArrayList<>();
+        List<String> taskKeys = new ArrayList<>();
+
+        for (String host : DiagConstants.HOSTS) {
+            tasks.add(() -> resolveToCheck(host, "DoH Google", DnsResolver.resolveDoHGoogle(host)));
+            taskKeys.add("DoH Google/" + host);
+            tasks.add(() -> resolveToCheck(host, "DoH Cloudflare", DnsResolver.resolveDoHCloudflare(host)));
+            taskKeys.add("DoH Cloudflare/" + host);
+            for (String provider : DiagConstants.DNS_PROVIDERS.keySet()) {
+                String providerIp = DiagConstants.DNS_PROVIDERS.get(provider);
+                tasks.add(() -> resolveToCheck(host, "UDP " + provider, DnsResolver.resolveUdp(providerIp, host)));
+                taskKeys.add("UDP " + provider + "/" + host);
+            }
+        }
+
+        ExecutorService pool = Executors.newFixedThreadPool(Math.min(8, tasks.size()), r -> {
+            Thread t = new Thread(r, "diag-dns");
+            t.setDaemon(true);
+            return t;
+        });
+        try {
+            List<Future<DiagCheck>> futures = new ArrayList<>();
+            for (Callable<DiagCheck> task : tasks) {
+                futures.add(pool.submit(task));
+            }
+            int idx = 0;
+            for (Future<DiagCheck> f : futures) {
+                String key = taskKeys.get(idx);
+                try {
+                    DiagCheck c = f.get(20, TimeUnit.SECONDS);
+                    submit(c);
+                } catch (Exception e) {
+                    submit(new DiagCheck("DNS", key, "FAIL", "query error: " + e.getMessage(), -1));
+                }
+                idx++;
+            }
+        } finally {
+            pool.shutdownNow();
+        }
+    }
+
+    static DiagCheck resolveToCheck(String host, String source, List<String> ips) {
+        if (ips.isEmpty()) {
+            return new DiagCheck("DNS", host + " / " + source, "FAIL", "no A records", -1);
+        }
+        boolean matchesKnown = false;
+        for (String ip : ips) {
+            if (DiagConstants.KNOWN_SERVER_IPS.contains(ip)) {
+                matchesKnown = true;
+                break;
+            }
+        }
+        if (matchesKnown) {
+            return new DiagCheck("DNS", host + " / " + source, "OK", String.join(", ", ips), -1);
+        }
+        String detail = "resolved to " + String.join(", ", ips) + " (DIFFERENT from known " + String.join(", ", DiagConstants.KNOWN_SERVER_IPS) + ")";
+        return new DiagCheck("DNS", host + " / " + source, "FAIL", detail, -1);
+    }
+
+    private void runConnectivityChecks() {
+        report.append("\n=== Connectivity ===\n");
+        for (String ip : DiagConstants.KNOWN_SERVER_IPS) {
+            for (int port : DiagConstants.TLS_PORTS) {
+                submit(tcpToCheck(ip, port));
+            }
+        }
+        submit(tcpToCheck("87.120.187.36", DiagConstants.DIRECT_PORT));
+
+        List<String> systemIps = DnsResolver.resolveSystem(DiagConstants.HOST_API);
+        for (String ip : systemIps) {
+            if (!DiagConstants.KNOWN_SERVER_IPS.contains(ip)) {
+                submit(tcpToCheck(ip, 443));
+            }
+        }
+    }
+
+    private DiagCheck tcpToCheck(String host, int port) {
+        NetProbe.TcpResult r = NetProbe.tcpConnect(host, port, DiagConstants.CONNECT_TIMEOUT_MS);
+        return new DiagCheck("TCP", host + ":" + port, r.ok() ? "OK" : "FAIL", r.detail(), r.latencyMs());
+    }
+
+    private void runHttpChecks() {
+        report.append("\n=== HTTP ===\n");
+        for (String host : DiagConstants.HOSTS) {
+            submit(httpToCheck("https://" + host + DiagConstants.VERSION_PATH));
+        }
+        submit(httpToCheck(DiagConstants.DIRECT_API + DiagConstants.VERSION_PATH));
+    }
+
+    private DiagCheck httpToCheck(String url) {
+        NetProbe.HttpResult r = NetProbe.httpGet(url, DiagConstants.READ_TIMEOUT_MS);
+        String detail = r.ok() ? r.detail() + (r.bodySnippet().isEmpty() ? "" : " body=" + r.bodySnippet()) : r.detail();
+        return new DiagCheck("HTTP", url, r.ok() ? "OK" : "FAIL", detail, r.latencyMs());
+    }
+
+    private String determineClientIp() {
+        String ip = null;
+        NetProbe.HttpResult direct = NetProbe.httpGet(DiagConstants.DIRECT_API + DiagConstants.CLIENT_IP_PATH, DiagConstants.READ_TIMEOUT_MS);
+        if (direct.ok()) {
+            ip = parseIp(direct.bodySnippet());
+        }
+        if (ip == null) {
+            NetProbe.HttpResult primary = NetProbe.httpGet(DiagConstants.PRIMARY_API + DiagConstants.CLIENT_IP_PATH, DiagConstants.READ_TIMEOUT_MS);
+            if (primary.ok()) {
+                ip = parseIp(primary.bodySnippet());
+            }
+        }
+        String result = ip != null ? ip : "unknown";
+        submit(new DiagCheck("INFO", "client public IP", ip != null ? "OK" : "FAIL", ip != null ? ip : "could not determine", -1));
+        report.append("=== Client IP ===\nClient public IP: ").append(result).append('\n');
+        return result;
+    }
+
+    static String parseIp(String snippet) {
+        if (snippet == null) {
+            return null;
+        }
+        try {
+            int start = snippet.indexOf("\"ip\"");
+            if (start < 0) {
+                return null;
+            }
+            int colon = snippet.indexOf(':', start);
+            int q1 = snippet.indexOf('"', colon);
+            int q2 = snippet.indexOf('"', q1 + 1);
+            if (q1 < 0 || q2 < 0) {
+                return null;
+            }
+            String ip = snippet.substring(q1 + 1, q2);
+            return ip.matches("[\\d.]+") ? ip : null;
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    private void submit(DiagCheck c) {
+        checks.add(c);
+        report.append(c.renderLine()).append('\n');
+        if (onCheck != null) {
+            onCheck.accept(c);
+        }
+        if (onLine != null) {
+            onLine.accept(c.renderLine());
+        }
+    }
+
+    private static String timestamp() {
+        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
+    }
+}

launcher/diag/src/main/java/me/sashegdev/zernmc/launcher/diag/ReportSender.java

@@ -0,0 +1,69 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.net.HttpURLConnection;
+import java.net.URI;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.List;
+
+public final class ReportSender {
+
+    public record SendResult(boolean ok, String endpoint, String detail) {
+    }
+
+    private ReportSender() {
+    }
+
+    public static String buildFilename(String clientIp) {
+        String ts = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
+        String ip = (clientIp == null || clientIp.isBlank()) ? "unknown" : clientIp;
+        return "diag_" + ts + "_" + ip + ".log";
+    }
+
+    public static SendResult send(Path logFile, String clientIp) throws IOException {
+        String content = Files.readString(logFile, StandardCharsets.UTF_8);
+        String name = buildFilename(clientIp);
+        String encoded = URLEncoder.encode(name, StandardCharsets.UTF_8);
+
+        List<String> endpoints = List.of(
+                DiagConstants.PRIMARY_API + DiagConstants.DIAG_UPLOAD_PATH + "?name=" + encoded,
+                DiagConstants.DIRECT_API + DiagConstants.DIAG_UPLOAD_PATH + "?name=" + encoded
+        );
+
+        String lastDetail = null;
+        for (String endpoint : endpoints) {
+            try {
+                HttpURLConnection conn = (HttpURLConnection) URI.create(endpoint).toURL().openConnection();
+                conn.setRequestMethod("POST");
+                conn.setConnectTimeout(DiagConstants.CONNECT_TIMEOUT_MS);
+                conn.setReadTimeout(DiagConstants.READ_TIMEOUT_MS);
+                conn.setDoOutput(true);
+                conn.setRequestProperty("Content-Type", "text/plain; charset=utf-8");
+                conn.setRequestProperty("User-Agent", "ZernMC-Diag/1.0");
+                byte[] body = content.getBytes(StandardCharsets.UTF_8);
+                conn.setFixedLengthStreamingMode(body.length);
+                try (OutputStream out = conn.getOutputStream()) {
+                    out.write(body);
+                }
+                int status = conn.getResponseCode();
+                boolean ok = status >= 200 && status < 300;
+                String detail = "HTTP " + status;
+                conn.disconnect();
+                return new SendResult(ok, endpoint, detail);
+            } catch (Exception e) {
+                lastDetail = e.getMessage();
+            }
+        }
+        return new SendResult(false, lastEndpointUsed(endpoints), lastDetail != null ? lastDetail : "all endpoints failed");
+    }
+
+    private static String lastEndpointUsed(List<String> endpoints) {
+        return endpoints.get(endpoints.size() - 1);
+    }
+}

launcher/diag/src/test/java/me/sashegdev/zernmc/launcher/diag/DiagCheckTest.java

@@ -0,0 +1,35 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class DiagCheckTest {
+
+    @Test
+    void renderLine_ok() {
+        DiagCheck c = new DiagCheck("DNS", "api.zernmc.ru / system", "OK", "87.120.187.36", 12);
+        String line = c.renderLine();
+        assertTrue(line.contains("[OK]"));
+        assertTrue(line.contains("api.zernmc.ru / system"));
+        assertTrue(line.contains("12 ms"));
+        assertTrue(line.contains("87.120.187.36"));
+    }
+
+    @Test
+    void renderLine_fail() {
+        DiagCheck c = new DiagCheck("TCP", "1.2.3.4:443", "FAIL", "connection refused", -1);
+        String line = c.renderLine();
+        assertTrue(line.contains("[FAIL]"));
+        assertFalse(line.contains("ms)"));
+        assertTrue(line.contains("connection refused"));
+    }
+
+    @Test
+    void ok_returnsStatus() {
+        assertTrue(new DiagCheck("a", "b", "OK", null, -1).ok());
+        assertFalse(new DiagCheck("a", "b", "FAIL", null, -1).ok());
+    }
+}

launcher/diag/src/test/java/me/sashegdev/zernmc/launcher/diag/DnsResolverTest.java

@@ -0,0 +1,52 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class DnsResolverTest {
+
+    @Test
+    void resolveToCheck_emptyIsFail() {
+        DiagCheck c = NetworkDiagnostics.resolveToCheck("api.zernmc.ru", "Google 8.8.8.8", List.of());
+        assertEquals("FAIL", c.status());
+        assertEquals("no A records", c.detail());
+    }
+
+    @Test
+    void resolveToCheck_knownIpIsOk() {
+        DiagCheck c = NetworkDiagnostics.resolveToCheck("api.zernmc.ru", "system", List.of("87.120.187.36"));
+        assertEquals("OK", c.status());
+        assertTrue(c.detail().contains("87.120.187.36"));
+    }
+
+    @Test
+    void resolveToCheck_unknownIpIsFail() {
+        DiagCheck c = NetworkDiagnostics.resolveToCheck("api.zernmc.ru", "system", List.of("1.2.3.4"));
+        assertEquals("FAIL", c.status());
+        assertTrue(c.detail().contains("DIFFERENT from known"));
+        assertTrue(c.detail().contains("1.2.3.4"));
+    }
+
+    @Test
+    void resolveToCheck_multipleIpsOneKnown() {
+        DiagCheck c = NetworkDiagnostics.resolveToCheck("zern.cc", "system", List.of("1.2.3.4", "87.120.187.36"));
+        assertEquals("OK", c.status());
+    }
+
+    @Test
+    void parseIp_valid() {
+        assertEquals("1.2.3.4", NetworkDiagnostics.parseIp("{\"ip\":\"1.2.3.4\"}"));
+    }
+
+    @Test
+    void parseIp_invalidReturnsNull() {
+        assertEquals(null, NetworkDiagnostics.parseIp("not json"));
+        assertEquals(null, NetworkDiagnostics.parseIp("{\"other\":\"x\"}"));
+        assertEquals(null, NetworkDiagnostics.parseIp(null));
+        assertEquals(null, NetworkDiagnostics.parseIp("{\"ip\":\"not-an-ip\"}"));
+    }
+}

launcher/diag/src/test/java/me/sashegdev/zernmc/launcher/diag/ReportSenderTest.java

@@ -0,0 +1,24 @@
+package me.sashegdev.zernmc.launcher.diag;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class ReportSenderTest {
+
+    @Test
+    void buildFilename_containsTimestampAndIp() {
+        String name = ReportSender.buildFilename("1.2.3.4");
+        assertTrue(name.matches("diag_\\d{8}_\\d{6}_[\\d.]+[.]log"), name);
+        assertTrue(name.contains("1.2.3.4"));
+    }
+
+    @Test
+    void buildFilename_unknownIp() {
+        String name = ReportSender.buildFilename(null);
+        assertTrue(name.contains("unknown"), name);
+        assertTrue(name.matches("diag_\\d{8}_\\d{6}_unknown[.]log"), name);
+        String blank = ReportSender.buildFilename("   ");
+        assertTrue(blank.contains("unknown"), blank);
+    }
+}

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/Main.java

@@ -37,6 +37,11 @@ public class Main {
         boolean jfxMode = argList.contains("--jfx");
         boolean cliMode = argList.contains("--cli");
 
+        if (argList.contains("--offline")) {
+            System.setProperty("zernmc.offline", "true");
+            LauncherLogger.info("Offline mode requested (--offline)");
+        }
+
         if (jfxMode) {
             launchJFX();
             return;
@@ -65,6 +70,7 @@ public class Main {
     }
 
     private static void startCLI() throws IOException {
+        DomainSelector.selectBest();
         ZHttpClient.checkAllServicesOnStartup(true);
 
         System.out.println(ZAnsi.cyan("Checking authorization..."));

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/api/LauncherAPI.java

@@ -88,7 +88,7 @@ public class LauncherAPI {
             }
             return ApiResponse.success(mcVersions);
         } catch (Exception e) {
-            System.out.println("[API] MC versions fetch failed: " + e.getMessage());
+            LauncherLogger.warn("[API] MC versions fetch failed: " + e.getMessage());
         }
         return ApiResponse.error("Failed to load Minecraft versions");
     }
@@ -136,7 +136,7 @@ public class LauncherAPI {
             }
             return ApiResponse.success(versions);
         } catch (Exception e) {
-            System.out.println("[API] Loader versions fetch failed: " + e.getMessage());
+            LauncherLogger.warn("[API] Loader versions fetch failed: " + e.getMessage());
             return ApiResponse.error("Failed to load loader versions");
         }
     }

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/api/auth/AuthService.java

@@ -26,10 +26,15 @@ public class AuthService {
             return ApiResponse.error(result.error != null ? result.error : "Registration failed");
         } catch (Exception e) {
             String msg = e.getMessage();
-            if (msg != null && msg.contains("HTTP 409")) {
-                return ApiResponse.error("Username already taken");
+            if (msg != null) {
+                java.util.regex.Matcher m = java.util.regex.Pattern.compile("HTTP (\\d{3})").matcher(msg);
+                if (m.find()) {
+                    int code = Integer.parseInt(m.group(1));
+                    String body = msg.substring(m.end()).trim();
+                    return ApiResponse.error(AuthManager.friendlyHttpError(code, body));
                 }
-            return ApiResponse.error("Registration error: " + msg);
+            }
+            return ApiResponse.error(AuthManager.friendlyConnectionError(e));
         }
     }
 
@@ -40,9 +45,9 @@ public class AuthService {
                 LoginResult loginResult = new LoginResult(AuthManager.getUsername(), AuthManager.getAccessToken());
                 return ApiResponse.success(loginResult);
             }
-            return ApiResponse.error(result.error != null ? result.error : "Invalid login or password");
+            return ApiResponse.error(result.error != null ? result.error : "Неверный логин или пароль");
         } catch (Exception e) {
-            return ApiResponse.error("Auth error: " + e.getMessage());
+            return ApiResponse.error(AuthManager.friendlyConnectionError(e));
         }
     }
 

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/api/launch/LaunchService.java

@@ -24,7 +24,7 @@ public class LaunchService {
 
     static {
         Runtime.getRuntime().addShutdownHook(new Thread(() -> {
-            System.out.println("[LAUNCH] Shutting down all running processes...");
+            LauncherLogger.info("[LAUNCH] Shutting down all running processes...");
             runningProcesses.values().forEach(p -> {
                 try {
                     p.destroy();
@@ -67,13 +67,44 @@ public class LaunchService {
 
             LauncherLogger.info("Launching: " + instanceName + " (serverPack=" + instance.isServerPack() + ")");
 
-            long t0 = System.currentTimeMillis();
-            LaunchCommandBuilder builder = new LaunchCommandBuilder(instance);
             LaunchOptions options = createOptions();
             options.setUsername(AuthManager.getUsername());
             options.setAccessToken(AuthManager.getAccessToken());
             options.setUuid(AuthManager.getUuid());
 
+            return launchProcess(instance, instanceName, options);
+        } catch (Exception e) {
+            LauncherLogger.error("Launch error for " + instanceName, e);
+            return ApiResponse.error("Launch error: " + e.getMessage());
+        }
+    }
+
+    public ApiResponse<ProcessInfo> launchOffline(String instanceName, String nickname) {
+        try {
+            Instance instance = InstanceManager.getInstance(instanceName);
+            if (instance == null) {
+                return ApiResponse.error("Pack not found: " + instanceName);
+            }
+
+            LauncherLogger.info("Offline launch: " + instanceName);
+            String safeName = (nickname == null || nickname.isBlank()) ? "Player" : nickname.trim();
+            LaunchOptions options = createOptions();
+            options.setUsername(safeName);
+            options.setAccessToken("0");
+            options.setUuid(java.util.UUID.nameUUIDFromBytes(
+                    ("OfflinePlayer:" + safeName).getBytes(java.nio.charset.StandardCharsets.UTF_8)).toString());
+
+            return launchProcess(instance, instanceName, options);
+        } catch (Exception e) {
+            LauncherLogger.error("Offline launch error for " + instanceName, e);
+            return ApiResponse.error("Offline launch error: " + e.getMessage());
+        }
+    }
+
+    private ApiResponse<ProcessInfo> launchProcess(Instance instance, String instanceName, LaunchOptions options) {
+        try {
+            long t0 = System.currentTimeMillis();
+            LaunchCommandBuilder builder = new LaunchCommandBuilder(instance);
             List<String> command = builder.build(options);
             LauncherLogger.info("Launch: command built in " + (System.currentTimeMillis() - t0) + " ms");
             LauncherLogger.info("Generated command for " + instanceName + ":");

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/auth/AuthManager.java

@@ -113,17 +113,62 @@ public class AuthManager {
                 saveSession();
                 userInfo = fetchUserInfo();
                 return AuthResult.ok();
-            } else if (resp.statusCode() == 422) {
-                return AuthResult.fail("Validation error: " + extractError(resp.body()));
             } else {
-                return AuthResult.fail(extractError(resp.body()));
+                return AuthResult.fail(friendlyHttpError(resp.statusCode(), resp.body()));
             }
         } catch (Exception e) {
-            e.printStackTrace();
-            return AuthResult.fail("Connection error: " + e.getMessage());
+            LauncherLogger.warn("authRequest failed (" + endpoint + "): " + e.getMessage());
+            return AuthResult.fail(friendlyConnectionError(e));
         }
     }
 
+    /**
+     * Maps an HTTP status code + raw body to a short, human-readable error message
+     * (in Russian) suitable for showing directly to the user.
+     */
+    public static String friendlyHttpError(int statusCode, String body) {
+        switch (statusCode) {
+            case 401:
+            case 403:
+                return "Неверный логин или пароль";
+            case 404:
+                return "Сервис временно недоступен, попробуйте позже";
+            case 409:
+                return "Логин уже занят";
+            case 422:
+                return "Некорректные данные: " + extractError(body);
+            case 429:
+                return "Слишком много попыток. Подождите немного.";
+            default:
+                if (statusCode >= 500) {
+                    return "Сервер временно недоступен, попробуйте позже";
+                }
+        }
+        String detail = extractError(body);
+        if (detail.isEmpty() || detail.startsWith("<")) {
+            return "Ошибка сервера (код " + statusCode + ")";
+        }
+        if (detail.length() > 120) {
+            detail = detail.substring(0, 117) + "...";
+        }
+        return detail;
+    }
+
+    /**
+     * Maps a network/IO exception to a short, human-readable message.
+     */
+    public static String friendlyConnectionError(Exception e) {
+        String m = e == null ? "" : String.valueOf(e.getMessage()).toLowerCase();
+        if (e instanceof java.net.SocketTimeoutException
+                || e instanceof java.net.ConnectException
+                || e instanceof java.net.UnknownHostException
+                || m.contains("timeout") || m.contains("connect") || m.contains("unknownhost")
+                || m.contains("refused")) {
+            return "Нет соединения с сервером. Проверьте интернет.";
+        }
+        return "Ошибка соединения с сервером. Попробуйте позже.";
+    }
+
     public static void logout() {
         if (session != null && session.refreshToken != null) {
             try {

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/Instance.java

@@ -1,5 +1,7 @@
 package me.sashegdev.zernmc.launcher.minecraft;
 
+import me.sashegdev.zernmc.launcher.utils.LauncherLogger;
+
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import java.io.IOException;
@@ -142,7 +144,7 @@ public class Instance {
             this.serverPackName = meta.serverPackName;
             this.presetId = meta.presetId;
         } catch (Exception e) {
-            System.err.println("[Instance] Failed to load metadata for " + name + ": " + e.getMessage());
+            LauncherLogger.warn("[Instance] Failed to load metadata for " + name + ": " + e.getMessage());
         }
     }
 

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/InstanceManager.java

@@ -1,5 +1,7 @@
 package me.sashegdev.zernmc.launcher.minecraft;
 
+import me.sashegdev.zernmc.launcher.utils.LauncherLogger;
+
 import me.sashegdev.zernmc.launcher.utils.Config;
 
 import java.io.IOException;
@@ -51,7 +53,7 @@ public class InstanceManager {
                      try {
                          Files.deleteIfExists(path);
                      } catch (IOException e) {
-                         System.err.println("Не удалось удалить: " + path);
+                         LauncherLogger.warn("Не удалось удалить: " + path);
                      }
                  });
             return true;

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/MinecraftLib.java

@@ -71,12 +71,12 @@ public class MinecraftLib {
      * Stub - will be expanded
      */
     public boolean installPack(String packName, String minecraftVersion, String loaderType, String loaderVersion) throws Exception {
-        System.out.println(ZAnsi.cyan("Starting full pack install: " + packName));
+        LauncherLogger.info("Starting full pack install: " + packName);
 
         // 1. Install Minecraft
         boolean mcInstalled = installMinecraft(minecraftVersion);
         if (!mcInstalled) {
-            System.out.println(ZAnsi.brightRed("Failed to install Minecraft " + minecraftVersion));
+            LauncherLogger.error("Failed to install Minecraft " + minecraftVersion);
             return false;
         }
 
@@ -84,40 +84,39 @@ public class MinecraftLib {
         if ("fabric".equalsIgnoreCase(loaderType)) {
             boolean fabricInstalled = installFabric(minecraftVersion, loaderVersion);
             if (!fabricInstalled) {
-                System.out.println(ZAnsi.brightRed("Failed to install Fabric"));
+                LauncherLogger.error("Failed to install Fabric");
                 return false;
             }
         } else if ("forge".equalsIgnoreCase(loaderType)) {
             boolean forgeInstalled = installForge(minecraftVersion, loaderVersion);
             if (!forgeInstalled) {
-                System.out.println(ZAnsi.brightRed("Failed to install Forge"));
+                LauncherLogger.error("Failed to install Forge");
                 return false;
             }
         } else if ("neoforge".equalsIgnoreCase(loaderType)) {
             boolean neoforgeInstalled = installNeoForge(minecraftVersion, loaderVersion);
             if (!neoforgeInstalled) {
-                System.out.println(ZAnsi.brightRed("Failed to install NeoForge"));
+                LauncherLogger.error("Failed to install NeoForge");
                 return false;
             }
         }
 
         // 3. In the future: diff and mod download
 
-        System.out.println(ZAnsi.brightGreen("Basic pack install complete!"));
+        LauncherLogger.info("Basic pack install complete!");
         return true;
     }
 
     //Launch
     public void launch(LaunchOptions options) throws Exception {
-        System.out.println(ZAnsi.brightGreen("Launching pack: " + instance.getName()));
+        LauncherLogger.info("Launching pack: " + instance.getName());
         cleanupOldLoaders();
         validateJarFiles();
 
         LaunchCommandBuilder builder = new LaunchCommandBuilder(instance);
         List<String> command = builder.build(options);
 
-        System.out.println(ZAnsi.cyan("Launch command (" + command.size() + " args):"));
-        command.forEach(arg -> System.out.println("  " + arg));
+        LauncherLogger.info("Launch command (" + command.size() + " args) written below");
 
         ProcessBuilder pb = new ProcessBuilder(command);
         pb.directory(instance.getPath().toFile());
@@ -126,12 +125,12 @@ public class MinecraftLib {
         Path cmdLogFile = instance.getPath().resolve("launch-command.log");
         try {
             Files.writeString(cmdLogFile, String.join(" \\\n  ", command));
-            System.out.println(ZAnsi.green("  Launch command written to " + cmdLogFile.toAbsolutePath()));
+            LauncherLogger.info("Launch command written to " + cmdLogFile.toAbsolutePath());
         } catch (Exception e) {
-            System.out.println(ZAnsi.yellow("  Failed to write launch command log: " + e.getMessage()));
+            LauncherLogger.warn("Failed to write launch command log: " + e.getMessage());
         }
 
-        System.out.println(ZAnsi.brightGreen("\nStarting Minecraft...\n"));
+        LauncherLogger.info("Starting Minecraft...");
         ConsoleUtils.clearScreen();
 
         Process process = pb.start();
@@ -168,7 +167,7 @@ public class MinecraftLib {
         outThread.join(1000);
         errThread.join(1000);
 
-        System.out.println(ZAnsi.yellow("\nMinecraft exited with code: " + exitCode));
+        LauncherLogger.info("Minecraft exited with code: " + exitCode);
     }
 
     private void safeDeleteDirectory(Path dir) {
@@ -215,7 +214,7 @@ public class MinecraftLib {
 
         if (currentLoaderVer == null) return;
 
-        System.out.println(ZAnsi.yellow("Cleaning old loader versions..."));
+        LauncherLogger.info("Cleaning old loader versions...");
 
         // Delete all old fabric-loader / forge
         Path libraries = instance.getPath().resolve("libraries");
@@ -247,14 +246,14 @@ public class MinecraftLib {
                       .filter(p -> !isValidJar(p))
                       .forEach(p -> {
                           try {
-                              System.out.println(ZAnsi.yellow("  Removing corrupt JAR: " + instance.getPath().relativize(p)));
+                              LauncherLogger.warn("Removing corrupt JAR: " + instance.getPath().relativize(p));
                               Files.delete(p);
                           } catch (IOException e) {
-                              System.out.println(ZAnsi.red("  Failed to delete: " + p.getFileName()));
+                              LauncherLogger.error("Failed to delete: " + p.getFileName());
                           }
                       });
             } catch (Exception e) {
-                System.out.println(ZAnsi.yellow("  Error scanning for corrupt JARs: " + e.getMessage()));
+                LauncherLogger.warn("Error scanning for corrupt JARs: " + e.getMessage());
             }
         }
     }

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/PackDownloader.java

@@ -184,8 +184,7 @@ public class PackDownloader {
                 boolean success = lib.installFabric(manifest.getMinecraftVersion(), manifest.getLoaderVersion());
                 LauncherLogger.info("installOrUpdatePack: Fabric install result=" + success);
                 if (!success) {
-                    System.err.println(ZAnsi.brightRed("Failed to install Fabric"));
-                    LauncherLogger.error("installOrUpdatePack: Fabric install failed");
+                    LauncherLogger.error("[INSTALL] Failed to install Fabric");
                     reportProgress("Failed to install Fabric", 0, "error", 0, 1);
                     return false;
                 }
@@ -195,8 +194,7 @@ public class PackDownloader {
                 boolean success = lib.installNeoForge(manifest.getMinecraftVersion(), manifest.getLoaderVersion());
                 LauncherLogger.info("installOrUpdatePack: NeoForge install result=" + success);
                 if (!success) {
-                    System.err.println(ZAnsi.brightRed("Failed to install NeoForge"));
-                    LauncherLogger.error("installOrUpdatePack: NeoForge install failed");
+                    LauncherLogger.error("[INSTALL] Failed to install NeoForge");
                     reportProgress("Failed to install NeoForge", 0, "error", 0, 1);
                     return false;
                 }
@@ -206,8 +204,7 @@ public class PackDownloader {
                 boolean success = lib.installForge(manifest.getMinecraftVersion(), manifest.getLoaderVersion());
                 LauncherLogger.info("installOrUpdatePack: Forge install result=" + success);
                 if (!success) {
-                    System.err.println(ZAnsi.brightRed("Failed to install Forge"));
-                    LauncherLogger.error("installOrUpdatePack: Forge install failed");
+                    LauncherLogger.error("[INSTALL] Failed to install Forge");
                     reportProgress("Failed to install Forge", 0, "error", 0, 1);
                     return false;
                 }
@@ -217,16 +214,14 @@ public class PackDownloader {
                 boolean success = lib.installMinecraft(manifest.getMinecraftVersion());
                 LauncherLogger.info("installOrUpdatePack: Vanilla install result=" + success);
                 if (!success) {
-                    System.err.println(ZAnsi.brightRed("Failed to install Vanilla Minecraft"));
-                    LauncherLogger.error("installOrUpdatePack: Vanilla install failed");
+                    LauncherLogger.error("[INSTALL] Failed to install Vanilla Minecraft");
                     reportProgress("Failed to install Vanilla Minecraft", 0, "error", 0, 1);
                     return false;
                 }
             }
             LauncherLogger.info("installOrUpdatePack: Minecraft+loader install completed successfully");
         } else {
-            LauncherLogger.info("installOrUpdatePack: Minecraft already installed, skipping");
-            System.out.println(ZAnsi.green("Minecraft already installed, skipping..."));
+            LauncherLogger.info("Minecraft already installed, skipping...");
         }
         
         reportProgress("Scanning local files...", 30, "Installing pack files", 4, 5);
@@ -239,7 +234,7 @@ public class PackDownloader {
         // If pack has no files (vanilla/loader only), skip diff
         if (manifest.files == null || manifest.files.isEmpty()) {
             LauncherLogger.info("installOrUpdatePack: no files in manifest, skipping diff");
-            System.out.println(ZAnsi.green("Pack contains no additional files"));
+            LauncherLogger.info("Pack contains no additional files");
             reportProgress("Installing...", 50, "Installing pack files", 4, 5);
             
             saveUserFilesSnapshot(localFiles);
@@ -253,7 +248,7 @@ public class PackDownloader {
             instance.setAssetIndex(resolveAssetIndex(manifest));
             
             reportProgress("Pack installed successfully!", 100, "Installing pack files", 4, 5);
-            System.out.println(ZAnsi.brightGreen("Pack installed successfully!"));
+            LauncherLogger.info("Pack installed successfully!");
             return true;
         }
         LauncherLogger.info("installOrUpdatePack: manifest has " + manifest.files.size() + " files, proceeding to diff");
@@ -302,7 +297,7 @@ public class PackDownloader {
             instance.setLoaderVersion(manifest.getLoaderVersion());
             instance.setAssetIndex(resolveAssetIndex(manifest));
             
-            System.out.println(ZAnsi.brightGreen("Pack installed successfully!"));
+            LauncherLogger.info("Pack installed successfully!");
             LauncherLogger.info("installOrUpdatePack: SUCCESS");
         } else {
             LauncherLogger.error("installOrUpdatePack: FAILED - applyDiff returned false without exception");
@@ -332,17 +327,17 @@ public class PackDownloader {
     }
 
     public boolean updatePack(String packName, String preset) throws Exception {
-        System.out.println(ZAnsi.cyan("Checking updates for " + instance.getName() + "..."));
+        LauncherLogger.info("Checking updates for " + instance.getName() + "...");
         
         PackManifest manifest = getPackManifest(packName);
         int serverVersion = manifest.getVersion();
         
         if (serverVersion <= instance.getServerVersion()) {
-            System.out.println(ZAnsi.green("Pack is already up to date (v" + instance.getServerVersion() + ")"));
+            LauncherLogger.info("Pack is already up to date (v" + instance.getServerVersion() + ")");
             return true;
         }
         
-        System.out.println(ZAnsi.yellow("Update available: v" + instance.getServerVersion() + " → v" + serverVersion));
+        LauncherLogger.info("Update available: v" + instance.getServerVersion() + " -> v" + serverVersion);
         
         // Scan local files
         Map<String, String> localFiles = scanLocalFiles();
@@ -351,7 +346,7 @@ public class PackDownloader {
         Set<String> protectedFiles = getUserModifiedFiles(localFiles);
         if (!protectedFiles.isEmpty()) {
             LauncherLogger.info("[DEBUG] Found " + protectedFiles.size() + " user-modified files (will not overwrite)");
-            System.out.println(ZAnsi.yellow("Found " + protectedFiles.size() + " user-modified files, they will not be overwritten"));
+            LauncherLogger.info("Found " + protectedFiles.size() + " user-modified files, they will not be overwritten");
         }
         
         // Get diff
@@ -366,7 +361,7 @@ public class PackDownloader {
             saveUserFilesSnapshot(updatedHashes);
             
             instance.setServerVersion(serverVersion);
-            System.out.println(ZAnsi.brightGreen("Pack updated to v" + serverVersion));
+            LauncherLogger.info("Pack updated to v" + serverVersion);
         }
         
         return success;
@@ -519,34 +514,30 @@ public class PackDownloader {
 
     private boolean applyDiff(DiffResponse diff, String packName, Set<String> protectedFiles, String preset) {
         LauncherLogger.info("applyDiff: start. toDownload=" + diff.getToDownload().size() + " toDelete=" + diff.getToDelete().size() + " protected=" + protectedFiles.size());
-        System.out.println(ZAnsi.cyan("\nApplying changes:"));
-        System.out.println("  Download: " + diff.getToDownload().size() + " files");
-        System.out.println("  Delete: " + diff.getToDelete().size() + " files");
-        if (!protectedFiles.isEmpty()) {
-            System.out.println(ZAnsi.yellow("  Protected: " + protectedFiles.size() + " user-modified files (skipped)"));
-        }
+        LauncherLogger.info("Apply changes: Download " + diff.getToDownload().size() + " files, Delete " + diff.getToDelete().size() + " files"
+                + (!protectedFiles.isEmpty() ? ", Protected " + protectedFiles.size() + " user-modified files (skipped)" : ""));
         
         // Create directories if needed
         try {
             Files.createDirectories(instance.getPath());
         } catch (IOException e) {
-            System.err.println(ZAnsi.red("Error creating directories: " + e.getMessage()));
+            LauncherLogger.error("Error creating directories: " + e.getMessage());
             return false;
         }
         
         // Delete files (skip protected)
         for (String filePath : diff.getToDelete()) {
             if (protectedFiles.contains(filePath)) {
-                System.out.println(ZAnsi.yellow("  Skipped delete (user-modified): " + filePath));
+                LauncherLogger.info("Skipped delete (user-modified): " + filePath);
                 continue;
             }
             Path fullPath = instance.getPath().resolve(filePath);
             try {
                 if (Files.deleteIfExists(fullPath)) {
-                    System.out.println(ZAnsi.yellow("  Deleted: " + filePath));
+                    LauncherLogger.info("Deleted: " + filePath);
                 }
             } catch (IOException e) {
-                System.err.println(ZAnsi.red("  Error deleting " + filePath + ": " + e.getMessage()));
+                LauncherLogger.error("Error deleting " + filePath + ": " + e.getMessage());
             }
         }
         
@@ -565,7 +556,7 @@ public class PackDownloader {
             
             if (protectedFiles.contains(path)) {
                 skipped++;
-                System.out.println(ZAnsi.yellow("  Skipped (user-modified): " + path));
+                LauncherLogger.info("Skipped (user-modified): " + path);
                 continue;
             }
             
@@ -597,7 +588,6 @@ public class PackDownloader {
                 }
                 if (!hashMatch) {
                     LauncherLogger.warn("applyDiff: skipping file " + path + " due to hash mismatch (expected=" + file.getHash() + " got=" + actualHash + ")");
-                    System.err.println(ZAnsi.yellow("  Skipped (hash mismatch): " + path));
                     skipped++;
                     continue;
                 }
@@ -642,8 +632,7 @@ public class PackDownloader {
                 
             } catch (Exception e) {
                 LauncherLogger.error("applyDiff: download FAILED for path=" + path + " error=" + e.getClass().getName() + ": " + e.getMessage());
-                System.err.println("\n" + ZAnsi.red("  Download error " + path + ": " + e.getMessage()));
-                System.err.println(ZAnsi.yellow("  Skipping file " + path + " due to download error"));
+                LauncherLogger.error("Download error " + path + ": " + e.getMessage() + " - skipping file");
                 skipped++;
                 continue;
             }
@@ -653,7 +642,7 @@ public class PackDownloader {
             ProgressBar.finish("Download");
         }
         if (skipped > 0) {
-            System.out.println(ZAnsi.cyan("  Skipped " + skipped + " user-modified files"));
+            LauncherLogger.info("Skipped " + skipped + " user-modified files");
         }
         
         return true;

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/installer/FabricInstaller.java

@@ -6,7 +6,9 @@ import me.sashegdev.zernmc.launcher.utils.LauncherLogger;
 import me.sashegdev.zernmc.launcher.utils.ProgressBar;
 import me.sashegdev.zernmc.launcher.utils.ZHttpClient;
 
+import java.io.BufferedReader;
 import java.io.IOException;
+import java.io.InputStreamReader;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.concurrent.TimeUnit;
@@ -33,6 +35,8 @@ public class FabricInstaller {
         instance.setAssetIndex(assetIndex);
         instance.setMinecraftVersion(minecraftVersion);
 
+        ProgressBar.showIndeterminate("Preparing Fabric installer");
+
         String installerVersion = getLatestInstallerVersion();
         String installerUrl = "https://maven.fabricmc.net/net/fabricmc/fabric-installer/"
                 + installerVersion + "/fabric-installer-" + installerVersion + ".jar";
@@ -40,7 +44,7 @@ public class FabricInstaller {
         Path installerJar = instancePath.resolve("fabric-installer.jar");
 
         if (!Files.exists(installerJar)) {
-            ProgressBar.show("Downloading Fabric Installer", 0, 100, "%");
+            ProgressBar.showIndeterminate("Downloading Fabric Installer");
             downloadFileWithFallback(installerUrl, installerJar);
             ProgressBar.finish("Fabric Installer downloaded");
         }
@@ -48,6 +52,7 @@ public class FabricInstaller {
         preDownloadFabricLibraries(minecraftVersion, loaderVersion);
 
         LauncherLogger.info("Running Fabric Installer...");
+        ProgressBar.showIndeterminate("Running Fabric Installer (may take a few minutes)");
 
         String fabricVersionId = "fabric-loader-" + loaderVersion + "-" + minecraftVersion;
 
@@ -60,17 +65,50 @@ public class FabricInstaller {
                 "-noprofile"
         );
 
-        pb.redirectOutput(ProcessBuilder.Redirect.INHERIT);
-        pb.redirectError(ProcessBuilder.Redirect.INHERIT);
+        pb.redirectErrorStream(true);
 
         Process process = pb.start();
-        boolean finished = process.waitFor(10, TimeUnit.MINUTES);
-        if (!finished) {
+
+        boolean hasErrors = false;
+
+            try (BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                if (line.contains("Downloading") || line.contains("Extracting")
+                        || line.contains("Installing") || line.contains("Creating")
+                        || line.contains("SUCCESS") || line.contains("successfully")) {
+                    ProgressBar.showIndeterminate("Fabric Installer: " + ProgressBar.cleanLine(line));
+                }
+
+                if (line.contains("Downloading") || line.contains("Extracting")) {
+                    LauncherLogger.info("  -> " + line);
+                } else if (line.contains("SUCCESS") || line.contains("successfully")) {
+                    LauncherLogger.info("  + " + line);
+                } else if (line.contains("WARNING") || line.contains("warning")) {
+                    LauncherLogger.warn("  ! " + line);
+                } else if (line.contains("ERROR") || line.contains("error") || line.contains("failed") || line.contains("timed out")) {
+                    LauncherLogger.error("  X " + line);
+                    if (line.contains("timed out") || line.contains("failed to download")) {
+                        hasErrors = true;
+                    }
+                } else if (!line.isBlank()) {
+                    LauncherLogger.info("  " + line);
+                }
+            }
+        }
+
+        int exitCode;
+        if (hasErrors) {
+            process.destroyForcibly();
+            exitCode = 1;
+        } else {
+            if (!process.waitFor(10, TimeUnit.MINUTES)) {
                 process.destroyForcibly();
                 LauncherLogger.error("Fabric Installer timed out after 10 minutes");
                 return false;
             }
-        int exitCode = process.exitValue();
+            exitCode = process.exitValue();
+        }
 
         if (exitCode != 0) {
             LauncherLogger.error("Fabric Installer failed (code " + exitCode + ")");

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/installer/ModLoaderInstaller.java

@@ -3,6 +3,7 @@ package me.sashegdev.zernmc.launcher.minecraft.installer;
 import me.sashegdev.zernmc.launcher.minecraft.Instance;
 import me.sashegdev.zernmc.launcher.utils.JavaResolver;
 import me.sashegdev.zernmc.launcher.utils.LauncherLogger;
+import me.sashegdev.zernmc.launcher.utils.ProgressBar;
 import me.sashegdev.zernmc.launcher.utils.ZHttpClient;
 
 import java.io.*;
@@ -57,15 +58,19 @@ public class ModLoaderInstaller {
         instance.setAssetIndex(assetIndex);
         createLauncherProfile();
 
+        ProgressBar.showIndeterminate("Preparing " + type.loaderName + " installer");
+
         String installerUrl = buildInstallerUrl(mcVersion, loaderVersion, type);
         String jarName = type.loaderName + "-installer.jar";
         Path installerJar = instance.getPath().resolve(jarName);
 
         LauncherLogger.info("Downloading " + type.loaderName + " Installer...");
+        ProgressBar.showIndeterminate("Downloading " + type.loaderName + " Installer");
         ZHttpClient.downloadFileWithSmartProxy(installerUrl, installerJar);
 
         LauncherLogger.info("Running " + type.loaderName + " Installer...");
         LauncherLogger.info("This may take a few minutes. Please wait...");
+        ProgressBar.showIndeterminate("Running " + type.loaderName + " Installer (may take a few minutes)");
 
         boolean success = runInstaller(installerJar, type);
 
@@ -145,6 +150,11 @@ public class ModLoaderInstaller {
                 while ((line = reader.readLine()) != null) {
                     output.append(line).append("\n");
 
+                    if (line.contains("Downloading") || line.contains("Extracting")
+                            || line.contains("Installing") || line.contains("Creating")
+                            || line.contains("SUCCESS") || line.contains("successfully")) {
+                        ProgressBar.showIndeterminate(type.loaderName + " Installer: " + ProgressBar.cleanLine(line));
+                    }
                     if (line.contains("Downloading") || line.contains("Extracting")) {
                         LauncherLogger.info("  -> " + line);
                     } else if (line.contains("SUCCESS") || line.contains("successfully")) {
@@ -218,6 +228,7 @@ public class ModLoaderInstaller {
 
     private void downloadMissingLibraries(LoaderType type) throws Exception {
         LauncherLogger.info("Checking and downloading missing libraries...");
+        ProgressBar.showIndeterminate("Downloading missing libraries");
         ZHttpClient.repairMissingLibraries(instance.getPath());
     }
 }

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/installer/VersionInstaller.java

@@ -86,15 +86,17 @@ public class VersionInstaller {
         String versionJson;
         try {
             // Prefers Zern server Mojang proxy, falls back to direct piston-meta
+            LauncherLogger.info("[VERSION] Fetching version json for " + versionId + " (server proxy, then direct piston-meta)");
             versionJson = ZHttpClient.getMojangVersionJson(versionId).toString();
+            LauncherLogger.info("[VERSION] Version json fetched for " + versionId);
         } catch (Exception e) {
-            System.err.println(ZAnsi.red("[VERSION] Failed to fetch version info: " + e.getMessage()));
+            LauncherLogger.error("[VERSION] Failed to fetch version info: " + e.getMessage());
             throw e;
         }
         try {
             Files.writeString(versionDir.resolve(versionId + ".json"), versionJson);
         } catch (Exception e) {
-            System.err.println(ZAnsi.red("[VERSION] Failed to write version info: " + e.getMessage()));
+            LauncherLogger.error("[VERSION] Failed to write version info: " + e.getMessage());
             throw e;
         }
         ProgressBar.show("Version info", 1, 1, "files");
@@ -103,16 +105,20 @@ public class VersionInstaller {
 
         // client.jar
         ProgressBar.show("Downloading client.jar", 0, 1, "files");
+        LauncherLogger.info("[VERSION] Downloading client.jar for " + versionId + "...");
         Path clientJar = versionDir.resolve(versionId + ".jar");
         if (!Files.exists(clientJar)) {
             try {
                 ZHttpClient.downloadFileWithSmartProxy(
                         versionData.getJSONObject("downloads").getJSONObject("client").getString("url"),
                         clientJar);
+                LauncherLogger.info("[VERSION] client.jar downloaded for " + versionId);
             } catch (Exception e) {
-                System.err.println(ZAnsi.red("[VERSION] Failed to download client.jar: " + e.getMessage()));
+                LauncherLogger.error("[VERSION] Failed to download client.jar: " + e.getMessage());
                 throw e;
             }
+        } else {
+            LauncherLogger.info("[VERSION] client.jar already present for " + versionId);
         }
         ProgressBar.show("Client.jar", 1, 1, "files");
 
@@ -241,7 +247,7 @@ public class VersionInstaller {
                 try {
                     ZHttpClient.downloadFileWithSmartProxy(url, target);
                 } catch (Exception e) {
-                    System.err.println(ZAnsi.yellow("[LIB] Failed to download " + path + ": " + e.getMessage()));
+                    LauncherLogger.warn("[LIB] Failed to download " + path + ": " + e.getMessage());
                 }
             }
             count++;
@@ -314,7 +320,7 @@ public class VersionInstaller {
                             synchronized (this) {
                                 failed[0]++;
                             }
-                            System.err.println("Failed to download " + hash);
+                            LauncherLogger.error("[VERSION] Failed to download asset " + hash);
                         } else {
                             try { Thread.sleep(500 * attempt); } catch (InterruptedException ignored) {}
                         }
@@ -330,7 +336,7 @@ public class VersionInstaller {
                     .get(10, TimeUnit.MINUTES);
         } catch (TimeoutException e) {
             futures.forEach(f -> f.cancel(true));
-            System.err.println("Asset download timed out after 10 minutes");
+            LauncherLogger.error("[VERSION] Asset download timed out after 10 minutes");
         } catch (CancellationException e) {
             // one of the futures was cancelled
         } catch (CompletionException e) {

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/launch/LaunchCommandBuilder.java

@@ -2,6 +2,7 @@ package me.sashegdev.zernmc.launcher.minecraft.launch;
 
 import me.sashegdev.zernmc.launcher.minecraft.Instance;
 import me.sashegdev.zernmc.launcher.minecraft.model.LaunchOptions;
+import me.sashegdev.zernmc.launcher.utils.LauncherLogger;
 import me.sashegdev.zernmc.launcher.utils.ZAnsi;
 import org.json.JSONObject;
 
@@ -36,7 +37,7 @@ public class LaunchCommandBuilder {
     }
 
     public List<String> build(LaunchOptions options) throws Exception {
-        System.out.println(ZAnsi.cyan("Generating launch command for " + instance.getName() + "..."));
+        LauncherLogger.info(ZAnsi.cyan("Generating launch command for " + instance.getName() + "..."));
 
         List<String> command = new ArrayList<>();
 
@@ -57,7 +58,7 @@ public class LaunchCommandBuilder {
             // with placeholder substitution. Do NOT manually add -p, -cp,
             // --add-modules, --add-opens, or -DignoreList. The version.json
             // defines all of these. This matches AstralRinth's approach.
-            System.out.println(ZAnsi.cyan("  Forge/NeoForge: using version.json args with placeholder substitution"));
+            LauncherLogger.info(ZAnsi.cyan("  Forge/NeoForge: using version.json args with placeholder substitution"));
 
             // Ensure version jar exists at versions/<versionId>/<versionId>.jar
             // so securejarhandler creates module "minecraft" (from Automatic-Module-Name)
@@ -92,9 +93,9 @@ public class LaunchCommandBuilder {
             boolean referencesClasspath = referencesClasspath(allJvmArgs) || referencesClasspath(allGameArgs);
             if (referencesClasspath) {
                 vars.put("classpath", writeClasspathFile(fullClasspath));
-                System.out.println(ZAnsi.green("  ${classpath} referenced, substituted full classpath"));
+                LauncherLogger.info(ZAnsi.green("  ${classpath} referenced, substituted full classpath"));
             } else {
-                System.out.println(ZAnsi.cyan("  ${classpath} not referenced by version.json, not substituting"));
+                LauncherLogger.info(ZAnsi.cyan("  ${classpath} not referenced by version.json, not substituting"));
             }
 
             boolean hasCpInJson = containsCpArg(allJvmArgs);
@@ -107,9 +108,9 @@ public class LaunchCommandBuilder {
                         command.add(resolved);
                     }
                 }
-                System.out.println(ZAnsi.green("  Using " + allJvmArgs.size() + " JVM args from version.json"));
+                LauncherLogger.info(ZAnsi.green("  Using " + allJvmArgs.size() + " JVM args from version.json"));
             } else {
-                System.out.println(ZAnsi.yellow("  WARNING: No JVM args in version.json, using manual fallback"));
+                LauncherLogger.info(ZAnsi.yellow("  WARNING: No JVM args in version.json, using manual fallback"));
                 command.addAll(getJvmArguments(options));
             }
 
@@ -141,7 +142,7 @@ public class LaunchCommandBuilder {
             if (!hasCpInJson) {
                 command.add("-cp");
                 command.add(writeClasspathFile(fullClasspath));
-                System.out.println(ZAnsi.green("  Added -cp classpath for main class lookup"));
+                LauncherLogger.info(ZAnsi.green("  Added -cp classpath for main class lookup"));
             }
 
             // Main class from version.json
@@ -151,9 +152,9 @@ public class LaunchCommandBuilder {
             }
             if (mainClass == null || mainClass.isEmpty()) {
                 mainClass = "cpw.mods.bootstraplauncher.BootstrapLauncher";
-                System.out.println(ZAnsi.yellow("  Using fallback main class: " + mainClass));
+                LauncherLogger.info(ZAnsi.yellow("  Using fallback main class: " + mainClass));
             } else {
-                System.out.println(ZAnsi.green("  Main class from manifest: " + mainClass));
+                LauncherLogger.info(ZAnsi.green("  Main class from manifest: " + mainClass));
             }
             command.add(mainClass);
 
@@ -167,9 +168,9 @@ public class LaunchCommandBuilder {
                         command.add(resolved);
                     }
                 }
-                System.out.println(ZAnsi.green("  Using " + allGameArgs.size() + " game args from version.json"));
+                LauncherLogger.info(ZAnsi.green("  Using " + allGameArgs.size() + " game args from version.json"));
             } else {
-                System.out.println(ZAnsi.yellow("  WARNING: No game args in version.json, using manual fallback"));
+                LauncherLogger.info(ZAnsi.yellow("  WARNING: No game args in version.json, using manual fallback"));
                 command.addAll(getVanillaGameArguments(options));
                 command.addAll(getModloaderLaunchArgs());
             }
@@ -183,24 +184,24 @@ public class LaunchCommandBuilder {
             command.add("-Djava.library.path=" + nativesDir.toAbsolutePath());
 
             if ("fabric".equals(loaderType)) {
-                System.out.println(ZAnsi.cyan("  Fabric: using vanilla classpath"));
+                LauncherLogger.info(ZAnsi.cyan("  Fabric: using vanilla classpath"));
                 command.add("-cp");
                 command.add(writeClasspathFile(buildVanillaClasspath()));
                 String mainClass = null;
                 if (manifest != null) {
                     mainClass = manifest.getMainClass();
-                    System.out.println(ZAnsi.cyan("  Main class from manifest: " + mainClass));
+                    LauncherLogger.info(ZAnsi.cyan("  Main class from manifest: " + mainClass));
                 }
                 if (mainClass == null || mainClass.isEmpty()) {
                     mainClass = getVanillaMainClass();
-                    System.out.println(ZAnsi.yellow("  Using fallback main class: " + mainClass));
+                    LauncherLogger.info(ZAnsi.yellow("  Using fallback main class: " + mainClass));
                 }
                 command.add(mainClass);
                 command.addAll(getVanillaGameArguments(options));
             } else if (manifest != null) {
                 String classpath = buildClasspathFromManifest(manifest, true);
                 if (classpath.isEmpty()) {
-                    System.out.println(ZAnsi.yellow("  manifest classpath empty, using vanilla classpath"));
+                    LauncherLogger.info(ZAnsi.yellow("  manifest classpath empty, using vanilla classpath"));
                     command.add("-cp");
                     command.add(writeClasspathFile(buildVanillaClasspath()));
                     command.add(getVanillaMainClass());
@@ -229,20 +230,20 @@ public class LaunchCommandBuilder {
             if (versionJson != null && Files.exists(versionJson)) {
                 String content = Files.readString(versionJson);
                 JSONObject json = new JSONObject(content);
-            System.out.println(ZAnsi.green("Found version.json: " + versionJson.getFileName()));
+            LauncherLogger.info(ZAnsi.green("Found version.json: " + versionJson.getFileName()));
                 VersionManifest manifest = new VersionManifest(json);
                 manifest.resolveParent(instance.getPath().resolve("versions"));
                 if (manifest.getInheritsFrom() != null) {
-                    System.out.println(ZAnsi.cyan("  inheritsFrom: " + manifest.getInheritsFrom()));
+                    LauncherLogger.info(ZAnsi.cyan("  inheritsFrom: " + manifest.getInheritsFrom()));
                 }
                 return manifest;
             } else {
-                System.out.println(ZAnsi.yellow("version.json not found for " + instance.getName()));
-                System.out.println(ZAnsi.yellow("  loaderType=" + instance.getLoaderType() + " mcVersion=" + instance.getMinecraftVersion() + " loaderVersion=" + instance.getLoaderVersion()));
-                System.out.println(ZAnsi.yellow("  path=" + instance.getPath()));
+                LauncherLogger.info(ZAnsi.yellow("version.json not found for " + instance.getName()));
+                LauncherLogger.info(ZAnsi.yellow("  loaderType=" + instance.getLoaderType() + " mcVersion=" + instance.getMinecraftVersion() + " loaderVersion=" + instance.getLoaderVersion()));
+                LauncherLogger.info(ZAnsi.yellow("  path=" + instance.getPath()));
             }
         } catch (Exception e) {
-            System.out.println(ZAnsi.yellow("Failed to load version.json: " + e.getMessage()));
+            LauncherLogger.info(ZAnsi.yellow("Failed to load version.json: " + e.getMessage()));
         }
         return null;
     }
@@ -496,14 +497,14 @@ public class LaunchCommandBuilder {
         String assetIndex = instance.getAssetIndex();
         if (assetIndex == null || assetIndex.isEmpty()) {
             assetIndex = instance.getMinecraftVersion();
-            System.out.println(ZAnsi.yellow("Asset index not found, using version: " + assetIndex));
+            LauncherLogger.info(ZAnsi.yellow("Asset index not found, using version: " + assetIndex));
         } else {
             // Validate that the index file exists. A wrong/stale asset index
             // (e.g. the Zern-OBT "1.20.1" bug, real index is "5") makes the game
             // fail to load the base resource pack (grey panorama, no sounds).
             Path indexPath = instance.getPath().resolve("assets").resolve("indexes").resolve(assetIndex + ".json");
             if (!Files.exists(indexPath)) {
-                System.out.println(ZAnsi.yellow("Asset index file missing: " + assetIndex + ".json, searching for existing index..."));
+                LauncherLogger.info(ZAnsi.yellow("Asset index file missing: " + assetIndex + ".json, searching for existing index..."));
                 try (java.util.stream.Stream<Path> stream = Files.list(instance.getPath().resolve("assets").resolve("indexes"))) {
                     java.util.List<Path> existing = stream
                             .filter(p -> p.getFileName().toString().endsWith(".json"))
@@ -512,16 +513,16 @@ public class LaunchCommandBuilder {
                     if (!existing.isEmpty()) {
                         String found = existing.get(existing.size() - 1).getFileName().toString()
                                 .replace(".json", "");
-                        System.out.println(ZAnsi.green("Using existing asset index: " + found + " (was " + assetIndex + ")"));
+                        LauncherLogger.info(ZAnsi.green("Using existing asset index: " + found + " (was " + assetIndex + ")"));
                         assetIndex = found;
                     } else {
-                        System.out.println(ZAnsi.yellow("No asset index files found in assets/indexes/"));
+                        LauncherLogger.info(ZAnsi.yellow("No asset index files found in assets/indexes/"));
                     }
                 } catch (Exception e) {
-                    System.out.println(ZAnsi.yellow("Failed to search asset indexes: " + e.getMessage()));
+                    LauncherLogger.info(ZAnsi.yellow("Failed to search asset indexes: " + e.getMessage()));
                 }
             }
-            System.out.println(ZAnsi.green("Using asset index: " + assetIndex));
+            LauncherLogger.info(ZAnsi.green("Using asset index: " + assetIndex));
         }
         args.add(assetIndex);
         args.add("--username");
@@ -612,7 +613,7 @@ public class LaunchCommandBuilder {
         List<String> paths = new ArrayList<>();
         Path librariesDir = instance.getPath().resolve("libraries");
 
-        System.out.println(ZAnsi.cyan("  buildClasspathFromManifest: " + manifest.getAllLibraries().size() + " libraries in manifest (including inherited)"));
+        LauncherLogger.info(ZAnsi.cyan("  buildClasspathFromManifest: " + manifest.getAllLibraries().size() + " libraries in manifest (including inherited)"));
 
         String loaderType = instance.getLoaderType().toLowerCase();
         boolean isForgeLike = "forge".equals(loaderType) || "neoforge".equals(loaderType);
@@ -628,7 +629,7 @@ public class LaunchCommandBuilder {
                 if (isValidJar(libPath)) {
                     paths.add(libPath.toAbsolutePath().toString());
                 } else {
-                    System.out.println(ZAnsi.yellow("  Corrupt library, deleting: " + lib.name));
+                    LauncherLogger.info(ZAnsi.yellow("  Corrupt library, deleting: " + lib.name));
                     Files.delete(libPath);
                 }
             } else {
@@ -638,7 +639,7 @@ public class LaunchCommandBuilder {
                     if (isValidJar(fallbackPath)) {
                         paths.add(fallbackPath.toAbsolutePath().toString());
                     } else {
-                        System.out.println(ZAnsi.yellow("  Corrupt library, deleting: " + lib.name));
+                        LauncherLogger.info(ZAnsi.yellow("  Corrupt library, deleting: " + lib.name));
                         Files.delete(fallbackPath);
                     }
                 } else {
@@ -647,23 +648,23 @@ public class LaunchCommandBuilder {
                     Path found = scanForJar(librariesDir, artifactName);
                     if (found != null) {
                         if (isValidJar(found)) {
-                            System.out.println(ZAnsi.green("  Found by scan: " + lib.name + " → " + librariesDir.relativize(found)));
+                            LauncherLogger.info(ZAnsi.green("  Found by scan: " + lib.name + " → " + librariesDir.relativize(found)));
                             paths.add(found.toAbsolutePath().toString());
                         } else {
-                            System.out.println(ZAnsi.yellow("  Corrupt library (scan), deleting: " + found.getFileName()));
+                            LauncherLogger.info(ZAnsi.yellow("  Corrupt library (scan), deleting: " + found.getFileName()));
                             Files.delete(found);
                         }
                     } else {
-                        System.out.println(ZAnsi.yellow("  Library not found (even after scan): " + lib.name));
+                        LauncherLogger.info(ZAnsi.yellow("  Library not found (even after scan): " + lib.name));
                     }
                 }
             }
         }
 
-        System.out.println(ZAnsi.cyan("  buildClasspathFromManifest: " + paths.size() + " libraries in classpath"));
+        LauncherLogger.info(ZAnsi.cyan("  buildClasspathFromManifest: " + paths.size() + " libraries in classpath"));
         if (isForgeLike) {
-            System.out.println(ZAnsi.cyan("  Version ID: " + getVersionId() + " (MC: " + instance.getMinecraftVersion() + ")"));
-            System.out.println(ZAnsi.cyan("  Paths dir: " + instance.getPath().resolve("versions")));
+            LauncherLogger.info(ZAnsi.cyan("  Version ID: " + getVersionId() + " (MC: " + instance.getMinecraftVersion() + ")"));
+            LauncherLogger.info(ZAnsi.cyan("  Paths dir: " + instance.getPath().resolve("versions")));
         }
 
         if (includeVersionJar) {
@@ -671,9 +672,9 @@ public class LaunchCommandBuilder {
             if (versionJar != null) {
                 if (isValidJar(versionJar)) {
                     paths.add(0, versionJar.toAbsolutePath().toString());
-                    System.out.println(ZAnsi.green("  Added version jar: " + versionJar.getFileName()));
+                    LauncherLogger.info(ZAnsi.green("  Added version jar: " + versionJar.getFileName()));
                 } else {
-                    System.out.println(ZAnsi.yellow("  Corrupt version jar, deleting: " + versionJar.getFileName()));
+                    LauncherLogger.info(ZAnsi.yellow("  Corrupt version jar, deleting: " + versionJar.getFileName()));
                     Files.delete(versionJar);
                 }
             }
@@ -785,7 +786,7 @@ public class LaunchCommandBuilder {
         Path targetJar = targetDir.resolve(versionId + ".jar");
 
         if (Files.exists(targetJar) && isValidJar(targetJar)) {
-            System.out.println(ZAnsi.green("  Version jar already exists: " + targetJar));
+            LauncherLogger.info(ZAnsi.green("  Version jar already exists: " + targetJar));
             return;
         }
 
@@ -795,11 +796,11 @@ public class LaunchCommandBuilder {
         Path vanillaJar = versionsDir.resolve(mcVersion).resolve(mcVersion + ".jar");
         if (Files.exists(vanillaJar) && isValidJar(vanillaJar)) {
             Files.copy(vanillaJar, targetJar);
-            System.out.println(ZAnsi.green("  Copied vanilla jar for securejarhandler: " + vanillaJar.getFileName() + " → " + targetJar));
+            LauncherLogger.info(ZAnsi.green("  Copied vanilla jar for securejarhandler: " + vanillaJar.getFileName() + " → " + targetJar));
             return;
         }
 
-        System.out.println(ZAnsi.yellow("  No vanilla jar found at " + vanillaJar));
+        LauncherLogger.info(ZAnsi.yellow("  No vanilla jar found at " + vanillaJar));
     }
 
     /**
@@ -833,7 +834,7 @@ public class LaunchCommandBuilder {
                     .findFirst()
                     .orElse(null);
                 if (found != null) {
-                    System.out.println(ZAnsi.green("  Found SRG client jar: " + found + " (module name: " + getModuleName(found) + ")"));
+                    LauncherLogger.info(ZAnsi.green("  Found SRG client jar: " + found + " (module name: " + getModuleName(found) + ")"));
                     return found;
                 }
             } catch (Exception e) { /* continue */ }
@@ -848,7 +849,7 @@ public class LaunchCommandBuilder {
                 .findFirst()
                 .orElse(null);
             if (found != null) {
-                System.out.println(ZAnsi.green("  Found SRG client jar (fallback scan): " + found + " (module name: " + getModuleName(found) + ")"));
+                LauncherLogger.info(ZAnsi.green("  Found SRG client jar (fallback scan): " + found + " (module name: " + getModuleName(found) + ")"));
                 return found;
             }
         } catch (Exception e) { /* continue */ }
@@ -903,12 +904,12 @@ public class LaunchCommandBuilder {
         for (String candidate : candidates) {
             Path jarPath = librariesDir.resolve(candidate);
             if (Files.exists(jarPath) && isValidJar(jarPath)) {
-                System.out.println(ZAnsi.green("  Found Forge jar: " + jarPath.getFileName()));
+                LauncherLogger.info(ZAnsi.green("  Found Forge jar: " + jarPath.getFileName()));
                 return jarPath;
             }
         }
 
-        System.out.println(ZAnsi.yellow("  No Forge client/universal jar found!"));
+        LauncherLogger.info(ZAnsi.yellow("  No Forge client/universal jar found!"));
         return null;
     }
 
@@ -1047,7 +1048,7 @@ public class LaunchCommandBuilder {
         Path tempFile = Files.createTempFile("zernmc-cp-", ".txt");
         Files.writeString(tempFile, classpath);
         tempFiles.add(tempFile);
-        System.out.println(ZAnsi.cyan("  Classpath too long (" + classpath.length() + " chars), using argfile: " + tempFile));
+        LauncherLogger.info(ZAnsi.cyan("  Classpath too long (" + classpath.length() + " chars), using argfile: " + tempFile));
         return "@" + tempFile.toAbsolutePath();
     }
 }

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/launch/VersionManifest.java

@@ -1,5 +1,7 @@
 package me.sashegdev.zernmc.launcher.minecraft.launch;
 
+import me.sashegdev.zernmc.launcher.utils.LauncherLogger;
+
 import org.json.JSONArray;
 import org.json.JSONObject;
 
@@ -75,7 +77,7 @@ public class VersionManifest {
                 this.parent = new VersionManifest(json);
                 this.parent.resolveParent(versionsDir);
             } catch (Exception e) {
-                System.out.println("Failed to load parent version " + inheritsFrom + ": " + e.getMessage());
+                LauncherLogger.warn("Failed to load parent version " + inheritsFrom + ": " + e.getMessage());
             }
         }
     }

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/ui/jfx/JFXLauncher.java

@@ -18,6 +18,7 @@ import me.sashegdev.zernmc.launcher.minecraft.PackDownloader;
 import me.sashegdev.zernmc.launcher.minecraft.ServerPack;
 import me.sashegdev.zernmc.launcher.minecraft.launch.LaunchCommandBuilder;
 import me.sashegdev.zernmc.launcher.utils.Config;
+import me.sashegdev.zernmc.launcher.utils.DomainSelector;
 import me.sashegdev.zernmc.launcher.utils.LauncherLogger;
 import me.sashegdev.zernmc.launcher.utils.Version;
 
@@ -216,7 +217,7 @@ public class JFXLauncher extends Application {
                 try {
                     String existingVersion = Files.readString(versionFile).trim();
                     if (existingVersion.equals(currentVersion)) {
-                        System.out.println("[JFX] Assets up to date (v" + currentVersion + ")");
+                        log("Assets up to date (v" + currentVersion + ")");
                         return;
                     }
                 } catch (Exception ignored) {}
@@ -233,16 +234,16 @@ public class JFXLauncher extends Application {
             
             String serverVersion = getServerVersion();
             if (serverVersion != null && !serverVersion.isEmpty()) {
-                System.out.println("[JFX] Loading assets via meta for version " + serverVersion);
+                log("Loading assets via meta for version " + serverVersion);
                 if (downloadAssetsFromMeta(serverVersion)) {
-                    System.out.println("[JFX] Assets loaded via meta");
+                    log("Assets loaded via meta");
                     Files.writeString(versionFile, currentVersion);
                     return;
                 }
-                System.out.println("[JFX] Meta unavailable, using fallback");
+                log("Meta unavailable, using fallback");
             }
             
-            System.out.println("[JFX] Extracting assets from JAR...");
+            log("Extracting assets from JAR...");
             Files.createDirectories(assetsDir);
             Path jarPath = Paths.get(JFXLauncher.class.getProtectionDomain().getCodeSource().getLocation().toURI());
             if (Files.exists(jarPath) && jarPath.toString().endsWith(".jar")) {
@@ -263,11 +264,11 @@ public class JFXLauncher extends Application {
                         }
                     }
                 }
-                System.out.println("[JFX] Assets extracted from JAR");
+                log("Assets extracted from JAR");
                 Files.writeString(versionFile, currentVersion);
             }
         } catch (Exception e) {
-            System.out.println("[JFX] Error extracting assets: " + e.getMessage());
+            log("Error extracting assets: " + e.getMessage());
         }
     }
     
@@ -332,7 +333,7 @@ public class JFXLauncher extends Application {
                 return true;
             }
         } catch (Exception e) {
-            System.out.println("[JFX] Error loading via meta: " + e.getMessage());
+            log("Error loading assets via meta: " + e.getMessage());
             return false;
         }
     }
@@ -363,6 +364,7 @@ public class JFXLauncher extends Application {
             log("Starting background network init...");
             Thread netInitThread = new Thread(() -> {
                 try {
+                    DomainSelector.selectBest();
                     ZHttpClient.checkAllServicesOnStartup();
                     log("Network init complete");
                 } catch (Exception e) {
@@ -391,9 +393,9 @@ public class JFXLauncher extends Application {
             engine.setOnAlert(e -> {
                 String msg = e.getData();
                 if (msg.startsWith("[LOG] ")) {
-                    System.out.println("[JS] " + msg.substring(6));
+                    log("[JS] " + msg.substring(6));
                 } else if (msg.startsWith("[ERR] ")) {
-                    System.err.println("[JS] " + msg.substring(6));
+                    log("[JS ERROR] " + msg.substring(6));
                 } else {
                     log("[UI] Alert: " + msg);
                 }
@@ -493,6 +495,8 @@ public class JFXLauncher extends Application {
         server.createContext("/api/account", this::handleAccount);
         server.createContext("/api/instances", this::handleInstances);
         server.createContext("/api/launch", this::handleLaunch);
+        server.createContext("/api/offline/status", this::handleOfflineStatus);
+        server.createContext("/api/offline-launch", this::handleOfflineLaunch);
         server.createContext("/api/install", this::handleInstall);
         server.createContext("/api/install/progress", this::handleInstallProgress);
         server.createContext("/api/network/status", this::handleNetworkStatus);
@@ -612,9 +616,8 @@ public class JFXLauncher extends Application {
                 sendJson(exchange, Map.of("success", false, "error", result.getError()));
             }
         } catch (Exception e) {
-            log("Login error: " + e.getMessage());
-            e.printStackTrace();
-            sendJson(exchange, Map.of("success", false, "error", e.getMessage()));
+            log("Login error: " + AuthManager.friendlyConnectionError(e));
+            sendJson(exchange, Map.of("success", false, "error", AuthManager.friendlyConnectionError(e)));
         }
     }
 
@@ -641,7 +644,6 @@ public class JFXLauncher extends Application {
         try {
             boolean loggedIn = AuthManager.isLoggedIn();
             boolean authExists = AuthManager.authFileExists();
-            System.out.println("[AUTH] handleAutoLogin: isLoggedIn=" + loggedIn + " authFile=" + authExists);
             log("handleAutoLogin: isLoggedIn=" + loggedIn + " authFile=" + authExists);
             if (AuthManager.tryAutoLogin()) {
                 Map<String, Object> data = new HashMap<>();
@@ -650,15 +652,12 @@ public class JFXLauncher extends Application {
                 data.put("role", AuthManager.getRole());
                 data.put("roleName", AuthManager.getRoleName());
                 sendJson(exchange, Map.of("success", true, "data", data, "autoLogin", true));
-                System.out.println("[AUTH] Auto-login performed: " + AuthManager.getUsername());
                 log("Auto-login performed: " + AuthManager.getUsername());
             } else {
-                System.out.println("[AUTH] handleAutoLogin: no valid session (authFile=" + authExists + ")");
                 log("handleAutoLogin: no valid session (authFile=" + authExists + ")");
                 sendJson(exchange, Map.of("success", false, "autoLogin", false));
             }
         } catch (Exception e) {
-            System.out.println("[AUTH] handleAutoLogin error: " + e.getMessage());
             log("handleAutoLogin error: " + e.getMessage());
             sendJson(exchange, Map.of("success", false, "error", e.getMessage()));
         }
@@ -721,6 +720,54 @@ public class JFXLauncher extends Application {
         }
     }
 
+    private void handleOfflineStatus(HttpExchange exchange) {
+        try {
+            boolean offline = isOfflineMode();
+            sendJson(exchange, Map.of("success", true, "offline", offline));
+        } catch (Exception e) {
+            sendJson(exchange, Map.of("success", false, "error", e.getMessage()));
+        }
+    }
+
+    private void handleOfflineLaunch(HttpExchange exchange) {
+        try {
+            Map<String, String> body = parseJson(exchange.getRequestBody());
+            String name = body.get("name");
+            String nickname = body.get("nickname");
+
+            Instance instance = InstanceManager.getInstance(name);
+            if (instance == null) {
+                sendJson(exchange, Map.of("success", false, "error", "Pack not found"));
+                return;
+            }
+
+            var result = api.launch().launchOffline(name, nickname);
+            if (result.isSuccess()) {
+                Map<String, Object> data = new HashMap<>();
+                data.put("pid", result.getData().getPid());
+                data.put("status", result.getData().getStatus());
+                sendJson(exchange, Map.of("success", true, "data", data));
+                log("Offline launched: " + name + " pid=" + result.getData().getPid());
+            } else {
+                log("Offline launch failed: " + result.getError());
+                sendJson(exchange, Map.of("success", false, "error", result.getError()));
+            }
+        } catch (Exception e) {
+            log("handleOfflineLaunch error: " + e.getMessage());
+            sendJson(exchange, Map.of("success", false, "error", e.getMessage()));
+        }
+    }
+
+    private boolean isOfflineMode() {
+        if ("true".equalsIgnoreCase(System.getProperty("zernmc.offline", "false"))) {
+            return true;
+        }
+        if (ZHttpClient.isNetworkInitialized() && !ZHttpClient.isZernServerHealthy()) {
+            return true;
+        }
+        return false;
+    }
+
     private void handleInstall(HttpExchange exchange) {
         if (!installInProgress.compareAndSet(false, true)) {
             sendJson(exchange, Map.of("success", false, "error", "Installation already in progress"));
@@ -769,8 +816,8 @@ public class JFXLauncher extends Application {
                         boolean success = false;
 
                         if (!ZHttpClient.isNetworkInitialized()) {
-                            log("Network init not finished, checking Mojang services synchronously...");
-                            ZHttpClient.forceCheckMojangServices();
+                            log("Network init not finished, running full service check (CLI-style)...");
+                            ZHttpClient.checkAllServicesOnStartup();
                         }
 
                         if ("zernmc".equalsIgnoreCase(loader)) {
@@ -895,17 +942,16 @@ public class JFXLauncher extends Application {
             exchange.sendResponseHeaders(200, 0);
 
             final OutputStream os = exchange.getResponseBody();
+            // Bounded queue: producers (LauncherLogger on the install thread) must
+            // never block on a slow/stalled SSE client. If the UI can't keep up,
+            // lines are dropped here - they still reach the log file and buffer.
+            final java.util.concurrent.BlockingQueue<String> queue =
+                new java.util.concurrent.LinkedBlockingQueue<>(5000);
 
             LogConsumer consumer = new LogConsumer() {
                 @Override
-                public synchronized void onLog(String line) {
-                    try {
-                        String data = "data: " + line.replace("\n", "").replace("\r", "") + "\n\n";
-                        os.write(data.getBytes(StandardCharsets.UTF_8));
-                        os.flush();
-                    } catch (Exception e) {
-                        removeLogConsumer(this);
-                    }
+                public void onLog(String line) {
+                    queue.offer(line);
                 }
             };
             consumerRef[0] = consumer;
@@ -915,9 +961,13 @@ public class JFXLauncher extends Application {
             Thread.currentThread().setName("sse-logs-stream");
             while (!Thread.currentThread().isInterrupted()) {
                 try {
+                    String line = queue.poll(10, java.util.concurrent.TimeUnit.SECONDS);
+                    if (line != null) {
+                        os.write(("data: " + line.replace("\n", "").replace("\r", "") + "\n\n").getBytes(StandardCharsets.UTF_8));
+                    } else {
                         os.write(": heartbeat\n\n".getBytes(StandardCharsets.UTF_8));
+                    }
                     os.flush();
-                    Thread.sleep(10000);
                 } catch (InterruptedException e) { break; } catch (Exception e) { break; }
             }
         } catch (Exception ignored) {} finally {
@@ -939,17 +989,14 @@ public class JFXLauncher extends Application {
             exchange.sendResponseHeaders(200, 0);
 
             final OutputStream os = exchange.getResponseBody();
+            // Bounded queue: producers must never block on a slow/stalled SSE client.
+            final java.util.concurrent.BlockingQueue<String> queue =
+                new java.util.concurrent.LinkedBlockingQueue<>(5000);
 
             LogConsumer consumer = new LogConsumer() {
                 @Override
-                public synchronized void onLog(String line) {
-                    try {
-                        String data = "data: " + line.replace("\n", "").replace("\r", "") + "\n\n";
-                        os.write(data.getBytes(StandardCharsets.UTF_8));
-                        os.flush();
-                    } catch (Exception e) {
-                        removeGameLogConsumer(this);
-                    }
+                public void onLog(String line) {
+                    queue.offer(line);
                 }
             };
             consumerRef[0] = consumer;
@@ -959,9 +1006,13 @@ public class JFXLauncher extends Application {
             Thread.currentThread().setName("sse-game-logs-stream");
             while (!Thread.currentThread().isInterrupted()) {
                 try {
+                    String line = queue.poll(10, java.util.concurrent.TimeUnit.SECONDS);
+                    if (line != null) {
+                        os.write(("data: " + line.replace("\n", "").replace("\r", "") + "\n\n").getBytes(StandardCharsets.UTF_8));
+                    } else {
                         os.write(": heartbeat\n\n".getBytes(StandardCharsets.UTF_8));
+                    }
                     os.flush();
-                    Thread.sleep(10000);
                 } catch (InterruptedException e) { break; } catch (Exception e) { break; }
             }
         } catch (Exception ignored) {} finally {
@@ -1080,7 +1131,7 @@ public class JFXLauncher extends Application {
                 sendJson(exchange, Map.of("success", false, "error", result.getError()));
             }
         } catch (Exception e) {
-            sendJson(exchange, Map.of("success", false, "error", e.getMessage()));
+            sendJson(exchange, Map.of("success", false, "error", AuthManager.friendlyConnectionError(e)));
         }
     }
 
@@ -1723,7 +1774,7 @@ public class JFXLauncher extends Application {
         }
     }
 
-    private void log(String msg) {
+    private static void log(String msg) {
         String timestamp = java.time.LocalTime.now().format(java.time.format.DateTimeFormatter.ofPattern("HH:mm:ss"));
         String entry = "[" + timestamp + "] " + msg;
         synchronized (launcherLogBuffer) {

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/utils/Config.java

@@ -13,7 +13,7 @@ public class Config {
     private static final Properties props = new Properties();
 
     private static volatile int maxMemory = 4096;
-    private static volatile String serverUrl = "https://api.zernmc.ru";
+    private static volatile String serverUrl = "https://api.zern.cc";
     private static volatile String lastUsername = "Player";
     private static volatile int windowWidth = 1280;
     private static volatile int windowHeight = 720;
@@ -144,6 +144,11 @@ public class Config {
         return serverUrl;
     }
 
+    public static void setServerUrl(String url) {
+        serverUrl = url != null && !url.isBlank() ? url : serverUrl;
+        save();
+    }
+
     public static String getLastUsername() {
         return lastUsername;
     }

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/utils/DomainSelector.java

@@ -0,0 +1,126 @@
+package me.sashegdev.zernmc.launcher.utils;
+
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Picks the fastest reachable ZernMC API domain at launcher startup.
+ * TSPU/SNI-обход: если основной api.zern.cc недоступен (заблокирован ТСПУ),
+ * пробиваем legacy-домены и гео-зеркала и переключаемся на первый живой/быстрый.
+ */
+public final class DomainSelector {
+
+    private static final HttpClient client = HttpClient.newBuilder()
+            .connectTimeout(Duration.ofSeconds(8))
+            .version(HttpClient.Version.HTTP_1_1)
+            .build();
+
+    private static final List<String> FALLBACK_CANDIDATES = List.of(
+            "https://api.zern.cc",
+            "https://api.zernmc.ru",
+            "https://api.zernmc.online",
+            "https://api.pl.zern.cc",
+            "https://api.swe.zern.cc"
+    );
+
+    private static final String MIRRORS_PATH = "/launcher/mirrors";
+    private static final String VERSION_PATH = "/launcher/version";
+
+    private DomainSelector() {
+    }
+
+    /**
+     * @return выбранный base URL или null, если ни один домен не ответил.
+     */
+    public static String selectBest() {
+        List<String> candidates = new ArrayList<>();
+        String configured = Config.getServerUrl();
+        if (configured != null && !configured.isBlank() && !candidates.contains(configured)) {
+            candidates.add(configured);
+        }
+        for (String c : FALLBACK_CANDIDATES) {
+            if (!candidates.contains(c)) {
+                candidates.add(c);
+            }
+        }
+        candidates.addAll(fetchMirrors());
+
+        String best = null;
+        long bestMs = Long.MAX_VALUE;
+        for (String base : candidates) {
+            Probe r = probe(base);
+            if (r.ok && r.latencyMs >= 0 && r.latencyMs < bestMs) {
+                bestMs = r.latencyMs;
+                best = base;
+            }
+        }
+
+        if (best == null) {
+            // nothing reachable: keep whatever is configured
+            System.err.println(ZAnsi.brightRed("DomainSelector: no reachable API domain"));
+            return null;
+        }
+
+        if (!best.equals(configured)) {
+            ZHttpClient.setBaseUrl(best);
+            Config.setServerUrl(best);
+            System.out.println(ZAnsi.cyan("Selected API domain: " + best)
+                    + " (" + bestMs + " ms)");
+        }
+        return best;
+    }
+
+    private static List<String> fetchMirrors() {
+        List<String> mirrors = new ArrayList<>();
+        for (String candidate : FALLBACK_CANDIDATES) {
+            Probe p = probe(candidate);
+            if (!p.ok || p.body == null) {
+                continue;
+            }
+            try {
+                org.json.JSONObject json = new org.json.JSONObject(p.body);
+                var arr = json.optJSONArray("mirrors");
+                if (arr == null) {
+                    continue;
+                }
+                for (int i = 0; i < arr.length(); i++) {
+                    String url = arr.optJSONObject(i) != null
+                            ? arr.optJSONObject(i).optString("url", null) : null;
+                    if (url != null && !url.isBlank() && !mirrors.contains(url)) {
+                        mirrors.add(url);
+                    }
+                }
+                break; // первый живой источник списка достаточен
+            } catch (Exception ignored) {
+                // continue to next candidate
+            }
+        }
+        return mirrors;
+    }
+
+    private static Probe probe(String baseUrl) {
+        long t0 = System.currentTimeMillis();
+        try {
+            HttpRequest request = HttpRequest.newBuilder()
+                    .uri(URI.create(baseUrl + MIRRORS_PATH))
+                    .timeout(Duration.ofSeconds(8))
+                    .GET()
+                    .header("User-Agent", "ZernMC-Launcher/DomainSelector")
+                    .build();
+            HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
+            long ms = System.currentTimeMillis() - t0;
+            boolean ok = response.statusCode() == 200;
+            return new Probe(ok, ms, ok ? response.body() : null);
+        } catch (Exception e) {
+            return new Probe(false, System.currentTimeMillis() - t0, null);
+        }
+    }
+
+    private record Probe(boolean ok, long latencyMs, String body) {
+    }
+}

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/utils/LauncherLogger.java

@@ -15,6 +15,7 @@ import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.ReentrantLock;
+import java.util.regex.Pattern;
 
 public class LauncherLogger {
 
@@ -25,6 +26,7 @@ public class LauncherLogger {
     private static final int STDOUT_QUEUE_CAPACITY = 2048;
     private static final BlockingQueue<String> stdoutQueue = new LinkedBlockingQueue<>(STDOUT_QUEUE_CAPACITY);
     private static final Thread stdoutWriterThread;
+    private static final Pattern ANSI_PATTERN = Pattern.compile("\u001B\\[[0-9;]*[A-Za-z]");
 
     static {
         stdoutWriterThread = new Thread(() -> {
@@ -97,9 +99,12 @@ public class LauncherLogger {
         // block application threads.
         offerStdout(line);
 
+        // File and UI log never get ANSI escape codes; the console keeps them.
+        String plainLine = ANSI_PATTERN.matcher(line).replaceAll("");
+
         // Forward to the JFX UI log so installer/progress output is visible
         // in the GUI. The bridge is a safe no-op when JavaFX is unavailable.
-        JFXBridge.appendLauncherLogFromLogger(line);
+        JFXBridge.appendLauncherLogFromLogger(plainLine);
 
         if (t != null) {
             StringWriter sw = new StringWriter();
@@ -120,7 +125,7 @@ public class LauncherLogger {
             }
             if (acquired) {
                 try {
-                    Files.writeString(logFile, line + "\n", StandardOpenOption.APPEND);
+                    Files.writeString(logFile, plainLine + "\n", StandardOpenOption.APPEND);
                     if (t != null) {
                         StringWriter sw = new StringWriter();
                         PrintWriter pw = new PrintWriter(sw);

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/utils/ProgressBar.java

@@ -4,14 +4,27 @@ import me.sashegdev.zernmc.launcher.ui.jfx.JFXBridge;
 
 import java.text.DecimalFormat;
 
+/**
+ * Progress reporting for installs/downloads.
+ *
+ * IMPORTANT: never writes directly to System.out/System.err. In JFX mode the
+ * launcher runs under javaw.exe whose stdout pipe is drained by the parent exe;
+ * once that pipe fills (or the exe stops reading), a synchronous
+ * System.out.write/flush blocks the calling (install/UI) thread forever.
+ * All console/progress output must go through LauncherLogger, which is
+ * non-blocking by design (bounded stdout queue + tryLock file write + SSE queue).
+ */
 public class ProgressBar {
 
-    private static final int BAR_LENGTH = 40;
     private static final DecimalFormat DF = new DecimalFormat("#.##");
 
     private static String currentLabel = "";
     private static long currentTotal = 0;
 
+    private static final long DOWNLOAD_LOG_INTERVAL_MS = 500;
+    private static volatile long lastDownloadLogMs = 0;
+    private static volatile long lastIndeterminateLogMs = 0;
+
     public static void show(String label, long current, long total, String unit) {
         currentLabel = label;
         currentTotal = total;
@@ -19,19 +32,11 @@ public class ProgressBar {
         JFXBridge.setInstallProgress(label, (int) current, (int) total);
 
         if (total <= 0) {
-            System.out.print("\r" + ZAnsi.cyan(label) + " ...");
+            LauncherLogger.info(label + " ...");
             return;
         }
-        double progress = (double) current / total;
-        int filled = (int) (progress * BAR_LENGTH);
-        String bar = "█".repeat(filled) + "░".repeat(BAR_LENGTH - filled);
-        int percent = (int) (progress * 100);
-
-        String text = String.format("%s [%s] %3d%% (%d/%d %s)",
-                ZAnsi.cyan(label), bar, percent, current, total, unit);
-
-        System.out.print("\r" + text);
-        System.out.flush();
+        int percent = (int) ((double) current / total * 100);
+        LauncherLogger.info(label + " " + percent + "% (" + current + "/" + total + " " + unit + ")");
     }
 
     public static void showDownload(String label, long downloaded, long totalBytes) {
@@ -40,25 +45,13 @@ public class ProgressBar {
 
         JFXBridge.setInstallProgress(label + " " + formatBytes(downloaded) + "/" + formatBytes(totalBytes), (int) downloaded, (int) totalBytes);
 
-        if (totalBytes <= 0) {
-            System.out.print("\r" + ZAnsi.cyan(label) + " ...");
-            return;
+        // Throttle console/file logging: called once per chunk during downloads.
+        long now = System.currentTimeMillis();
+        if (now - lastDownloadLogMs >= DOWNLOAD_LOG_INTERVAL_MS) {
+            lastDownloadLogMs = now;
+            LauncherLogger.info(label + " " + formatBytes(downloaded)
+                    + (totalBytes > 0 ? "/" + formatBytes(totalBytes) : ""));
         }
-
-        double progress = (double) downloaded / totalBytes;
-        int filled = (int) (progress * BAR_LENGTH);
-        String bar = "█".repeat(filled) + "░".repeat(BAR_LENGTH - filled);
-        String percent = DF.format(progress * 100);
-
-        String text = String.format("%s [%s] %6s%%  %s / %s",
-                ZAnsi.cyan(label),
-                bar,
-                percent,
-                formatBytes(downloaded),
-                formatBytes(totalBytes));
-
-        System.out.print("\r" + text);
-        System.out.flush();
     }
 
     public static void showAnimated(String label, long current, long total, String unit) {
@@ -67,18 +60,51 @@ public class ProgressBar {
 
         JFXBridge.setInstallProgress(label, (int) current, (int) (total > 0 ? total : 100));
 
-        if (total <= 0) {
-            char[] spinner = {'|', '/', '-', '\\'};
-            int idx = (int) (current / 1024) % 4;
-            System.out.print("\r" + label + " [" + spinner[idx] + "] " + formatBytes(current));
-        } else {
-            show(label, (int) ((current * 100) / total), 100, unit);
+        long now = System.currentTimeMillis();
+        if (now - lastDownloadLogMs >= DOWNLOAD_LOG_INTERVAL_MS) {
+            lastDownloadLogMs = now;
+            LauncherLogger.info(label + ": " + formatBytes(current)
+                    + (total > 0 ? "/" + formatBytes(total) + " " + unit : ""));
         }
     }
 
     public static void finish(String message) {
-        System.out.println("\r" + ZAnsi.brightGreen(message + " done ✓"));
-        System.out.flush();
+        LauncherLogger.info(message + " done");
+    }
+
+    /**
+     * Shows a stage without a known total (e.g. running the Forge/NeoForge/Fabric
+     * installer subprocess). Always updates the UI label so the user sees what the
+     * launcher is doing right now; console/file logging is throttled to avoid spam.
+     */
+    public static void showIndeterminate(String label) {
+        currentLabel = label;
+        currentTotal = 0;
+
+        JFXBridge.setInstallProgress(label, 0, 0);
+
+        long now = System.currentTimeMillis();
+        if (now - lastIndeterminateLogMs >= DOWNLOAD_LOG_INTERVAL_MS) {
+            lastIndeterminateLogMs = now;
+            LauncherLogger.info(label + " ...");
+        }
+    }
+
+    /**
+     * Strips ANSI codes, indentation and [category] prefixes from a child-process
+     * output line so it can be used as a short, human-readable progress label.
+     */
+    public static String cleanLine(String line) {
+        if (line == null) return "";
+        String s = line.replaceAll("\\u001B\\[[;\\d]*m", "").trim();
+        int bracket = s.indexOf("] ");
+        if (s.startsWith("[") && bracket > 0) {
+            s = s.substring(bracket + 2).trim();
+        }
+        if (s.length() > 60) {
+            s = s.substring(0, 57) + "...";
+        }
+        return s;
     }
 
     public static void setStage(String stageName, int stageIndex, int stageCount) {
@@ -86,8 +112,7 @@ public class ProgressBar {
     }
 
     public static void clearLine() {
-        System.out.print("\r" + " ".repeat(110) + "\r");
-        System.out.flush();
+        // No-op: console progress now goes through LauncherLogger.
     }
 
     public static String formatBytes(long bytes) {

launcher/launcher/src/main/java/sashegdev/zernmc/launcher/utils/ZHttpClient.java

@@ -49,7 +49,7 @@ public class ZHttpClient {
             .executor(CLIENT_EXECUTOR)
             .build();
 
-    private static String BASE_URL = "https://api.zernmc.ru";
+    private static String BASE_URL = "https://api.zern.cc";
 
     private static final AtomicBoolean useProxyMode = new AtomicBoolean(false);
     private static final AtomicBoolean proxyTested = new AtomicBoolean(false);
@@ -64,7 +64,7 @@ public class ZHttpClient {
     }
 
     public enum ServiceType {
-        ZERN_SERVER("https://api.zernmc.ru", true),
+        ZERN_SERVER("https://api.zern.cc", true),
         FABRIC_META("https://meta.fabricmc.net", false),
         FABRIC_MAVEN("https://maven.fabricmc.net", false),
         MOJANG_META("https://piston-meta.mojang.com", false),
@@ -148,12 +148,19 @@ public class ZHttpClient {
                     serviceFailCount.put(service, MAX_FAILS_BEFORE_PROXY);
                 }
             }
+            LauncherLogger.info("[NET] " + service.name() + ": "
+                    + (isHealthy ? "OK" : "unavailable") +
+                    (serviceProxyMode.get(service) ? " (proxy mode)" : " (direct)"));
         }
 
         if (!serviceHealthy.get(ServiceType.ZERN_SERVER)) {
             if (verbose) {
                 System.out.println(ZAnsi.brightRed("Critical error: Zern server is unreachable!"));
             }
+            LauncherLogger.warn("[NET] Critical: Zern server unreachable");
+        } else {
+            String ip = getClientPublicIp();
+            LauncherLogger.info("[NET] Client public IP: " + (ip != null ? ip : "unknown"));
         }
 
         proxyTested.set(true);
@@ -163,6 +170,29 @@ public class ZHttpClient {
         }
     }
 
+    /**
+     * Asks the Zern server what public IP it sees for this client (used to
+     * attribute user logs when login/registration fails). Returns null on failure.
+     */
+    public static String getClientPublicIp() {
+        try {
+            HttpRequest request = HttpRequest.newBuilder()
+                    .uri(URI.create(BASE_URL + "/launcher/ip"))
+                    .timeout(Duration.ofMillis(15000))
+                    .GET()
+                    .header("User-Agent", "ZernMC-Launcher/IPCheck")
+                    .build();
+            HttpResponse<String> response = sendBounded(request, HttpResponse.BodyHandlers.ofString(), 15);
+            if (response.statusCode() == 200) {
+                JSONObject json = new JSONObject(response.body());
+                return json.optString("ip", null);
+            }
+        } catch (Exception e) {
+            return null;
+        }
+        return null;
+    }
+
     public static void forceCheckMojangServices() {
         System.out.println(ZAnsi.cyan("Forcing Mojang services check..."));
 
@@ -183,6 +213,9 @@ public class ZHttpClient {
     }
 
     private static boolean checkServiceHealth(ServiceType service) {
+        if (service == ServiceType.ZERN_SERVER) {
+            return checkDirectConnection(BASE_URL);
+        }
         return checkDirectConnection(service.getBaseUrl());
     }
 
@@ -238,7 +271,7 @@ public class ZHttpClient {
             if (isHealthy && serviceProxyMode.get(service)) {
                 serviceProxyMode.put(service, false);
                 serviceFailCount.put(service, 0);
-                System.out.println(ZAnsi.green("[NET] " + service.name() + " restored, switched to direct connection"));
+                LauncherLogger.info("[NET] " + service.name() + " restored, switched to direct connection");
             } else if (!isHealthy && !serviceProxyMode.get(service)) {
                 int fails = serviceFailCount.getOrDefault(service, 0) + 1;
                 serviceFailCount.put(service, fails);
@@ -246,7 +279,7 @@ public class ZHttpClient {
 
                 if (fails >= MAX_FAILS_BEFORE_PROXY) {
                     serviceProxyMode.put(service, true);
-                    System.out.println(ZAnsi.yellow("[NET] " + service.name() + " unavailable, proxy mode enabled"));
+                    LauncherLogger.warn("[NET] " + service.name() + " unavailable, proxy mode enabled");
                 }
             }
         }
@@ -290,6 +323,7 @@ public class ZHttpClient {
                msg.contains("connection") ||
                msg.contains("timeout") ||
                msg.contains("refused") ||
+               msg.contains("received within") ||
                msg.contains("closed") ||
                msg.contains("reset") ||
                msg.contains("abort");
@@ -315,7 +349,7 @@ public class ZHttpClient {
 
         if (fails >= MAX_FAILS_BEFORE_PROXY && !serviceProxyMode.get(service)) {
             serviceProxyMode.put(service, true);
-            System.out.println(ZAnsi.yellow("[NET] " + service.name() + " blocked, switching to proxy"));
+            LauncherLogger.warn("[NET] " + service.name() + " blocked, switching to proxy");
         }
     }
 
@@ -497,7 +531,7 @@ public class ZHttpClient {
                 last = e;
                 if (!isRetryableError(e)) throw e;
                 if (attempt < maxAttempts) {
-                    System.out.println(ZAnsi.yellow("[NET] Server request retry " + attempt + "/" + maxAttempts + " for " + endpoint));
+                    LauncherLogger.warn("[NET] Server request retry " + attempt + "/" + maxAttempts + " for " + endpoint + " (" + e.getMessage() + ")");
                     try { Thread.sleep(500L * attempt); } catch (InterruptedException ie) {
                         Thread.currentThread().interrupt();
                         throw ie;
@@ -543,7 +577,7 @@ public class ZHttpClient {
         try {
             return getMojangVersionManifestViaServer();
         } catch (Exception e) {
-            System.out.println(ZAnsi.yellow("[NET] Server manifest proxy failed (" + e.getMessage() + "), trying direct piston-meta..."));
+            LauncherLogger.warn("[NET] Server manifest proxy failed (" + e.getMessage() + "), trying direct piston-meta...");
             return new JSONObject(getWithSmartProxy("https://piston-meta.mojang.com/mc/game/version_manifest_v2.json"));
         }
     }
@@ -565,17 +599,30 @@ public class ZHttpClient {
     }
 
     public static JSONObject getMojangVersionJson(String versionId) throws IOException, InterruptedException {
+        long deadline = System.currentTimeMillis() + 90_000;
+        LauncherLogger.info("[NET] Fetching version info for " + versionId + " via server proxy...");
         try {
-            return getMojangVersionViaServer(versionId);
+            JSONObject result = getMojangVersionViaServer(versionId);
+            LauncherLogger.info("[NET] Version info for " + versionId + " fetched via proxy (" + (System.currentTimeMillis() - (deadline - 90_000)) + "ms)");
+            return result;
         } catch (Exception e) {
-            System.out.println(ZAnsi.yellow("[NET] Server version proxy failed (" + e.getMessage() + "), trying direct piston-meta..."));
+            if (System.currentTimeMillis() >= deadline) {
+                throw new IOException("Version " + versionId + " fetch timed out after 90s: " + e.getMessage(), e);
+            }
+            LauncherLogger.warn("[NET] Server version proxy failed (" + e.getMessage() + "), trying direct piston-meta...");
             JSONObject manifest = getMojangVersionManifest();
             JSONArray versions = manifest.getJSONArray("versions");
 
             for (int i = 0; i < versions.length(); i++) {
                 JSONObject v = versions.getJSONObject(i);
                 if (v.getString("id").equals(versionId)) {
-                    return new JSONObject(getWithSmartProxy(v.getString("url")));
+                    if (System.currentTimeMillis() >= deadline) {
+                        throw new IOException("Version " + versionId + " fetch timed out after 90s");
+                    }
+                    LauncherLogger.info("[NET] Fetching version info for " + versionId + " directly...");
+                    JSONObject result = new JSONObject(getWithSmartProxy(v.getString("url")));
+                    LauncherLogger.info("[NET] Version info for " + versionId + " fetched directly");
+                    return result;
                 }
             }
             throw new IOException("Version " + versionId + " not found");
@@ -616,12 +663,12 @@ public class ZHttpClient {
                     try {
                         repairLibrariesFromJson(versionJson, minecraftDir);
                     } catch (Exception e) {
-                        System.out.println(ZAnsi.yellow("[LIB] Repair skipped for " + versionDir.getFileName() + ": " + e.getMessage()));
+                        LauncherLogger.warn("[LIB] Repair skipped for " + versionDir.getFileName() + ": " + e.getMessage());
                     }
                 }
             });
         } catch (IOException e) {
-            System.out.println(ZAnsi.yellow("[LIB] Repair scan failed: " + e.getMessage()));
+            LauncherLogger.warn("[LIB] Repair scan failed: " + e.getMessage());
         }
     }
 
@@ -661,12 +708,12 @@ public class ZHttpClient {
                 }
             } catch (Exception e) {
                 String libName = lib.optString("name", lib.optString("path", "?"));
-                System.out.println(ZAnsi.yellow("[LIB] Repair failed for " + libName + ": " + e.getMessage()));
+                LauncherLogger.warn("[LIB] Repair failed for " + libName + ": " + e.getMessage());
             }
         }
 
         if (repaired > 0) {
-            System.out.println(ZAnsi.green("[LIB] Repaired " + repaired + " missing libraries"));
+            LauncherLogger.info("[LIB] Repaired " + repaired + " missing libraries");
         }
     }
 
@@ -766,6 +813,10 @@ public class ZHttpClient {
         return proxyTested.get();
     }
 
+    public static boolean isZernServerHealthy() {
+        return serviceHealthy.getOrDefault(ServiceType.ZERN_SERVER, false);
+    }
+
     public static Map<String, Object> getNetworkStatus() {
         Map<String, Object> status = new HashMap<>();
         status.put("initialized", proxyTested.get());

launcher/launcher/src/resources/ui/index.html

@@ -39,6 +39,7 @@
                     <div class="field">
                         <label for="password" data-i18n="login.password">Password</label>
                         <input type="password" id="password" autocomplete="current-password" required>
+                        <span class="field-hint hidden" id="password-hint" data-i18n="login.passTooShort"></span>
                     </div>
                     <div class="field hidden" id="confirm-field">
                         <label for="confirm-password" data-i18n="login.confirm">Confirm Password</label>
@@ -57,6 +58,38 @@
             </div>
         </div>
 
+        <!-- Offline Screen -->
+        <div id="offline-screen" class="screen hidden">
+            <div class="offline-container">
+                <div class="offline-badge">
+                    <svg width="44" height="44" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M1 1l22 22"/><path d="M16.72 11.06A10.94 10.94 0 0 1 19 12.55"/><path d="M5 12.55a10.94 10.94 0 0 1 5.17-2.39"/><path d="M10.71 5.05A16 16 0 0 1 22.58 9"/><path d="M1.42 9a15.91 15.91 0 0 1 4.7-2.88"/><path d="M8.53 16.11a6 6 0 0 1 6.95 0"/><line x1="12" y1="20" x2="12.01" y2="20"/></svg>
+                </div>
+                <h2 class="offline-title" data-i18n="offline.title">Offline Mode</h2>
+                <p class="offline-subtitle" data-i18n="offline.subtitle">The Zern server is unreachable. You can still launch locally installed packs without an account.</p>
+
+                <form id="offline-form" class="login-form">
+                    <div class="field">
+                        <label for="offline-nickname" data-i18n="offline.nickname">Nickname</label>
+                        <input type="text" id="offline-nickname" maxlength="16" autocomplete="off">
+                    </div>
+                    <div class="field">
+                        <label for="offline-instance" data-i18n="offline.instance">Pack</label>
+                        <select id="offline-instance"></select>
+                    </div>
+                    <p id="offline-error" class="error-msg hidden"></p>
+                    <button type="submit" class="btn-primary" id="offline-launch-btn">
+                        <span class="btn-label" data-i18n="offline.launch">Launch Offline</span>
+                        <div class="spinner hidden"></div>
+                    </button>
+                </form>
+
+                <div class="offline-footer">
+                    <button type="button" class="btn-ghost" id="offline-retry-btn" data-i18n="offline.retry">Try again online</button>
+                    <button type="button" class="btn-ghost" id="offline-exit-btn" data-i18n="offline.exit">Exit</button>
+                </div>
+            </div>
+        </div>
+
         <!-- Loading Overlay -->
         <div id="loading-overlay" class="overlay hidden">
             <div class="loader-ring"></div>

launcher/launcher/src/resources/ui/launcher.js

@@ -12,7 +12,7 @@ const LOCALES = {
         'login.hasAccount': 'Already have an account?',
         'login.confirm': 'Confirm Password',
         'login.passMismatch': 'Passwords do not match',
-        'login.passTooShort': 'Password must be at least 3 characters',
+        'login.passTooShort': 'Password must be at least 6 characters',
         'login.signingIn': 'Signing in...',
         'loading.text': 'Loading...',
         'sidebar.serverPacks': 'Server Packs', 'sidebar.localPacks': 'Local Packs',
@@ -88,6 +88,24 @@ const LOCALES = {
         'toast.loggedOut': 'Logged out',
         'toast.enterCredentials': 'Enter username and password',
         'toast.loginFailed': 'Login failed',
+        'login.errNetwork': 'Could not reach the server. Check your connection.',
+        'login.errInvalidInput': 'Invalid data. The password must be at least 6 characters.',
+        'login.errTaken': 'This username is already taken.',
+        'login.errBadCredentials': 'Wrong username or password.',
+        'login.errServer': 'The server returned an error. Try again later.',
+        'offline.title': 'Offline Mode',
+        'offline.subtitle': 'The Zern server is unreachable. You can still launch locally installed packs without an account.',
+        'offline.nickname': 'Nickname',
+        'offline.instance': 'Pack',
+        'offline.noInstances': 'No locally installed packs found',
+        'offline.launch': 'Launch Offline',
+        'offline.launching': 'Launching...',
+        'offline.needNickname': 'Enter a nickname',
+        'offline.nickTooLong': 'Nickname must be at most 16 characters',
+        'offline.needInstance': 'Select a pack',
+        'offline.retry': 'Try again online',
+        'offline.exit': 'Exit',
+        'offline.stillOffline': 'Server is still unreachable',
         'toast.launching': 'Launching {name}...',
         'toast.launchFailed': 'Launch failed',
         'toast.updated': '{name} updated to v{version}!',
@@ -203,7 +221,7 @@ const LOCALES = {
         'login.hasAccount': 'Уже есть аккаунт?',
         'login.confirm': 'Подтвердите пароль',
         'login.passMismatch': 'Пароли не совпадают',
-        'login.passTooShort': 'Пароль должен быть минимум 3 символа',
+        'login.passTooShort': 'Пароль должен быть минимум 6 символов',
         'login.signingIn': 'Вход...',
         'loading.text': 'Загрузка...',
         'sidebar.serverPacks': 'Серверные сборки', 'sidebar.localPacks': 'Локальные сборки',
@@ -279,6 +297,24 @@ const LOCALES = {
         'toast.loggedOut': 'Вы вышли',
         'toast.enterCredentials': 'Введите логин и пароль',
         'toast.loginFailed': 'Ошибка входа',
+        'login.errNetwork': 'Не удалось связаться с сервером. Проверьте подключение.',
+        'login.errInvalidInput': 'Некорректные данные. Пароль должен быть минимум 6 символов.',
+        'login.errTaken': 'Это имя пользователя уже занято.',
+        'login.errBadCredentials': 'Неверный логин или пароль.',
+        'login.errServer': 'Сервер вернул ошибку. Попробуйте позже.',
+        'offline.title': 'Оффлайн-режим',
+        'offline.subtitle': 'Сервер Zern недоступен. Вы можете запустить локально установленные сборки без аккаунта.',
+        'offline.nickname': 'Никнейм',
+        'offline.instance': 'Сборка',
+        'offline.noInstances': 'Локально установленные сборки не найдены',
+        'offline.launch': 'Запустить оффлайн',
+        'offline.launching': 'Запуск...',
+        'offline.needNickname': 'Введите никнейм',
+        'offline.nickTooLong': 'Никнейм должен быть не длиннее 16 символов',
+        'offline.needInstance': 'Выберите сборку',
+        'offline.retry': 'Попробовать снова онлайн',
+        'offline.exit': 'Выйти',
+        'offline.stillOffline': 'Сервер всё ещё недоступен',
         'toast.launching': 'Запуск {name}...',
         'toast.launchFailed': 'Ошибка запуска',
         'toast.updated': '{name} обновлён до v{version}!',
@@ -534,6 +570,12 @@ class ZernMCLauncher {
     // ==================== AUTH ====================
     async checkAuth() {
         this.showLoading(true);
+        const status = await this.req('/offline/status');
+        if (status.success && status.offline) {
+            this.showOffline();
+            this.showLoading(false);
+            return;
+        }
         const auto = await this.req('/auto-login');
         if (auto.success && auto.autoLogin) {
             this.state.account = auto.data;
@@ -565,7 +607,7 @@ class ZernMCLauncher {
         if (this._registerMode) {
             const confirm = document.getElementById('confirm-password').value;
             if (password !== confirm) { this.showLoginError(t('login.passMismatch')); return; }
-            if (password.length < 3) { this.showLoginError(t('login.passTooShort')); return; }
+            if (password.length < 6) { this.showLoginError(t('login.passTooShort')); return; }
         }
 
         btn.disabled = true;
@@ -594,7 +636,48 @@ class ZernMCLauncher {
                     return;
                 }
             }
-            this.showLoginError(r.error || t('toast.loginFailed'));
+            this.showLoginError(this.friendlyError(r.error) || r.error || t('toast.loginFailed'));
+        }
+    }
+
+    friendlyError(err) {
+        if (!err) return null;
+        const s = String(err);
+        if (/failed to fetch|fetch failed|networkerror|ENOTFOUND|ECONNREFUSED|ECONNRESET|timeout|aborted/i.test(s)) {
+            return t('login.errNetwork');
+        }
+        if (s.includes('HTTP 422') || /at least 6|string should have/i.test(s)) {
+            return t('login.errInvalidInput');
+        }
+        if (s.includes('HTTP 409') || /already taken/i.test(s)) {
+            return t('login.errTaken');
+        }
+        if (s.includes('HTTP 401') || /invalid.*(login|password)|wrong.*(login|password)/i.test(s)) {
+            return t('login.errBadCredentials');
+        }
+        if (/HTTP \d{3}/.test(s)) {
+            return t('login.errServer');
+        }
+        return null;
+    }
+
+    validatePassword() {
+        if (!this._registerMode) return;
+        const password = document.getElementById('password');
+        const hint = document.getElementById('password-hint');
+        const btn = document.getElementById('login-btn');
+        const tooShort = password.value.length < 6;
+        if (tooShort) {
+            password.classList.add('invalid');
+            hint.classList.remove('hidden');
+        } else {
+            password.classList.remove('invalid');
+            hint.classList.add('hidden');
+        }
+        if (btn) btn.disabled = tooShort;
+        const errEl = document.getElementById('login-error');
+        if (errEl && !errEl.classList.contains('hidden')) {
+            errEl.classList.add('hidden');
         }
     }
 
@@ -622,10 +705,14 @@ class ZernMCLauncher {
             if (isReg) {
                 confirmField.classList.remove('hidden');
                 document.getElementById('confirm-password').required = true;
+                this.validatePassword();
             } else {
                 confirmField.classList.add('hidden');
                 document.getElementById('confirm-password').required = false;
                 document.getElementById('confirm-password').value = '';
+                document.getElementById('login-btn').disabled = false;
+                document.getElementById('password').classList.remove('invalid');
+                document.getElementById('password-hint').classList.add('hidden');
             }
 
             document.getElementById('login-error').classList.add('hidden');
@@ -689,9 +776,113 @@ class ZernMCLauncher {
         }
     }
 
+    // ==================== OFFLINE MODE ====================
+    showOffline() {
+        document.getElementById('login-screen').classList.add('hidden');
+        document.getElementById('main-screen').classList.add('hidden');
+        document.getElementById('offline-screen').classList.remove('hidden');
+        this.loadOfflineInstances();
+    }
+
+    async loadOfflineInstances() {
+        const select = document.getElementById('offline-instance');
+        if (!select) return;
+        select.innerHTML = '';
+        const r = await this.req('/instances');
+        let instances = (r.success && r.data) ? r.data : [];
+        instances = instances.filter(function(inst) { return inst.name; });
+        if (instances.length === 0) {
+            const opt = document.createElement('option');
+            opt.textContent = t('offline.noInstances');
+            opt.value = '';
+            select.appendChild(opt);
+            return;
+        }
+        instances.forEach(function(inst) {
+            const opt = document.createElement('option');
+            opt.value = inst.name;
+            let label = inst.name;
+            if (inst.minecraftVersion) label += ' (' + inst.minecraftVersion + ')';
+            opt.textContent = label;
+            select.appendChild(opt);
+        });
+        this.state.offlineInstances = instances;
+    }
+
+    async handleOfflineLaunch(e) {
+        e.preventDefault();
+        const nickname = document.getElementById('offline-nickname').value.trim();
+        const name = document.getElementById('offline-instance').value;
+        const errEl = document.getElementById('offline-error');
+        const btn = document.getElementById('offline-launch-btn');
+        const label = btn.querySelector('.btn-label');
+        const spinner = btn.querySelector('.spinner');
+
+        errEl.classList.add('hidden');
+        if (!nickname) {
+            errEl.textContent = t('offline.needNickname');
+            errEl.classList.remove('hidden');
+            return;
+        }
+        if (nickname.length > 16) {
+            errEl.textContent = t('offline.nickTooLong');
+            errEl.classList.remove('hidden');
+            return;
+        }
+        if (!name) {
+            errEl.textContent = t('offline.needInstance');
+            errEl.classList.remove('hidden');
+            return;
+        }
+
+        btn.disabled = true;
+        label.textContent = t('offline.launching');
+        spinner.classList.remove('hidden');
+
+        const r = await this.req('/offline-launch', {
+            method: 'POST',
+            body: JSON.stringify({ name: name, nickname: nickname }),
+            timeout: 120000
+        });
+
+        btn.disabled = false;
+        label.textContent = t('offline.launch');
+        spinner.classList.add('hidden');
+
+        if (r.success) {
+            this.toast(tr('toast.launched', null, {pid: String(r.data?.pid || '')}), 'success');
+        } else {
+            errEl.textContent = r.error || t('toast.launchFailed');
+            errEl.classList.remove('hidden');
+        }
+    }
+
+    async retryOnline() {
+        this.showLoading(true);
+        document.getElementById('offline-screen').classList.add('hidden');
+        const status = await this.req('/offline/status');
+        if (status.success && status.offline) {
+            this.showOffline();
+            this.showLoading(false);
+            this.toast(t('offline.stillOffline'), 'warning');
+            return;
+        }
+        await this.checkAuth();
+    }
+
     // ==================== NAV ====================
     bindEvents() {
         document.getElementById('login-form').addEventListener('submit', e => this.handleLogin(e));
+        const offlineForm = document.getElementById('offline-form');
+        if (offlineForm) offlineForm.addEventListener('submit', e => this.handleOfflineLaunch(e));
+        const retryBtn = document.getElementById('offline-retry-btn');
+        if (retryBtn) retryBtn.addEventListener('click', () => this.retryOnline());
+        const exitBtn = document.getElementById('offline-exit-btn');
+        if (exitBtn) exitBtn.addEventListener('click', () => this.req('/shutdown', { method: 'POST' }));
+        const pwInput = document.getElementById('password');
+        if (pwInput) pwInput.addEventListener('input', () => this.validatePassword());
+        const confirmInput = document.getElementById('confirm-password');
+        if (confirmInput) confirmInput.addEventListener('input', () => this.validatePassword());
         document.getElementById('login-footer').addEventListener('click', () => this.toggleMode());
         document.getElementById('logout-btn').addEventListener('click', () => this.logout());
         document.getElementById('settings-btn').addEventListener('click', () => this.switchView('settings'));
@@ -1868,13 +2059,28 @@ class ZernMCLauncher {
                 modalP.classList.remove('hidden');
                 const pct = (r.data.percent || 0) + '%';
                 const label = r.data.label || 'Installing...';
+                const indeterminate = r.data.inProgress && (!r.data.total || r.data.total <= 0);
 
-                document.getElementById('progress-fill').style.width = pct;
+                const fill = document.getElementById('progress-fill');
+                if (indeterminate) {
+                    fill.classList.add('indeterminate');
+                    fill.style.width = '';
+                } else {
+                    fill.classList.remove('indeterminate');
+                    fill.style.width = pct;
+                }
                 document.getElementById('progress-label').textContent = label;
 
                 const inlineProgress = document.getElementById('inline-install-progress');
                 if (!inlineProgress.classList.contains('hidden')) {
-                    document.getElementById('inline-progress-fill').style.width = pct;
+                    const inlineFill = document.getElementById('inline-progress-fill');
+                    if (indeterminate) {
+                        inlineFill.classList.add('indeterminate');
+                        inlineFill.style.width = '';
+                    } else {
+                        inlineFill.classList.remove('indeterminate');
+                        inlineFill.style.width = pct;
+                    }
                     document.getElementById('inline-progress-label').textContent = label;
                     const inlineStage = document.getElementById('inline-progress-stage');
                     if (r.data.stageName && r.data.stageCount > 1) {

launcher/launcher/src/resources/ui/style.css

@@ -99,6 +99,14 @@ body {
     border-color: var(--accent);
     box-shadow: 0 0 0 2px var(--accent-glow);
 }
+.field input.invalid {
+    border-color: var(--error);
+    box-shadow: 0 0 0 2px rgba(248,113,113,0.15);
+}
+.field .field-hint {
+    font-size: 12px; color: var(--error); line-height: 1.4;
+}
+.field .field-hint.hidden { display: none; }
 .field select {
     width: 100%; padding: 10px 12px; font-size: 15px;
     background: var(--bg-surface); border: 1px solid var(--border);
@@ -642,6 +650,15 @@ body {
     background: linear-gradient(90deg, var(--accent), #ff6b6b);
     border-radius: 3px; transition: width 0.3s ease;
 }
+.progress-fill.indeterminate {
+    width: 30%;
+    transition: none;
+    animation: indeterminate 1.3s ease-in-out infinite;
+}
+@keyframes indeterminate {
+    0% { margin-left: -30%; }
+    100% { margin-left: 100%; }
+}
 .progress-label { font-size: 13px; color: var(--text-secondary); margin-top: 8px; text-align: center; }
 .progress-stage { font-size: 11px; color: var(--text-muted); margin-top: 4px; text-align: center; }
 
@@ -900,3 +917,40 @@ body {
 .pack-entry.disabled .pack-entry-name::after { content: ' (' attr(data-disabled-text) ')'; color: var(--error); font-size: 11px; }
 .admin-pack-disabled { color: var(--error) !important; font-weight: 600; }
 .admin-pack-enabled { color: var(--success) !important; font-weight: 600; }
+
+/* ========== OFFLINE MODE ========== */
+.offline-container {
+    position: relative; z-index: 1;
+    background: var(--bg-elevated);
+    border-radius: var(--radius-md);
+    padding: 32px 32px 24px;
+    width: 100%;
+    max-width: 380px;
+    box-shadow: 0 8px 40px rgba(0,0,0,0.5);
+    text-align: center;
+}
+.offline-badge {
+    width: 64px; height: 64px;
+    margin: 0 auto 14px;
+    display: flex; align-items: center; justify-content: center;
+    background: rgba(233,69,96,0.12);
+    border: 1px solid rgba(233,69,96,0.3);
+    border-radius: 14px;
+    color: var(--accent);
+}
+.offline-title { font-size: 22px; font-weight: 700; color: var(--text); }
+.offline-subtitle {
+    color: var(--text-muted); font-size: 13px; margin: 8px 0 20px; line-height: 1.5;
+}
+.offline-container .login-form { text-align: left; }
+.offline-footer {
+    display: flex; gap: 8px; justify-content: center; margin-top: 18px;
+}
+.btn-ghost {
+    padding: 9px 14px; font-size: 13px;
+    background: transparent; color: var(--text-secondary);
+    border: 1px solid var(--border); border-radius: 4px;
+    cursor: pointer; font-family: var(--font);
+    transition: border-color 150ms ease, color 150ms ease;
+}
+.btn-ghost:hover { border-color: var(--accent); color: var(--accent); }

launcher/pom.xml

@@ -14,12 +14,13 @@
 
 <modules>
         <module>bootstrap</module>
+        <module>diag</module>
         <module>launcher</module>
     </modules>
 
     <properties>
         <revision>1.0.16</revision>
-        <hotfix>3</hotfix>
+        <hotfix>13</hotfix>
         <maven.compiler.source>21</maven.compiler.source>
         <maven.compiler.target>21</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
@@ -95,6 +96,11 @@
                 <version>23.0.1</version>
                 <classifier>win</classifier>
             </dependency>
+            <dependency>
+                <groupId>dnsjava</groupId>
+                <artifactId>dnsjava</artifactId>
+                <version>3.6.5</version>
+            </dependency>
             <dependency>
                 <groupId>org.openjfx</groupId>
                 <artifactId>javafx-media</artifactId>

server/auth.py

@@ -383,6 +383,7 @@ async def register(body: RegisterRequest, request: Request):
     
     allowed, wait = check_rate_limit(ip)
     if not allowed:
+        logger.warning("register rate limited", username=body.username, client_ip=ip)
         raise HTTPException(429, f"Слишком много попыток. Подождите {wait} секунд")
     
     with get_db() as conn:
@@ -392,6 +393,7 @@ async def register(body: RegisterRequest, request: Request):
         ).fetchone()
         
         if existing:
+            logger.warning("register failed: username taken", username=body.username, client_ip=ip)
             raise HTTPException(409, "Пользователь с таким именем уже существует")
         
         uuid = generate_uuid()
@@ -405,6 +407,7 @@ async def register(body: RegisterRequest, request: Request):
         )
         
         user_id = cursor.lastrowid
+        logger.info("register ok", username=body.username, user_id=user_id, client_ip=ip)
         
         # Создаем сессию
         session_token = secrets.token_urlsafe(32)
@@ -456,6 +459,7 @@ async def login(body: LoginRequest, request: Request):
     
     allowed, wait = check_rate_limit(ip)
     if not allowed:
+        logger.warning("login rate limited", username=body.username, client_ip=ip)
         raise HTTPException(429, f"Слишком много попыток. Подождите {wait} секунд")
     
     with get_db() as conn:
@@ -465,15 +469,20 @@ async def login(body: LoginRequest, request: Request):
         ).fetchone()
         
         if not user or not verify_password(body.password, user["password_hash"]):
+            logger.warning("login failed: bad credentials", username=body.username, client_ip=ip)
             record_login_attempt(ip, False)
             raise HTTPException(401, "Неверное имя пользователя или пароль")
         
         if not user["is_active"]:
+            logger.warning("login failed: account deactivated", username=body.username, client_ip=ip)
             raise HTTPException(403, "Аккаунт деактивирован")
         
         if user["banned_until"] and user["banned_until"] > time.time():
+            logger.warning("login failed: account banned", username=body.username, client_ip=ip)
             raise HTTPException(403, "Аккаунт забанен")
         
+        logger.info("login ok", username=user["username"], user_id=user["id"], client_ip=ip)
+        
         record_login_attempt(ip, True)
         
         now = time.time()

server/main.py

@@ -48,8 +48,11 @@ WHITELIST_DIR = Path(__file__).parent / "whitelist"
 
 # Mirror configuration
 LAUNCHER_MIRRORS = {
-    "main": "https://api.zernmc.ru",
-    "mirror-1": "https://api.zernmc.online",
+    "main":     "https://api.zern.cc",          # primary
+    "mirror-1": "https://api.zernmc.ru",        # legacy
+    "mirror-2": "https://api.zernmc.online",    # legacy
+    "geo-pl":   "https://api.pl.zern.cc",
+    "geo-swe":  "https://api.swe.zern.cc",
 }
 
 # Server role: "main" or "mirror"
@@ -71,6 +74,9 @@ BLOCKLIST_CACHE_FILE = Path("data/blocklist_cache.txt")
 # Crash reports directory
 CRASH_REPORTS_DIR = Path("data/crash_reports")
 
+# Network diagnostics reports directory
+DIAG_REPORTS_DIR = Path("data/diag_reports")
+
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
@@ -1350,6 +1356,14 @@ def generate_launcher_builds_meta():
             # CLI exe is not shipped to users
             if rel_path == "zernmc-cli.exe":
                 continue
+            # zernmc.exe embeds the launcher version, so its hash changes on
+            # every build even when the bootstrap code is unchanged. Exclude it
+            # from the incremental update: a new exe is only delivered via a
+            # full ZIP reinstall. Without this the bootstrap would re-download
+            # and re-stage its own exe on every launcher version bump, and the
+            # detached .cmd helper fails with "file not found".
+            if rel_path == "zernmc.exe":
+                continue
             stat = file_path.stat()
             
             # Calculate hash
@@ -1391,6 +1405,8 @@ def generate_version_meta(version_path: Path, version: str) -> dict:
     for file_path in version_path.rglob("*"):
         if file_path.is_file() and file_path.name != "meta.json":
             rel_path = str(file_path.relative_to(version_path))
+            if rel_path in ("zernmc.exe", "zernmc-cli.exe"):
+                continue
             stat = file_path.stat()
             file_hash = calculate_file_hash(file_path)
             files.append({
@@ -1488,13 +1504,18 @@ def extract_new_format_versions():
     # Find all ZernMC-win-*.zip files
     new_format_zips = list(BUILDS_DIR.glob("ZernMC-win-*.zip"))
     
+    total = len(new_format_zips)
+    extracted = 0
+    skipped = 0
+    failed = 0
+    
     for zip_file in new_format_zips:
         version = zip_file.stem.replace("ZernMC-win-", "")
         extract_dir = VERSIONS_DIR / version
         
         # Skip if already extracted and meta exists
         if extract_dir.exists() and (extract_dir / "meta.json").exists():
-            logger.debug(f"Version {version} already extracted")
+            skipped += 1
             continue
         
         logger.info(f"Extracting {zip_file.name} to versions/{version}/...")
@@ -1511,10 +1532,14 @@ def extract_new_format_versions():
             # writes versions/<v>/meta.json, so every scan would re-extract the zip.
             generate_version_meta(extract_dir, version)
             
+            extracted += 1
             logger.info(f"Extracted {zip_file.name} successfully")
         except Exception as e:
+            failed += 1
             logger.error(f"Failed to extract {zip_file.name}: {e}")
     
+    logger.info(f"Version scan complete: {total} total, {extracted} extracted, {skipped} skipped (already present), {failed} failed")
+
 
 # ====================== END ЛАУНЧЕР МЕТА СИСТЕМА ======================
 
@@ -1594,6 +1619,14 @@ def get_legacy_zips() -> list:
     return zips
 
 
+@app.get("/launcher/ip")
+async def get_launcher_client_ip(request: Request):
+    """Return the public IP that the server sees for this client."""
+    from middleware import get_client_ip
+    client_ip = get_client_ip(request)
+    return {"ip": client_ip}
+
+
 @app.get("/launcher/version")
 async def get_launcher_version():
     """Return launcher version information"""
@@ -1965,6 +1998,36 @@ async def receive_crash_report(request: Request):
     return {"status": "ok", "id": report_id}
 
 
+@app.post("/diag/upload")
+async def receive_diag_report(request: Request):
+    """Receive and store network diagnostics reports from the diag utility"""
+    try:
+        body = await request.body()
+    except Exception:
+        raise HTTPException(status_code=400, detail="Failed to read body")
+
+    if not body:
+        raise HTTPException(status_code=400, detail="Empty body")
+
+    ip = request.client.host if request.client else "unknown"
+    name = request.query_params.get("name", "").strip()
+    if not name or "/" in name or "\\" in name or ".." in name:
+        name = f"diag_{datetime.utcnow().strftime('%Y%m%d_%H%M%S')}_{ip}.log"
+
+    report_path = DIAG_REPORTS_DIR / name
+
+    try:
+        DIAG_REPORTS_DIR.mkdir(parents=True, exist_ok=True)
+        async with aiofiles.open(report_path, "w", encoding="utf-8") as f:
+            await f.write(body.decode("utf-8", errors="replace"))
+        logger.info(f"Diag report saved: {report_path.name} from {ip}")
+    except Exception as e:
+        logger.error(f"Failed to save diag report: {e}")
+        raise HTTPException(status_code=500, detail="Failed to save report")
+
+    return {"status": "ok", "name": report_path.name}
+
+
 # ====================== НОВОСТИ ======================
 
 NEWS_DIR = Path(__file__).parent / "news"
@@ -2195,19 +2258,34 @@ async def proxy_mojang_version(version_id: str, request: Request):
     # Сначала получаем манифест, чтобы найти URL версии
     manifest_url = "https://piston-meta.mojang.com/mc/game/version_manifest_v2.json"
     
-    cache_key = f"version_url_{version_id}"
-    version_url = proxy_cache.get(cache_key)
+    # Cache the final version JSON, not just the version URL. piston-meta is
+    # slow/unreliable from some regions, so full serialization of the version
+    # JSON (plus a warm-up) keeps installs from stalling on install time.
+    cache_key = f"version_json_{version_id}"
+    cached = proxy_cache.get(cache_key)
+    if cached is not None:
+        logger.info(f"Proxy served from cache: Mojang version {version_id}")
+        return JSONResponse(content=cached)
+
+    version_url = proxy_cache.get(f"version_url_{version_id}")
 
     if not version_url:
         try:
+            # Reuse the manifest already cached by /proxy/mojang/version_manifest
+            manifest = proxy_cache.get(manifest_url)
+            if manifest is None:
                 response = await proxy_client.get(manifest_url)
                 response.raise_for_status()
                 manifest = response.json()
+                proxy_cache[manifest_url] = manifest
+                logger.info("Proxy success: Mojang manifest")
+            else:
+                logger.info("Proxy served manifest from cache")
             
             for version in manifest.get("versions", []):
                 if version.get("id") == version_id:
                     version_url = version.get("url")
-                    proxy_cache[cache_key] = version_url
+                    proxy_cache[f"version_url_{version_id}"] = version_url
                     break
                     
             if not version_url:
@@ -2222,6 +2300,7 @@ async def proxy_mojang_version(version_id: str, request: Request):
         response.raise_for_status()
         data = response.json()
         
+        proxy_cache[cache_key] = data
         logger.info(f"Proxy success: Mojang version {version_id}")
         return JSONResponse(content=data)