diff --git a/src/Tools/Setup/isabelle/setup/Build_Scala.java b/src/Tools/Setup/isabelle/setup/Build_Scala.java
--- a/src/Tools/Setup/isabelle/setup/Build_Scala.java
+++ b/src/Tools/Setup/isabelle/setup/Build_Scala.java
@@ -1,213 +1,244 @@
 /*  Title:      Tools/Setup/isabelle/setup/Build_Scala.java
     Author:     Makarius
 
 Build Isabelle/Scala modules.
 */
 
 package isabelle.setup;
 
 
+import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.IOException;
+import java.io.OutputStream;
 import java.math.BigInteger;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Properties;
+import java.util.jar.Attributes;
+import java.util.jar.JarEntry;
+import java.util.jar.JarOutputStream;
+import java.util.jar.Manifest;
 import java.util.stream.Stream;
 
 
 public class Build_Scala
 {
+    /** component directory context **/
+
     public static class Context
     {
         private final Path component_dir;
         private Properties props;
 
         public Context(Path dir) throws IOException
         {
             component_dir = dir;
             props = new Properties();
             Path path = component_dir.resolve("etc/scala.props");
             if (Files.exists(path)) { props.load(Files.newBufferedReader(path)); }
         }
 
         @Override public String toString() { return component_dir.toString(); }
 
         public String component_name() { return component_dir.toFile().getName(); }
         public String name() { return props.getProperty("name", component_name()); }
         public String description() { return props.getProperty("description", name()); }
 
         public String lib_name() { return props.getProperty("lib", "lib") + "/" + name(); }
         public String jar_name() { return lib_name() + ".jar"; }
         public String shasum_name() { return lib_name() + ".shasum"; }
 
         public String main() { return props.getProperty("main", ""); }
 
         public String[] sources() { return props.getProperty("sources", "").split("\\s+"); }
         public String[] resources() { return props.getProperty("resources", "").split("\\s+"); }
         public String[] services() { return props.getProperty("services", "").split("\\s+"); }
 
         public Path path(String file) { return component_dir.resolve(file); }
         public boolean exists(String file) { return Files.exists(path(file)); }
 
         public String item_name(String s)
         {
             int i = s.indexOf(':');
             return i > 0 ? s.substring(0, i) : s;
         }
 
         public String item_target(String s)
         {
             int i = s.indexOf(':');
             return i > 0 ? s.substring(i + 1) : s;
         }
 
         public String shasum(String file)
             throws IOException, NoSuchAlgorithmException
         {
             if (exists(file)) {
                 MessageDigest sha = MessageDigest.getInstance("SHA");
                 sha.update(Files.readAllBytes(path(file)));
                 String digest = String.format(Locale.ROOT, "%040x", new BigInteger(1, sha.digest()));
                 return digest + " *" + file + "\n";
             }
             else { return ""; }
         }
     }
 
+
+
+    /** create jar **/
+
+    public static void create_jar(Path dir, String main, Path jar)
+        throws IOException
+    {
+        Files.deleteIfExists(jar);
+
+        Manifest manifest = new Manifest();
+        Attributes attributes = manifest.getMainAttributes();
+        attributes.put(Attributes.Name.MANIFEST_VERSION, "1.0");
+        attributes.put(new Attributes.Name("Created-By"),
+            System.getProperty("java.version") + " (" + System.getProperty("java.vendor") + ")");
+        if (!main.isEmpty()) { attributes.put(Attributes.Name.MAIN_CLASS, main); }
+
+        try (JarOutputStream out =
+            new JarOutputStream(new BufferedOutputStream(Files.newOutputStream(jar)), manifest))
+        {
+            for (Path path : Files.walk(dir).sorted().toArray(Path[]::new)) {
+                boolean is_dir = Files.isDirectory(path);
+                boolean is_file = Files.isRegularFile(path);
+                if (is_dir || is_file) {
+                    String name = Environment.slashes(dir.relativize(path).toString());
+                    JarEntry entry = new JarEntry(is_dir ? name + "/" : name);
+                    entry.setTime(path.toFile().lastModified());
+                    out.putNextEntry(entry);
+                    if (is_file) { out.write(Files.readAllBytes(path)); }
+                    out.closeEntry();
+                }
+            }
+        }
+    }
+
+
+
+    /** build scala **/
+
     public static void build_scala(Context context, boolean fresh)
         throws IOException, InterruptedException, NoSuchAlgorithmException
     {
         String jar_name = context.jar_name();
         String shasum_name = context.shasum_name();
 
         String[] sources = context.sources();
         String[] resources = context.resources();
 
         if (sources.length == 0) {
             Files.deleteIfExists(context.path(jar_name));
             Files.deleteIfExists(context.path(shasum_name));
         }
         else {
             String shasum_old =
                 context.exists(shasum_name) ? Files.readString(context.path(shasum_name)) : "";
             String shasum_sources;
             {
                 StringBuilder _shasum = new StringBuilder();
                 for (String s : resources) {
                     _shasum.append(context.shasum(context.item_name(s)));
                 }
                 for (String s : sources) { _shasum.append(context.shasum(s)); }
                 shasum_sources = _shasum.toString();
             }
             if (fresh || !shasum_old.equals(context.shasum(jar_name) + shasum_sources)) {
                 System.out.println("### Building " + context.description() + " ...");
 
                 String java_home = Environment.getenv("JAVA_HOME");
                 String scala_home = Environment.getenv("SCALA_HOME");
                 String scalac_options = Environment.getenv("ISABELLE_SCALAC_OPTIONS");
                 String isabelle_class_path = Environment.getenv("ISABELLE_CLASSPATH");
 
                 if (java_home.isEmpty()) {
                     throw new RuntimeException("Unknown JAVA_HOME -- Java unavailable");
                 }
                 if (scala_home.isEmpty()) {
                     throw new RuntimeException("Unknown SCALA_HOME -- Scala unavailable");
                 }
 
                 Path build_dir = Files.createTempDirectory("isabelle");
                 try {
                     /* classpath */
 
                     List<String> classpath = new LinkedList<String>();
                     for (String s : isabelle_class_path.split(":", -1)) {
                         classpath.add(Environment.platform_path(s));
                     }
 
                     Map<String,String> env = new HashMap<String,String>(Environment.settings());
                     env.put("CLASSPATH", String.join(File.pathSeparator, classpath));
 
 
                     /* compile sources */
 
                     List<String> cmd = new LinkedList<String>();
                     Environment.Exec_Result res;
 
                     cmd.add(Environment.platform_path(scala_home + "/bin/scalac"));
                     for (String s : scalac_options.split("\\s+")) { cmd.add(s); }
                     cmd.add("-d");
                     cmd.add(build_dir.toString());
                     for (String s : sources) { cmd.add(context.path(s).toString()); }
 
                     res = Environment.exec_process(cmd, build_dir.toFile(), env, false);
                     if (!res.ok()) throw new RuntimeException(res.err());
 
 
                     /* copy resources */
 
                     for (String s : context.resources()) {
                         String name = context.item_name(s);
                         String target = context.item_target(s);
                         Path file_name = Path.of(name).normalize().getFileName();
                         Path target_path = Path.of(target).normalize();
 
                         Path target_dir;
                         Path target_file;
                         {
                             if (target.endsWith("/") || target.endsWith("/.")) {
                                 target_dir = build_dir.resolve(target_path);
                                 target_file = target_dir.resolve(file_name);
                             }
                             else {
                                 target_file = build_dir.resolve(target_path);
                                 target_dir = target_file.getParent();
                             }
                         }
                         Files.createDirectories(target_dir);
                         Files.copy(context.path(name), target_file,
                             StandardCopyOption.COPY_ATTRIBUTES);
                     }
 
 
-                    /* jar */
+                    /* packaging */
 
-                    cmd.clear();
-                    cmd.add(Environment.platform_path(java_home + "/bin/jar"));
-                    cmd.add("-c");
-                    cmd.add("-f");
-                    cmd.add(context.path(jar_name).toString());
-                    if (!context.main().isEmpty()) {
-                        cmd.add("-e");
-                        cmd.add(context.main());
-                    }
-                    cmd.add(".");
-
-                    res = Environment.exec_process(cmd, build_dir.toFile(), env, false);
-                    if (!res.ok()) throw new RuntimeException(res.err());
-
-
-                    /* shasum */
+                    create_jar(build_dir, context.main(), context.path(jar_name));
 
                     String shasum = context.shasum(jar_name) + shasum_sources;
                     Files.writeString(context.path(shasum_name), shasum);
                 }
                 finally {
                     try (Stream<Path> walk = Files.walk(build_dir)) {
                         walk.sorted(Comparator.reverseOrder())
                             .map(Path::toFile)
                             .forEach(File::delete);
                     }
                 }
             }
         }
     }
 }
diff --git a/src/Tools/Setup/isabelle/setup/Environment.java b/src/Tools/Setup/isabelle/setup/Environment.java
--- a/src/Tools/Setup/isabelle/setup/Environment.java
+++ b/src/Tools/Setup/isabelle/setup/Environment.java
@@ -1,382 +1,382 @@
 /*  Title:      Pure/System/isabelle_env.scala
     Author:     Makarius
 
 Fundamental Isabelle system environment: quasi-static module with
 optional init operation.
 */
 
 package isabelle.setup;
 
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.function.BiFunction;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 
 public class Environment
 {
     /** Support for Cygwin as POSIX emulation on Windows **/
 
     public static Boolean is_windows()
     {
         return System.getProperty("os.name", "").startsWith("Windows");
     }
 
     public static String quote(String s)
     {
         return "\"" + s + "\"";
     }
 
 
 
     /* system path representations */
 
-    private static String slashes(String s) { return s.replace('\\', '/'); }
+    public static String slashes(String s) { return s.replace('\\', '/'); }
 
     public static String standard_path(String cygwin_root, String platform_path)
     {
         if (is_windows()) {
             String backslashes = platform_path.replace('/', '\\');
 
             Pattern root_pattern =
                 Pattern.compile("(?i)" + Pattern.quote(cygwin_root) + "(?:\\\\+|\\z)(.*)");
             Matcher root_matcher = root_pattern.matcher(backslashes);
 
             Pattern drive_pattern = Pattern.compile("([a-zA-Z]):\\\\*(.*)");
             Matcher drive_matcher = drive_pattern.matcher(backslashes);
 
             if (root_matcher.matches()) {
                 String rest = root_matcher.group(1);
                 return "/" + slashes(rest);
             }
             else if (drive_matcher.matches()) {
                 String letter = drive_matcher.group(1).toLowerCase(Locale.ROOT);
                 String rest = drive_matcher.group(2);
                 return "/cygdrive/" + letter + (rest.isEmpty() ? "" : "/" + slashes(rest));
             }
             else { return slashes(backslashes); }
         }
         else { return platform_path; }
     }
 
     public static String platform_path(String cygwin_root, String standard_path)
     {
         if (is_windows()) {
             StringBuilder result_path = new StringBuilder();
 
             Pattern cygdrive_pattern = Pattern.compile("/cygdrive/([a-zA-Z])($|/.*)");
             Matcher cygdrive_matcher = cygdrive_pattern.matcher(standard_path);
 
             Pattern named_root_pattern = Pattern.compile("//+([^/]*)(.*)");
             Matcher named_root_matcher = named_root_pattern.matcher(standard_path);
 
             String rest;
             if (cygdrive_matcher.matches()) {
                 String drive = cygdrive_matcher.group(1).toUpperCase(Locale.ROOT);
                 rest = cygdrive_matcher.group(2);
                 result_path.append(drive);
                 result_path.append(':');
                 result_path.append(File.separatorChar);
             }
             else if (named_root_matcher.matches()) {
                 String root = named_root_matcher.group(1);
                 rest = named_root_matcher.group(2);
                 result_path.append(File.separatorChar);
                 result_path.append(File.separatorChar);
                 result_path.append(root);
             }
             else {
                 if (standard_path.startsWith("/")) { result_path.append(cygwin_root); }
                 rest = standard_path;
             }
 
             for (String p : rest.split("/", -1)) {
                 if (!p.isEmpty()) {
                     int len = result_path.length();
                     if (len > 0 && result_path.charAt(len - 1) != File.separatorChar) {
                         result_path.append(File.separatorChar);
                     }
                     result_path.append(p);
                 }
             }
 
             return result_path.toString();
         }
         else { return standard_path; }
     }
 
 
     /* raw process */
 
     public static ProcessBuilder process_builder(
         List<String> cmd, File cwd, Map<String,String> env, boolean redirect)
     {
         ProcessBuilder builder = new ProcessBuilder();
 
         // fragile on Windows:
         // see https://docs.microsoft.com/en-us/cpp/cpp/main-function-command-line-args?view=msvc-160
         builder.command(cmd);
 
         if (cwd != null) builder.directory(cwd);
         if (env != null) {
             builder.environment().clear();
             builder.environment().putAll(env);
         }
         builder.redirectErrorStream(redirect);
 
         return builder;
     }
 
     public static class Exec_Result
     {
         private final int _rc;
         private final String _out;
         private final String _err;
 
         Exec_Result(int rc, String out, String err)
         {
             _rc = rc;
             _out = out;
             _err = err;
         }
 
         public int rc() { return _rc; }
         public boolean ok() { return _rc == 0; }
         public String out() { return _out; }
         public String err() { return _err; }
     }
 
     public static Exec_Result exec_process(
         List<String> command_line,
         File cwd,
         Map<String,String> env,
         boolean redirect) throws IOException, InterruptedException
     {
         Path out_file = Files.createTempFile(null, null);
         Path err_file = Files.createTempFile(null, null);
         Exec_Result res;
         try {
             ProcessBuilder builder = process_builder(command_line, cwd, env, redirect);
             builder.redirectOutput(out_file.toFile());
             builder.redirectError(err_file.toFile());
 
             Process proc = builder.start();
             proc.getOutputStream().close();
             try { proc.waitFor(); }
             finally {
                 proc.getInputStream().close();
                 proc.getErrorStream().close();
                 proc.destroy();
                 Thread.interrupted();
             }
 
             int rc = proc.exitValue();
             String out = Files.readString(out_file);
             String err = Files.readString(err_file);
             res = new Exec_Result(rc, out, err);
         }
         finally {
             Files.deleteIfExists(out_file);
             Files.deleteIfExists(err_file);
         }
         return res;
     }
 
 
     /* init (e.g. after extraction via 7zip) */
 
     private static String bootstrap_directory(
         String preference, String variable, String property, String description)
     {
         String a = preference;  // explicit argument
         String b = System.getenv(variable);  // e.g. inherited from running isabelle tool
         String c = System.getProperty(property);  // e.g. via JVM application boot process
         String dir;
 
         if (a != null && !a.isEmpty()) { dir = a; }
         else if (b != null && !b.isEmpty()) { dir = b; }
         else if (c != null && !c.isEmpty()) { dir = c; }
         else { throw new RuntimeException("Unknown " + description + " directory"); }
 
         if ((new File(dir)).isDirectory()) { return dir; }
         else { throw new RuntimeException("Bad " + description + " directory " + quote(dir)); }
     }
 
     private static void cygwin_exec(String isabelle_root, List<String> cmd)
         throws IOException, InterruptedException
     {
         File cwd = new File(isabelle_root);
         Map<String,String> env = new HashMap<String,String>(System.getenv());
         env.put("CYGWIN", "nodosfilewarning");
         Exec_Result res = exec_process(cmd, cwd, env, true);
         if (!res.ok()) throw new RuntimeException(res.out());
     }
 
     public static void cygwin_link(String content, File target) throws IOException
     {
         Path target_path = target.toPath();
         Files.writeString(target_path, "!<symlink>" + content + "\u0000");
         Files.setAttribute(target_path, "dos:system", true);
     }
 
     public static void cygwin_init(String isabelle_root, String cygwin_root)
         throws IOException, InterruptedException
     {
         if (is_windows()) {
             File uninitialized_file = new File(cygwin_root, "isabelle\\uninitialized");
             boolean uninitialized = uninitialized_file.isFile() && uninitialized_file.delete();
 
             if (uninitialized) {
                 Path symlinks_path = (new File(cygwin_root + "\\isabelle\\symlinks")).toPath();
                 String[] symlinks = Files.readAllLines(symlinks_path).toArray(new String[0]);
 
                 // recover symlinks
                 int i = 0;
                 int m = symlinks.length;
                 int n = (m > 0 && symlinks[m - 1].isEmpty()) ? m - 1 : m;
                 while (i < n) {
                     if (i + 1 < n) {
                         String target = symlinks[i];
                         String content = symlinks[i + 1];
                         cygwin_link(content, new File(isabelle_root, target));
                         i += 2;
                     } else { throw new RuntimeException("Unbalanced symlinks list"); }
                 }
 
                 cygwin_exec(isabelle_root,
                     List.of(cygwin_root + "\\bin\\dash.exe", "/isabelle/rebaseall"));
                 cygwin_exec(isabelle_root,
                     List.of(cygwin_root + "\\bin\\bash.exe", "/isabelle/postinstall"));
             }
         }
     }
 
 
     /* implicit settings environment */
 
     private static volatile Map<String,String> _settings = null;
 
     public static Map<String,String> settings()
         throws IOException, InterruptedException
     {
         if (_settings == null) { init("", ""); }  // unsynchronized check
         return _settings;
     }
 
     public static String getenv(String name)
         throws IOException, InterruptedException
     {
         return settings().getOrDefault(name, "");
     }
 
     public static synchronized void init(String _isabelle_root, String _cygwin_root)
         throws IOException, InterruptedException
     {
         if (_settings == null) {
             String isabelle_root =
                 bootstrap_directory(_isabelle_root, "ISABELLE_ROOT", "isabelle.root", "Isabelle root");
 
             String cygwin_root = "";
             if (is_windows()) {
                 cygwin_root = bootstrap_directory(_cygwin_root, "CYGWIN_ROOT", "cygwin.root", "Cygwin root");
                 cygwin_init(isabelle_root, cygwin_root);
             }
 
             Map<String,String> env = new HashMap<String,String>(System.getenv());
 
             BiFunction<String,String,Void> env_default =
                 (String a, String b) -> { if (!b.isEmpty()) env.putIfAbsent(a, b); return null; };
 
             String temp_windows = is_windows() ? System.getenv("TEMP") : null;
 
             env_default.apply("CYGWIN_ROOT", cygwin_root);
             env_default.apply("TEMP_WINDOWS",
                 (temp_windows != null && temp_windows.contains("\\")) ? temp_windows : "");
             env_default.apply("ISABELLE_JDK_HOME",
                 standard_path(cygwin_root, System.getProperty("java.home", "")));
             env_default.apply("HOME", System.getProperty("user.home", ""));
             env_default.apply("ISABELLE_APP", System.getProperty("isabelle.app", ""));
 
             Map<String,String> settings = new HashMap<String,String>();
             Path settings_file = Files.createTempFile(null, null);
             try {
                 List<String> cmd = new LinkedList<String>();
                 if (is_windows()) {
                     cmd.add(cygwin_root + "\\bin\\bash");
                     cmd.add("-l");
                     cmd.add(standard_path(cygwin_root, isabelle_root + "\\bin\\isabelle"));
                 } else {
                     cmd.add(isabelle_root + "/bin/isabelle");
                 }
                 cmd.add("getenv");
                 cmd.add("-d");
                 cmd.add(settings_file.toString());
 
                 Exec_Result res = exec_process(cmd, null, env, true);
                 if (!res.ok()) throw new RuntimeException(res.out());
 
                 for (String s : Files.readString(settings_file).split("\u0000", -1)) {
                     int i = s.indexOf('=');
                     if (i > 0) { settings.put(s.substring(0, i), s.substring(i + 1)); }
                     else if (i < 0 && !s.isEmpty()) { settings.put(s, ""); }
                 }
             }
             finally { Files.delete(settings_file); }
 
             if (is_windows()) { settings.put("CYGWIN_ROOT", cygwin_root); }
 
             settings.put("PATH", settings.get("PATH_JVM"));
             settings.remove("PATH_JVM");
 
             _settings = Map.copyOf(settings);
         }
     }
 
 
     /* Cygwin root (after init) */
 
     public static String cygwin_root()
         throws IOException, InterruptedException
     {
         return getenv("CYGWIN_ROOT");
     }
 
     public static String standard_path(String platform_path)
         throws IOException, InterruptedException
     {
         return standard_path(cygwin_root(), platform_path);
     }
 
     public static String platform_path(String standard_path)
         throws IOException, InterruptedException
     {
         return platform_path(cygwin_root(), standard_path);
     }
 
 
     /* kill process (via bash) */
 
     static public boolean kill_process(String group_pid, String signal)
         throws IOException, InterruptedException
     {
         List<String> cmd = new LinkedList<String>();
         if (is_windows()) {
             cmd.add(cygwin_root() + "\\bin\\bash.exe");
         }
         else {
             cmd.add("/usr/bin/env");
             cmd.add("bash");
         }
         cmd.add("-c");
         cmd.add("kill -" + signal + " -" + group_pid);
         return exec_process(cmd, null, null, false).ok();
     }
 }