diff --git a/.bach/.gitignore b/.bach/.gitignore
index cf1662d0e..d16551da0 100644
--- a/.bach/.gitignore
+++ b/.bach/.gitignore
@@ -1,5 +1,6 @@
 /bin/
 /out/
+/src/run/
 /tool/*/
 /tool/*/**
 
diff --git a/src/bach.run/Bach.java b/src/bach.run/Bach.java
new file mode 100644
index 000000000..0738d277a
--- /dev/null
+++ b/src/bach.run/Bach.java
@@ -0,0 +1,248 @@
+/*
+ * Copyright (c) 2024 Christian Stein
+ * Licensed under the Universal Permissive License v 1.0 -> https://opensource.org/license/upl
+ */
+
+// TODO import module java.base;
+
+import java.io.*;
+import java.net.*;
+import java.nio.file.*;
+import java.util.*;
+
+@SuppressWarnings("unused")
+interface Bach {
+  static void build() {
+    /* java @build */ {
+      var build = Path.of("build");
+      if (Files.isRegularFile(build)) {
+        System.out.println("Running java @build ...");
+        Internal.java("@" + build);
+        return;
+      }
+      System.out.println("Running java @build not possible.");
+      System.out.println("  Create a `build` argument file to enable it.");
+    }
+    /* java Build.java */ {
+      var candidates =
+          List.of(
+              Path.of("Build.java"),
+              Path.of(".bach/Build.java"),
+              Path.of(".bach/src/Build.java"),
+              Path.of(".bach/src/run/Build.java"),
+              Path.of(".bach/src/run.bach/run/Build.java"));
+      for (var build : candidates) {
+        if (Files.isRegularFile(build)) {
+          System.out.println("Running java " + build + " ...");
+          Internal.java(build.toString());
+          return;
+        }
+      }
+      System.out.println("Running java Build.java not possible.");
+      System.out.println("  Create a `Build.java` file to enable it.");
+    }
+    // zero-configuration
+    System.out.println("TODO: java @bach build");
+    System.out.println("TODO: java .bach/src/run/bach/Main.java build");
+    System.out.println("TODO: java .bach/src/run.bach/run/bach/Main.java build");
+    // zero-installation + zero-configuration
+    System.out.println("TODO: init(temp) && java ${temp}/.bach/src/run/bach/Main.java build");
+  }
+
+  static void init() {
+    new Installer().install();
+  }
+
+  static void status() {
+    var directory = Path.of("");
+    System.out.printf(
+        """
+           ___      ___      ___      ___
+          /\\  \\    /\\  \\    /\\  \\    /\\__\\
+         /::\\  \\  /::\\  \\  /::\\  \\  /:/__/_
+        /::\\:\\__\\/::\\:\\__\\/:/\\:\\__\\/::\\/\\__\\
+        \\:\\::/  /\\/\\::/  /\\:\\ \\/__/\\/\\::/  / Java %s
+         \\::/  /   /:/  /  \\:\\__\\    /:/  / %s
+          \\/__/    \\/__/    \\/__/    \\/__/ %s
+        """,
+        Runtime.version(), System.getProperty("os.name"), directory.toUri());
+
+    System.out.println("\nModule declarations");
+    var matcher = directory.getFileSystem().getPathMatcher("glob:**module-info.java");
+    try (var stream = Files.find(directory, 9, (p, _) -> matcher.matches(p))) {
+      for (var path : stream.toList()) {
+        System.out.println(" -> " + path.toUri());
+      }
+    } catch (Exception exception) {
+      throw new RuntimeException("Find in %s failed".formatted(directory), exception);
+    }
+  }
+
+  interface Internal {
+    boolean DEBUG = Boolean.getBoolean("-Debug".substring(2));
+
+    static void debug(String message) {
+      if (DEBUG) System.out.println(message);
+    }
+
+    static void copy(String source, Path target, CopyOption... options) throws Exception {
+      debug("<< %s".formatted(source));
+      Files.createDirectories(target.getParent());
+      try (var stream =
+          source.startsWith("http")
+              ? URI.create(source).toURL().openStream()
+              : Files.newInputStream(Path.of(source))) {
+        var size = Files.copy(stream, target, options);
+        debug(">> %,7d %s".formatted(size, target.getFileName()));
+      }
+    }
+
+    static void delete(Path path) throws Exception {
+      var start = path.normalize().toAbsolutePath();
+      if (Files.notExists(start)) return;
+      for (var root : start.getFileSystem().getRootDirectories()) {
+        if (start.equals(root)) {
+          debug("deletion of root directory?! " + path);
+          return;
+        }
+      }
+      debug("delete directory tree " + start);
+      try (var stream = Files.walk(start)) {
+        var files = stream.sorted((p, q) -> -p.compareTo(q));
+        for (var file : files.toArray(Path[]::new)) Files.deleteIfExists(file);
+      }
+    }
+
+    static boolean head(String source) throws Exception {
+      var url = URI.create(source).toURL();
+      var con = (HttpURLConnection) url.openConnection();
+      try {
+        con.setRequestMethod("HEAD");
+        var status = con.getResponseCode();
+        debug("%d <- HEAD %s".formatted(status, source));
+        if (status < 299) return true;
+      } finally {
+        con.disconnect();
+      }
+      return false;
+    }
+
+    static void java(String... args) {
+      var java = Path.of(System.getProperty("java.home"), "bin", "java" /*.exe*/);
+      var code = run(List.of(java.toString()), args);
+      if (code == 0) return;
+      throw new RuntimeException("Non-zero error code: " + code);
+    }
+
+    static int run(List<String> command, String... arguments) {
+      debug("| " + String.join(" ", command));
+      var out = System.out;
+      var err = System.err;
+      record LinePrinter(InputStream stream, PrintStream writer) implements Runnable {
+        @Override
+        public void run() {
+          new BufferedReader(new InputStreamReader(stream)).lines().forEach(writer::println);
+        }
+      }
+      var processBuilder = new ProcessBuilder(new ArrayList<>(command));
+      processBuilder.command().addAll(List.of(arguments));
+      try {
+        var process = processBuilder.start();
+        var threadBuilder = Thread.ofVirtual();
+        threadBuilder.name("-out").start(new LinePrinter(process.getInputStream(), out));
+        threadBuilder.name("-err").start(new LinePrinter(process.getErrorStream(), err));
+        return process.isAlive() ? process.waitFor() : process.exitValue();
+      } catch (InterruptedException exception) {
+        Thread.currentThread().interrupt();
+        return -1;
+      } catch (Exception exception) {
+        exception.printStackTrace(err);
+        return 1;
+      }
+    }
+
+    static void unzip(Path zip, Path dir, int sub) throws Exception {
+      debug("<< %s".formatted(zip.toUri()));
+      debug(">> %s".formatted(dir.toUri()));
+      var files = new ArrayList<Path>();
+      try (var fs = FileSystems.newFileSystem(zip)) {
+        for (var root : fs.getRootDirectories()) {
+          try (var stream = Files.walk(root)) {
+            var list = stream.filter(Files::isRegularFile).toList();
+            for (var file : list) {
+              var relative = root.relativize(file);
+              var source = sub == 0 ? relative : relative.subpath(sub, relative.getNameCount());
+              var target = dir.resolve(source.toString());
+              // debug(target.toUri().toString());
+              Files.createDirectories(target.getParent());
+              Files.copy(file, target, StandardCopyOption.REPLACE_EXISTING);
+              files.add(target);
+            }
+          }
+        }
+      }
+      debug(">> %d files copied".formatted(files.size()));
+    }
+  }
+
+  record Installer(String version, Path home, Path path) {
+    // defaults to git head reference of the `main` branch
+    static String VERSION = System.getProperty("-Dversion".substring(2), "main");
+    // defaults to the current working directory
+    static Path HOME = Path.of(System.getProperty("-Dhome".substring(2), ""));
+    // git submodule add <repository> [<path>] <- .bach/src[/run.bach]/run/bach
+    static Path PATH = Path.of(System.getProperty("-Dpath".substring(2), ".bach/src/run/bach"));
+
+    Installer() {
+      this(VERSION);
+    }
+
+    Installer(String version) {
+      this(version, HOME, PATH);
+    }
+
+    void install() {
+      try {
+        installSources();
+        installArgumentFiles();
+      } catch (Exception exception) {
+        System.err.println("Install failed: " + exception.getMessage());
+      }
+    }
+
+    void installSources() throws Exception {
+      var uris =
+          List.of(
+              "https://github.com/sormuras/run.bach/archive/refs/tags/" + version + ".zip",
+              "https://github.com/sormuras/run.bach/archive/refs/heads/" + version + ".zip");
+      for (var uri : uris) {
+        if (Internal.head(uri)) {
+          installSourcesFromUri(uri);
+          return;
+        }
+      }
+    }
+
+    void installSourcesFromUri(String uri) throws Exception {
+      var tmp = Files.createTempDirectory("run.bach-" + version + "-");
+      var dir = Files.createDirectories(home.resolve(path));
+      var zip = tmp.resolve("run.bach-" + version + ".zip");
+      System.out.println("Installing Bach [" + version + "] into " + path.toUri() + "...");
+      // download and unzip
+      Internal.copy(uri, zip, StandardCopyOption.REPLACE_EXISTING);
+      Internal.unzip(zip, dir, 1);
+      // clean up
+      Internal.delete(tmp);
+    }
+
+    void installArgumentFiles() throws Exception {
+      var bach = home.resolve("bach");
+      if (!Files.exists(bach)) {
+        var program = home.resolve(path).resolve("Main.java");
+        var command = home.relativize(program).toString().replace('\\', '/');
+        var lines = List.of("# Argument file for launching Bach's main application", command);
+        Files.write(bach, lines);
+      }
+    }
+  }
+}