diff --git a/runner/src/docker.js b/runner/src/docker.js
new file mode 100644
index 0000000..e347756
--- /dev/null
+++ b/runner/src/docker.js
@@ -0,0 +1,126 @@
+// Docker-Adapter: baut `docker run`-Argumente mit festem Sicherheitsprofil und kapselt die docker-CLI (spawn, nie Shell).
+import { spawn } from 'node:child_process';
+
+const SUB_RE = /^[a-z0-9-]{1,63}$/;
+const ENV_NAME_RE = /^[A-Z_][A-Z0-9_]*$/;
+const NAME_RE = /^[a-zA-Z0-9][a-zA-Z0-9_.-]{0,127}$/;
+const NETWORK = 'preview-sandbox';
+// Feste, unkritische Umgebung im Container (R9): Caches landen im gemounteten Cache-Verzeichnis.
+const FIXED_ENV = ['HOME=/cache/home', 'npm_config_cache=/cache/npm', 'COREPACK_HOME=/cache/corepack'];
+const FIXED_NAMES = new Set(FIXED_ENV.map((e) => e.split('=')[0]));
+
+function securityArgs({ memory, network, name, workDir, cacheDir, env }) {
+  if (name !== undefined && !NAME_RE.test(name)) throw new Error('Ungültiger Containername');
+  const args = [];
+  if (name !== undefined) args.push('--name', name);
+  args.push(
+    '--init',
+    '--memory', memory,
+    '--cpus', '1',
+    '--pids-limit', '512',
+    '--cap-drop', 'ALL',
+    '--security-opt', 'no-new-privileges',
+    '--user', '1000:1000',
+    '--network', network,
+    '-v', `${workDir}:/work`,
+    '-v', `${cacheDir}:/cache`,
+    '-w', '/work',
+  );
+  for (const e of FIXED_ENV) args.push('-e', e);
+  for (const [k, v] of Object.entries(env || {})) {
+    if (!ENV_NAME_RE.test(k) || FIXED_NAMES.has(k)) throw new Error(`Ungültiger Variablenname: ${k}`);
+    if (String(v).includes('\0')) throw new Error(`Ungültiger Wert für ${k}`);
+    args.push('-e', k); // nur der Name; der Wert reist über die Umgebung des docker-Prozesses
+  }
+  return args;
+}
+
+export function buildRunArgs({ image = 'node:20', name, workDir, cacheDir, env, cmd = [], memory = '1g', network = NETWORK }) {
+  return ['run', '--rm', ...securityArgs({ memory, network, name, workDir, cacheDir, env }), image, ...cmd];
+}
+
+export function devRunArgs({ image = 'node:20', sub, workDir, cacheDir, env, cmd = [], memory = '512m', network = NETWORK }) {
+  if (typeof sub !== 'string' || !SUB_RE.test(sub)) throw new Error('Ungültige Subdomain');
+  return [
+    'run', '-d', '--restart', 'no', '--label', `webklar.preview=${sub}`,
+    ...securityArgs({ memory, network, name: `preview-dev-${sub}`, workDir, cacheDir, env }),
+    image, ...cmd,
+  ];
+}
+
+export const spawnDocker = (args, opts) => spawn('docker', args, { stdio: ['ignore', 'pipe', 'pipe'], ...opts });
+
+function lineSplitter(onLine) {
+  let buf = '';
+  return {
+    push(chunk) {
+      buf += chunk;
+      const parts = buf.split(/\r?\n/);
+      buf = parts.pop();
+      for (const l of parts) onLine(l);
+    },
+    flush() { if (buf !== '') onLine(buf); buf = ''; },
+  };
+}
+
+const checkName = (n) => { if (typeof n !== 'string' || !NAME_RE.test(n)) throw new Error('Ungültiger Containername'); };
+
+export function createDocker({ exec = spawnDocker, baseEnv = process.env } = {}) {
+  // Minimale Basis-Umgebung: die Runner-Geheimnisse (Tokens) dürfen nie in docker/Container gelangen.
+  const minimalBase = {};
+  for (const k of ['PATH', 'DOCKER_HOST']) if (baseEnv[k] !== undefined) minimalBase[k] = baseEnv[k];
+
+  function run(args, { env = {}, timeoutMs, onLine } = {}) {
+    for (const [k, v] of Object.entries(env)) {
+      if (String(v).includes('\0')) return Promise.reject(new Error(`Ungültiger Wert für ${k}`));
+    }
+    return new Promise((resolve, reject) => {
+      const child = exec(args, { env: { ...minimalBase, ...env } });
+      const split = lineSplitter((l) => { if (onLine) onLine(l); });
+      const split2 = lineSplitter((l) => { if (onLine) onLine(l); });
+      child.stdout?.setEncoding?.('utf8');
+      child.stderr?.setEncoding?.('utf8');
+      child.stdout?.on('data', (d) => split.push(String(d)));
+      child.stderr?.on('data', (d) => split2.push(String(d)));
+      let done = false;
+      let timer;
+      const finish = (res) => {
+        if (done) return;
+        done = true;
+        clearTimeout(timer);
+        split.flush(); split2.flush();
+        resolve(res);
+      };
+      child.on('error', (e) => { if (!done) { done = true; clearTimeout(timer); reject(e); } });
+      child.on('close', (code) => finish({ code: code ?? 1 }));
+      if (timeoutMs > 0) {
+        timer = setTimeout(() => {
+          try { child.kill('SIGKILL'); } catch { /* schon beendet */ }
+          const i = args.indexOf('--name');
+          if (i !== -1 && args[i + 1]) {
+            try { exec(['rm', '-f', args[i + 1]], { env: minimalBase })?.on?.('error', () => {}); } catch { /* egal */ }
+          }
+          finish({ code: 124 });
+        }, timeoutMs);
+      }
+    });
+  }
+
+  // Kurze docker-Aufrufe: stdout einsammeln.
+  async function capture(args) {
+    const out = [];
+    const r = await run(args, { onLine: (l) => out.push(l) });
+    return { code: r.code, lines: out };
+  }
+
+  return {
+    run,
+    async ps(label) {
+      const { code, lines } = await capture(['ps', '--filter', `label=${label}`, '--format', '{{.Names}}']);
+      if (code !== 0) throw new Error(`docker ps fehlgeschlagen (${code})`);
+      return lines.map((l) => l.trim()).filter(Boolean);
+    },
+    async rm(name) { checkName(name); return capture(['rm', '-f', name]); },
+    async stop(name) { checkName(name); return capture(['rm', '-f', name]); },
+  };
+}
diff --git a/runner/test/docker.test.js b/runner/test/docker.test.js
new file mode 100644
index 0000000..5f4951b
--- /dev/null
+++ b/runner/test/docker.test.js
@@ -0,0 +1,120 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { EventEmitter } from 'node:events';
+import { PassThrough } from 'node:stream';
+import { buildRunArgs, devRunArgs, createDocker, spawnDocker } from '../src/docker.js';
+
+const base = { image: 'node:20', workDir: '/srv/w/build/1', cacheDir: '/srv/c/repo', cmd: ['npm', 'ci'] };
+const pair = (args, flag, val) => args.some((a, i) => a === flag && args[i + 1] === val);
+
+test('buildRunArgs: komplettes Sicherheitsprofil', () => {
+  const a = buildRunArgs(base);
+  assert.deepEqual(a.slice(0, 2), ['run', '--rm']);
+  assert.ok(a.includes('--init'));
+  for (const [f, v] of [['--memory', '1g'], ['--cpus', '1'], ['--pids-limit', '512'], ['--cap-drop', 'ALL'], ['--security-opt', 'no-new-privileges'], ['--user', '1000:1000'], ['--network', 'preview-sandbox'], ['-w', '/work'], ['-v', '/srv/w/build/1:/work'], ['-v', '/srv/c/repo:/cache'], ['-e', 'HOME=/cache/home'], ['-e', 'npm_config_cache=/cache/npm'], ['-e', 'COREPACK_HOME=/cache/corepack']]) {
+    assert.ok(pair(a, f, v), `${f} ${v}`);
+  }
+  assert.equal(a.filter((x) => x === '-v').length, 2);
+  assert.deepEqual(a.slice(-3), ['node:20', 'npm', 'ci']);
+});
+
+test('buildRunArgs: Variablen nur als Name, Werte nie in args', () => {
+  const a = buildRunArgs({ ...base, env: { API_KEY: 'geheim-wert', X: 'abc' }, memory: '1g' });
+  assert.ok(pair(a, '-e', 'API_KEY') && pair(a, '-e', 'X'));
+  assert.ok(!a.join(' ').includes('geheim-wert'));
+});
+
+test('buildRunArgs: ungültiger Name/NUL/Name-Validierung', () => {
+  assert.throws(() => buildRunArgs({ ...base, env: { 'a b': '1' } }));
+  assert.throws(() => buildRunArgs({ ...base, env: { A: 'x\0y' } }));
+  assert.throws(() => buildRunArgs({ ...base, env: { HOME: 'x' } }));
+  assert.throws(() => buildRunArgs({ ...base, name: '-x' }));
+});
+
+test('buildRunArgs: memory/name optional', () => {
+  const a = buildRunArgs({ ...base, name: 'job-1', memory: '2g' });
+  assert.ok(pair(a, '--memory', '2g') && pair(a, '--name', 'job-1'));
+});
+
+test('devRunArgs: detached, Name, Label, ohne --rm, 512m', () => {
+  const a = devRunArgs({ ...base, sub: 'demo-1', cmd: ['npm', 'run', 'dev'] });
+  assert.ok(!a.includes('--rm'));
+  assert.ok(a.includes('-d'));
+  assert.ok(pair(a, '--name', 'preview-dev-demo-1'));
+  assert.ok(pair(a, '--label', 'webklar.preview=demo-1'));
+  assert.ok(pair(a, '--restart', 'no'));
+  assert.ok(pair(a, '--memory', '512m'));
+  assert.ok(pair(a, '--cap-drop', 'ALL') && pair(a, '--user', '1000:1000'));
+  assert.deepEqual(a.slice(-4), ['node:20', 'npm', 'run', 'dev']);
+});
+
+test('devRunArgs: Subdomain wird validiert', () => {
+  for (const sub of ['', 'A', 'a/b', '-x;', 'x'.repeat(64), undefined]) assert.throws(() => devRunArgs({ ...base, sub }), sub);
+});
+
+// Fake-Kindprozess
+function fakeChild() {
+  const c = new EventEmitter();
+  c.stdout = new PassThrough(); c.stderr = new PassThrough();
+  c.killed = []; c.kill = (s) => { c.killed.push(s); };
+  return c;
+}
+
+test('run: streamt Zeilen, liefert Exit-Code, Umgebung minimal + Job-Env', async () => {
+  const calls = [];
+  const child = fakeChild();
+  const docker = createDocker({ exec: (args, opts) => { calls.push({ args, opts }); return child; }, baseEnv: { PATH: '/bin', DOCKER_HOST: 'unix:///x', PREVIEW_RUNNER_TOKEN: 'leak' } });
+  const lines = [];
+  const p = docker.run(['run', '-e', 'K'], { env: { K: 'v' }, onLine: (l) => lines.push(l) });
+  child.stdout.write('eins\nzw');
+  child.stderr.write('fehler\n');
+  child.stdout.write('ei\n');
+  child.stdout.end(); child.stderr.end();
+  await new Promise((r) => setImmediate(r));
+  child.emit('close', 3);
+  assert.deepEqual(await p, { code: 3 });
+  assert.deepEqual(lines.sort(), ['eins', 'fehler', 'zwei']);
+  assert.deepEqual(calls[0].opts.env, { PATH: '/bin', DOCKER_HOST: 'unix:///x', K: 'v' });
+});
+
+test('run: NUL im Wert ⇒ Fehler vor dem Start', async () => {
+  let n = 0;
+  const docker = createDocker({ exec: () => { n++; return fakeChild(); } });
+  await assert.rejects(docker.run(['run'], { env: { A: 'x\0' } }));
+  assert.equal(n, 0);
+});
+
+test('run: Zeitlimit ⇒ Kill, docker rm -f, code 124', async () => {
+  const calls = [];
+  const child = fakeChild();
+  const docker = createDocker({ exec: (args) => { calls.push(args); return calls.length === 1 ? child : Object.assign(fakeChild(), { __rm: true }); } });
+  const p = docker.run(['run', '--name', 'job-9', 'img'], { timeoutMs: 20 });
+  const r = await p;
+  assert.deepEqual(r, { code: 124 });
+  assert.deepEqual(child.killed, ['SIGKILL']);
+  assert.deepEqual(calls[1], ['rm', '-f', 'job-9']);
+});
+
+test('ps/stop/rm', async () => {
+  const calls = [];
+  const exec = (args) => {
+    calls.push(args);
+    const c = fakeChild();
+    setImmediate(() => { c.stdout.write('preview-dev-a\npreview-dev-b\n\n'); c.stdout.end(); c.stderr.end(); c.emit('close', 0); });
+    return c;
+  };
+  const docker = createDocker({ exec });
+  assert.deepEqual(await docker.ps('webklar.preview'), ['preview-dev-a', 'preview-dev-b']);
+  assert.deepEqual(calls[0], ['ps', '--filter', 'label=webklar.preview', '--format', '{{.Names}}']);
+  await docker.stop('preview-dev-a');
+  await docker.rm('preview-dev-a');
+  assert.deepEqual(calls[1], ['rm', '-f', 'preview-dev-a']);
+  assert.deepEqual(calls[2], ['rm', '-f', 'preview-dev-a']);
+  assert.equal(typeof spawnDocker, 'function');
+});
+
+test('rm/stop: ungültiger Name wird abgelehnt', async () => {
+  const docker = createDocker({ exec: () => { throw new Error('nicht aufrufen'); } });
+  await assert.rejects(docker.rm('--all'));
+  await assert.rejects(docker.stop('a b'));
+});