diff --git a/runner/src/detect.js b/runner/src/detect.js
index f48276a..d8a49f8 100644
--- a/runner/src/detect.js
+++ b/runner/src/detect.js
@@ -56,14 +56,18 @@ export function detectProject(files, { mode, index, previewJson } = {}) {
   const hasDev = hasScript(scripts, 'dev');
   const m = mode === 'build' || mode === 'dev' ? mode : 'auto';
 
-  const base = { pm, install: installCmd(pm, files), buildCmd: hasBuild ? [pm, 'run', 'build'] : null, devCmd: hasDev ? devCmdFor(pm, devPort) : null, outputDirs, devPort };
+  const base = { index: indexFile, pm, install: installCmd(pm, files), buildCmd: hasBuild ? [pm, 'run', 'build'] : null, devCmd: hasDev ? devCmdFor(pm, devPort) : null, outputDirs, devPort };
   const asBuild = () => ({ kind: 'build', ...base });
   const asDev = () => ({ kind: 'dev', ...base });
-  const asStatic = (hint) => ({ kind: 'static', ...base, install: [], buildCmd: null, devCmd: null, outputDirs: [], index: indexFile, ...(hint ? { hint } : {}) });
+  const asStatic = (hint) => ({ kind: 'static', ...base, install: [], buildCmd: null, devCmd: null, outputDirs: [], ...(hint ? { hint } : {}) });
 
   if (m === 'build') return hasBuild ? asBuild() : { ...asBuild(), error: 'Kein build-Skript in package.json' };
   if (m === 'dev') return hasDev ? asDev() : { ...asDev(), error: 'Kein dev-Skript in package.json' };
 
+  // R21: .webklar-preview.json-Typ zuerst. 'static' mit index.html bleibt statisch (auch mit build-Skript),
+  // 'node_build' baut ausdrücklich (kein Dev-Rückfall). Ohne Typ: eigene Erkennung.
+  if (pj.type === 'static' && hasIndex) return asStatic();
+  if (pj.type === 'node_build' && hasBuild) return { ...asBuild(), explicitType: true };
   if (hasIndex && !hasBuild) return asStatic();
   if (hasBuild) return asBuild();
   if (hasDev) return asDev();
diff --git a/runner/src/jobs.js b/runner/src/jobs.js
index bb8cc4c..314f256 100644
--- a/runner/src/jobs.js
+++ b/runner/src/jobs.js
@@ -294,6 +294,16 @@ export function createJobs({ config, docker, fs: fsOver = {}, git, mem = readMem
     } catch { return workDir; }
   }
 
+  // Erstes Deploy (noch kein <sub>-Ordner): Quellstand statisch veröffentlichen statt 403/leer (Verhalten des bisherigen Pfads).
+  async function firstDeployFallback(job, workDir, d, problem, onLine) {
+    if (job.mode === 'build') return false;
+    const target = join(config.previewsRoot, job.sub);
+    if (await fs.lstat(target).then(() => true, () => false)) return false;
+    onLine(`${problem} – erstes Deploy, Quellstand wird statisch veröffentlicht (Hinweis: Build fehlgeschlagen)`);
+    await publish(job, await webrootOf(workDir, job.index || d.index || ''), { skipGit: true, skipNodeModules: true, onLine });
+    return true;
+  }
+
   // ---- Ablauf eines Build-Laufs ----
   const execute = (run, job) => holdCache(job.repo, () => executeRun(run, job));
   async function executeRun(run, job) {
@@ -307,10 +317,17 @@ export function createJobs({ config, docker, fs: fsOver = {}, git, mem = readMem
       const d = prep.detected;
       run.detected = d;
       if (d.error) throw new Error(d.error);
-      if (prep.error) throw new Error(prep.error);
+      // Build-/Installationsproblem: erstes Deploy ⇒ Quellstand statisch (wie bisher), sonst Fehler (alte Preview bleibt)
+      const fallbackOr = async (problem) => {
+        if (!(await firstDeployFallback(job, workDir, d, problem, onLine))) throw new Error(problem);
+        run.result = 'static';
+        run.hint = 'Build fehlgeschlagen – Quellstand statisch veröffentlicht';
+      };
+      if (prep.error) { await fallbackOr(prep.error); final = 'done'; }
+      else
       if (d.kind === 'static') {
         if (d.hint) onLine(d.hint);
-        await publish(job, await webrootOf(workDir, job.index || ''), { skipGit: true, onLine });
+        await publish(job, await webrootOf(workDir, d.index || job.index || ''), { skipGit: true, onLine });
         run.result = 'static';
       } else if (d.kind === 'dev') {
         run.result = 'dev';
@@ -325,14 +342,8 @@ export function createJobs({ config, docker, fs: fsOver = {}, git, mem = readMem
           if (!out) problem = `Kein Ausgabeordner gefunden (gesucht: ${d.outputDirs.join(', ')})`;
         }
         if (problem) {
-          if (job.mode === 'auto' && d.devCmd) { onLine(`${problem} – Dev-Server wird verwendet`); run.result = 'dev'; }
-          else if (!out && !r.code && job.mode !== 'build') {
-            // Build lief, erzeugte aber keinen Ausgabeordner mit index.html: wie bisher den Quellstand statisch
-            // veröffentlichen (index-Unterordner, Kandidat/Platzhalter) statt die Subdomain zu verlieren.
-            onLine(`${problem} – Quellstand wird statisch veröffentlicht`);
-            await publish(job, await webrootOf(workDir, job.index || ''), { skipGit: true, skipNodeModules: true, onLine });
-            run.result = 'static';
-          } else throw new Error(problem);
+          if (job.mode === 'auto' && d.devCmd && !d.explicitType) { onLine(`${problem} – Dev-Server wird verwendet`); run.result = 'dev'; }
+          else await fallbackOr(problem);
         } else {
           await publish(job, out, { skipGit: false, onLine });
           run.result = 'build';
diff --git a/runner/test/index-fallback.test.js b/runner/test/index-fallback.test.js
index e674f13..93b7a4e 100644
--- a/runner/test/index-fallback.test.js
+++ b/runner/test/index-fallback.test.js
@@ -91,10 +91,71 @@ test('Build-Ausgabe mit index.html wird unverändert veröffentlicht', async ()
   assert.deepEqual(readdirSync(s.out).sort(), ['index.html', 'o.html']);
 });
 
-test('fehlgeschlagener Build bleibt ein Fehler (alter Stand bleibt)', async () => {
-  const s = setup({ files: { 'package.json': JSON.stringify({ scripts: { build: 'x' } }) }, dockerImpl: (args) => ({ code: args.includes('build') ? 1 : 0 }) });
+const BUILD_PKG = JSON.stringify({ scripts: { build: 'x' } });
+const failBuild = (args) => ({ code: args.includes('build') ? 1 : 0 });
+
+test('bestehender <sub>-Ordner + fehlgeschlagener Build ⇒ failed, alter Stand unverändert', async () => {
+  const s = setup({ files: { 'package.json': BUILD_PKG, 'x.html': 'QUELLE' }, dockerImpl: failBuild });
+  mkdirSync(s.out, { recursive: true }); writeFileSync(join(s.out, 'index.html'), 'ALT');
   const r = await wait(s.jobs, s.jobs.submit(job()));
   assert.equal(r.state, 'failed');
+  assert.equal(readFileSync(join(s.out, 'index.html'), 'utf8'), 'ALT');
+});
+
+test('erstes Deploy + fehlgeschlagener Build ⇒ Quellstand statisch (Kandidat), result static, Hinweis', async () => {
+  const s = setup({ files: { 'package.json': BUILD_PKG, 'x.html': 'QUELLE' }, dockerImpl: failBuild });
+  const r = await wait(s.jobs, s.jobs.submit(job()));
+  assert.equal(r.state, 'done'); assert.equal(r.result, 'static'); assert.match(r.hint, /Build fehlgeschlagen/);
+  assert.equal(readFileSync(join(s.out, 'index.html'), 'utf8'), 'QUELLE');
+  assert.ok(r.log.some((l) => /erstes Deploy/.test(l)));
+});
+
+test('erstes Deploy + Installationsfehler ⇒ statischer Quellstand', async () => {
+  const s = setup({ files: { 'package.json': BUILD_PKG }, dockerImpl: () => ({ code: 1 }) });
+  const r = await wait(s.jobs, s.jobs.submit(job({ displayName: 'Shop' })));
+  assert.equal(r.result, 'static');
+  assert.match(readFileSync(join(s.out, 'index.html'), 'utf8'), /<h1>Shop<\/h1>/);
+});
+
+test('R21: json type static + index.html + build-Skript ⇒ static, kein Container', async () => {
+  const s = setup({ files: { 'package.json': BUILD_PKG, 'index.html': 'S', '.webklar-preview.json': '{"type":"static"}' }, dockerImpl: () => { throw new Error('kein Container'); } });
+  const r = await wait(s.jobs, s.jobs.submit(job()));
+  assert.equal(r.state, 'done'); assert.equal(r.result, 'static');
+});
+
+test('R21: json type node_build ⇒ build (auch mit index.html); kein Dev-Rückfall', async () => {
+  const mk = (extra) => setup({ files: { 'package.json': JSON.stringify({ scripts: { build: 'x', dev: 'y' } }), 'index.html': 'S', '.webklar-preview.json': '{"type":"node_build"}', ...extra },
+    dockerImpl: (args) => { if (args.includes('build')) { mkdirSync(join(workOf(args), 'dist'), { recursive: true }); writeFileSync(join(workOf(args), 'dist', 'index.html'), 'B'); } return { code: 0 }; } });
+  let s = mk();
+  let r = await wait(s.jobs, s.jobs.submit(job()));
+  assert.equal(r.result, 'build'); assert.equal(readFileSync(join(s.out, 'index.html'), 'utf8'), 'B');
+  s = setup({ files: { 'package.json': JSON.stringify({ scripts: { build: 'x', dev: 'y' } }), '.webklar-preview.json': '{"type":"node_build"}' }, dockerImpl: failBuild });
+  mkdirSync(s.out, { recursive: true });
+  r = await wait(s.jobs, s.jobs.submit(job()));
+  assert.equal(r.state, 'failed');
+});
+
+test('R21: ohne json-Typ + index.html + build-Skript ⇒ build', async () => {
+  const s = setup({ files: { 'package.json': BUILD_PKG, 'index.html': 'S' }, dockerImpl: (args) => { if (args.includes('build')) { mkdirSync(join(workOf(args), 'dist'), { recursive: true }); writeFileSync(join(workOf(args), 'dist', 'index.html'), 'B'); } return { code: 0 }; } });
+  const r = await wait(s.jobs, s.jobs.submit(job()));
+  assert.equal(r.result, 'build');
+});
+
+test('R21: Modus build aus dem Portal schlägt json type static', async () => {
+  const s = setup({ files: { 'package.json': BUILD_PKG, 'index.html': 'S', '.webklar-preview.json': '{"type":"static"}' }, dockerImpl: (args) => { if (args.includes('build')) { mkdirSync(join(workOf(args), 'dist'), { recursive: true }); writeFileSync(join(workOf(args), 'dist', 'index.html'), 'B'); } return { code: 0 }; } });
+  const r = await wait(s.jobs, s.jobs.submit(job({ mode: 'build' })));
+  assert.equal(r.result, 'build');
+});
+
+test('json index-Unterordner wird beim Veröffentlichen genutzt (static und Build-Rückfall)', async () => {
+  let s = setup({ files: { 'public/index.html': 'PUB', 'root.html': 'r', '.webklar-preview.json': '{"index":"public"}' } });
+  await wait(s.jobs, s.jobs.submit(job()));
+  assert.deepEqual(readdirSync(s.out), ['index.html']);
+  s = setup({ files: { 'package.json': BUILD_PKG, 'public/home.html': 'H', '.webklar-preview.json': '{"index":"public"}' }, dockerImpl: failBuild });
+  const r = await wait(s.jobs, s.jobs.submit(job()));
+  assert.equal(r.result, 'static');
+  assert.equal(readFileSync(join(s.out, 'index.html'), 'utf8'), 'H');
+  assert.ok(!existsSync(join(s.out, 'package.json')));
 });
 
 test('validateJob: displayName optional, ≤100 Zeichen, keine Steuerzeichen', () => {
diff --git a/runner/test/jobs.test.js b/runner/test/jobs.test.js
index a8f56ed..213be7f 100644
--- a/runner/test/jobs.test.js
+++ b/runner/test/jobs.test.js
@@ -250,6 +250,7 @@ test('I8: npm ci scheitert ⇒ Wiederholung mit npm install (Protokoll, Build l
 
 test('I8: auch npm install scheitert ⇒ Installationsfehler', async () => {
   const s = setup({ files: { 'package.json': PKG(), 'package-lock.json': '{}' }, dockerImpl: () => ({ code: 1 }) });
+  mkdirSync(join(s.config.previewsRoot, 'demo'));
   const r = await wait(s.jobs, s.jobs.submit(job()));
   assert.equal(r.state, 'failed'); assert.match(r.error, /Installation fehlgeschlagen/);
   assert.equal(s.calls.length, 2);
diff --git a/test/previewIndexParity.test.js b/test/previewIndexParity.test.js
index 01441e5..130e9b6 100644
--- a/test/previewIndexParity.test.js
+++ b/test/previewIndexParity.test.js
@@ -12,6 +12,7 @@ const FIXTURES = {
   mehrere: { 'a.html': 'aaaa', 'z.html': 'zzzzzzzz', 'css/s.css': 'c' },
   bevorzugt: { 'about.html': 'AAAAAAAAAA', 'main.html': 'm' },
   index: { 'index.html': 'I', 'other.html': 'o' },
+  typStatic: { 'index.html': 'I', 'package.json': '{"scripts":{"build":"x"}}', '.webklar-preview.json': '{"type":"static"}', 'a.css': 'c' },
   unterordner: { 'site/home.html': 'H', 'site/a.css': 'c', 'root.html': 'r' },
 }