diff --git a/packages/vitec/Classes/Command/SsrWarmCommand.php b/packages/vitec/Classes/Command/SsrWarmCommand.php
new file mode 100644
index 0000000..c53b786
--- /dev/null
+++ b/packages/vitec/Classes/Command/SsrWarmCommand.php
@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Evomedien\Vitec\Command;
+
+use Evomedien\Vitec\Service\SsrPurgeService;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+#[AsCommand(
+    name: 'vitec:ssr-warm',
+    description: 'Start a background warm run on the SSR node (all sitemap pages, or the given paths)',
+)]
+final class SsrWarmCommand extends Command
+{
+    public function __construct(private readonly SsrPurgeService $purgeService)
+    {
+        parent::__construct();
+    }
+
+    protected function configure(): void
+    {
+        $this->addArgument('paths', InputArgument::IS_ARRAY, 'Paths to warm; none = every page of sitemap.xml');
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $result = $this->purgeService->warm((array)$input->getArgument('paths'));
+        $output->writeln(($result['success'] ? '<info>OK</info> ' : '<error>FAILED</error> ') . $result['message']);
+        return $result['success'] ? Command::SUCCESS : Command::FAILURE;
+    }
+}
diff --git a/packages/vitec/Classes/Controller/Backend/SsrController.php b/packages/vitec/Classes/Controller/Backend/SsrController.php
index b10a7b5..485ba42 100644
--- a/packages/vitec/Classes/Controller/Backend/SsrController.php
+++ b/packages/vitec/Classes/Controller/Backend/SsrController.php
@@ -102,6 +102,22 @@ final class SsrController
         return new RedirectResponse((string)$this->uriBuilder->buildUriFromRoute('web_vitecssr'), 303);
     }
 
+    /**
+     * "Warm cache" button: asks the node to render every page of the
+     * sitemap in the background (0066-FE). Returns at once; progress is
+     * the "Cache warming" row of the status table.
+     */
+    public function warmAction(ServerRequestInterface $request): ResponseInterface
+    {
+        $result = $this->purgeService->warm();
+        $this->flash(
+            $result['message'],
+            $result['success'] ? 'Cache warming' : 'Cache warming failed',
+            $result['success']
+        );
+        return new RedirectResponse((string)$this->uriBuilder->buildUriFromRoute('web_vitecssr'), 303);
+    }
+
     /**
      * Ajax route vitec_ssr_purge_page: purge exactly one page, called by
      * the page tree context menu item (ssr-context-menu.js).
diff --git a/packages/vitec/Classes/Service/SsrPurgeService.php b/packages/vitec/Classes/Service/SsrPurgeService.php
index c26d643..b198583 100644
--- a/packages/vitec/Classes/Service/SsrPurgeService.php
+++ b/packages/vitec/Classes/Service/SsrPurgeService.php
@@ -76,6 +76,79 @@ final class SsrPurgeService
         return max(1, (int)($this->getConfig()['SSR_FAILOVER_AFTER'] ?? 2));
     }
 
+    /**
+     * POST /__warm on the node (contract 0066-FE), derived from
+     * SSR_PURGE_ENDPOINT; SSR_WARM_ENDPOINT overrides explicitly.
+     */
+    public function getWarmEndpoint(): string
+    {
+        $explicit = $this->getConfig()['SSR_WARM_ENDPOINT'] ?? '';
+        if ($explicit !== '') {
+            return $explicit;
+        }
+        $purge = $this->getConfig()['SSR_PURGE_ENDPOINT'] ?? '';
+        return $purge === '' ? '' : str_replace('/__purge', '/__warm', $purge);
+    }
+
+    /**
+     * Starts a background warm run on the node: no paths (or '*') = every
+     * page of sitemap.xml, otherwise exactly the given paths. The node
+     * answers at once and renders in the background; progress shows up as
+     * "warming" in /__health and /__stats. Not written to the purge log -
+     * a warm run evicts nothing, and the log feeds the purge statistics.
+     *
+     * @param string[] $paths
+     * @return array{success:bool, httpCode:int, message:string, data:array}
+     */
+    public function warm(array $paths = []): array
+    {
+        if (!$this->isConfigured()) {
+            return ['success' => false, 'httpCode' => 0, 'message' => 'not configured (var/vitec-ssr-purge.env missing)', 'data' => []];
+        }
+        $paths = $this->normalize($paths);
+        $payload = ($paths === [] || $paths === ['*']) ? ['source' => 'sitemap'] : ['paths' => $paths];
+        try {
+            $response = $this->requestFactory->request($this->getWarmEndpoint(), 'POST', [
+                'headers' => [
+                    'X-Purge-Secret' => $this->getConfig()['SSR_PURGE_SECRET'],
+                    'Content-Type' => 'application/json',
+                ],
+                'body' => json_encode($payload, JSON_THROW_ON_ERROR),
+                // The node reads the sitemap (index + sub-sitemaps) before
+                // it answers; the pages themselves are not awaited.
+                'timeout' => 30,
+                'connect_timeout' => 3,
+                'http_errors' => false,
+            ]);
+            $code = $response->getStatusCode();
+            $body = (string)$response->getBody();
+            $data = json_decode($body, true);
+            $data = is_array($data) ? $data : [];
+            if ($code === 200 && !empty($data['started'])) {
+                $message = sprintf(
+                    'Warm run started: %d pages queued (source: %s, %d at a time)',
+                    (int)($data['queued'] ?? 0),
+                    (string)($data['source'] ?? '?'),
+                    (int)($data['concurrency'] ?? 0)
+                );
+                return ['success' => true, 'httpCode' => $code, 'message' => $message, 'data' => $data];
+            }
+            if ($code === 200 && !empty($data['running'])) {
+                $w = (array)($data['warming'] ?? []);
+                $message = sprintf(
+                    'A warm run is already active: %d of %d pages done',
+                    (int)($w['done'] ?? 0) + (int)($w['skipped'] ?? 0) + (int)($w['failed'] ?? 0),
+                    (int)($w['queued'] ?? 0)
+                );
+                return ['success' => true, 'httpCode' => $code, 'message' => $message, 'data' => $data];
+            }
+            $message = 'HTTP ' . $code . ' - ' . (string)($data['error'] ?? substr($body, 0, 200));
+            return ['success' => false, 'httpCode' => $code, 'message' => $message, 'data' => $data];
+        } catch (\Throwable $e) {
+            return ['success' => false, 'httpCode' => 0, 'message' => substr($e->getMessage(), 0, 200), 'data' => []];
+        }
+    }
+
     /**
      * Normalizes, dedupes and sends the paths; logs the outcome.
      * Never throws - editors' saves must not fail on a purge problem.
diff --git a/packages/vitec/Classes/UserFunc/ProductFeatureJsonRenderer.php b/packages/vitec/Classes/UserFunc/ProductFeatureJsonRenderer.php
index 73fe9b2..a79016c 100644
--- a/packages/vitec/Classes/UserFunc/ProductFeatureJsonRenderer.php
+++ b/packages/vitec/Classes/UserFunc/ProductFeatureJsonRenderer.php
@@ -21,6 +21,12 @@ use TYPO3\CMS\Core\Utility\GeneralUtility;
  *
  * Extends ProductListJsonRenderer purely to reuse its serializeProduct()
  * and image handling - same filters, same shape, one source of truth.
+ *
+ * "No product" returns an EMPTY STRING, never json_encode(null): headless
+ * only decodes strings that look like objects/arrays, so the text "null"
+ * went out as the string "null" and crashed the front end (ticket
+ * 0068-FE). The TypoScript sets ifEmptyReturnNull = 1 on this field,
+ * which turns the empty string into a real JSON null.
  */
 final class ProductFeatureJsonRenderer extends ProductListJsonRenderer
 {
@@ -33,7 +39,7 @@ final class ProductFeatureJsonRenderer extends ProductListJsonRenderer
                 ->convertFlexFormContentToArray((string)($row['pi_flexform'] ?? ''));
             $productUid = (int)($flexFormData['settings']['product'] ?? 0);
             if ($productUid <= 0) {
-                return (string)json_encode(null);
+                return '';
             }
 
             $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)
@@ -47,12 +53,12 @@ final class ProductFeatureJsonRenderer extends ProductListJsonRenderer
                 )
                 ->executeQuery()->fetchAssociative();
             if (!$product) {
-                return (string)json_encode(null);
+                return '';
             }
 
             return (string)json_encode($this->serializeProduct($product), JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
         } catch (\Throwable) {
-            return (string)json_encode(null);
+            return '';
         }
     }
 }
diff --git a/packages/vitec/Configuration/Backend/Modules.php b/packages/vitec/Configuration/Backend/Modules.php
index debfeed..807da14 100644
--- a/packages/vitec/Configuration/Backend/Modules.php
+++ b/packages/vitec/Configuration/Backend/Modules.php
@@ -147,6 +147,10 @@ return [
                 'target' => \Evomedien\Vitec\Controller\Backend\SsrController::class . '::purgeAction',
                 'methods' => ['POST'],
             ],
+            'warm' => [
+                'target' => \Evomedien\Vitec\Controller\Backend\SsrController::class . '::warmAction',
+                'methods' => ['POST'],
+            ],
         ],
     ],
 ];
diff --git a/packages/vitec/Configuration/Sets/Vitecset/setup.typoscript b/packages/vitec/Configuration/Sets/Vitecset/setup.typoscript
index b454fb2..e7b68ce 100755
--- a/packages/vitec/Configuration/Sets/Vitecset/setup.typoscript
+++ b/packages/vitec/Configuration/Sets/Vitecset/setup.typoscript
@@ -77,6 +77,9 @@ tt_content {
                 fields {
                     productfeature = USER
                     productfeature.userFunc = Evomedien\Vitec\UserFunc\ProductFeatureJsonRenderer->render
+                    # No product selected/visible -> real JSON null, not
+                    # the string "null" (ticket 0068-FE).
+                    productfeature.ifEmptyReturnNull = 1
                 }
             }
         }
diff --git a/packages/vitec/Resources/Private/Templates/Ssr/Index.html b/packages/vitec/Resources/Private/Templates/Ssr/Index.html
index 30afc17..8655773 100644
--- a/packages/vitec/Resources/Private/Templates/Ssr/Index.html
+++ b/packages/vitec/Resources/Private/Templates/Ssr/Index.html
@@ -32,6 +32,33 @@
                     </f:if>
                 </td>
             </tr>
+            <tr>
+                <th>Cache warming</th>
+                <td>
+                    <f:if condition="{health.warming.running}">
+                        <f:then>
+                            <span class="badge badge-info">running</span>
+                            {health.warming.done} of {health.warming.queued} pages rendered
+                            ({health.warming.skipped} still fresh, {health.warming.failed} failed)
+                            <br><small>Reload this module to follow the progress.</small>
+                        </f:then>
+                        <f:else>
+                            <f:if condition="{health.warming.startedAt}">
+                                <f:then>
+                                    Last run: {health.warming.done} of {health.warming.queued} pages rendered
+                                    ({health.warming.skipped} still fresh,
+                                    <f:if condition="{health.warming.failed}">
+                                        <f:then><span class="badge badge-danger">{health.warming.failed} failed</span></f:then>
+                                        <f:else>0 failed</f:else>
+                                    </f:if>)
+                                    <f:if condition="{health.warming.aborted}"> <span class="badge badge-warning">aborted by restart</span></f:if>
+                                </f:then>
+                                <f:else><span class="text-muted">no run since the server started</span></f:else>
+                            </f:if>
+                        </f:else>
+                    </f:if>
+                </td>
+            </tr>
             <tr>
                 <th>Purge configuration</th>
                 <td>
@@ -60,6 +87,14 @@
             <button type="submit" class="btn btn-warning">Purge everything (*)</button>
             <small class="text-muted"> — needed after menu/footer changes while auto-purge is off</small>
         </form>
+
+        <h3 style="margin-top:24px">Warm cache</h3>
+        <form action="{f:be.uri(route: 'web_vitecssr.warm')}" method="post"
+              onsubmit="return confirm('This renders every sitemap page (800+) in the background and sends several thousand requests to TYPO3 within a few minutes. Continue?');">
+            <button type="submit" class="btn btn-success">Warm cache (all sitemap pages)</button>
+            <small class="text-muted"> — pre-renders every page in the background, so no visitor has to
+                wait for a first render. Useful after "Purge everything" or a deploy; takes a few minutes.</small>
+        </form>
     </div>
 </div>