diff --git a/modules/helpdesk/lib/Module/Helpdesk/Service/DomainDetailService.php b/modules/helpdesk/lib/Module/Helpdesk/Service/DomainDetailService.php
new file mode 100644
index 0000000..0f0cdd8
--- /dev/null
+++ b/modules/helpdesk/lib/Module/Helpdesk/Service/DomainDetailService.php
@@ -0,0 +1,226 @@
+<?php
+
+namespace MintyPHP\Module\Helpdesk\Service;
+
+use MintyPHP\Module\Helpdesk\Repository\HandoverRepository;
+use MintyPHP\Module\Helpdesk\Repository\UpdateRepository;
+
+/**
+ * Service for loading domain detail data (master data, customer, contract, handovers).
+ *
+ * Provides loadDomain() for the synchronous page load and loadDomainDetails()
+ * for the async data endpoint.
+ */
+class DomainDetailService
+{
+    public function __construct(
+        private readonly BcODataGateway $bcODataGateway,
+        private readonly EffectiveHelpdeskSettingsService $settingsGateway,
+        private readonly HandoverRepository $handoverRepository,
+        private readonly ?UpdateRepository $updateRepository = null
+    ) {
+    }
+
+    /**
+     * Load domain master data (1 OData call).
+     *
+     * Used by the main page load — customer, contract, handovers loaded async.
+     *
+     * @api Called from domain($id) action
+     * @return array{status: string, domain?: array<string, mixed>, error?: string}
+     */
+    public function loadDomain(string $domainNo): array
+    {
+        $domainNo = trim($domainNo);
+        if ($domainNo === '') {
+            return ['status' => 'not_found'];
+        }
+
+        if (!$this->settingsGateway->isConfigured()) {
+            return ['status' => 'not_configured', 'error' => 'BC connection not configured'];
+        }
+
+        try {
+            $domain = $this->bcODataGateway->getDomain($domainNo);
+        } catch (\Throwable) {
+            return ['status' => 'error', 'error' => 'BC connection failed'];
+        }
+
+        if ($domain === null) {
+            return ['status' => 'not_found'];
+        }
+
+        return [
+            'status' => 'success',
+            'domain' => $domain,
+        ];
+    }
+
+    /**
+     * Load all detail data for a domain (for async data endpoint).
+     *
+     * @api Called from domain-detail-data endpoint
+     * @return array{
+     *   ok: bool,
+     *   customer?: array<string, mixed>|null,
+     *   contract?: array<string, mixed>|null,
+     *   handovers?: list<array<string, mixed>>,
+     *   handover_stats?: array{total: int, draft: int, in_progress: int, completed: int, archived: int},
+     *   related_domains?: list<array<string, mixed>>,
+     *   error?: string
+     * }
+     */
+    public function loadDomainDetails(string $domainNo, string $customerNo, int $tenantId): array
+    {
+        $domainNo = trim($domainNo);
+        $customerNo = trim($customerNo);
+
+        if ($domainNo === '') {
+            return ['ok' => false, 'error' => 'Missing domain number'];
+        }
+
+        $customer = null;
+        if ($customerNo !== '') {
+            try {
+                $customer = $this->bcODataGateway->getCustomer($customerNo);
+            } catch (\Throwable) {
+                // Best-effort — continue without customer data
+            }
+        }
+
+        $contract = $this->loadContractForDomain($domainNo);
+
+        $handovers = $this->handoverRepository->findByDomainNo($tenantId, $domainNo);
+        $handoverStats = $this->aggregateHandoverStats($handovers);
+
+        $relatedDomains = [];
+        if ($customerNo !== '') {
+            try {
+                $allCustomerDomains = $this->bcODataGateway->getDomainsForCustomer($customerNo);
+                $relatedDomains = array_values(array_filter(
+                    $allCustomerDomains,
+                    static fn (array $d): bool => trim((string) ($d['No'] ?? '')) !== $domainNo
+                ));
+            } catch (\Throwable) {
+                // Best-effort — continue without related domains
+            }
+        }
+
+        $updates = [];
+        if ($this->updateRepository !== null) {
+            $updates = $this->prepareUpdatesForResponse(
+                $this->updateRepository->findByDomainNo($tenantId, $domainNo)
+            );
+        }
+
+        return [
+            'ok' => true,
+            'customer' => $customer,
+            'contract' => $contract,
+            'handovers' => $this->prepareHandoversForResponse($handovers),
+            'handover_stats' => $handoverStats,
+            'updates' => $updates,
+            'related_domains' => $relatedDomains,
+        ];
+    }
+
+    /**
+     * Load contract line info for a specific domain from BC.
+     *
+     * @return array<string, mixed>|null
+     */
+    private function loadContractForDomain(string $domainNo): ?array
+    {
+        try {
+            $contractLines = $this->bcODataGateway->listDomainContractLines();
+        } catch (\Throwable) {
+            return null;
+        }
+
+        foreach ($contractLines as $line) {
+            $lineNo = trim((string) ($line['No'] ?? ''));
+            if ($lineNo === $domainNo) {
+                return [
+                    'contract_type' => trim((string) ($line['PI_Header_Type'] ?? '')),
+                    'contract_no' => trim((string) ($line['Header_No'] ?? '')),
+                    'contract_description' => trim((string) ($line['PI_Header_Description'] ?? '')),
+                    'header_state' => trim((string) ($line['PI_Header_State'] ?? '')),
+                    'line_state' => trim((string) ($line['Line_State'] ?? '')),
+                ];
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * @param list<array<string, mixed>> $handovers
+     * @return array{total: int, draft: int, in_progress: int, completed: int, archived: int}
+     */
+    private function aggregateHandoverStats(array $handovers): array
+    {
+        $stats = ['total' => 0, 'draft' => 0, 'in_progress' => 0, 'completed' => 0, 'archived' => 0];
+
+        foreach ($handovers as $handover) {
+            $stats['total']++;
+            $status = trim((string) ($handover['status'] ?? ''));
+            if (isset($stats[$status])) {
+                $stats[$status]++;
+            }
+        }
+
+        return $stats;
+    }
+
+    /**
+     * Prepare update rows for the JSON response.
+     *
+     * @param list<array<string, mixed>> $updates
+     * @return list<array<string, mixed>>
+     */
+    private function prepareUpdatesForResponse(array $updates): array
+    {
+        $prepared = [];
+        foreach ($updates as $update) {
+            $categoryCode = (string) ($update['category_code'] ?? '');
+            $status = (string) ($update['status'] ?? '');
+            $prepared[] = [
+                'ticket_no' => (string) ($update['ticket_no'] ?? ''),
+                'category_code' => $categoryCode,
+                'category_label' => UpdateService::categoryLabel($categoryCode),
+                'category_variant' => UpdateService::categoryVariant($categoryCode),
+                'gitea_path' => (string) ($update['gitea_path'] ?? ''),
+                'status' => $status,
+                'status_label' => UpdateService::statusLabel($status),
+                'status_variant' => UpdateService::statusVariant($status),
+                'created_at' => (string) ($update['created_at'] ?? ''),
+            ];
+        }
+
+        return $prepared;
+    }
+
+    /**
+     * Prepare handover rows for the JSON response (strip internal fields).
+     *
+     * @param list<array<string, mixed>> $handovers
+     * @return list<array<string, mixed>>
+     */
+    private function prepareHandoversForResponse(array $handovers): array
+    {
+        $prepared = [];
+        foreach ($handovers as $handover) {
+            $prepared[] = [
+                'id' => (int) ($handover['id'] ?? 0),
+                'product_code' => (string) ($handover['product_code'] ?? ''),
+                'product_name' => (string) ($handover['product_name'] ?? ''),
+                'product_bc_description' => (string) ($handover['product_bc_description'] ?? ''),
+                'status' => (string) ($handover['status'] ?? ''),
+                'created_by_name' => (string) ($handover['created_by_name'] ?? ''),
+                'created_at' => (string) ($handover['created_at'] ?? ''),
+            ];
+        }
+
+        return $prepared;
+    }
+}
diff --git a/modules/helpdesk/pages/helpdesk/domain($id).php b/modules/helpdesk/pages/helpdesk/domain($id).php
new file mode 100644
index 0000000..d0e167b
--- /dev/null
+++ b/modules/helpdesk/pages/helpdesk/domain($id).php
@@ -0,0 +1,59 @@
+<?php
+
+use MintyPHP\Buffer;
+use MintyPHP\Module\Helpdesk\HelpdeskAuthorizationPolicy;
+use MintyPHP\Module\Helpdesk\Service\DomainDetailService;
+use MintyPHP\Router;
+use MintyPHP\Support\Flash;
+use MintyPHP\Support\Guard;
+
+Guard::requireLogin();
+Guard::requireAbilityOrForbidden(HelpdeskAuthorizationPolicy::ABILITY_ACCESS);
+
+$domainNo = trim((string) ($id ?? ''));
+
+if ($domainNo === '') {
+    Router::redirect('helpdesk/domains');
+
+    return;
+}
+
+$domainDetailService = app(DomainDetailService::class);
+$result = $domainDetailService->loadDomain($domainNo);
+
+$resultStatus = (string) ($result['status'] ?? '');
+
+if ($resultStatus === 'not_found') {
+    Flash::error(t('Domain not found'), 'helpdesk-domains', 'domain_not_found');
+    Router::redirect('helpdesk/domains');
+
+    return;
+}
+
+if ($resultStatus === 'not_configured') {
+    Flash::error(t('BC connection is not configured'), 'helpdesk-domains', 'not_configured');
+    Router::redirect('helpdesk/domains');
+
+    return;
+}
+
+$domain = $result['domain'] ?? [];
+$hasError = $resultStatus === 'error';
+$errorMessage = $result['error'] ?? '';
+
+$domainUrl = (string) ($domain['URL'] ?? '');
+$customerNo = (string) ($domain['Customer_No'] ?? '');
+$customerName = (string) ($domain['Customer_Name'] ?? '');
+$domainState = (string) ($domain['State'] ?? '');
+$domainAdministration = (string) ($domain['Administration'] ?? '');
+
+$pageTitle = $domainUrl !== '' ? $domainUrl : $domainNo;
+
+Buffer::set('title', $pageTitle . ' — ' . t('Helpdesk'));
+Buffer::set('style_groups', json_encode(['helpdesk']));
+$breadcrumbs = [
+    ['label' => t('Home'), 'path' => 'admin'],
+    ['label' => t('Helpdesk'), 'path' => 'helpdesk'],
+    ['label' => t('Domains'), 'path' => 'helpdesk/domains'],
+    ['label' => $pageTitle],
+];
diff --git a/modules/helpdesk/pages/helpdesk/domain(default).phtml b/modules/helpdesk/pages/helpdesk/domain(default).phtml
new file mode 100644
index 0000000..4e61bef
--- /dev/null
+++ b/modules/helpdesk/pages/helpdesk/domain(default).phtml
@@ -0,0 +1,234 @@
+<?php
+
+/**
+ * @var string $domainNo
+ * @var array $domain
+ * @var bool $hasError
+ * @var string $errorMessage
+ * @var string $domainUrl
+ * @var string $customerNo
+ * @var string $customerName
+ * @var string $domainState
+ * @var string $domainAdministration
+ * @var string $pageTitle
+ */
+
+$domainNo = $domainNo ?? '';
+$domain = is_array($domain ?? null) ? $domain : [];
+$hasError = $hasError ?? false;
+$errorMessage = $errorMessage ?? '';
+$domainUrl = $domainUrl ?? '';
+$customerNo = $customerNo ?? '';
+$customerName = $customerName ?? '';
+$domainState = $domainState ?? '';
+$domainAdministration = $domainAdministration ?? '';
+$pageTitle = $pageTitle ?? $domainNo;
+
+$stateVariantMap = [
+    'Aktiv' => 'success',
+    'In Vorbereitung' => 'warning',
+];
+$stateVariant = $stateVariantMap[$domainState] ?? 'neutral';
+
+?>
+<div class="app-details-container"
+     data-domain-no="<?php e($domainNo); ?>"
+     data-customer-no="<?php e($customerNo); ?>"
+     data-customer-name="<?php e($customerName); ?>"
+     data-detail-url="<?php e(lurl('helpdesk/domain-detail-data')); ?>"
+     data-debitor-base-url="<?php e(lurl('helpdesk/debitor/')); ?>"
+     data-handover-edit-base-url="<?php e(lurl('helpdesk/handovers/edit/')); ?>"
+     data-domain-base-url="<?php e(lurl('helpdesk/domain/')); ?>"
+     data-ticket-base-url="<?php e(lurl('helpdesk/ticket/')); ?>"
+>
+  <section>
+    <?php
+    $titlebar = [
+        'title' => $pageTitle,
+        'backHref' => lurl('helpdesk/domains'),
+        'backTitle' => t('Back to domains'),
+        'actions' => [],
+    ];
+    require templatePath('partials/app-details-titlebar.phtml');
+    ?>
+
+    <?php require templatePath('partials/app-flash.phtml'); ?>
+
+    <?php if ($hasError): ?>
+      <div class="notice" data-variant="error" role="alert">
+        <p><?php e(t('Could not connect to Business Central.')); ?></p>
+        <?php if ($errorMessage !== ''): ?>
+          <small><?php e($errorMessage); ?></small>
+        <?php endif; ?>
+      </div>
+    <?php elseif ($domain !== []): ?>
+
+      <div class="app-tabs" data-tabs data-app-component="tabs" data-tabs-param="tab" data-tabs-storage-key="helpdesk-domain-detail">
+        <div class="app-tabs-nav">
+          <button type="button" data-tab="overview" data-tab-default>
+            <?php e(t('Overview')); ?>
+          </button>
+        </div>
+
+        <!-- Overview panel -->
+        <div data-tab-panel="overview" data-tab-panel-wide>
+
+          <!-- Loading skeleton -->
+          <div id="domain-loading" aria-busy="true">
+            <div class="helpdesk-domain-overview-grid">
+              <div class="helpdesk-skeleton-block" style="height: 180px;"></div>
+              <div class="helpdesk-skeleton-block" style="height: 180px;"></div>
+            </div>
+            <div class="helpdesk-skeleton-block" style="height: 120px; margin-top: calc(var(--app-spacing) * 1.25);"></div>
+          </div>
+
+          <!-- Content (hidden until async load) -->
+          <div id="domain-content" hidden>
+
+            <!-- Customer + Contract side by side -->
+            <div class="helpdesk-domain-overview-grid">
+
+              <!-- Customer Info -->
+              <details class="app-details-card" open>
+                <summary>
+                  <span class="app-details-card-summary-title"><?php e(t('Customer information')); ?></span>
+                </summary>
+                <div class="app-details-card-container">
+                  <div id="domain-customer-info">
+                    <p class="text-muted"><?php e(t('Loading...')); ?></p>
+                  </div>
+                </div>
+              </details>
+
+              <!-- Contract Info -->
+              <details class="app-details-card" id="domain-contract-section" open hidden>
+                <summary>
+                  <span class="app-details-card-summary-title"><?php e(t('Contract information')); ?></span>
+                </summary>
+                <div class="app-details-card-container">
+                  <div id="domain-contract-info">
+                    <p class="text-muted"><?php e(t('Loading...')); ?></p>
+                  </div>
+                </div>
+              </details>
+
+            </div>
+
+            <!-- Handovers (full width) -->
+            <details class="app-details-card" open >
+              <summary>
+                <span class="app-details-card-summary-title"><?php e(t('Handovers')); ?></span>
+                <span class="app-details-card-summary-meta">
+                  <span class="badge" data-variant="neutral" id="domain-handover-count">0</span>
+                </span>
+              </summary>
+              <div class="app-details-card-container">
+                <div id="domain-handovers-list"></div>
+              </div>
+            </details>
+
+            <!-- Updates (full width) -->
+            <details class="app-details-card" id="domain-updates-section" open hidden>
+              <summary>
+                <span class="app-details-card-summary-title"><?php e(t('Updates')); ?></span>
+                <span class="app-details-card-summary-meta">
+                  <span class="badge" data-variant="neutral" id="domain-update-count">0</span>
+                </span>
+              </summary>
+              <div class="app-details-card-container">
+                <div id="domain-updates-list"></div>
+              </div>
+            </details>
+
+          </div>
+        </div>
+      </div>
+
+    <?php endif; ?>
+  </section>
+
+  <?php if (!$hasError && $domain !== []): ?>
+  <aside id="app-details-aside-section">
+    <div class="app-details-aside-section">
+
+      <hgroup>
+        <h2><?php e($domainNo); ?></h2>
+        <?php if ($domainUrl !== ''): ?>
+          <p><?php e($domainUrl); ?></p>
+        <?php endif; ?>
+      </hgroup>
+
+      <div class="badge-list">
+        <?php if ($domainState !== ''): ?>
+          <span class="badge" data-variant="<?php e($stateVariant); ?>"><?php e($domainState); ?></span>
+        <?php endif; ?>
+        <?php if ($domainAdministration !== ''): ?>
+          <span class="badge" data-variant="neutral"><?php e($domainAdministration); ?></span>
+        <?php endif; ?>
+      </div>
+
+      <hr>
+
+      <?php if ($domainUrl !== ''): ?>
+        <a href="<?php e('https://' . ltrim($domainUrl, 'htps:/')); ?>" target="_blank" rel="noopener" class="secondary outline small" role="button">
+          <i class="bi bi-box-arrow-up-right" aria-hidden="true"></i>
+          <?php e(t('Open domain')); ?>
+        </a>
+      <?php endif; ?>
+
+      <div id="domain-related-section" hidden>
+        <hr>
+        <details name="domain-aside" open>
+          <summary><?php e(t('Related domains')); ?></summary>
+          <div id="domain-related-domains"></div>
+        </details>
+      </div>
+
+    </div>
+  </aside>
+  <?php endif; ?>
+</div>
+
+<?php if (!$hasError && $domain !== []): ?>
+<script type="application/json" id="helpdesk-domain-i18n"><?php gridJsonForJs([
+    'Loading...' => t('Loading...'),
+    'Network error — please try again' => t('Network error — please try again'),
+    'No handovers for this domain yet' => t('No handovers for this domain yet'),
+    'No contract information available' => t('No contract information available'),
+    'Create handover' => t('Create handover'),
+    'Product' => t('Product'),
+    'Status' => t('Status'),
+    'Created by' => t('Created by'),
+    'Created' => t('Created'),
+    'Name' => t('Name'),
+    'Customer No.' => t('Customer No.'),
+    'Address' => t('Address'),
+    'City' => t('City'),
+    'Postal code' => t('Postal code'),
+    'Phone' => t('Phone'),
+    'E-Mail' => t('E-Mail'),
+    'Salesperson' => t('Salesperson'),
+    'Support type' => t('Support type'),
+    'Contract type' => t('Contract type'),
+    'Contract No.' => t('Contract No.'),
+    'Description' => t('Description'),
+    'Contract state' => t('Contract state'),
+    'Line state' => t('Line state'),
+    'URL' => t('URL'),
+    'No.' => t('No.'),
+    'State' => t('State'),
+    'Total' => t('Total'),
+    'Draft' => t('Draft'),
+    'In progress' => t('In progress'),
+    'Completed' => t('Completed'),
+    'Archived' => t('Archived'),
+    'No updates for this domain yet' => t('No updates for this domain yet'),
+    'Ticket' => t('Ticket'),
+    'Type' => t('Type'),
+    'Gitea link' => t('Gitea link'),
+    'Update' => t('Update'),
+    'Hotfix' => t('Hotfix'),
+]); ?></script>
+
+<script type="module" src="<?php e(assetVersion('modules/helpdesk/js/helpdesk-domain-detail.js')); ?>"></script>
+<?php endif; ?>
diff --git a/modules/helpdesk/pages/helpdesk/domain-detail-data().php b/modules/helpdesk/pages/helpdesk/domain-detail-data().php
new file mode 100644
index 0000000..e997be5
--- /dev/null
+++ b/modules/helpdesk/pages/helpdesk/domain-detail-data().php
@@ -0,0 +1,29 @@
+<?php
+
+use MintyPHP\Http\SessionStoreInterface;
+use MintyPHP\Module\Helpdesk\HelpdeskAuthorizationPolicy;
+use MintyPHP\Module\Helpdesk\Service\DomainDetailService;
+use MintyPHP\Router;
+use MintyPHP\Support\Guard;
+
+Guard::requireLogin();
+Guard::requireAbilityOrForbidden(HelpdeskAuthorizationPolicy::ABILITY_ACCESS);
+gridRequireGetRequest();
+
+$request = requestInput();
+$domainNo = trim((string) $request->query('domainNo', ''));
+$customerNo = trim((string) $request->query('customerNo', ''));
+
+if ($domainNo === '') {
+    Router::json(['ok' => false, 'error' => 'Missing domain number']);
+
+    return;
+}
+
+$session = app(SessionStoreInterface::class)->all();
+$tenantId = (int) ($session['current_tenant']['id'] ?? 0);
+
+$service = app(DomainDetailService::class);
+$result = $service->loadDomainDetails($domainNo, $customerNo, $tenantId);
+
+Router::json($result);
diff --git a/modules/helpdesk/tests/Module/Helpdesk/Service/DomainDetailServiceTest.php b/modules/helpdesk/tests/Module/Helpdesk/Service/DomainDetailServiceTest.php
new file mode 100644
index 0000000..2d093d5
--- /dev/null
+++ b/modules/helpdesk/tests/Module/Helpdesk/Service/DomainDetailServiceTest.php
@@ -0,0 +1,205 @@
+<?php
+
+namespace MintyPHP\Tests\Module\Helpdesk\Service;
+
+use MintyPHP\Module\Helpdesk\Repository\HandoverRepository;
+use MintyPHP\Module\Helpdesk\Service\BcODataGateway;
+use MintyPHP\Module\Helpdesk\Service\DomainDetailService;
+use MintyPHP\Module\Helpdesk\Service\EffectiveHelpdeskSettingsService;
+use PHPUnit\Framework\TestCase;
+
+class DomainDetailServiceTest extends TestCase
+{
+    private const TENANT_ID = 1;
+
+    private function createService(
+        ?BcODataGateway $gateway = null,
+        ?EffectiveHelpdeskSettingsService $settings = null,
+        ?HandoverRepository $repository = null,
+    ): DomainDetailService {
+        $gateway = $gateway ?? $this->createMock(BcODataGateway::class);
+        $settings = $settings ?? $this->createConfiguredSettings(true);
+        $repository = $repository ?? $this->createMock(HandoverRepository::class);
+
+        return new DomainDetailService($gateway, $settings, $repository);
+    }
+
+    private function createConfiguredSettings(bool $configured): EffectiveHelpdeskSettingsService
+    {
+        $mock = $this->createMock(EffectiveHelpdeskSettingsService::class);
+        $mock->method('isConfigured')->willReturn($configured);
+
+        return $mock;
+    }
+
+    // ── loadDomain tests ─────────────────────────────────────────
+
+    public function testLoadDomainHappyPath(): void
+    {
+        $gateway = $this->createMock(BcODataGateway::class);
+        $gateway->method('getDomain')->willReturn([
+            'No' => 'DNS00001',
+            'Customer_No' => 'D10001',
+            'Customer_Name' => 'Acme Corp',
+            'URL' => 'example.com',
+            'State' => 'Aktiv',
+            'Administration' => 'Intern',
+        ]);
+
+        $service = $this->createService($gateway);
+        $result = $service->loadDomain('DNS00001');
+
+        $this->assertSame('success', $result['status']);
+        $this->assertSame('DNS00001', $result['domain']['No']);
+        $this->assertSame('example.com', $result['domain']['URL']);
+    }
+
+    public function testLoadDomainNotFound(): void
+    {
+        $gateway = $this->createMock(BcODataGateway::class);
+        $gateway->method('getDomain')->willReturn(null);
+
+        $service = $this->createService($gateway);
+        $result = $service->loadDomain('INVALID');
+
+        $this->assertSame('not_found', $result['status']);
+    }
+
+    public function testLoadDomainEmptyNo(): void
+    {
+        $service = $this->createService();
+        $result = $service->loadDomain('');
+
+        $this->assertSame('not_found', $result['status']);
+    }
+
+    public function testLoadDomainNotConfigured(): void
+    {
+        $service = $this->createService(settings: $this->createConfiguredSettings(false));
+        $result = $service->loadDomain('DNS00001');
+
+        $this->assertSame('not_configured', $result['status']);
+    }
+
+    public function testLoadDomainBcError(): void
+    {
+        $gateway = $this->createMock(BcODataGateway::class);
+        $gateway->method('getDomain')->willThrowException(new \RuntimeException('Connection failed'));
+
+        $service = $this->createService($gateway);
+        $result = $service->loadDomain('DNS00001');
+
+        $this->assertSame('error', $result['status']);
+        $this->assertSame('BC connection failed', $result['error']);
+    }
+
+    // ── loadDomainDetails tests ──────────────────────────────────
+
+    public function testLoadDomainDetailsHappyPath(): void
+    {
+        $gateway = $this->createMock(BcODataGateway::class);
+        $gateway->method('getCustomer')->willReturn([
+            'No' => 'D10001',
+            'Name' => 'Acme Corp',
+            'Address' => 'Main St 1',
+        ]);
+        $gateway->method('listDomainContractLines')->willReturn([
+            ['No' => 'DNS00001', 'Header_No' => 'V1000', 'PI_Header_Type' => 'WEBSITE', 'PI_Header_Description' => 'Website Contract', 'PI_Header_State' => 'Aktiv', 'Line_State' => 'Aktiv'],
+            ['No' => 'DNS00002', 'Header_No' => 'V2000', 'PI_Header_Type' => 'SW&H', 'PI_Header_Description' => 'Other', 'PI_Header_State' => 'Aktiv', 'Line_State' => 'Aktiv'],
+        ]);
+        $gateway->method('getDomainsForCustomer')->willReturn([
+            ['No' => 'DNS00001', 'URL' => 'example.com', 'State' => 'Aktiv'],
+            ['No' => 'DNS00002', 'URL' => 'other.com', 'State' => 'Aktiv'],
+        ]);
+
+        $repo = $this->createMock(HandoverRepository::class);
+        $repo->method('findByDomainNo')->willReturn([
+            ['id' => 1, 'product_code' => 'PROD-A', 'product_name' => 'Product A', 'product_bc_description' => '', 'status' => 'draft', 'created_by_name' => 'John', 'created_at' => '2026-01-01 10:00:00'],
+            ['id' => 2, 'product_code' => 'PROD-A', 'product_name' => 'Product A', 'product_bc_description' => '', 'status' => 'completed', 'created_by_name' => 'Jane', 'created_at' => '2026-02-15 14:00:00'],
+        ]);
+
+        $service = $this->createService($gateway, repository: $repo);
+        $result = $service->loadDomainDetails('DNS00001', 'D10001', self::TENANT_ID);
+
+        $this->assertTrue($result['ok']);
+        $this->assertSame('Acme Corp', $result['customer']['Name']);
+        $this->assertSame('WEBSITE', $result['contract']['contract_type']);
+        $this->assertSame('V1000', $result['contract']['contract_no']);
+        $this->assertCount(2, $result['handovers']);
+        $this->assertSame(2, $result['handover_stats']['total']);
+        $this->assertSame(1, $result['handover_stats']['draft']);
+        $this->assertSame(1, $result['handover_stats']['completed']);
+        $this->assertCount(1, $result['related_domains']);
+        $this->assertSame('DNS00002', $result['related_domains'][0]['No']);
+    }
+
+    public function testLoadDomainDetailsNoContract(): void
+    {
+        $gateway = $this->createMock(BcODataGateway::class);
+        $gateway->method('getCustomer')->willReturn(['No' => 'D10001', 'Name' => 'Acme']);
+        $gateway->method('listDomainContractLines')->willReturn([]);
+        $gateway->method('getDomainsForCustomer')->willReturn([]);
+
+        $repo = $this->createMock(HandoverRepository::class);
+        $repo->method('findByDomainNo')->willReturn([]);
+
+        $service = $this->createService($gateway, repository: $repo);
+        $result = $service->loadDomainDetails('DNS00001', 'D10001', self::TENANT_ID);
+
+        $this->assertTrue($result['ok']);
+        $this->assertNull($result['contract']);
+        $this->assertSame(0, $result['handover_stats']['total']);
+        $this->assertEmpty($result['related_domains']);
+    }
+
+    public function testLoadDomainDetailsEmptyDomainNo(): void
+    {
+        $service = $this->createService();
+        $result = $service->loadDomainDetails('', 'D10001', self::TENANT_ID);
+
+        $this->assertFalse($result['ok']);
+        $this->assertSame('Missing domain number', $result['error']);
+    }
+
+    public function testLoadDomainDetailsCustomerFetchFails(): void
+    {
+        $gateway = $this->createMock(BcODataGateway::class);
+        $gateway->method('getCustomer')->willThrowException(new \RuntimeException('BC error'));
+        $gateway->method('listDomainContractLines')->willReturn([]);
+        $gateway->method('getDomainsForCustomer')->willReturn([]);
+
+        $repo = $this->createMock(HandoverRepository::class);
+        $repo->method('findByDomainNo')->willReturn([]);
+
+        $service = $this->createService($gateway, repository: $repo);
+        $result = $service->loadDomainDetails('DNS00001', 'D10001', self::TENANT_ID);
+
+        $this->assertTrue($result['ok']);
+        $this->assertNull($result['customer']);
+    }
+
+    public function testLoadDomainDetailsHandoverStatAggregation(): void
+    {
+        $gateway = $this->createMock(BcODataGateway::class);
+        $gateway->method('getCustomer')->willReturn(null);
+        $gateway->method('listDomainContractLines')->willReturn([]);
+        $gateway->method('getDomainsForCustomer')->willReturn([]);
+
+        $repo = $this->createMock(HandoverRepository::class);
+        $repo->method('findByDomainNo')->willReturn([
+            ['id' => 1, 'product_code' => 'P', 'product_name' => '', 'product_bc_description' => '', 'status' => 'draft', 'created_by_name' => '', 'created_at' => ''],
+            ['id' => 2, 'product_code' => 'P', 'product_name' => '', 'product_bc_description' => '', 'status' => 'in_progress', 'created_by_name' => '', 'created_at' => ''],
+            ['id' => 3, 'product_code' => 'P', 'product_name' => '', 'product_bc_description' => '', 'status' => 'in_progress', 'created_by_name' => '', 'created_at' => ''],
+            ['id' => 4, 'product_code' => 'P', 'product_name' => '', 'product_bc_description' => '', 'status' => 'archived', 'created_by_name' => '', 'created_at' => ''],
+        ]);
+
+        $service = $this->createService($gateway, repository: $repo);
+        $result = $service->loadDomainDetails('DNS00001', '', self::TENANT_ID);
+
+        $this->assertSame(4, $result['handover_stats']['total']);
+        $this->assertSame(1, $result['handover_stats']['draft']);
+        $this->assertSame(2, $result['handover_stats']['in_progress']);
+        $this->assertSame(0, $result['handover_stats']['completed']);
+        $this->assertSame(1, $result['handover_stats']['archived']);
+    }
+}
diff --git a/modules/helpdesk/web/js/helpdesk-domain-detail.js b/modules/helpdesk/web/js/helpdesk-domain-detail.js
new file mode 100644
index 0000000..2c27e2d
--- /dev/null
+++ b/modules/helpdesk/web/js/helpdesk-domain-detail.js
@@ -0,0 +1,321 @@
+/**
+ * Helpdesk domain detail page — read-only dashboard.
+ *
+ * Fetches customer, contract, handover, and related domain data
+ * from a single async endpoint and renders all sections.
+ *
+ * All dynamic values are escaped via the esc() helper before insertion
+ * into innerHTML. This matches the pattern used in helpdesk-detail.js
+ * and other helpdesk JS modules in this codebase.
+ */
+import { renderEmptyState } from './helpdesk-empty-state.js';
+
+function esc(str) {
+  const d = document.createElement('div');
+  d.textContent = String(str ?? '');
+  return d.innerHTML;
+}
+
+function formatDate(dateStr) {
+  if (!dateStr) return '—';
+  const d = new Date(dateStr);
+  if (isNaN(d.getTime())) return String(dateStr);
+  return d.toLocaleDateString('de-DE', { day: '2-digit', month: '2-digit', year: 'numeric' });
+}
+
+const STATUS_LABEL_MAP = {
+  draft: 'Draft',
+  in_progress: 'In progress',
+  completed: 'Completed',
+  archived: 'Archived',
+};
+
+const container = document.querySelector('.app-details-container[data-domain-no]');
+if (container) {
+  init(container);
+}
+
+function init(container) {
+  const domainNo = container.dataset.domainNo || '';
+  const customerNo = container.dataset.customerNo || '';
+  const detailUrl = container.dataset.detailUrl || '';
+  const debitorBaseUrl = container.dataset.debitorBaseUrl || '';
+  const handoverEditBaseUrl = container.dataset.handoverEditBaseUrl || '';
+  const domainBaseUrl = container.dataset.domainBaseUrl || '';
+  const ticketBaseUrl = container.dataset.ticketBaseUrl || '';
+
+  if (!domainNo || !detailUrl) return;
+
+  const i18nEl = document.getElementById('helpdesk-domain-i18n');
+  const i18n = i18nEl ? JSON.parse(i18nEl.textContent) : {};
+  const t = (key) => i18n[key] || key;
+
+  fetchDomainDetails();
+
+  async function fetchDomainDetails() {
+    const loadingEl = document.getElementById('domain-loading');
+    const contentEl = document.getElementById('domain-content');
+
+    try {
+      const params = new URLSearchParams({ domainNo, customerNo });
+      const res = await fetch(detailUrl + '?' + params, { credentials: 'same-origin' });
+      const data = await res.json();
+
+      if (!data.ok) {
+        showError(data.error || t('Network error — please try again'));
+        return;
+      }
+
+      renderCustomerInfo(data.customer);
+      renderContractInfo(data.contract);
+      renderHandoversList(data.handovers || []);
+      renderUpdatesList(data.updates || []);
+      renderRelatedDomains(data.related_domains || []);
+
+      if (loadingEl) loadingEl.hidden = true;
+      if (contentEl) contentEl.hidden = false;
+    } catch {
+      showError(t('Network error — please try again'));
+    }
+  }
+
+  function showError(message) {
+    const loadingEl = document.getElementById('domain-loading');
+    if (loadingEl) {
+      // safe-html: esc() escapes all dynamic content
+      loadingEl.innerHTML = '<div class="notice" data-variant="error" role="alert"><p>' + esc(message) + '</p></div>';
+      loadingEl.removeAttribute('aria-busy');
+    }
+  }
+
+  function renderCustomerInfo(customer) {
+    const el = document.getElementById('domain-customer-info');
+    if (!el) return;
+
+    if (!customer) {
+      el.textContent = '';
+      const p = document.createElement('p');
+      p.className = 'text-muted';
+      p.textContent = t('No contract information available');
+      el.appendChild(p);
+      return;
+    }
+
+    const name = customer.Name || '';
+    const no = customer.No || '';
+    const address = customer.Address || '';
+    const city = customer.City || '';
+    const postCode = customer.Post_Code || '';
+    const phone = customer.Phone_No || '';
+    const email = customer.E_Mail || '';
+    const salesperson = customer.Salesperson_Code || '';
+    const supportType = customer.Support_Type || '';
+
+    const debitorLink = no && debitorBaseUrl
+      ? '<a href="' + esc(debitorBaseUrl + encodeURIComponent(no)) + '">' + esc(name || no) + '</a>'
+      : esc(name || no);
+
+    // safe-html: all dynamic values are escaped via esc() before insertion
+    el.innerHTML =
+      '<dl class="helpdesk-ticket-meta">' +
+        '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Name')) + '</dt><dd>' + debitorLink + '</dd></div>' +
+        '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Customer No.')) + '</dt><dd>' + esc(no) + '</dd></div>' +
+        '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Phone')) + '</dt><dd>' + (phone ? '<a href="tel:' + esc(phone) + '">' + esc(phone) + '</a>' : '—') + '</dd></div>' +
+        (salesperson ? '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Salesperson')) + '</dt><dd>' + esc(salesperson) + '</dd></div>' : '') +
+        (supportType ? '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Support type')) + '</dt><dd>' + esc(supportType) + '</dd></div>' : '') +
+      '</dl>';
+  }
+
+  function renderContractInfo(contract) {
+    const section = document.getElementById('domain-contract-section');
+    const el = document.getElementById('domain-contract-info');
+    if (!el || !section) return;
+
+    if (!contract || !contract.contract_type) {
+      section.hidden = true;
+      return;
+    }
+
+    section.hidden = false;
+    // safe-html: all dynamic values are escaped via esc() before insertion
+    el.innerHTML =
+      '<dl class="helpdesk-ticket-meta">' +
+        '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Contract type')) + '</dt><dd>' + esc(contract.contract_type) + '</dd></div>' +
+        '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Description')) + '</dt><dd>' + esc(contract.contract_description || '—') + '</dd></div>' +
+        '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Contract No.')) + '</dt><dd>' + esc(contract.contract_no || '—') + '</dd></div>' +
+        (contract.header_state ? '<div class="helpdesk-ticket-meta-item"><dt>' + esc(t('Contract state')) + '</dt><dd>' + esc(contract.header_state) + '</dd></div>' : '') +
+      '</dl>';
+  }
+
+  function renderHandoversList(handovers) {
+    const el = document.getElementById('domain-handovers-list');
+    const countEl = document.getElementById('domain-handover-count');
+    if (!el) return;
+
+    if (countEl) countEl.textContent = String(handovers.length);
+
+    if (!handovers || handovers.length === 0) {
+      el.innerHTML = renderEmptyState({ // safe-html: renderEmptyState escapes internally
+        message: t('No handovers for this domain yet'),
+        size: 'compact',
+        icon: true,
+      });
+      return;
+    }
+
+    const statusVariantMap = {
+      draft: 'neutral',
+      in_progress: 'info',
+      completed: 'success',
+      archived: 'neutral',
+    };
+
+    const returnPath = 'helpdesk/domain/' + encodeURIComponent(domainNo);
+
+    let items = '';
+    for (const h of handovers) {
+      const editUrl = handoverEditBaseUrl + encodeURIComponent(h.id) + '?return=' + encodeURIComponent(returnPath);
+      const productLabel = h.product_name || h.product_bc_description || h.product_code || '—';
+      const statusVariant = statusVariantMap[h.status] || 'neutral';
+      const statusLabel = t(STATUS_LABEL_MAP[h.status] || h.status);
+      const meta = [h.created_by_name, formatDate(h.created_at)].filter(Boolean).join(' · ');
+
+      // safe-html: all dynamic values are escaped via esc()
+      items +=
+        '<a href="' + esc(editUrl) + '" class="helpdesk-domain-handover-item">' +
+          '<div class="helpdesk-domain-handover-item-main">' +
+            '<span class="helpdesk-domain-handover-item-product">' + esc(productLabel) + '</span>' +
+            '<span class="badge" data-variant="' + esc(statusVariant) + '">' + esc(statusLabel) + '</span>' +
+          '</div>' +
+          (meta ? '<div class="helpdesk-domain-handover-item-meta">' + esc(meta) + '</div>' : '') +
+        '</a>';
+    }
+
+    // safe-html: all content built from esc()-escaped values
+    el.innerHTML = '<div class="helpdesk-domain-handover-list">' + items + '</div>';
+  }
+
+  function renderUpdatesList(updates) {
+    const section = document.getElementById('domain-updates-section');
+    const el = document.getElementById('domain-updates-list');
+    const countEl = document.getElementById('domain-update-count');
+    if (!el || !section) return;
+
+    if (!updates || updates.length === 0) {
+      section.hidden = true;
+      return;
+    }
+
+    section.hidden = false;
+    if (countEl) countEl.textContent = String(updates.length);
+
+    // Build update items using DOM methods for safety
+    const listDiv = document.createElement('div');
+    listDiv.className = 'helpdesk-domain-handover-list';
+
+    for (const u of updates) {
+      const ticketNo = u.ticket_no || '';
+      const ticketUrl = ticketNo && ticketBaseUrl ? ticketBaseUrl + encodeURIComponent(ticketNo) : '';
+      const categoryLabel = u.category_label || u.category_code || '';
+      const categoryVariant = u.category_variant || 'neutral';
+      const giteaUrl = u.gitea_path || '';
+
+      const item = document.createElement('div');
+      item.className = 'helpdesk-domain-handover-item';
+
+      const main = document.createElement('div');
+      main.className = 'helpdesk-domain-handover-item-main';
+
+      const productSpan = document.createElement('span');
+      productSpan.className = 'helpdesk-domain-handover-item-product';
+      if (ticketUrl) {
+        const link = document.createElement('a');
+        link.href = ticketUrl;
+        link.textContent = ticketNo;
+        productSpan.appendChild(link);
+      } else {
+        productSpan.textContent = ticketNo;
+      }
+      main.appendChild(productSpan);
+
+      const badge = document.createElement('span');
+      badge.className = 'badge';
+      badge.dataset.variant = categoryVariant;
+      badge.textContent = categoryLabel;
+      main.appendChild(badge);
+
+      item.appendChild(main);
+
+      const metaParts = [];
+      if (giteaUrl) {
+        // Show last path segment as clickable link
+        const parts = giteaUrl.replace(/\/+$/, '').split('/');
+        const shortLabel = parts[parts.length - 1] || giteaUrl;
+        const giteaLink = document.createElement('a');
+        giteaLink.href = giteaUrl;
+        giteaLink.target = '_blank';
+        giteaLink.rel = 'noopener';
+        giteaLink.textContent = shortLabel;
+        metaParts.push(giteaLink);
+      }
+      const dateStr = formatDate(u.created_at);
+      if (dateStr && dateStr !== '\u2014') {
+        const dateSpan = document.createElement('span');
+        dateSpan.textContent = dateStr;
+        metaParts.push(dateSpan);
+      }
+      if (metaParts.length) {
+        const metaDiv = document.createElement('div');
+        metaDiv.className = 'helpdesk-domain-handover-item-meta';
+        metaParts.forEach((part, i) => {
+          if (i > 0) metaDiv.appendChild(document.createTextNode(' \u00b7 '));
+          metaDiv.appendChild(part);
+        });
+        item.appendChild(metaDiv);
+      }
+
+      listDiv.appendChild(item);
+    }
+
+    el.textContent = '';
+    el.appendChild(listDiv);
+  }
+
+  function renderRelatedDomains(domains) {
+    const section = document.getElementById('domain-related-section');
+    const el = document.getElementById('domain-related-domains');
+    if (!el || !section) return;
+
+    if (!domains || domains.length === 0) {
+      section.hidden = true;
+      return;
+    }
+
+    section.hidden = false;
+
+    const stateVariantMap = {
+      'Aktiv': 'success',
+      'In Vorbereitung': 'warning',
+    };
+
+    let items = '';
+    for (const d of domains) {
+      const url = d.URL || '';
+      const no = d.No || '';
+      const state = d.State || '';
+      const variant = stateVariantMap[state] || 'neutral';
+      const detailLink = domainBaseUrl + encodeURIComponent(no);
+
+      // safe-html: all dynamic values are escaped via esc()
+      items +=
+        '<a href="' + esc(detailLink) + '" class="helpdesk-domain-related-item">' +
+          '<span class="helpdesk-domain-related-item-url">' + esc(url || no) + '</span>' +
+          '<span class="badge small" data-variant="' + esc(variant) + '">' + esc(state) + '</span>' +
+        '</a>';
+    }
+
+    // safe-html: all content built from esc()-escaped values
+    el.innerHTML = items;
+  }
+
+}