diff --git a/infrastructure/production/fleet/apps/platform-api-config.yaml b/infrastructure/production/fleet/apps/platform-api-config.yaml
index 7e087bb..7cdd253 100644
--- a/infrastructure/production/fleet/apps/platform-api-config.yaml
+++ b/infrastructure/production/fleet/apps/platform-api-config.yaml
@@ -19,9 +19,11 @@ data:
   STALWART_ADMIN_USER: "admin@dezky.eu"
   STALWART_PROVISIONING_ENABLED: "true"
   # Base for per-tenant service mail domains ({slug}.dezky.eu) AND the
-  # reserved namespace for customer domains: only the dezky tenant may claim
-  # the apex; nothing under it can be added as a customer domain.
+  # reserved namespace for customer domains: only the company's own tenant
+  # (PLATFORM_TENANT_SLUG) may claim the apex; nothing under it can be added
+  # as a customer domain.
   PLATFORM_TENANT_DOMAIN: "dezky.eu"
+  PLATFORM_TENANT_SLUG: "dezky-aps"
   # JWT validation for portal/operator-issued access tokens. Public Authentik
   # URLs on purpose: the token `iss` claim is the public URL, and the pod can
   # hairpin to it through the node's public IP.
diff --git a/services/platform-api/src/domains/domains.service.guards.spec.ts b/services/platform-api/src/domains/domains.service.guards.spec.ts
index 79e5aa6..167939a 100644
--- a/services/platform-api/src/domains/domains.service.guards.spec.ts
+++ b/services/platform-api/src/domains/domains.service.guards.spec.ts
@@ -73,10 +73,23 @@ describe('DomainsService.add guards', () => {
     await expect(svc.add(tenant('dezky'), `mail.${BASE}`, ACTOR)).rejects.toThrow(/reserved/)
   })
 
-  it('allows the dezky tenant to claim the platform apex', async () => {
+  it('allows the platform tenant to claim the platform apex', async () => {
     const { svc, created } = makeService()
     const view = await svc.add(tenant('dezky'), BASE, ACTOR)
     expect(view.domain).toBe(BASE)
     expect(created).toHaveLength(1)
   })
+
+  it('respects PLATFORM_TENANT_SLUG for the apex allowance', async () => {
+    process.env.PLATFORM_TENANT_SLUG = 'dezky-aps'
+    try {
+      const { svc, created } = makeService()
+      await expect(svc.add(tenant('dezky'), BASE, ACTOR)).rejects.toThrow(/reserved/)
+      const view = await svc.add(tenant('dezky-aps'), BASE, ACTOR)
+      expect(view.domain).toBe(BASE)
+      expect(created).toHaveLength(1)
+    } finally {
+      delete process.env.PLATFORM_TENANT_SLUG
+    }
+  })
 })
diff --git a/services/platform-api/src/domains/domains.service.ts b/services/platform-api/src/domains/domains.service.ts
index 03c5a6f..6b9d520 100644
--- a/services/platform-api/src/domains/domains.service.ts
+++ b/services/platform-api/src/domains/domains.service.ts
@@ -81,11 +81,12 @@ export class DomainsService {
 
     // The platform's own namespace is reserved. The apex (PLATFORM_TENANT_DOMAIN,
     // e.g. dezky.eu) doubles as dezky's employee mail domain — only the company's
-    // own tenant (slug "dezky") may claim it. Everything under it is off limits
-    // for everyone: that's where per-tenant service domains ({slug}.dezky.eu)
-    // and the infrastructure hosts (auth/api/app/mail/…) live.
+    // own tenant (PLATFORM_TENANT_SLUG, prod: dezky-aps) may claim it. Everything
+    // under it is off limits for everyone: that's where per-tenant service
+    // domains ({slug}.dezky.eu) and the infrastructure hosts (auth/api/app/mail/…) live.
     const platformBase = (process.env.PLATFORM_TENANT_DOMAIN || 'dezky.local').toLowerCase()
-    if (domain === platformBase && tenant.slug !== 'dezky') {
+    const platformSlug = (process.env.PLATFORM_TENANT_SLUG || 'dezky').toLowerCase()
+    if (domain === platformBase && tenant.slug !== platformSlug) {
       throw new ConflictException(`Domain "${domain}" is reserved`)
     }
     if (domain.endsWith(`.${platformBase}`)) {