diff --git a/README.md b/README.md
index 0d97daa..4c3d3d0 100644
--- a/README.md
+++ b/README.md
@@ -25,3 +25,8 @@ pattern contract documented in
 [`docs/INTERFACE_PATTERN_MIGRATION.md`](docs/INTERFACE_PATTERN_MIGRATION.md).
 Manifest-provided documentation topics back contextual help for tenant fields,
 governance limits, permission blockers, and lifecycle consequences.
+
+Core's `module_entitlements` tenant-setting key is reserved. Generic tenant
+updates preserve it even when replacing the remaining settings document;
+system and tenant module administrators change it through the Admin module's
+dedicated, revision-checked module policy APIs.
diff --git a/src/govoplan_tenancy/backend/api/v1/routes.py b/src/govoplan_tenancy/backend/api/v1/routes.py
index 14c1636..a9a40d4 100644
--- a/src/govoplan_tenancy/backend/api/v1/routes.py
+++ b/src/govoplan_tenancy/backend/api/v1/routes.py
@@ -18,6 +18,7 @@ from govoplan_core.core.access import (
     TenantContextSwitcher,
 )
 from govoplan_core.core.change_sequence import ChangeSequenceEntry, decode_sequence_watermark, encode_sequence_watermark, record_change, sequence_watermark_is_expired
+from govoplan_core.core.module_entitlements import MODULE_ENTITLEMENTS_KEY
 from govoplan_core.core.principal_cache import invalidate_auth_principals
 from govoplan_core.core.runtime import get_registry
 from govoplan_core.db.session import get_session
@@ -667,7 +668,14 @@ def _apply_tenant_content_updates(tenant: Tenant, payload: TenantUpdateRequest)
     if payload.default_locale is not None:
         tenant.default_locale = _normalized_tenant_locale(payload.default_locale)
     if payload.settings is not None:
-        tenant.settings = payload.settings
+        current_settings = dict(tenant.settings or {})
+        next_settings = dict(payload.settings)
+        next_settings.pop(MODULE_ENTITLEMENTS_KEY, None)
+        if MODULE_ENTITLEMENTS_KEY in current_settings:
+            next_settings[MODULE_ENTITLEMENTS_KEY] = current_settings[
+                MODULE_ENTITLEMENTS_KEY
+            ]
+        tenant.settings = next_settings
 
 
 def _normalized_optional_text(value: str | None) -> str | None:
diff --git a/src/govoplan_tenancy/backend/manifest.py b/src/govoplan_tenancy/backend/manifest.py
index 7ab3261..781b11e 100644
--- a/src/govoplan_tenancy/backend/manifest.py
+++ b/src/govoplan_tenancy/backend/manifest.py
@@ -60,7 +60,7 @@ manifest = ModuleManifest(
             id="tenancy.lifecycle-and-settings",
             title="Administer tenant lifecycle and settings",
             summary="Tenancy adds explicit tenant creation, activation, context resolution, and tenant-owned settings over Core's shared scope storage.",
-            body="A tenant is a concrete administrative and data boundary. Tenant lifecycle changes must preserve ownership and recovery guarantees for module-owned records. Tenancy contributes system tenant management and tenant settings to the shared administration workspace; without this module, the Core and Access baseline can operate in single-scope compatibility mode.",
+            body="A tenant is a concrete administrative and data boundary. Tenant lifecycle changes must preserve ownership and recovery guarantees for module-owned records. Tenancy contributes system tenant management and tenant settings to the shared administration workspace; without this module, the Core and Access baseline can operate in single-scope compatibility mode. Core-reserved module entitlement settings are managed only through the Admin module's tenant-module policy endpoints and are preserved when generic tenant settings are replaced.",
             documentation_types=("admin",),
             audience=("system_admin", "tenant_admin", "operator"),
             related_modules=("access", "admin", "audit"),
diff --git a/tests/test_tenant_lifecycle.py b/tests/test_tenant_lifecycle.py
index 0dbba93..4565de6 100644
--- a/tests/test_tenant_lifecycle.py
+++ b/tests/test_tenant_lifecycle.py
@@ -12,6 +12,7 @@ from govoplan_tenancy.backend.api.v1.routes import (
     _require_tenant_update_permissions,
 )
 from govoplan_tenancy.backend.api.v1.schemas import TenantUpdateRequest
+from govoplan_core.core.module_entitlements import MODULE_ENTITLEMENTS_KEY
 from govoplan_tenancy.backend.lifecycle import (
     TENANT_EVENT_CREATED,
     TENANT_EVENT_DELETION_REQUESTED,
@@ -121,6 +122,26 @@ class TenantUpdateHelperTests(unittest.TestCase):
         self.assertEqual("en", tenant.default_locale)
         self.assertEqual({"theme": "contrast"}, tenant.settings)
 
+    def test_tenant_content_update_preserves_reserved_module_entitlements(self) -> None:
+        entitlement = {"schema_version": 1, "revision": 4}
+        tenant = SimpleNamespace(
+            name="Old",
+            description=None,
+            default_locale="en",
+            settings={MODULE_ENTITLEMENTS_KEY: entitlement, "theme": "old"},
+        )
+        payload = TenantUpdateRequest(
+            settings={
+                "theme": "contrast",
+                MODULE_ENTITLEMENTS_KEY: {"revision": 999},
+            }
+        )
+
+        _apply_tenant_content_updates(tenant, payload)  # type: ignore[arg-type]
+
+        self.assertEqual("contrast", tenant.settings["theme"])
+        self.assertEqual(entitlement, tenant.settings[MODULE_ENTITLEMENTS_KEY])
+
     def test_tenant_status_update_prevents_suspending_current_tenant(self) -> None:
         tenant = SimpleNamespace(id="tenant-1", is_active=True)
         principal = FakePrincipal({"system:tenants:suspend"}, tenant_id="tenant-1")