diff --git a/script/hassfest/model.py b/script/hassfest/model.py
index 6b500daa9b3..fa1580b0317 100644
--- a/script/hassfest/model.py
+++ b/script/hassfest/model.py
@@ -55,7 +55,13 @@ class Brand:
         return brands
 
     path: pathlib.Path = attr.ib()
-    brand: dict[str, Any] | None = attr.ib(default=None)
+    _brand: dict[str, Any] | None = attr.ib(default=None)
+
+    @property
+    def brand(self) -> dict[str, Any]:
+        """Guarded access to brand."""
+        assert self._brand is not None, "brand has not been loaded"
+        return self._brand
 
     @property
     def domain(self) -> str:
@@ -65,19 +71,16 @@ class Brand:
     @property
     def name(self) -> str | None:
         """Return name of the integration."""
-        assert self.brand is not None, "brand has not been loaded"
         return self.brand.get("name")
 
     @property
     def integrations(self) -> list[str]:
         """Return the sub integrations of this brand."""
-        assert self.brand is not None, "brand has not been loaded"
         return self.brand.get("integrations", [])
 
     @property
     def iot_standards(self) -> list[str]:
         """Return list of supported IoT standards."""
-        assert self.brand is not None, "brand has not been loaded"
         return self.brand.get("iot_standards", [])
 
     def load_brand(self, config: Config) -> None:
@@ -94,7 +97,7 @@ class Brand:
             )
             return
 
-        self.brand = brand
+        self._brand = brand
 
 
 @attr.s
@@ -127,11 +130,17 @@ class Integration:
         return integrations
 
     path: pathlib.Path = attr.ib()
-    manifest: dict[str, Any] | None = attr.ib(default=None)
+    _manifest: dict[str, Any] | None = attr.ib(default=None)
     errors: list[Error] = attr.ib(factory=list)
     warnings: list[Error] = attr.ib(factory=list)
     translated_name: bool = attr.ib(default=False)
 
+    @property
+    def manifest(self) -> dict[str, Any]:
+        """Guarded access to manifest."""
+        assert self._manifest is not None, "manifest has not been loaded"
+        return self._manifest
+
     @property
     def domain(self) -> str:
         """Integration domain."""
@@ -145,62 +154,52 @@ class Integration:
     @property
     def disabled(self) -> str | None:
         """Return if integration is disabled."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("disabled")
 
     @property
     def name(self) -> str:
         """Return name of the integration."""
-        assert self.manifest is not None, "manifest has not been loaded"
         name: str = self.manifest["name"]
         return name
 
     @property
     def quality_scale(self) -> str | None:
         """Return quality scale of the integration."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("quality_scale")
 
     @property
     def config_flow(self) -> bool:
         """Return if the integration has a config flow."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("config_flow", False)
 
     @property
     def requirements(self) -> list[str]:
         """List of requirements."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("requirements", [])
 
     @property
     def dependencies(self) -> list[str]:
         """List of dependencies."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("dependencies", [])
 
     @property
     def supported_by(self) -> str:
         """Return the integration supported by this virtual integration."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("supported_by", {})
 
     @property
     def integration_type(self) -> str:
         """Get integration_type."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("integration_type", "hub")
 
     @property
     def iot_class(self) -> str | None:
         """Return the integration IoT Class."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("iot_class")
 
     @property
     def iot_standards(self) -> list[str]:
         """Return the IoT standard supported by this virtual integration."""
-        assert self.manifest is not None, "manifest has not been loaded"
         return self.manifest.get("iot_standards", [])
 
     def add_error(self, *args: Any, **kwargs: Any) -> None:
@@ -224,4 +223,4 @@ class Integration:
             self.add_error("model", f"Manifest contains invalid JSON: {err}")
             return
 
-        self.manifest = manifest
+        self._manifest = manifest
diff --git a/tests/hassfest/test_version.py b/tests/hassfest/test_version.py
index 7f12fb83fd7..eee184404b8 100644
--- a/tests/hassfest/test_version.py
+++ b/tests/hassfest/test_version.py
@@ -13,7 +13,7 @@ from script.hassfest.model import Integration
 def integration():
     """Fixture for hassfest integration model."""
     integration = Integration("")
-    integration.manifest = {
+    integration._manifest = {
         "domain": "test",
         "documentation": "https://example.com",
         "name": "test",