diff --git a/README.md b/README.md
index ff1a250..e201830 100644
--- a/README.md
+++ b/README.md
@@ -268,7 +268,9 @@ try await StorageRouter.shared.forceMigration(for: StorageKey.modernToken)
 #### Automated Startup Sweep
 When registering a catalog, you can enable `migrateImmediately` to perform a global sweep of all legacy keys for every key in the catalog. 
 
-> [!NOTE]
+> [!IMPORTANT]
+> **Catalog Enforcement**: Once any catalog is registered, *all* storage operations require the key to be in a registered catalog. Any unregistered key will throw `StorageError.unregisteredKey`.
+>
 > **Modular Registration**: `registerCatalog` is additive. You can call it multiple times from different modules to build an aggregate registry. The library will throw an error if multiple catalogs attempt to register the same key name.
 
 ```swift
diff --git a/Sources/LocalData/Documentation.docc/GettingStarted.md b/Sources/LocalData/Documentation.docc/GettingStarted.md
index fae9d78..e5541ee 100644
--- a/Sources/LocalData/Documentation.docc/GettingStarted.md
+++ b/Sources/LocalData/Documentation.docc/GettingStarted.md
@@ -35,6 +35,10 @@ await StorageRouter.shared.updateStorageConfiguration(storageConfig)
 
 Catalogs are mandatory if you want auditing and duplicate detection.
 
+> [!IMPORTANT]
+> Once any catalog is registered, *all* storage operations require the key to be present in a registered catalog.
+> Unregistered keys will throw `StorageError.unregisteredKey`.
+
 ```swift
 struct AuthCatalog: StorageKeyCatalog {
     let allKeys: [AnyStorageKey] = [
diff --git a/Sources/LocalData/Documentation.docc/KeyAndCatalogDiscipline.md b/Sources/LocalData/Documentation.docc/KeyAndCatalogDiscipline.md
index f0e0c59..f473910 100644
--- a/Sources/LocalData/Documentation.docc/KeyAndCatalogDiscipline.md
+++ b/Sources/LocalData/Documentation.docc/KeyAndCatalogDiscipline.md
@@ -18,6 +18,10 @@ Catalog registration enforces correctness:
 - Duplicate key names across catalogs are rejected.
 - Unregistered keys throw ``StorageError/unregisteredKey(_:)`` at runtime.
 
+> [!IMPORTANT]
+> Once any catalog is registered, *all* storage operations require keys to be registered.
+> If you add a new module or feature, you must register its catalog before using its keys.
+
 If you skip catalog registration, LocalData cannot guarantee that all writes are auditable.
 
 ## Modular catalogs
diff --git a/Sources/LocalData/Services/StorageRouter.swift b/Sources/LocalData/Services/StorageRouter.swift
index 04817de..d6ceecc 100644
--- a/Sources/LocalData/Services/StorageRouter.swift
+++ b/Sources/LocalData/Services/StorageRouter.swift
@@ -89,7 +89,10 @@ public actor StorageRouter: StorageProviding {
     }
 
     /// Registers a catalog of known storage keys for audit and validation.
-    /// When registered, all storage operations will verify keys are listed.
+    ///
+    /// - Important: Once any catalog is registered, *all* storage operations require keys
+    ///   to be present in a registered catalog. Unregistered keys throw
+    ///   ``StorageError/unregisteredKey(_:)``.
     /// - Parameters:
     ///   - catalog: The catalog type to register.
     ///   - migrateImmediately: If true, triggers a proactive migration (sweep) for all keys in the catalog.