diff --git a/CHANGES.ja.md b/CHANGES.ja.md
index eafa5c428..fc1c127d7 100644
--- a/CHANGES.ja.md
+++ b/CHANGES.ja.md
@@ -1,6 +1,15 @@
 変更点
 ======
 
+4.46 ()
+--------------------------
+
+- `AuthorizationFailRequest.Reason` 列挙型
+  * `INVALID_SCOPE` を追加。
+  * `UNAUTHORIZED_CLIENT` を追加。
+  * `TEMPORARILY_UNAVAILABLE` を追加。
+
+
 4.45 (2026 年 05 月 18 日)
 --------------------------
 
diff --git a/CHANGES.md b/CHANGES.md
index f083fa094..6b984af65 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,6 +1,15 @@
 CHANGES
 =======
 
+4.46 ()
+-----------------
+
+- `AuthorizationFailRequest.Reason` enum
+  * Added `INVALID_SCOPE`
+  * Added `UNAUTHORIZED_CLIENT`
+  * Added `TEMPORARILY_UNAVAILABLE`
+
+
 4.45 (2026-05-18)
 -----------------
 
diff --git a/src/main/java/com/authlete/common/dto/AuthorizationFailRequest.java b/src/main/java/com/authlete/common/dto/AuthorizationFailRequest.java
index 4a690ba4a..1645428cb 100644
--- a/src/main/java/com/authlete/common/dto/AuthorizationFailRequest.java
+++ b/src/main/java/com/authlete/common/dto/AuthorizationFailRequest.java
@@ -261,6 +261,38 @@ public enum Reason
          * @since 2.62
          */
         INVALID_TARGET,
+
+        /**
+         * The requested scope is invalid.
+         *
+         * <p>
+         * Using this reason will result in {@code error=invalid_scope}.
+         * </p>
+         *
+         * @since 3.0.33
+         */
+        INVALID_SCOPE,
+
+        /**
+         * The client is not authorized to perform the requested operation.
+         *
+         * <p>
+         *  Using this reason will result in {@code error=unauthorized_client}.
+         * </p>
+         * @since 3.0.33
+         */
+        UNAUTHORIZED_CLIENT,
+
+        /**
+         * The requested operation is temporarily unavailable and cannot be performed at this time.
+         *
+         * <p>
+         *  Using this reason will result in {@code error=temporarily_unavailable}.
+         * </p>
+         *
+         * @since 3.0.33
+         */
+        TEMPORARILY_UNAVAILABLE,
     }