diff --git a/binary-compatibility-validator/android/api/binary-compatibility-validator-android.api b/binary-compatibility-validator/android/api/binary-compatibility-validator-android.api
index c0d95ff5d..7b87b3490 100644
--- a/binary-compatibility-validator/android/api/binary-compatibility-validator-android.api
+++ b/binary-compatibility-validator/android/api/binary-compatibility-validator-android.api
@@ -5624,6 +5624,10 @@ public final class net/mamoe/mirai/utils/MiraiLoggerWithSwitch : net/mamoe/mirai
 	public fun warning0 (Ljava/lang/String;Ljava/lang/Throwable;)V
 }
 
+public abstract interface annotation class net/mamoe/mirai/utils/NotStableForInheritance : java/lang/annotation/Annotation {
+	public abstract fun message ()Ljava/lang/String;
+}
+
 public final class net/mamoe/mirai/utils/OverFileSizeMaxException : java/lang/IllegalStateException {
 	public fun <init> ()V
 }
diff --git a/binary-compatibility-validator/api/binary-compatibility-validator.api b/binary-compatibility-validator/api/binary-compatibility-validator.api
index 13ea6ff11..617212022 100644
--- a/binary-compatibility-validator/api/binary-compatibility-validator.api
+++ b/binary-compatibility-validator/api/binary-compatibility-validator.api
@@ -5624,6 +5624,10 @@ public final class net/mamoe/mirai/utils/MiraiLoggerWithSwitch : net/mamoe/mirai
 	public fun warning0 (Ljava/lang/String;Ljava/lang/Throwable;)V
 }
 
+public abstract interface annotation class net/mamoe/mirai/utils/NotStableForInheritance : java/lang/annotation/Annotation {
+	public abstract fun message ()Ljava/lang/String;
+}
+
 public final class net/mamoe/mirai/utils/OverFileSizeMaxException : java/lang/IllegalStateException {
 	public fun <init> ()V
 }
diff --git a/mirai-core-api/src/commonMain/kotlin/Bot.kt b/mirai-core-api/src/commonMain/kotlin/Bot.kt
index a544232e8..d6aecf7bb 100644
--- a/mirai-core-api/src/commonMain/kotlin/Bot.kt
+++ b/mirai-core-api/src/commonMain/kotlin/Bot.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("NOTHING_TO_INLINE")
@@ -22,6 +22,7 @@ import net.mamoe.mirai.message.action.MemberNudge
 import net.mamoe.mirai.network.LoginFailedException
 import net.mamoe.mirai.utils.BotConfiguration
 import net.mamoe.mirai.utils.MiraiLogger
+import net.mamoe.mirai.utils.NotStableForInheritance
 import java.util.concurrent.ConcurrentHashMap
 
 /**
@@ -41,6 +42,7 @@ public suspend inline fun <B : Bot> B.alsoLogin(): B = also { login() }
  *
  * @see BotFactory 构造 [Bot] 的工厂, [Bot] 唯一的构造方式.
  */
+@NotStableForInheritance
 public interface Bot : CoroutineScope, ContactOrBot, UserOrBot {
     /**
      * Bot 配置
diff --git a/mirai-core-api/src/commonMain/kotlin/IMirai.kt b/mirai-core-api/src/commonMain/kotlin/IMirai.kt
index 9688a397f..cd29fe42c 100644
--- a/mirai-core-api/src/commonMain/kotlin/IMirai.kt
+++ b/mirai-core-api/src/commonMain/kotlin/IMirai.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("INTERFACE_NOT_SUPPORTED", "PropertyName")
@@ -33,6 +33,7 @@ import net.mamoe.mirai.message.data.MessageSource.Key.recall
 import net.mamoe.mirai.utils.FileCacheStrategy
 import net.mamoe.mirai.utils.MiraiExperimentalApi
 import net.mamoe.mirai.utils.MiraiInternalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * [IMirai] 实例.
@@ -75,6 +76,7 @@ public val Mirai: IMirai
  *
  * @see Mirai 获取实例
  */
+@NotStableForInheritance
 public interface IMirai : LowLevelApiAccessor {
     /**
      * 请优先使用 [BotFactory.INSTANCE]
diff --git a/mirai-core-api/src/commonMain/kotlin/LowLevelApiAccessor.kt b/mirai-core-api/src/commonMain/kotlin/LowLevelApiAccessor.kt
index 1cc3bff8c..dd325bdd7 100644
--- a/mirai-core-api/src/commonMain/kotlin/LowLevelApiAccessor.kt
+++ b/mirai-core-api/src/commonMain/kotlin/LowLevelApiAccessor.kt
@@ -16,10 +16,7 @@ import net.mamoe.kjbb.JvmBlockingBridge
 import net.mamoe.mirai.contact.*
 import net.mamoe.mirai.data.*
 import net.mamoe.mirai.message.data.Voice
-import net.mamoe.mirai.utils.ExternalResource
-import net.mamoe.mirai.utils.MiraiExperimentalApi
-import net.mamoe.mirai.utils.MiraiInternalApi
-import net.mamoe.mirai.utils.WeakRef
+import net.mamoe.mirai.utils.*
 import kotlin.annotation.AnnotationTarget.*
 
 /**
@@ -41,6 +38,7 @@ public annotation class LowLevelApi
  * **警告**: 所有的低级 API 都可能在任意时刻不经过任何警告和迭代就被修改. 因此非常不建议在任何情况下使用这些 API.
  */
 @LowLevelApi
+@NotStableForInheritance
 public interface LowLevelApiAccessor {
     /**
      * 主动刷新 keys, 如 SKey, PSKey 等.
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/AnonymousMember.kt b/mirai-core-api/src/commonMain/kotlin/contact/AnonymousMember.kt
index 4a3530631..1ea417f17 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/AnonymousMember.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/AnonymousMember.kt
@@ -7,19 +7,22 @@
  * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
+@file:Suppress("DeprecatedCallableAddReplaceWith")
+
 package net.mamoe.mirai.contact
 
 import net.mamoe.mirai.message.action.MemberNudge
 import net.mamoe.mirai.message.data.Image
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.utils.ExternalResource
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 匿名
  *
  * 代表匿名群成员
  */
-@Suppress("DeprecatedCallableAddReplaceWith")
+@NotStableForInheritance
 public interface AnonymousMember : Member {
     /** 该匿名群成员 ID */
     public val anonymousId: String
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/Contact.kt b/mirai-core-api/src/commonMain/kotlin/contact/Contact.kt
index 20b06664f..7e0e87e55 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/Contact.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/Contact.kt
@@ -1,23 +1,27 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("EXPERIMENTAL_API_USAGE", "NOTHING_TO_INLINE", "EXPERIMENTAL_OVERRIDE")
 @file:OptIn(JavaFriendlyAPI::class)
+@file:JvmBlockingBridge
 
 package net.mamoe.mirai.contact
 
 import kotlinx.coroutines.CoroutineScope
 import net.mamoe.kjbb.JvmBlockingBridge
-import net.mamoe.mirai.*
+import net.mamoe.mirai.Bot
+import net.mamoe.mirai.IMirai
+import net.mamoe.mirai.Mirai
 import net.mamoe.mirai.event.events.*
 import net.mamoe.mirai.message.MessageReceipt
 import net.mamoe.mirai.message.data.*
+import net.mamoe.mirai.recallMessage
 import net.mamoe.mirai.utils.*
 import net.mamoe.mirai.utils.ExternalResource.Companion.sendAsImageTo
 import net.mamoe.mirai.utils.ExternalResource.Companion.uploadAsImage
@@ -27,7 +31,7 @@ import java.io.InputStream
 /**
  * 联系对象, 即可以与 [Bot] 互动的对象. 包含 [用户][User], 和 [群][Group].
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public interface Contact : ContactOrBot, CoroutineScope {
     /**
      * 这个联系对象所属 [Bot].
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/ContactOrBot.kt b/mirai-core-api/src/commonMain/kotlin/contact/ContactOrBot.kt
index e568bb624..4f3e1d2ab 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/ContactOrBot.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/ContactOrBot.kt
@@ -1,16 +1,17 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 package net.mamoe.mirai.contact
 
 import kotlinx.coroutines.CoroutineScope
 import net.mamoe.mirai.Bot
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 拥有 [id] 的对象.
@@ -21,6 +22,7 @@ import net.mamoe.mirai.Bot
  * @see Contact
  * @see Bot
  */
+@NotStableForInheritance
 public interface ContactOrBot : CoroutineScope {
     /**
      * QQ 号或群号.
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/FileSupported.kt b/mirai-core-api/src/commonMain/kotlin/contact/FileSupported.kt
index bfe386726..467c3953d 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/FileSupported.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/FileSupported.kt
@@ -1,15 +1,16 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 
 package net.mamoe.mirai.contact
 
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.RemoteFile
 
 /**
@@ -19,6 +20,7 @@ import net.mamoe.mirai.utils.RemoteFile
  *
  * @since 2.5
  */
+@NotStableForInheritance
 public interface FileSupported : Contact {
     /**
      * 文件根目录. 可通过 [RemoteFile.listFiles] 获取目录下文件列表.
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/Friend.kt b/mirai-core-api/src/commonMain/kotlin/contact/Friend.kt
index 6c30a132b..e387f6bcf 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/Friend.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/Friend.kt
@@ -8,6 +8,7 @@
  */
 
 @file:Suppress("EXPERIMENTAL_API_USAGE", "unused", "UnusedImport")
+@file:JvmBlockingBridge
 
 package net.mamoe.mirai.contact
 
@@ -21,6 +22,7 @@ import net.mamoe.mirai.message.action.Nudge
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.message.data.isContentEmpty
 import net.mamoe.mirai.message.data.toPlainText
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 代表一位好友.
@@ -31,7 +33,7 @@ import net.mamoe.mirai.message.data.toPlainText
  *
  * @see FriendMessageEvent
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public interface Friend : User, CoroutineScope, VoiceSupported {
     /**
      * QQ 号码
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/Group.kt b/mirai-core-api/src/commonMain/kotlin/contact/Group.kt
index 58f9f58e7..ef699125e 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/Group.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/Group.kt
@@ -1,13 +1,14 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("EXPERIMENTAL_API_USAGE", "unused", "UnusedImport", "NOTHING_TO_INLINE")
+@file:JvmBlockingBridge
 
 package net.mamoe.mirai.contact
 
@@ -23,15 +24,13 @@ import net.mamoe.mirai.data.covertToGroupAnnouncement
 import net.mamoe.mirai.event.events.*
 import net.mamoe.mirai.message.MessageReceipt
 import net.mamoe.mirai.message.data.*
-import net.mamoe.mirai.utils.ExternalResource
-import net.mamoe.mirai.utils.ExternalResource.Companion.uploadAsVoice
 import net.mamoe.mirai.utils.MiraiExperimentalApi
-import net.mamoe.mirai.utils.OverFileSizeMaxException
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 群.
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public interface Group : Contact, CoroutineScope, FileSupported, VoiceSupported {
     /**
      * 群名称.
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/Member.kt b/mirai-core-api/src/commonMain/kotlin/contact/Member.kt
index 7e6b5bdf2..ba957cdf1 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/Member.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/Member.kt
@@ -1,13 +1,14 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("unused", "UnusedImport")
+@file:JvmBlockingBridge
 
 package net.mamoe.mirai.contact
 
@@ -19,6 +20,7 @@ import net.mamoe.mirai.message.action.MemberNudge
 import net.mamoe.mirai.message.action.Nudge
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.message.data.isContentEmpty
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.WeakRefProperty
 
 /**
@@ -34,7 +36,7 @@ import net.mamoe.mirai.utils.WeakRefProperty
  * - [Member.asFriend] 转换为 [Friend]
  * - [Member.asStranger] 转换为 [Stranger]
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public interface Member : User {
     /**
      * 所在的群.
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/NormalMember.kt b/mirai-core-api/src/commonMain/kotlin/contact/NormalMember.kt
index f166ec59a..92e2e9dd2 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/NormalMember.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/NormalMember.kt
@@ -1,12 +1,14 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
+@file:JvmBlockingBridge
+
 package net.mamoe.mirai.contact
 
 import net.mamoe.kjbb.JvmBlockingBridge
@@ -18,6 +20,7 @@ import net.mamoe.mirai.message.action.Nudge
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.message.data.isContentEmpty
 import net.mamoe.mirai.message.data.toPlainText
+import net.mamoe.mirai.utils.NotStableForInheritance
 import kotlin.time.Duration
 import kotlin.time.DurationUnit
 import kotlin.time.ExperimentalTime
@@ -28,7 +31,7 @@ import kotlin.time.ExperimentalTime
  * 群成员可能也是好友, 但他们在对象类型上不同.
  * 群成员可以通过 [asFriend] 得到相关好友对象.
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public interface NormalMember : Member {
     /**
      * 群名片. 可能为空.
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt b/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt
index ff6123018..20fde162c 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("unused")
@@ -20,11 +20,13 @@ import net.mamoe.mirai.utils.BotConfiguration.MiraiProtocol.ANDROID_PAD
 import net.mamoe.mirai.utils.BotConfiguration.MiraiProtocol.ANDROID_PHONE
 import net.mamoe.mirai.utils.ExternalResource
 import net.mamoe.mirai.utils.MiraiInternalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.toLongUnsigned
 
 /**
  * 其他设备. 如当 [Bot] 以 [ANDROID_PHONE] 登录时, 还可以有其他设备以 [ANDROID_PAD], iOS, PC 或其他设备登录.
  */
+@NotStableForInheritance
 public interface OtherClient : Contact {
     public val info: OtherClientInfo
 
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/Stranger.kt b/mirai-core-api/src/commonMain/kotlin/contact/Stranger.kt
index ed18af9a8..8494947a3 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/Stranger.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/Stranger.kt
@@ -1,13 +1,14 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("EXPERIMENTAL_API_USAGE", "unused", "UnusedImport")
+@file:JvmBlockingBridge
 
 package net.mamoe.mirai.contact
 
@@ -21,6 +22,7 @@ import net.mamoe.mirai.message.action.StrangerNudge
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.message.data.isContentEmpty
 import net.mamoe.mirai.message.data.toPlainText
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 代表一位陌生人.
@@ -39,7 +41,7 @@ import net.mamoe.mirai.message.data.toPlainText
  *
  * @see StrangerMessageEvent
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public interface Stranger : User, CoroutineScope {
     /**
      * QQ 号码
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/TempUser.kt b/mirai-core-api/src/commonMain/kotlin/contact/TempUser.kt
index b278434de..cccb036fe 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/TempUser.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/TempUser.kt
@@ -10,6 +10,7 @@
 package net.mamoe.mirai.contact
 
 import net.mamoe.mirai.utils.MiraiInternalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 临时会话用户, 非群成员.
@@ -17,4 +18,5 @@ import net.mamoe.mirai.utils.MiraiInternalApi
  * [#429](https://github.com/mamoe/mirai/issues/429)
  */
 @MiraiInternalApi("其他渠道的临时会话暂未支持. ")
+@NotStableForInheritance
 public interface TempUser : User
\ No newline at end of file
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/User.kt b/mirai-core-api/src/commonMain/kotlin/contact/User.kt
index a9ddde4ac..8de9b4a6a 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/User.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/User.kt
@@ -1,13 +1,14 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("EXPERIMENTAL_API_USAGE", "unused")
+@file:JvmBlockingBridge
 
 package net.mamoe.mirai.contact
 
@@ -25,6 +26,7 @@ import net.mamoe.mirai.message.action.UserNudge
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.message.data.isContentEmpty
 import net.mamoe.mirai.message.data.toPlainText
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 代表一个 **用户**.
@@ -36,7 +38,7 @@ import net.mamoe.mirai.message.data.toPlainText
  *
  * 对于同一个 [Bot] 任何一个人的 [User] 实例都是单一的.
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public interface User : Contact, UserOrBot, CoroutineScope {
     /**
      * QQ 号码
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/UserOrBot.kt b/mirai-core-api/src/commonMain/kotlin/contact/UserOrBot.kt
index a4fe53641..576856800 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/UserOrBot.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/UserOrBot.kt
@@ -1,16 +1,17 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 package net.mamoe.mirai.contact
 
 import net.mamoe.mirai.Bot
 import net.mamoe.mirai.message.action.Nudge
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * @see User
@@ -18,6 +19,7 @@ import net.mamoe.mirai.message.action.Nudge
  *
  * @see ContactOrBot
  */
+@NotStableForInheritance
 public interface UserOrBot : ContactOrBot {
     /**
      * 昵称
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/VoiceSupported.kt b/mirai-core-api/src/commonMain/kotlin/contact/VoiceSupported.kt
index 54cf615ff..5db799a70 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/VoiceSupported.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/VoiceSupported.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 package net.mamoe.mirai.contact
@@ -13,6 +13,7 @@ import net.mamoe.kjbb.JvmBlockingBridge
 import net.mamoe.mirai.message.data.Voice
 import net.mamoe.mirai.utils.ExternalResource
 import net.mamoe.mirai.utils.ExternalResource.Companion.uploadAsVoice
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.OverFileSizeMaxException
 
 /**
@@ -20,6 +21,7 @@ import net.mamoe.mirai.utils.OverFileSizeMaxException
  *
  * @since 2.7
  */
+@NotStableForInheritance
 public interface VoiceSupported : Contact {
     /**
      * 上传一个语音消息以备发送.
diff --git a/mirai-core-api/src/commonMain/kotlin/event/Listener.kt b/mirai-core-api/src/commonMain/kotlin/event/Listener.kt
index e01cb2a0a..87b836f7d 100644
--- a/mirai-core-api/src/commonMain/kotlin/event/Listener.kt
+++ b/mirai-core-api/src/commonMain/kotlin/event/Listener.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("unused", "DEPRECATION", "INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
@@ -16,6 +16,7 @@ package net.mamoe.mirai.event
 import kotlinx.coroutines.CompletableJob
 import kotlinx.coroutines.sync.Mutex
 import net.mamoe.mirai.event.EventPriority.*
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 订阅者的状态
@@ -43,6 +44,7 @@ public enum class ListeningStatus {
  *
  * 取消监听: [complete]
  */
+@NotStableForInheritance
 public interface Listener<in E : Event> : CompletableJob {
 
     // Impl notes:
diff --git a/mirai-core-api/src/commonMain/kotlin/message/MessageReceipt.kt b/mirai-core-api/src/commonMain/kotlin/message/MessageReceipt.kt
index d7ac48b33..311738ef3 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/MessageReceipt.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/MessageReceipt.kt
@@ -1,13 +1,14 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("NOTHING_TO_INLINE", "FunctionName", "unused")
+@file:JvmBlockingBridge
 
 package net.mamoe.mirai.message
 
@@ -21,6 +22,7 @@ import net.mamoe.mirai.message.data.*
 import net.mamoe.mirai.message.data.MessageSource.Key.quote
 import net.mamoe.mirai.message.data.MessageSource.Key.recallIn
 import net.mamoe.mirai.utils.MiraiInternalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 /**
  * 发送消息后得到的回执. 可用于撤回, 引用回复等.
@@ -39,7 +41,7 @@ import net.mamoe.mirai.utils.MiraiInternalApi
  * @see MessageReceipt.sourceIds 源 ids
  * @see MessageReceipt.sourceTime 源时间
  */
-@JvmBlockingBridge
+@NotStableForInheritance
 public open class MessageReceipt<out C : Contact>
 @MiraiInternalApi
 @Deprecated("Do not call it directly", level = DeprecationLevel.ERROR)
diff --git a/mirai-core-api/src/commonMain/kotlin/message/MessageSerializers.kt b/mirai-core-api/src/commonMain/kotlin/message/MessageSerializers.kt
index 9b715e6a4..29423fcf9 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/MessageSerializers.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/MessageSerializers.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 package net.mamoe.mirai.message
@@ -22,6 +22,7 @@ import net.mamoe.mirai.message.data.MessageChain
 import net.mamoe.mirai.message.data.MessageChain.Companion.serializeToJsonString
 import net.mamoe.mirai.message.data.SingleMessage
 import net.mamoe.mirai.utils.MiraiExperimentalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 import kotlin.reflect.KClass
 
 /**
@@ -38,6 +39,7 @@ import kotlin.reflect.KClass
  *
  * @see MessageSerializers.INSTANCE
  */
+@NotStableForInheritance
 public interface MessageSerializers {
     /**
      * 包含 [SingleMessage] 多态序列化和 [Message] [ContextualSerializer] 信息的 [SerializersModule].
diff --git a/mirai-core-api/src/commonMain/kotlin/message/code/CodableMessage.kt b/mirai-core-api/src/commonMain/kotlin/message/code/CodableMessage.kt
index f355f598d..eb0625dea 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/code/CodableMessage.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/code/CodableMessage.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 package net.mamoe.mirai.message.code
@@ -12,6 +12,7 @@ package net.mamoe.mirai.message.code
 import net.mamoe.mirai.message.code.MiraiCode.deserializeMiraiCode
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.utils.MiraiExperimentalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 
 
 /**
@@ -19,8 +20,12 @@ import net.mamoe.mirai.utils.MiraiExperimentalApi
  *
  * 从字符串解析 mirai 码：[MiraiCode.deserializeMiraiCode]
  *
+ * ### 不适合第三方实现
+ * 即使自定义消息类型实现了接口 [CodableMessage], 在 [MiraiCode.deserializeMiraiCode] 时也无法解析消息类型. 因此实现没有意义.
+ *
  * @see MiraiCode
  */
+@NotStableForInheritance
 public interface CodableMessage : Message {
     /**
      * 转换为 mirai 码.
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/FileMessage.kt b/mirai-core-api/src/commonMain/kotlin/message/data/FileMessage.kt
index cbc4ed78f..500305b65 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/FileMessage.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/FileMessage.kt
@@ -39,6 +39,7 @@ import net.mamoe.mirai.utils.*
  */
 @Serializable(FileMessage.Serializer::class)
 @SerialName(FileMessage.SERIAL_NAME)
+@NotStableForInheritance
 public interface FileMessage : MessageContent, ConstrainSingle, CodableMessage {
     /**
      * 服务器需要的某种 ID.
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/HummerMessage.kt b/mirai-core-api/src/commonMain/kotlin/message/data/HummerMessage.kt
index 3ec5f5b9f..bd76a4c1e 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/HummerMessage.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/HummerMessage.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("unused", "NOTHING_TO_INLINE")
@@ -14,6 +14,7 @@
 package net.mamoe.mirai.message.data
 
 import net.mamoe.mirai.utils.MiraiExperimentalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.castOrNull
 
 /**
@@ -27,6 +28,7 @@ import net.mamoe.mirai.utils.castOrNull
  * @see VipFace VIP 表情
  */
 @MiraiExperimentalApi
+@NotStableForInheritance
 public interface HummerMessage : MessageContent, ConstrainSingle {
     public companion object Key :
         AbstractPolymorphicMessageKey<MessageContent, HummerMessage>(MessageContent, { it.castOrNull() })
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/Image.kt b/mirai-core-api/src/commonMain/kotlin/message/data/Image.kt
index 47c050142..4977aecc5 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/Image.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/Image.kt
@@ -70,6 +70,7 @@ import kotlin.LazyThreadSafetyMode.NONE
  * @see Image.flash 转换普通图片为闪照
  */
 @Serializable(Image.Serializer::class)
+@NotStableForInheritance
 public interface Image : Message, MessageContent, CodableMessage {
 
     /**
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/MarketFace.kt b/mirai-core-api/src/commonMain/kotlin/message/data/MarketFace.kt
index 4eb9a3fb4..e1bfa808e 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/MarketFace.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/MarketFace.kt
@@ -1,15 +1,16 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 package net.mamoe.mirai.message.data
 
 import net.mamoe.mirai.utils.MiraiExperimentalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.safeCast
 
 /**
@@ -19,6 +20,7 @@ import net.mamoe.mirai.utils.safeCast
  *
  * @see Dice
  */
+@NotStableForInheritance
 public interface MarketFace : HummerMessage {
     /**
      * 如 `[开心]`
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/MessageChain.kt b/mirai-core-api/src/commonMain/kotlin/message/data/MessageChain.kt
index b32e7a4c4..af4cc731d 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/MessageChain.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/MessageChain.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:JvmMultifileClass
@@ -33,6 +33,7 @@ import net.mamoe.mirai.message.data.MessageSource.Key.quote
 import net.mamoe.mirai.message.data.MessageSource.Key.recall
 import net.mamoe.mirai.message.data.MessageSource.Key.recallIn
 import net.mamoe.mirai.utils.MiraiExperimentalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.safeCast
 import java.util.stream.Stream
 import kotlin.reflect.KProperty
@@ -184,6 +185,7 @@ import kotlin.streams.asSequence
  *
  */
 @Serializable(MessageChain.Serializer::class)
+@NotStableForInheritance
 public sealed interface MessageChain :
     Message, List<SingleMessage>, RandomAccess, CodableMessage {
 
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/MessageSource.kt b/mirai-core-api/src/commonMain/kotlin/message/data/MessageSource.kt
index 3ecefe977..d5516de9f 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/MessageSource.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/MessageSource.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:JvmMultifileClass
@@ -30,6 +30,7 @@ import net.mamoe.mirai.message.data.MessageSource.Key.quote
 import net.mamoe.mirai.message.data.MessageSource.Key.recall
 import net.mamoe.mirai.utils.LazyProperty
 import net.mamoe.mirai.utils.MiraiInternalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.safeCast
 
 /**
@@ -474,6 +475,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
         public final override val fromId: Long get() = sender.id
         public final override val targetId: Long get() = target.id
 
+        @NotStableForInheritance
         public abstract class ToFriend @MiraiInternalApi constructor() : Outgoing() {
             public companion object Key : AbstractPolymorphicMessageKey<Outgoing, ToFriend>(Outgoing, { it.safeCast() })
 
@@ -482,6 +484,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
             //  final override fun toString(): String = "OnlineMessageSource.ToFriend(target=${target.ids})"
         }
 
+        @NotStableForInheritance
         public abstract class ToStranger @MiraiInternalApi constructor() : Outgoing() {
             public companion object Key :
                 AbstractPolymorphicMessageKey<Outgoing, ToStranger>(Outgoing, { it.safeCast() })
@@ -491,6 +494,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
             //  final override fun toString(): String = "OnlineMessageSource.ToFriend(target=${target.ids})"
         }
 
+        @NotStableForInheritance
         public abstract class ToTemp @MiraiInternalApi constructor() : Outgoing() {
             public companion object Key : AbstractPolymorphicMessageKey<Outgoing, ToTemp>(Outgoing, { it.safeCast() })
 
@@ -499,6 +503,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
             public final override val subject: Member get() = target
         }
 
+        @NotStableForInheritance
         public abstract class ToGroup @MiraiInternalApi constructor() : Outgoing() {
             public companion object Key : AbstractPolymorphicMessageKey<Outgoing, ToGroup>(Outgoing, { it.safeCast() })
 
@@ -516,6 +521,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
         public final override val fromId: Long get() = sender.id
         public final override val targetId: Long get() = target.id
 
+        @NotStableForInheritance
         public abstract class FromFriend @MiraiInternalApi constructor() : Incoming() {
             public companion object Key :
                 AbstractPolymorphicMessageKey<Incoming, FromFriend>(Incoming, { it.safeCast() })
@@ -526,6 +532,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
             // final override fun toString(): String = "OnlineMessageSource.FromFriend(from=${sender.ids})"
         }
 
+        @NotStableForInheritance
         public abstract class FromTemp @MiraiInternalApi constructor() : Incoming() {
             public companion object Key :
                 AbstractPolymorphicMessageKey<Incoming, FromTemp>(Incoming, { it.safeCast() })
@@ -536,6 +543,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
             public final override val target: Bot get() = sender.bot
         }
 
+        @NotStableForInheritance
         public abstract class FromStranger @MiraiInternalApi constructor() : Incoming() {
             public companion object Key :
                 AbstractPolymorphicMessageKey<Incoming, FromStranger>(Incoming, { it.safeCast() })
@@ -545,6 +553,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
             public final override val target: Bot get() = sender.bot
         }
 
+        @NotStableForInheritance
         public abstract class FromGroup @MiraiInternalApi constructor() : Incoming() {
             public companion object Key :
                 AbstractPolymorphicMessageKey<Incoming, FromGroup>(Incoming, { it.safeCast() })
@@ -567,6 +576,7 @@ public sealed class OnlineMessageSource : MessageSource() { // TODO: 2021/1/10 E
  *
  * 要获得 [OfflineMessageSource], 使用 [MessageSourceBuilder]. 或通过 [OnlineMessageSource.toOffline] 转换得到 (一般没有必要).
  */
+@NotStableForInheritance
 public abstract class OfflineMessageSource : MessageSource() { // TODO: 2021/1/10 Extract to separate file in Kotlin 1.5
     public companion object Key :
         AbstractPolymorphicMessageKey<MessageSource, OfflineMessageSource>(MessageSource, { it.safeCast() })
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/RichMessage.kt b/mirai-core-api/src/commonMain/kotlin/message/data/RichMessage.kt
index 8496f2d4e..3c5b119a8 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/RichMessage.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/RichMessage.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:JvmName("MessageUtils")
@@ -18,6 +18,7 @@ import kotlinx.serialization.Serializable
 import net.mamoe.mirai.message.code.CodableMessage
 import net.mamoe.mirai.message.code.internal.appendStringAsMiraiCode
 import net.mamoe.mirai.utils.MiraiExperimentalApi
+import net.mamoe.mirai.utils.NotStableForInheritance
 import net.mamoe.mirai.utils.safeCast
 import kotlin.annotation.AnnotationTarget.*
 
@@ -33,6 +34,7 @@ import kotlin.annotation.AnnotationTarget.*
  */
 // not using sealed class for customized implementations
 // using polymorphic serializer from Message.Serializer
+@NotStableForInheritance
 public interface RichMessage : MessageContent, ConstrainSingle {
     override val key: MessageKey<RichMessage> get() = Key
 
@@ -164,6 +166,7 @@ public class SimpleServiceMessage(
  * @see LightApp 小程序类型消息
  * @see SimpleServiceMessage
  */
+@NotStableForInheritance
 public interface ServiceMessage : RichMessage, CodableMessage {
     public companion object Key :
         AbstractPolymorphicMessageKey<RichMessage, ServiceMessage>(RichMessage, { it.safeCast() })
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/UnsupportedMessage.kt b/mirai-core-api/src/commonMain/kotlin/message/data/UnsupportedMessage.kt
index 11f63c0b0..f5ee48b6a 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/UnsupportedMessage.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/UnsupportedMessage.kt
@@ -19,10 +19,7 @@ import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 import net.mamoe.mirai.IMirai
 import net.mamoe.mirai.Mirai
-import net.mamoe.mirai.utils.chunkedHexToBytes
-import net.mamoe.mirai.utils.copy
-import net.mamoe.mirai.utils.map
-import net.mamoe.mirai.utils.toUHexString
+import net.mamoe.mirai.utils.*
 
 /**
  * mirai 尚未支持的消息类型.
@@ -32,6 +29,7 @@ import net.mamoe.mirai.utils.toUHexString
  */
 @SerialName(UnsupportedMessage.SERIAL_NAME)
 @Serializable(UnsupportedMessage.Serializer::class)
+@NotStableForInheritance
 public interface UnsupportedMessage : MessageContent {
     override fun contentToString(): String =
         "[不支持的消息#${struct.contentHashCode()}]" // to produce 'stable' and reliable text
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/Voice.kt b/mirai-core-api/src/commonMain/kotlin/message/data/Voice.kt
index 563e5bcf8..063fdc561 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/Voice.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/Voice.kt
@@ -26,6 +26,7 @@ import net.mamoe.mirai.utils.ExternalResource.Companion.uploadAsVoice
  */
 @Serializable
 @MiraiExperimentalApi
+@NotStableForInheritance
 public abstract class PttMessage : MessageContent {
 
     public companion object Key :
diff --git a/mirai-core-api/src/commonMain/kotlin/utils/Annotations.kt b/mirai-core-api/src/commonMain/kotlin/utils/Annotations.kt
index 5187ad6ca..f9e1751f1 100644
--- a/mirai-core-api/src/commonMain/kotlin/utils/Annotations.kt
+++ b/mirai-core-api/src/commonMain/kotlin/utils/Annotations.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 package net.mamoe.mirai.utils
@@ -53,6 +53,20 @@ public annotation class MiraiExperimentalApi(
     public val message: String = ""
 )
 
+/**
+ * 标记一个定义在使用上是稳定的 (如果没有特殊说明), 但只应该由 mirai 内部实现.
+ *
+ * 用户自行实现将可能造成对未来版本的不兼容, 因为新的抽象函数或属性会在未经警告的前提下添加. 自行实现还可能因 mirai 内部实现有部分硬编码成分而不兼容.
+ *
+ * @since 2.7
+ */
+@Retention(AnnotationRetention.BINARY)
+@Target(CLASS, PROPERTY, FUNCTION)
+@MustBeDocumented
+public annotation class NotStableForInheritance(
+    public val message: String = "This declaration is not stable for inheritance."
+)
+
 /**
  * 标记一个正计划在 [version] 版本时删除 (对外隐藏) 的 API.
  */
diff --git a/mirai-core-api/src/commonMain/kotlin/utils/RemoteFile.kt b/mirai-core-api/src/commonMain/kotlin/utils/RemoteFile.kt
index 7c628d216..2c876d760 100644
--- a/mirai-core-api/src/commonMain/kotlin/utils/RemoteFile.kt
+++ b/mirai-core-api/src/commonMain/kotlin/utils/RemoteFile.kt
@@ -1,10 +1,10 @@
 /*
  * Copyright 2019-2021 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("unused")
@@ -97,6 +97,7 @@ import java.io.File
  * @see FileSupported
  * @since 2.5
  */
+@NotStableForInheritance
 public interface RemoteFile {
     /**
      * 文件名或目录名.