feat(toolkit): Add notification for AWS Core plugin no longer required

.changes/next-release/feature-38facbaf-0a30-40f0-9946-630c1248401f.json

@@ -0,0 +1,4 @@
+{
+  "type" : "feature",
+  "description" : "Removed dependency on the AWS Core plugin. AWS Toolkit no longer requires AWS Core to be installed."
+}

plugins/core/resources/resources/software/aws/toolkits/resources/MessagesBundle.properties

@@ -346,6 +346,9 @@ aws.toolkit.experimental.title=Experimental Features
 aws.toolkit_deprecation.message=Support for {0} {1} is being deprecated - an upcoming release will require a version based on {2} or newer.
 aws.toolkit_deprecation.message.gateway=Upgrade JetBrains Gateway to version {2} or newer to use the next release of the toolkit. Support for {0} {1} is being deprecated.
 aws.toolkit_deprecation.title=AWS Toolkit deprecation notice
+aws.toolkit_core_notice.title=AWS Core plugin is no longer required
+aws.toolkit_core_notice.message=Starting with AWS Toolkit 4.0, the AWS Core plugin is no longer needed and can be safely uninstalled.
+aws.toolkit_core_notice.manage_plugins=Manage Plugins
 aws_builder_id.service_name=AWS Builder ID
 aws_builder_id.sign_out=Sign out of AWS Builder ID
 aws_connection.credentials.label=Credentials:

plugins/toolkit/jetbrains-core/resources/META-INF/plugin.xml

@@ -370,6 +370,10 @@
         <!-- Min Version Notice -->
         <postStartupActivity implementation="software.aws.toolkits.jetbrains.core.notification.MinimumVersionChange"/>
         <notificationGroup id="aws.toolkit_deprecation" displayType="STICKY_BALLOON" key="aws.toolkit_deprecation.title"/>
+
+        <!-- AWS Core Plugin Notice -->
+        <postStartupActivity implementation="software.aws.toolkits.jetbrains.core.notification.AwsCorePluginNotice"/>
+        <notificationGroup id="aws.toolkit_core_notice" displayType="STICKY_BALLOON" key="aws.toolkit_core_notice.title"/>
         <notificationGroup id="aws.toolkit_telemetry" displayType="STICKY_BALLOON" key="aws.settings.telemetry.prompt.title"/>
 
 

plugins/toolkit/jetbrains-core/src/software/aws/toolkits/jetbrains/core/notification/AwsCorePluginNotice.kt

@@ -0,0 +1,54 @@
+// Copyright 2026 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package software.aws.toolkits.jetbrains.core.notification
+
+import com.intellij.ide.plugins.PluginManagerConfigurable
+import com.intellij.ide.plugins.PluginManagerCore
+import com.intellij.ide.util.PropertiesComponent
+import com.intellij.notification.NotificationAction
+import com.intellij.notification.NotificationGroupManager
+import com.intellij.notification.NotificationType
+import com.intellij.openapi.application.ApplicationManager
+import com.intellij.openapi.extensions.PluginId
+import com.intellij.openapi.options.ShowSettingsUtil
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.startup.ProjectActivity
+import software.aws.toolkits.resources.message
+
+class AwsCorePluginNotice : ProjectActivity {
+    override suspend fun execute(project: Project) {
+        if (ApplicationManager.getApplication().isUnitTestMode) return
+        if (PropertiesComponent.getInstance().getBoolean(IGNORE_PROMPT)) return
+        if (!PluginManagerCore.isPluginInstalled(PluginId.getId(CORE_PLUGIN_ID))) return
+
+        val notificationGroup = NotificationGroupManager.getInstance().getNotificationGroup("aws.toolkit_core_notice")
+        notificationGroup.createNotification(
+            message("aws.toolkit_core_notice.title"),
+            message("aws.toolkit_core_notice.message"),
+            NotificationType.INFORMATION
+        )
+            .addAction(
+                NotificationAction.createSimpleExpiring(message("aws.toolkit_core_notice.manage_plugins")) {
+                    ShowSettingsUtil.getInstance().showSettingsDialog(
+                        project,
+                        PluginManagerConfigurable::class.java
+                    ) { configurable: PluginManagerConfigurable ->
+                        configurable.openInstalledTab(CORE_PLUGIN_NAME)
+                    }
+                }
+            )
+            .addAction(
+                NotificationAction.createSimpleExpiring(message("general.notification.action.hide_forever")) {
+                    PropertiesComponent.getInstance().setValue(IGNORE_PROMPT, true)
+                }
+            )
+            .notify(project)
+    }
+
+    companion object {
+        const val CORE_PLUGIN_ID = "aws.toolkit.core"
+        const val CORE_PLUGIN_NAME = "AWS Core"
+        const val IGNORE_PROMPT = "aws.toolkit_core_notice.dismissed"
+    }
+}