Address comments.

Co-authored-by: Copilot <copilot@github.com>

Author: ethanyhou

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/events/CopilotEventConstants.java

@@ -160,4 +160,10 @@ public class CopilotEventConstants {
    * Event when a rate limit warning is received from the language server.
    */
   public static final String TOPIC_RATE_LIMIT_WARNING = TOPIC_CHAT + "RATE_LIMIT_WARNING";
+
+  /**
+   * Event when custom prompts, skills, agents, or instructions change on the language server. Clients should re-fetch
+   * conversation templates on receipt.
+   */
+  public static final String TOPIC_CHAT_DID_CHANGE_CUSTOMIZATION_FILES = TOPIC_CHAT + "DID_CHANGE_CUSTOMIZATION_FILES";
 }

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/lsp/CopilotLanguageClient.java

@@ -254,6 +254,28 @@ public void onRateLimitWarning(RateLimitWarningParams params) {
     }
   }
 
+  /**
+   * Notify when custom skills change (global or workspace). Signal-only; clients re-fetch templates.
+   */
+  @JsonNotification("copilot/customSkill/didChange")
+  public void onDidChangeCustomSkill(Object params) {
+    notifyCustomizationFilesChanged();
+  }
+
+  /**
+   * Notify when custom prompts change (global or workspace). Signal-only; clients re-fetch templates.
+   */
+  @JsonNotification("copilot/customPrompt/didChange")
+  public void onDidChangeCustomPrompt(Object params) {
+    notifyCustomizationFilesChanged();
+  }
+
+  private void notifyCustomizationFilesChanged() {
+    if (eventBroker != null) {
+      eventBroker.post(CopilotEventConstants.TOPIC_CHAT_DID_CHANGE_CUSTOMIZATION_FILES, null);
+    }
+  }
+
   /**
    * Handles the Dynamic OAuth request for MCP.
    * Shows a dialog with multiple input fields and returns the user's input values.

com.microsoft.copilot.eclipse.ui.test/src/com/microsoft/copilot/eclipse/ui/chat/services/ChatCompletionServiceTest.java

@@ -15,6 +15,8 @@
 import java.util.concurrent.CompletableFuture;
 
 import org.eclipse.core.runtime.jobs.Job;
+import org.eclipse.ui.IWorkbench;
+import org.eclipse.ui.PlatformUI;
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -39,6 +41,7 @@ class ChatCompletionServiceTest {
 
   private static ChatCompletionService chatCompletionService;
   private static MockedStatic<CopilotUi> copilotUiMock;
+  private static MockedStatic<PlatformUI> platformUiMock;
 
   @BeforeAll
   static void setUp() {
@@ -53,6 +56,12 @@ static void setUp() {
     copilotUiMock = Mockito.mockStatic(CopilotUi.class);
     copilotUiMock.when(CopilotUi::getPlugin).thenReturn(mockPlugin);
 
+    // Mock PlatformUI so the constructor can safely obtain an IEventBroker
+    IWorkbench mockWorkbench = mock(IWorkbench.class);
+    when(mockWorkbench.getService(any())).thenReturn(null);
+    platformUiMock = Mockito.mockStatic(PlatformUI.class);
+    platformUiMock.when(PlatformUI::getWorkbench).thenReturn(mockWorkbench);
+
     ConversationTemplate template = new ConversationTemplate("test", null, null,
         List.of(CopilotScope.CHAT_PANEL), null);
     ConversationTemplate[] templates = new ConversationTemplate[] { template };
@@ -76,6 +85,9 @@ static void tearDown() {
     if (copilotUiMock != null) {
       copilotUiMock.close();
     }
+    if (platformUiMock != null) {
+      platformUiMock.close();
+    }
   }
 
   @Test

com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/services/ChatCompletionService.java

@@ -19,13 +19,17 @@
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.jobs.Job;
+import org.eclipse.e4.core.services.events.IEventBroker;
 import org.eclipse.jface.util.IPropertyChangeListener;
 import org.eclipse.lsp4j.WorkspaceFolder;
+import org.eclipse.ui.PlatformUI;
+import org.osgi.service.event.EventHandler;
 
 import com.microsoft.copilot.eclipse.core.AuthStatusManager;
 import com.microsoft.copilot.eclipse.core.Constants;
 import com.microsoft.copilot.eclipse.core.CopilotAuthStatusListener;
 import com.microsoft.copilot.eclipse.core.CopilotCore;
+import com.microsoft.copilot.eclipse.core.events.CopilotEventConstants;
 import com.microsoft.copilot.eclipse.core.FeatureFlags;
 import com.microsoft.copilot.eclipse.core.lsp.CopilotLanguageServerConnection;
 import com.microsoft.copilot.eclipse.core.lsp.protocol.ChatMode;
@@ -43,9 +47,9 @@ public class ChatCompletionService implements CopilotAuthStatusListener {
   public static final String AGENT_MARK = "@";
   public static final String TEMPLATE_MARK = "/";
 
-  private volatile List<ConversationTemplate> templates = new ArrayList<>();
-  private volatile List<ConversationAgent> agents = new ArrayList<>();
-  private volatile Set<String> allCommands = new HashSet<>();
+  private volatile List<ConversationTemplate> templates = List.of();
+  private volatile List<ConversationAgent> agents = List.of();
+  private volatile Set<String> allCommands = Set.of();
   // Exclude intelliJ sepcific slash commands
   private static final Set<String> EXCLUDED_COMMANDS = Set.of("help", "feedback");
   public static final String REFRESH_JOB_FAMILY =
@@ -54,6 +58,8 @@ public class ChatCompletionService implements CopilotAuthStatusListener {
   private AuthStatusManager authStatusManager;
   private IResourceChangeListener skillFileListener;
   private IPropertyChangeListener preferenceListener;
+  private IEventBroker eventBroker;
+  private EventHandler customPromptsChangedHandler;
 
   private static final String SKILL_FILE_NAME = "SKILL.md";
   private static final String PROMPT_FILE_SUFFIX = ".prompt.md";
@@ -73,6 +79,12 @@ public ChatCompletionService(CopilotLanguageServerConnection lsConnection, AuthS
       }
     };
     CopilotUi.getPlugin().getLanguageServerSettingManager().registerPropertyChangeListener(preferenceListener);
+    this.eventBroker = PlatformUI.getWorkbench().getService(IEventBroker.class);
+    if (this.eventBroker != null) {
+      this.customPromptsChangedHandler = event -> fetchAsync();
+      this.eventBroker.subscribe(CopilotEventConstants.TOPIC_CHAT_DID_CHANGE_CUSTOMIZATION_FILES,
+          customPromptsChangedHandler);
+    }
     syncCommands(this.authStatusManager.getCopilotStatus());
   }
 
@@ -140,9 +152,10 @@ private void initConversationTemplates() {
     }
 
     // Atomically swap the cached data so readers always see a consistent snapshot.
-    this.templates = newTemplates;
-    this.agents = newAgents;
-    this.allCommands = newCommands;
+    // Publish immutable snapshots so readers cannot accidentally mutate a live collection.
+    this.templates = List.copyOf(newTemplates);
+    this.agents = List.copyOf(newAgents);
+    this.allCommands = Set.copyOf(newCommands);
   }
 
   /**
@@ -228,9 +241,9 @@ private void syncCommands(String status) {
         fetchAsync();
         break;
       default:
-        this.allCommands = new HashSet<>();
-        this.templates = new ArrayList<>();
-        this.agents = new ArrayList<>();
+        this.allCommands = Set.of();
+        this.templates = List.of();
+        this.agents = List.of();
         break;
     }
   }