fix: add null-safety to welcome template rendering with fallback to local content

The persistent welcome content cache could contain stale JSON with wrong field
names, causing silent NPE on pooled thread and empty welcome panel. Now skips
announcements with null/empty messages, falls back to ResourceBundle for null
remote fields, and clears stale cache on rendering failure.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: stephanj

docusaurus/static/api/welcome.json

@@ -18,9 +18,7 @@
     { "emoji": "\uD83D\uDC40", "name": "Chat History", "description": "All chats are saved and can be restored or removed" },
     { "emoji": "\uD83E\uDDE0", "name": "Project Scanner", "description": "Add source code (full project or by package) to prompt context (or clipboard) when using Anthropic, OpenAI or Gemini." }
   ],
-  "announcements": [
-    { "type": "success", "message": "\uD83C\uDF89 New in v0.9.4: Agent Mode with parallel sub-agents! Enable in Agent Settings to let the LLM autonomously read, write, and edit files in your project." }
-  ],
+  "announcements": [],
   "tip": "You can modify the endpoints for different LLM providers and the default command skills in the plugin settings.",
   "enjoy": "Enjoy!",
   "socialLinks": [

src/main/java/com/devoxx/genie/ui/webview/handler/WebViewMessageRenderer.java

@@ -3,6 +3,7 @@
 import com.devoxx.genie.model.request.ChatMessageContext;
 import com.devoxx.genie.model.welcome.WelcomeContent;
 import com.devoxx.genie.service.welcome.WelcomeContentService;
+import com.devoxx.genie.ui.settings.DevoxxGenieStateService;
 import com.devoxx.genie.ui.webview.WebServer;
 import com.devoxx.genie.ui.webview.template.ChatMessageTemplate;
 import com.devoxx.genie.ui.webview.template.WelcomeTemplate;
@@ -67,13 +68,23 @@ private void showWelcomeContent(ResourceBundle resourceBundle) {
             return;
         }
 
-        // Use the WelcomeTemplate to generate HTML, with remote content if available
-        WelcomeContent remoteContent = WelcomeContentService.getInstance().getWelcomeContent();
-        WelcomeTemplate welcomeTemplate = new WelcomeTemplate(webServer, resourceBundle, remoteContent);
-        String welcomeContent = welcomeTemplate.generate();
+        String welcomeContent;
+        try {
+            // Use the WelcomeTemplate to generate HTML, with remote content if available
+            WelcomeContent remoteContent = WelcomeContentService.getInstance().getWelcomeContent();
+            WelcomeTemplate welcomeTemplate = new WelcomeTemplate(webServer, resourceBundle, remoteContent);
+            welcomeContent = welcomeTemplate.generate();
+        } catch (Exception e) {
+            log.warn("Failed to generate welcome content from remote, falling back to local", e);
+            // Clear stale cached content that may have caused the error
+            DevoxxGenieStateService.getInstance().setWelcomeContentCachedJson("");
+            WelcomeTemplate welcomeTemplate = new WelcomeTemplate(webServer, resourceBundle);
+            welcomeContent = welcomeTemplate.generate();
+        }
 
         // Only inject welcome content if no chat messages are already present (defense-in-depth).
-        // Content is from trusted internal WelcomeTemplate, not user input.
+        // Content is from trusted internal WelcomeTemplate, not user input — all values are
+        // from the plugin's own ResourceBundle or the remote welcome.json with escapeHtml applied.
         jsExecutor.executeJavaScript(
                 "(function() {" +
                 "  var container = document.getElementById('conversation-container');" +

src/main/java/com/devoxx/genie/ui/webview/template/WelcomeTemplate.java

@@ -50,11 +50,11 @@ public WelcomeTemplate(WebServer webServer, ResourceBundle resourceBundle, @Null
 
     @NotNull
     private String generateFromRemoteContent(@NotNull String htmlTemplate, @NotNull String customPromptCommands) {
-        String title = escapeHtml(remoteContent.getTitle());
-        String description = escapeHtml(remoteContent.getDescription());
-        String instructions = escapeHtml(remoteContent.getInstructions());
-        String tip = escapeHtml(remoteContent.getTip());
-        String enjoy = escapeHtml(remoteContent.getEnjoy());
+        String title = escapeHtml(nullSafe(remoteContent.getTitle(), resourceBundle.getString("welcome.title")));
+        String description = escapeHtml(nullSafe(remoteContent.getDescription(), resourceBundle.getString("welcome.description")));
+        String instructions = escapeHtml(nullSafe(remoteContent.getInstructions(), resourceBundle.getString("welcome.instructions")));
+        String tip = escapeHtml(nullSafe(remoteContent.getTip(), resourceBundle.getString("welcome.tip")));
+        String enjoy = escapeHtml(nullSafe(remoteContent.getEnjoy(), resourceBundle.getString("welcome.enjoy")));
         String featuresHtml = buildFeaturesHtml(remoteContent.getFeatures());
         String announcementsHtml = buildAnnouncementsHtml(remoteContent.getAnnouncements());
         String socialLinksHtml = buildSocialLinksHtml(remoteContent.getSocialLinks());
@@ -122,11 +122,15 @@ private String buildAnnouncementsHtml(@Nullable List<WelcomeAnnouncement> announ
         }
         StringBuilder sb = new StringBuilder();
         for (WelcomeAnnouncement announcement : announcements) {
+            String message = announcement.getMessage();
+            if (message == null || message.isEmpty()) {
+                continue;
+            }
             String type = announcement.getType() != null ? announcement.getType() : "info";
             sb.append("<div class=\"announcement announcement-")
                     .append(escapeHtml(type))
                     .append("\">")
-                    .append(escapeHtml(announcement.getMessage()))
+                    .append(escapeHtml(message))
                     .append("</div>\n");
         }
         return sb.toString();
@@ -205,4 +209,9 @@ private String getDefaultFeaturesHtml() {
     private String getDefaultSocialLinksHtml() {
         return "<p>Follow us on Bluesky : <a href=\"https://bsky.app/profile/devoxxgenie.bsky.social\">@DevoxxGenie.bsky.social</a></p>";
     }
+
+    @NotNull
+    private static String nullSafe(@Nullable String value, @NotNull String fallback) {
+        return value != null && !value.isEmpty() ? value : fallback;
+    }
 }

src/test/java/com/devoxx/genie/ui/webview/template/WelcomeTemplateTest.java

@@ -205,6 +205,91 @@ void generate_withNoConstructorArgs_usesLocalFallback() {
         assertTrue(html.contains("Welcome to DevoxxGenie"));
     }
 
+    @Test
+    void generate_withNullAnnouncementMessage_skipsAnnouncement() {
+        WelcomeContent content = createRemoteContent();
+        WelcomeAnnouncement announcement = new WelcomeAnnouncement();
+        announcement.setType("info");
+        announcement.setMessage(null); // null message — should be skipped
+        content.setAnnouncements(List.of(announcement));
+
+        WelcomeTemplate template = new WelcomeTemplate(webServer, resourceBundle, content);
+
+        String html = template.generate();
+
+        assertNotNull(html);
+        assertFalse(html.contains("announcement-info"), "Announcement with null message should be skipped");
+        assertFalse(html.contains("${"), "No unresolved placeholders should remain");
+    }
+
+    @Test
+    void generate_withEmptyAnnouncementMessage_skipsAnnouncement() {
+        WelcomeContent content = createRemoteContent();
+        WelcomeAnnouncement announcement = new WelcomeAnnouncement();
+        announcement.setType("warning");
+        announcement.setMessage(""); // empty message — should be skipped
+        content.setAnnouncements(List.of(announcement));
+
+        WelcomeTemplate template = new WelcomeTemplate(webServer, resourceBundle, content);
+
+        String html = template.generate();
+
+        assertNotNull(html);
+        assertFalse(html.contains("announcement-warning"), "Announcement with empty message should be skipped");
+    }
+
+    @Test
+    void generate_withNullTitle_fallsBackToResourceBundle() {
+        WelcomeContent content = createRemoteContent();
+        content.setTitle(null); // null field — should fall back to resource bundle
+
+        WelcomeTemplate template = new WelcomeTemplate(webServer, resourceBundle, content);
+
+        String html = template.generate();
+
+        assertNotNull(html);
+        assertTrue(html.contains("Welcome to DevoxxGenie"), "Null remote title should fall back to resource bundle");
+        assertFalse(html.contains("${"), "No unresolved placeholders should remain");
+    }
+
+    @Test
+    void generate_withAllNullRemoteFields_fallsBackToResourceBundle() {
+        WelcomeContent content = new WelcomeContent();
+        content.setSchemaVersion(1);
+        // All text fields are null
+
+        WelcomeTemplate template = new WelcomeTemplate(webServer, resourceBundle, content);
+
+        String html = template.generate();
+
+        assertNotNull(html);
+        assertTrue(html.contains("Welcome to DevoxxGenie"));
+        assertTrue(html.contains("Test description"));
+        assertTrue(html.contains("Test instructions"));
+        assertFalse(html.contains("${"), "No unresolved placeholders should remain");
+    }
+
+    @Test
+    void generate_withMixedNullAndValidAnnouncements_rendersOnlyValid() {
+        WelcomeContent content = createRemoteContent();
+        WelcomeAnnouncement nullMsg = new WelcomeAnnouncement();
+        nullMsg.setType("info");
+        nullMsg.setMessage(null);
+        WelcomeAnnouncement validMsg = new WelcomeAnnouncement();
+        validMsg.setType("success");
+        validMsg.setMessage("This one is valid!");
+        content.setAnnouncements(List.of(nullMsg, validMsg));
+
+        WelcomeTemplate template = new WelcomeTemplate(webServer, resourceBundle, content);
+
+        String html = template.generate();
+
+        assertNotNull(html);
+        assertFalse(html.contains("announcement-info"), "Null message announcement should be skipped");
+        assertTrue(html.contains("announcement-success"), "Valid announcement should be rendered");
+        assertTrue(html.contains("This one is valid!"));
+    }
+
     private WelcomeContent createRemoteContent() {
         WelcomeContent content = new WelcomeContent();
         content.setSchemaVersion(1);