keep background task notifications out of the transcript

The harness delivers a finished background task to the agent by writing it as the user's next
message, so Claude's file holds a raw <task-notification> envelope as a user turn. Live it never
shows, because the same event travels separately as task:notification — it appeared only when a
refresh rebuilt the conversation from the file, as a bubble on the owner's side he never typed.

Same defect as INTERRUPTION_MARKERS and the same fix. Anchored to the start of the message so
quoting one inside a real message stays yours. Also skipped when picking a session's title, where
it is no more a title than a slash command is.

Verified against a live transcript: 38 user bubbles before, 32 after, the 6 removed being exactly
the notifications.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/api/chat/claude-sessions.ts

@@ -178,7 +178,11 @@ function summarizeTranscript(filePath: string, id: string): TranscriptSummary |
           sawFirstUserEntry = true;
           bornFromClear = text.startsWith('<command-name>/clear</command-name>');
         }
-        if (text && !firstUserText && !text.startsWith('<command-name>')) firstUserText = text;
+        // A resumed session can open with a background task reporting in, which is no more a title than a
+        // slash command is — see `isTaskNotification`.
+        if (text && !firstUserText && !text.startsWith('<command-name>') && !isTaskNotification(text)) {
+          firstUserText = text;
+        }
       }
     }
   }
@@ -384,8 +388,23 @@ function blockText(content: unknown): string {
   return '';
 }
 
-const userOrInterruption = (text: string): ClaudeChatMessage =>
-  INTERRUPTION_MARKERS.has(text.trim()) ? { role: 'interrupted' } : { role: 'user', text };
+/**
+ * A background task reporting in. The harness delivers these to the agent by writing them as the *user's*
+ * next message — the same trick as `INTERRUPTION_MARKERS`, and the same consequence: replayed literally,
+ * the transcript shows a raw XML envelope in a bubble on your side of the conversation that you never
+ * typed. Live it never appears, because a finished task travels as its own `task:notification` event; it
+ * surfaces only when a refresh rebuilds the conversation from Claude's file.
+ *
+ * Anchored to the start of the message rather than matched anywhere in it, so quoting one inside a real
+ * message — this file's own conversation does exactly that — stays yours.
+ */
+const isTaskNotification = (text: string) => text.trimStart().startsWith('<task-notification>');
+
+function userMessageFrom(text: string): ClaudeChatMessage | null {
+  if (isTaskNotification(text)) return null;
+  if (INTERRUPTION_MARKERS.has(text.trim())) return { role: 'interrupted' };
+  return { role: 'user', text };
+}
 
 export type ClaudeSessionDetail = { id: string; model: string; cwd: string; messages: ClaudeChatMessage[] };
 
@@ -430,13 +449,15 @@ function parseClaudeTranscript(filePath: string, sessionId: string, fallbackCwd
 
     if (entry.type === 'user' && !entry.isMeta) {
       if (typeof content === 'string') {
-        if (content.trim()) messages.push(userOrInterruption(content));
+        const message = content.trim() ? userMessageFrom(content) : null;
+        if (message) messages.push(message);
         continue;
       }
       if (Array.isArray(content)) {
         for (const block of content as ContentBlock[]) {
           if (block.type === 'text' && block.text?.trim()) {
-            messages.push(userOrInterruption(block.text));
+            const message = userMessageFrom(block.text);
+            if (message) messages.push(message);
           } else if (block.type === 'tool_result') {
             const tool = toolById.get(block.tool_use_id);
             if (tool) {