Respect thread author kinds and markdown link boundaries

Treat structured author kinds as authoritative so system rows render as System and legacy authorless rows retain human behavior. Parse markdown links before mentions so labels containing @agent remain intact, with regression coverage for both review findings.

Generated-By: PostHog Code
Task-Id: 152cf34b-23c8-4e87-be9e-12d727e08edd

Author: k11kirky

packages/ui/src/features/canvas/components/MentionText.test.tsx

@@ -31,6 +31,17 @@ describe("MentionText", () => {
     expect(screen.queryByText("@agent")).not.toBeInTheDocument();
   });
 
+  it("keeps agent text inside a markdown link label", () => {
+    render(
+      <MentionText content="[My @agent report](https://posthog.com/report) has been created" />,
+    );
+
+    expect(
+      screen.getByRole("link", { name: "My @agent report" }),
+    ).toHaveAttribute("href", "https://posthog.com/report");
+    expect(screen.queryByText("@agent")).not.toBeInTheDocument();
+  });
+
   it("inherits the surrounding message text size", () => {
     render(<MentionText content="A thread reply" />);
 

packages/ui/src/features/canvas/components/MentionText.tsx

@@ -36,30 +36,40 @@ export function MentionText({
       entries.push({ segment, key: `${offset}` });
       offset += length;
     };
-    const pushText = (text: string) => {
+    const pushAgentMentions = (text: string) => {
       let cursor = 0;
       for (const match of text.matchAll(/(^|\s)(@agent)\b/gi)) {
         const mentionStart = (match.index ?? 0) + match[1].length;
-        for (const part of splitLinkSegments(
-          text.slice(cursor, mentionStart),
-        )) {
-          push(part, part.text.length);
+        if (mentionStart > cursor) {
+          push(
+            { type: "text", text: text.slice(cursor, mentionStart) },
+            mentionStart - cursor,
+          );
         }
         push({ type: "agent", text: match[2] }, match[2].length);
         cursor = mentionStart + match[2].length;
       }
-      for (const part of splitLinkSegments(text.slice(cursor))) {
-        push(part, part.text.length);
+      if (cursor < text.length) {
+        push({ type: "text", text: text.slice(cursor) }, text.length - cursor);
+      }
+    };
+    const pushMentions = (text: string) => {
+      for (const segment of splitMentionSegments(text)) {
+        if (segment.type === "mention") {
+          push(
+            { type: "mention", name: segment.name, email: segment.email },
+            segment.text.length,
+          );
+        } else {
+          pushAgentMentions(segment.text);
+        }
       }
     };
-    for (const segment of splitMentionSegments(content)) {
-      if (segment.type === "mention") {
-        push(
-          { type: "mention", name: segment.name, email: segment.email },
-          segment.text.length,
-        );
+    for (const segment of splitLinkSegments(content)) {
+      if (segment.type === "link") {
+        push(segment, segment.text.length);
       } else {
-        pushText(segment.text);
+        pushMentions(segment.text);
       }
     }
     return entries;

packages/ui/src/features/canvas/components/ThreadPanel.test.tsx

@@ -74,6 +74,57 @@ describe("ThreadMessageRow", () => {
     expect(screen.getByText("Agent")).toBeInTheDocument();
     expect(screen.queryByText("Unknown")).not.toBeInTheDocument();
   });
+
+  it("renders system announcements as System without human actions", () => {
+    render(
+      <ThreadMessageRow
+        message={{
+          id: "system-announcement",
+          task: "task",
+          author_kind: "system",
+          event: "status_changed",
+          payload: {},
+          content: "Status changed",
+          created_at: "2026-07-17T00:00:00Z",
+          author: null,
+        }}
+        isTaskAuthor
+        isOwnMessage={false}
+        canForward
+        onSendToAgent={() => {}}
+        onDelete={() => {}}
+      />,
+    );
+
+    expect(screen.getByText("System")).toBeInTheDocument();
+    expect(
+      screen.queryByRole("button", { name: "Message actions" }),
+    ).not.toBeInTheDocument();
+  });
+
+  it("keeps legacy authorless rows as human messages", () => {
+    render(
+      <ThreadMessageRow
+        message={{
+          id: "legacy-message",
+          task: "task",
+          content: "Author removed",
+          created_at: "2026-07-17T00:00:00Z",
+          author: null,
+        }}
+        isTaskAuthor
+        isOwnMessage={false}
+        canForward
+        onSendToAgent={() => {}}
+        onDelete={() => {}}
+      />,
+    );
+
+    expect(screen.getByText("Unknown")).toBeInTheDocument();
+    expect(
+      screen.getByRole("button", { name: "Message actions" }),
+    ).toBeInTheDocument();
+  });
 });
 
 describe("UserPromptRow", () => {

packages/ui/src/features/canvas/components/ThreadPanel.tsx

@@ -105,10 +105,11 @@ export function ThreadMessageRow({
   onDelete: () => void;
 }) {
   const forwarded = !!message.forwarded_to_agent_at;
-  const isAgent =
-    message.author_kind === "agent" ||
-    (!message.author_kind && !message.author);
-  const showMenu = !isAgent && ((isTaskAuthor && !forwarded) || isOwnMessage);
+  const authorKind = message.author_kind ?? "human";
+  const isAgent = authorKind === "agent";
+  const isSystem = authorKind === "system";
+  const showMenu =
+    authorKind === "human" && ((isTaskAuthor && !forwarded) || isOwnMessage);
 
   return (
     <ThreadItem>
@@ -117,6 +118,8 @@ export function ThreadMessageRow({
           <AvatarFallback>
             {isAgent ? (
               <RobotIcon size={14} />
+            ) : isSystem ? (
+              "S"
             ) : (
               getUserInitials(message.author)
             )}
@@ -126,7 +129,11 @@ export function ThreadMessageRow({
       <ThreadItemContent>
         <ThreadItemHeader>
           <ThreadItemAuthor>
-            {isAgent ? "Agent" : userDisplayName(message.author)}
+            {isAgent
+              ? "Agent"
+              : isSystem
+                ? "System"
+                : userDisplayName(message.author)}
           </ThreadItemAuthor>
           <ThreadTimestamp dateTime={message.created_at} />
         </ThreadItemHeader>