fix(canvas): normalize forwarded agent prompts

Generated-By: PostHog Code
Task-Id: 87a79e23-20c4-440b-818b-28154924ffbc

Author: k11kirky

packages/core/src/canvas/threadTimeline.test.ts

@@ -3,6 +3,7 @@ import {
   buildThreadTimeline,
   deriveThreadAgentStatus,
   hasAgentMention,
+  normalizeAgentPromptText,
   shouldSuspendThreadSession,
 } from "./threadTimeline";
 
@@ -18,6 +19,24 @@ describe("hasAgentMention", () => {
   });
 });
 
+describe("normalizeAgentPromptText", () => {
+  it.each([
+    [
+      "forwarded thread comment",
+      "[Thread comment from Peter Kirkham] @agent which model are you?",
+      "which model are you?",
+    ],
+    ["direct prompt", "which model are you?", "which model are you?"],
+    [
+      "direct prompt with mention",
+      "@agent which model are you?",
+      "which model are you?",
+    ],
+  ])("normalizes a %s", (_name, content, expected) => {
+    expect(normalizeAgentPromptText(content)).toBe(expected);
+  });
+});
+
 describe("buildThreadTimeline", () => {
   it("interleaves prompts, human replies, and agent turns chronologically", () => {
     const timeline = buildThreadTimeline({

packages/core/src/canvas/threadTimeline.ts

@@ -69,11 +69,22 @@ export interface ThreadAgentStatus {
 }
 
 const AGENT_MENTION_PATTERN = /(^|\s)@agent\b/i;
+const THREAD_COMMENT_ATTRIBUTION_PATTERN =
+  /^\[Thread comment from [^\]\r\n]+\]\s*/i;
+const LEADING_AGENT_MENTION_PATTERN = /^@agent\b[\s:]*/i;
 
 export function hasAgentMention(content: string): boolean {
   return AGENT_MENTION_PATTERN.test(content);
 }
 
+export function normalizeAgentPromptText(content: string): string {
+  return content
+    .trim()
+    .replace(THREAD_COMMENT_ATTRIBUTION_PATTERN, "")
+    .replace(LEADING_AGENT_MENTION_PATTERN, "")
+    .trim();
+}
+
 export function deriveThreadAgentStatus({
   hasActivity = false,
   hasError = false,

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

@@ -30,4 +30,21 @@ describe("UserPromptRow", () => {
     expect(screen.getByText("@agent")).toBeInTheDocument();
     expect(screen.getByText("Investigate this")).toBeInTheDocument();
   });
+
+  it("hides forwarded thread attribution and duplicate agent mentions", () => {
+    render(
+      <UserPromptRow
+        message={{
+          id: "prompt",
+          text: "[Thread comment from Peter Kirkham] @agent which model are you?",
+          timestamp: 1,
+        }}
+        author={{ id: 1, uuid: "user", email: "user@example.com" }}
+      />,
+    );
+
+    expect(screen.getAllByText("@agent")).toHaveLength(1);
+    expect(screen.getByText("which model are you?")).toBeInTheDocument();
+    expect(screen.queryByText(/Thread comment from/)).not.toBeInTheDocument();
+  });
 });

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

@@ -11,6 +11,7 @@ import {
   buildThreadTimeline,
   deriveThreadAgentStatus,
   hasAgentMention,
+  normalizeAgentPromptText,
   shouldSuspendThreadSession,
   type ThreadAgentMessage,
   type ThreadAgentStatus,
@@ -271,6 +272,8 @@ export function UserPromptRow({
   message: ThreadAgentMessage;
   author: TaskThreadMessage["author"];
 }) {
+  const promptText = normalizeAgentPromptText(message.text);
+
   return (
     <ThreadItem>
       <ThreadItemGutter>
@@ -288,7 +291,7 @@ export function UserPromptRow({
           )}
         </ThreadItemHeader>
         <ThreadItemBody className="wrap-break-word whitespace-pre-wrap">
-          <span className={mentionChipClass}>@agent</span> {message.text}
+          <span className={mentionChipClass}>@agent</span> {promptText}
         </ThreadItemBody>
       </ThreadItemContent>
     </ThreadItem>