Move thread auto-posts server-side; keep client rendering support

The canvas-created and turn-complete thread posts now come from the PostHog backend (PostHog/posthog#70371) so they land even when no client is open. This PR keeps only the rendering side: markdown [label](url) links in thread messages, and authorless messages shown as "Agent" with a robot avatar.

Generated-By: PostHog Code
Task-Id: ea09a661-1f6d-4bd8-a046-24be60909d28

Author: k11kirky

packages/shared/src/analytics-events.ts

@@ -873,8 +873,7 @@ export type ChannelActionType =
   | "mention_member"
   | "view_activity"
   | "open_mention"
-  | "canvas_mode_toggle"
-  | "thread_auto_post";
+  | "canvas_mode_toggle";
 
 export interface ChannelActionProperties {
   action_type: ChannelActionType;
@@ -893,8 +892,6 @@ export interface ChannelActionProperties {
   suggestion_label?: string;
   /** For canvas_mode_toggle: whether canvas mode is being armed. */
   armed?: boolean;
-  /** For thread_auto_post: which auto-comment was posted. */
-  auto_post_kind?: "canvas_created" | "turn_complete";
   /** Whether the underlying mutation resolved successfully. */
   success?: boolean;
 }

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

@@ -65,16 +65,21 @@ function ThreadMessageRow({
 }) {
   const forwarded = !!message.forwarded_to_agent_at;
   const showMenu = (isTaskAuthor && !forwarded) || isOwnMessage;
+  // Authorless messages are posted by the backend on the agent's behalf
+  // (canvas created, turn complete).
+  const isAgent = !message.author;
 
   return (
     <div className="group flex gap-2 rounded-md px-2 py-1.5 hover:bg-fill-secondary">
       <Avatar size="xs" className="mt-0.5 shrink-0">
-        <AvatarFallback>{getUserInitials(message.author)}</AvatarFallback>
+        <AvatarFallback>
+          {isAgent ? <RobotIcon size={12} /> : getUserInitials(message.author)}
+        </AvatarFallback>
       </Avatar>
       <div className="min-w-0 flex-1">
         <div className="flex items-baseline gap-2">
           <Text size="1" weight="medium" className="truncate">
-            {userDisplayName(message.author)}
+            {isAgent ? "Agent" : userDisplayName(message.author)}
           </Text>
           <Text size="1" className="shrink-0 text-muted-foreground">
             {formatRelativeTimeShort(message.created_at)}

packages/ui/src/features/canvas/freeform/canvasThreadAutoPost.test.ts

@@ -1,29 +1,15 @@
-import type { PostHogAPIClient } from "@posthog/api-client/posthog-client";
 import { useServiceOptional } from "@posthog/di/react";
-import { ANALYTICS_EVENTS } from "@posthog/shared/analytics-events";
-import type { UserBasic } from "@posthog/shared/domain-types";
-import { useOptionalAuthenticatedClient } from "@posthog/ui/features/auth/authClient";
 import {
   type CanvasTerminalStatus,
   hasCanvasGenerationStarted,
   isCanvasGenerating,
   resolveCanvasGenerationStatus,
 } from "@posthog/ui/features/canvas/freeform/canvasGenerationStatus";
-import { buildCanvasGenerationThreadPosts } from "@posthog/ui/features/canvas/freeform/canvasThreadAutoPost";
-import { taskThreadQueryKey } from "@posthog/ui/features/canvas/hooks/useTaskThread";
-import {
-  type TrackedCanvasGeneration,
-  useCanvasGenerationTrackerStore,
-} from "@posthog/ui/features/canvas/stores/canvasGenerationTrackerStore";
+import { useCanvasGenerationTrackerStore } from "@posthog/ui/features/canvas/stores/canvasGenerationTrackerStore";
 import { NotificationBus } from "@posthog/ui/features/notifications/notifications";
 import { useSessionStore } from "@posthog/ui/features/sessions/sessionStore";
 import { taskDetailQuery } from "@posthog/ui/features/tasks/queries";
-import { track } from "@posthog/ui/shell/analytics";
-import {
-  type QueryClient,
-  useQueries,
-  useQueryClient,
-} from "@tanstack/react-query";
+import { useQueries } from "@tanstack/react-query";
 import { useEffect, useMemo, useRef } from "react";
 
 // Poll cadence for the run status of a tracked generation task. Matches the
@@ -66,38 +52,6 @@ function emitCanvasGenerationNotification(
   // "cancelled" is user-initiated — stay silent.
 }
 
-// Drop the finished generation's updates into the task's thread: the one-time
-// "[name](link) has been created" comment and a turn-complete note tagging the
-// task creator. Posted by the client that started the generation (the thread
-// API has no agent author), best-effort per message.
-async function postThreadUpdates(
-  client: PostHogAPIClient,
-  queryClient: QueryClient,
-  entry: TrackedCanvasGeneration,
-  status: CanvasTerminalStatus,
-  creator: UserBasic | null | undefined,
-): Promise<void> {
-  for (const post of buildCanvasGenerationThreadPosts(entry, status, creator)) {
-    let success = true;
-    try {
-      await client.createTaskThreadMessage(entry.taskId, post.content);
-    } catch {
-      success = false;
-    }
-    track(ANALYTICS_EVENTS.CHANNEL_ACTION, {
-      action_type: "thread_auto_post",
-      surface: "canvas",
-      channel_id: entry.channelId,
-      task_id: entry.taskId,
-      auto_post_kind: post.kind,
-      success,
-    });
-  }
-  void queryClient.invalidateQueries({
-    queryKey: taskThreadQueryKey(entry.taskId),
-  });
-}
-
 // Watches every canvas generation started in this client (registered in the
 // tracker store) and fires a toast — with a link to the canvas — the moment each
 // one stops generating. Mounted on the persistent channel layout so it keeps
@@ -116,10 +70,6 @@ export function useCanvasGenerationToasts(): void {
   const bus = useServiceOptional<NotificationBus>(NotificationBus);
   const busRef = useRef(bus);
   busRef.current = bus;
-  const client = useOptionalAuthenticatedClient();
-  const clientRef = useRef(client);
-  clientRef.current = client;
-  const queryClient = useQueryClient();
 
   const taskIds = useMemo(() => Object.keys(tracked), [tracked]);
 
@@ -146,7 +96,7 @@ export function useCanvasGenerationToasts(): void {
       latestRun,
       session,
     });
-    return { id, generating, latestRun, session, task: details[i]?.data };
+    return { id, generating, latestRun, session };
   });
 
   // A stable signature so the transition effect only runs on real changes.
@@ -189,23 +139,15 @@ export function useCanvasGenerationToasts(): void {
 
       toastedRef.current.add(st.id);
       const entry = useCanvasGenerationTrackerStore.getState().tracked[st.id];
-      if (entry) {
-        const status = resolveCanvasGenerationStatus({
-          latestRun: st.latestRun,
-          session: st.session,
-        });
-        if (busRef.current) {
-          emitCanvasGenerationNotification(busRef.current, entry, status);
-        }
-        if (clientRef.current) {
-          void postThreadUpdates(
-            clientRef.current,
-            queryClient,
-            entry,
-            status,
-            st.task?.created_by,
-          );
-        }
+      if (entry && busRef.current) {
+        emitCanvasGenerationNotification(
+          busRef.current,
+          entry,
+          resolveCanvasGenerationStatus({
+            latestRun: st.latestRun,
+            session: st.session,
+          }),
+        );
       }
       // Stop tracking (and polling) this task now that it's done.
       untrack(st.id);

packages/ui/src/features/canvas/freeform/canvasThreadAutoPost.ts

@@ -178,13 +178,9 @@ export function useGenerateFreeformCanvas(args: {
         await setGenerationTask(dashboardId, task.id).catch(() => {});
         // Track this run so a toast (with a link back here) fires when it
         // finishes, even after the user navigates to another canvas.
-        useCanvasGenerationTrackerStore.getState().track({
-          taskId: task.id,
-          dashboardId,
-          channelId,
-          name,
-          createsCanvas: !currentCode?.trim(),
-        });
+        useCanvasGenerationTrackerStore
+          .getState()
+          .track({ taskId: task.id, dashboardId, channelId, name });
         // Refresh the workspace cache so the new cloud workspace row appears and
         // the task view resolves the cloud run instead of the repo-picker prompt.
         void queryClient.invalidateQueries({

packages/ui/src/features/canvas/freeform/useCanvasGenerationToasts.ts

@@ -10,8 +10,6 @@ export interface TrackedCanvasGeneration {
   dashboardId: string;
   channelId: string;
   name: string;
-  /** True when this run builds the canvas for the first time (not an edit). */
-  createsCanvas: boolean;
 }
 
 interface CanvasGenerationTrackerState {