Hold channel loading state until the feed is complete so it opens at the latest message

The channel scroller's one-shot initial end-scroll fired against partial
content (the synthesized "joined" opener renders as soon as the backend
channel resolves, before the task cards arrive), and the engine never
re-scrolls for late rows unless autoScroll forces it. Fold the feed-messages
loading state into the gate and hold the spinner while any feed data is
still loading, so the scroller mounts once with complete data and lands at
the most recent message.

Generated-By: PostHog Code
Task-Id: d887d524-7d87-4d7a-b38c-b20289937ad1

Author: adboio

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

@@ -695,7 +695,12 @@ export function ChannelFeedView({
     return merged;
   }, [tasks, systemMessages]);
 
-  if (isLoading && entries.length === 0 && pending.length === 0) {
+  // Hold the loading state even when some entries already exist (the "joined"
+  // opener renders as soon as the channel resolves, before the task cards):
+  // mounting the scroller around partial content spends its one-shot initial
+  // end-scroll on a near-empty list, and it never re-scrolls when the real
+  // cards arrive. Pending kickoffs bail out so an optimistic post shows now.
+  if (isLoading && pending.length === 0) {
     return (
       <div className="flex flex-1 items-center justify-center">
         <Spinner />

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

@@ -69,18 +69,26 @@ export function WebsiteChannelHome({ channelId }: { channelId: string }) {
   const { tasks, isLoading: isLoadingFeed } = useChannelFeed(
     backendChannel?.id,
   );
-  // Until the backend channel resolves there's no feed to ask for, and the feed
-  // query is disabled — which reports isLoading:false, indistinguishable from
-  // "this channel is empty". useBackendChannel reports loading for the whole
-  // identity-resolution window (settling if the resolve fails), so fold it in:
-  // we can't call a channel empty until we know which channel it is.
-  const isLoading = isLoadingChannels || isResolvingChannel || isLoadingFeed;
   // Marking this channel read lives in ChannelHeader (rendered by every channel
   // surface), so opening Artifacts or CONTEXT.md counts as reading it too.
 
   // Durable "PostHog agent" rows (CONTEXT.md being built, …) live on the
   // backend channel — the same id the feed tasks use, not the folder id.
-  const { messages: feedMessages } = useChannelFeedMessages(backendChannel?.id);
+  const { messages: feedMessages, isLoading: isLoadingMessages } =
+    useChannelFeedMessages(backendChannel?.id);
+  // Until the backend channel resolves there's no feed to ask for, and the feed
+  // query is disabled — which reports isLoading:false, indistinguishable from
+  // "this channel is empty". useBackendChannel reports loading for the whole
+  // identity-resolution window (settling if the resolve fails), so fold it in:
+  // we can't call a channel empty until we know which channel it is. Messages
+  // loading is included so the scroller mounts once with the complete feed and
+  // its one-shot initial end-scroll lands at the latest message (it never
+  // re-fires for late-arriving rows).
+  const isLoading =
+    isLoadingChannels ||
+    isResolvingChannel ||
+    isLoadingFeed ||
+    isLoadingMessages;
   // The Slack-style "joined" opener, derived from the channel row so it renders
   // (and sorts first) even where the feed endpoint isn't deployed.
   const systemMessages = useMemo(() => {