fix(channels): open the unread reply from sidebar Activity

docs/buzz-help.md

@@ -821,6 +821,9 @@ for 30 days expires.
   **Open Activity** opens the page. The card's **Unread only** switch is
   separate from the Activity page's filters and hides reactions when on. The preview is not shown on touch
   devices or while the Activity page is open.
+- **Channel activity**: rest the pointer on a channel or Solo chat in the
+  sidebar to see its working agents and **Unread threads**. Choosing an unread
+  thread opens it at the reply shown, expanding the replies it is nested under.
 - **Sidebar width**: drag the sidebar's right edge, or focus its resize handle
   and use the Left/Right arrow keys. Double-click the handle to reset the width.
   Messages and plugin pages share the saved width within the same community

src/bundled/channels/ChannelSidebarItem.tsx

@@ -47,7 +47,7 @@ type ItemProps = {
   working: boolean;
   selected: string | undefined;
   onSelect: (id: string) => void;
-  onOpenThread: (channelId: string, rootId: string) => void;
+  onOpenThread: (channelId: string, messageId: string, rootId: string) => void;
   onOpenMessage: (channelId: string, messageId: string) => void;
   onOpenWorkingAgent?: (
     channelId: string,
@@ -268,7 +268,9 @@ function ChannelSidebarItemCore({
             agentProfiles={agentProfiles}
             {...(onOpenWorkingAgent ? { onOpenWorkingAgent } : {})}
             {...(onOpenAgentActivity ? { onOpenAgentActivity } : {})}
-            onOpenThread={(item) => onOpenThread(item.channelId, item.rootId)}
+            onOpenThread={(item) =>
+              onOpenThread(item.channelId, item.latestMessageId, item.rootId)
+            }
             onOpenMention={(item) =>
               onOpenMessage(item.channelId, item.messageId)
             }

src/bundled/channels/ChannelsPage.tsx

@@ -24,6 +24,7 @@ import { Avatar } from "../../shared/design-system/ui/Avatar";
 import { useToastNotification } from "../../shared/design-system/ui/Toast";
 import { useReturnHighlight } from "../../features/messages/use-return-highlight";
 import { useMessageOpening } from "../../features/messages/use-message-opening";
+import { beginReveal } from "../../features/messages/use-message-reveal";
 import { ChannelBody } from "./ChannelBody";
 import {
   entryPane,
@@ -677,6 +678,12 @@ function ChannelWorkspace({
     navigation?.target.kind === "conversation"
       ? navigation.target.threadRootId
       : undefined;
+  useLayoutEffect(() => {
+    // The message's reveal waits for its channel, timeline or thread to load;
+    // focus the person moves meanwhile counts from now.
+    if (requestedMessage && navigation && !navigation.signal.aborted)
+      beginReveal(navigation.signal);
+  }, [requestedMessage, navigation]);
   const membersRequested =
     navigation?.target.kind === "conversation" &&
     navigation.target.panel === "members";

src/features/channel-navigation/ChannelInventory.test.tsx

@@ -907,6 +907,70 @@ it("copies a channel link that opens the same channel", async () => {
   ).toBeInTheDocument();
 });
 
+it("opens an Activity thread row at the reply it previews, in its thread", async () => {
+  const root = "d".repeat(64);
+  const reply = "e".repeat(64);
+  const h = fixture();
+  const item = {
+    channelId: "beta",
+    rootId: root,
+    latestMessageId: reply,
+    authorId: "b".repeat(64),
+    preview: "Nested reply",
+    unreadCount: 1,
+    createdAt: 1,
+  };
+  // Stable per channel, as external-store snapshots must be.
+  const snapshots = new Map(
+    ["alpha", "beta", "gamma"].map((id) => [
+      id,
+      {
+        channelId: id,
+        items: id === "beta" ? [item] : [],
+        coverage: "observed" as const,
+        freshness: "observed" as const,
+      },
+    ]),
+  );
+  const unread = h.session.unread;
+  h.session.unread = {
+    ...unread,
+    activity: (id) => snapshots.get(id) ?? unread.activity(id),
+    subscribeActivity: () => () => {},
+  };
+  // The sidebar reads back the attempt it started to hand off focus return.
+  let opened: unknown;
+  vi.mocked(h.navigator.open).mockImplementation(async (next) => {
+    opened = next;
+    return { status: "opened" };
+  });
+  Object.assign(h.navigator, {
+    snapshot: () => ({
+      attempt: {
+        id: "visit",
+        entry: { id: "entry", target: opened },
+        signal: new AbortController().signal,
+      },
+    }),
+  });
+  render(h.view("alpha"));
+  const beta = await screen.findByRole("button", { name: /^beta/ });
+  beta.focus();
+  await userEvent.keyboard("{Enter}");
+  const popup = await screen.findByRole("dialog", { name: "Activity in beta" });
+  await userEvent.click(
+    within(popup).getByRole("button", { name: /^Open unread thread from/ }),
+  );
+  expect(h.navigator.open).toHaveBeenLastCalledWith(
+    expect.objectContaining({
+      kind: "conversation",
+      channelId: "beta",
+      messageId: reply,
+      threadRootId: root,
+    }),
+  );
+});
+
 it("offers DMs a Move conversation menu and relocates them into a saved group", async () => {
   const saved: SidebarPreferences = {
     sections: [{ id: "work", name: "Work", order: 0 }],

src/features/channel-navigation/ChannelInventory.tsx

@@ -467,11 +467,6 @@ export function ChannelInventory({
     },
     [viewer, relay, queries, handoff, sidebar.list, navigator, scope],
   );
-  const openActivityThread = useCallback(
-    (channelId: string, rootId: string) =>
-      openActivityMessage(channelId, rootId, rootId),
-    [openActivityMessage],
-  );
   const openWorkingAgent = useCallback(
     (channelId: string, _agent: string, messageId: string | undefined) => {
       const root =
@@ -1543,7 +1538,7 @@ export function ChannelInventory({
                       working={workingChannels.has(channel.id)}
                       selected={composingMessage ? undefined : selected}
                       onSelect={select}
-                      onOpenThread={openActivityThread}
+                      onOpenThread={openActivityMessage}
                       onOpenMessage={openActivityMessage}
                       onOpenWorkingAgent={openWorkingAgent}
                       onOpenAgentActivity={openAgentActivity}

src/features/channel-navigation/SoloInventory.test.tsx

@@ -543,11 +543,13 @@ it("offers unread thread navigation and mark-read through the shared activity po
       name: "Open unread thread from Owned Agent: Needs review",
     }),
   );
+  // The row opens the reply it previews, in its thread, not the thread root.
   expect(f.open).toHaveBeenLastCalledWith(
     expect.objectContaining({
       kind: "conversation",
       channelId: id,
-      messageId: root,
+      messageId: "e".repeat(64),
+      threadRootId: root,
     }),
   );
 });

src/features/channel-navigation/SoloInventory.tsx

@@ -169,12 +169,12 @@ export function SoloInventory({
     [navigator, scope],
   );
   const openMessage = useCallback(
-    (channelId: string, messageId?: string) => {
+    (channelId: string, messageId?: string, threadRootId?: string) => {
       if (handoff && handoff.session !== session) return;
       const destination =
         messageId && session.viewer
           ? buzzLinkTarget(
-              `buzz://message?channel=${channelId}&id=${messageId}`,
+              `buzz://message?channel=${channelId}&id=${messageId}${threadRootId ? `&thread=${threadRootId}` : ""}`,
               {
                 viewer: session.viewer,
                 communityOrigin: scope.slice(0, -(session.viewer.length + 1)),
@@ -224,7 +224,9 @@ export function SoloInventory({
         Icon={ChatIcon}
         onSelect={() => void open(item.id)}
         onRename={rename}
-        onOpenThread={(thread) => openMessage(thread.channelId, thread.rootId)}
+        onOpenThread={(thread) =>
+          openMessage(thread.channelId, thread.latestMessageId, thread.rootId)
+        }
         onOpenMention={(mention) =>
           openMessage(mention.channelId, mention.messageId)
         }