fix(desktop): sync new sessions across windows

Broadcast session-list mutations from scratch windows so the main sidebar refreshes without manual reloads.

apps/desktop/src/app/desktop-controller.tsx

@@ -77,6 +77,7 @@ import {
   setSessionsLoading,
   setSessionsTotal
 } from '../store/session'
+import { onSessionsChanged } from '../store/session-sync'
 import { clearSessionTodos, setSessionTodos, todoListActive } from '../store/todos'
 import { openUpdatesWindow, startUpdatePoller, stopUpdatePoller } from '../store/updates'
 import { isSecondaryWindow } from '../store/windows'
@@ -464,6 +465,17 @@ export function DesktopController() {
     void refreshSessions()
   }, [refreshSessions])
 
+  // Another window mutated the shared session list (e.g. a chat started in the
+  // pop-out). Re-pull so the sidebar reflects it. Pop-outs have no sidebar, so
+  // only real windows bother.
+  useEffect(() => {
+    if (isSecondaryWindow()) {
+      return
+    }
+
+    return onSessionsChanged(() => void refreshSessions().catch(() => undefined))
+  }, [refreshSessions])
+
   // ALL-profiles view pages one profile at a time: fetch that profile's next
   // page and merge it in place, leaving every other profile's rows untouched.
   const loadMoreSessionsForProfile = useCallback(async (profile: string) => {

apps/desktop/src/app/session/hooks/use-message-stream.ts

@@ -47,6 +47,7 @@ import {
   setTurnStartedAt,
   setYoloActive
 } from '@/store/session'
+import { broadcastSessionsChanged } from '@/store/session-sync'
 import { clearSessionSubagents, pruneDelegateFallbackSubagents, upsertSubagent } from '@/store/subagents'
 import { setSessionTodos } from '@/store/todos'
 import { recordToolDiff } from '@/store/tool-diffs'
@@ -641,6 +642,9 @@ export function useMessageStream({
       })
 
       void refreshSessions().catch(() => undefined)
+      // Sync the freshly-titled row to other windows (e.g. main, when the turn
+      // ran in the pop-out).
+      broadcastSessionsChanged()
 
       if (compactedTurnRef.current.delete(sessionId)) {
         shouldHydrate = false

apps/desktop/src/app/session/hooks/use-session-actions.ts

@@ -42,6 +42,7 @@ import {
   setYoloActive,
   workspaceCwdForNewSession
 } from '@/store/session'
+import { broadcastSessionsChanged } from '@/store/session-sync'
 import { reportBackendContract } from '@/store/updates'
 import { isWatchWindow } from '@/store/windows'
 import type { SessionCreateResponse, SessionInfo, SessionResumeResponse, SessionRuntimeInfo, UsageStats } from '@/types/hermes'
@@ -472,6 +473,9 @@ export function useSessionActions({
           // server later returns its own preview/title and supersedes this.
           upsertOptimisticSession(created, stored, null, preview?.trim() || null)
           navigate(sessionRoute(stored), { replace: true })
+          // Other windows (e.g. the main window when this is the pop-out) can't
+          // see this session until they re-pull the shared list.
+          broadcastSessionsChanged()
         }
 
         setFreshDraftReady(false)

apps/desktop/src/store/session-sync.ts

@@ -0,0 +1,25 @@
+// Cross-window session-list sync. Each desktop window is its own renderer
+// process with its own gateway socket and session store, so a mutation in one
+// (e.g. a new chat started in the compact pop-out) never reaches another
+// window. This bus pings every window to re-pull the shared session list; the
+// data already lives in the backend, the other window just doesn't know to look.
+const CHANNEL = 'hermes:sessions'
+
+const channel = typeof BroadcastChannel === 'undefined' ? null : new BroadcastChannel(CHANNEL)
+
+// A window that mutated the session list (created / titled a chat) tells the
+// others to refresh. A BroadcastChannel never delivers to its own poster, so the
+// caller refreshes locally as it already does.
+export function broadcastSessionsChanged(): void {
+  channel?.postMessage(1)
+}
+
+export function onSessionsChanged(handler: () => void): () => void {
+  if (!channel) {
+    return () => {}
+  }
+
+  channel.addEventListener('message', handler)
+
+  return () => channel.removeEventListener('message', handler)
+}