[eric] agents: rehydrate browser-agent children the trimmed session-list poll leaves message-less (feed no longer blanks)

frontend/src/app/pages/AgentChat/shell/BrowserAgentInlineFeed.tsx

@@ -197,14 +197,18 @@ const BrowserAgentInlineFeed: React.FC<Props> = ({ parentSessionId, browserId })
     shallowEqual,
   );
 
+  // A child that arrived only through the trimmed session-list poll carries its message_count but no messages; fetch the full children so its history renders instead of showing a blank feed.
+  const needsChildFetch =
+    browserSessions.length === 0 ||
+    browserSessions.some((s) => (s.message_count ?? 0) > 0 && s.messages.length === 0);
   useEffect(() => {
-    if (browserSessions.length === 0 && fetchedForSession.current !== parentSessionId) {
+    if (needsChildFetch && fetchedForSession.current !== parentSessionId) {
       fetchedForSession.current = parentSessionId;
       dispatch(fetchBrowserAgentChildren(parentSessionId))
         .unwrap()
         .catch(() => { fetchedForSession.current = null; });
     }
-  }, [browserSessions.length, parentSessionId, dispatch]);
+  }, [needsChildFetch, parentSessionId, dispatch]);
 
   const sessionsWithHistoricalEntries = useMemo(() => {
     return browserSessions.map((session) => {

frontend/src/shared/state/agentsSlice.ts

@@ -1416,13 +1416,17 @@ const agentsSlice = createSlice({
       })
       .addCase(fetchBrowserAgentChildren.fulfilled, (state, action) => {
         for (const session of action.payload) {
-          if (!state.sessions[session.id]) {
+          const existing = state.sessions[session.id];
+          if (!existing) {
             state.sessions[session.id] = {
               ...session,
               name: normalizeSessionName(session.name),
               tool_group_meta: session.tool_group_meta ?? {},
               pending_approvals: session.pending_approvals ?? [],
             };
+          } else if (existing.messages.length === 0 && session.messages.length > 0) {
+            // Hydrate a child the trimmed session-list poll left message-less; don't touch one mid-stream (already has messages).
+            existing.messages = session.messages;
           }
         }
       })