diff --git a/convex/tickets.ts b/convex/tickets.ts
index 5bc60f5..1107660 100644
--- a/convex/tickets.ts
+++ b/convex/tickets.ts
@@ -3111,7 +3111,19 @@ export const listChatMessages = query({
       if (machine) {
         const fiveMinutesAgo = now - 5 * 60 * 1000
         liveChat.hasMachine = true
-        liveChat.machineOnline = Boolean(machine.lastHeartbeatAt && machine.lastHeartbeatAt > fiveMinutesAgo)
+        // Usa tabela de heartbeats (fonte de verdade) com fallback para campo legado
+        let lastHeartbeatAt: number | null = null
+        const hb = await ctx.db
+          .query("machineHeartbeats")
+          .withIndex("by_machine", (q) => q.eq("machineId", machine._id))
+          .first()
+        if (hb?.lastHeartbeatAt) {
+          lastHeartbeatAt = hb.lastHeartbeatAt
+        } else if (machine.lastHeartbeatAt) {
+          lastHeartbeatAt = machine.lastHeartbeatAt
+        }
+
+        liveChat.machineOnline = Boolean(lastHeartbeatAt && lastHeartbeatAt > fiveMinutesAgo)
         liveChat.machineHostname = machine.hostname
 
         // Verificar sessao ativa