diff --git a/convex/liveChat.ts b/convex/liveChat.ts
index 2361784..8009d20 100644
--- a/convex/liveChat.ts
+++ b/convex/liveChat.ts
@@ -16,6 +16,18 @@ function hashToken(token: string) {
   return toHex(sha256(utf8(token)))
 }
 
+async function getLastHeartbeatAt(ctx: MutationCtx | QueryCtx, machineId: Id<"machines">) {
+  const heartbeat = await ctx.db
+    .query("machineHeartbeats")
+    .withIndex("by_machine", (q) => q.eq("machineId", machineId))
+    .first()
+
+  if (heartbeat?.lastHeartbeatAt) return heartbeat.lastHeartbeatAt
+
+  const machine = await ctx.db.get(machineId)
+  return machine?.lastHeartbeatAt ?? null
+}
+
 async function validateMachineToken(
   ctx: MutationCtx | QueryCtx,
   machineToken: string
@@ -84,8 +96,9 @@ export const startSession = mutation({
       throw new ConvexError("Máquina não encontrada")
     }
 
+    const lastHeartbeatAt = await getLastHeartbeatAt(ctx, machine._id)
     const fiveMinutesAgo = Date.now() - 5 * 60 * 1000
-    if (!machine.lastHeartbeatAt || machine.lastHeartbeatAt < fiveMinutesAgo) {
+    if (!lastHeartbeatAt || lastHeartbeatAt < fiveMinutesAgo) {
       throw new ConvexError("Máquina offline. A máquina precisa estar online para iniciar o chat.")
     }
 
@@ -567,8 +580,9 @@ export const getTicketSession = query({
 
     // Verificar se maquina esta online (sempre, mesmo sem sessao)
     const machine = ticket.machineId ? await ctx.db.get(ticket.machineId) : null
+    const lastHeartbeatAt = machine ? await getLastHeartbeatAt(ctx, machine._id) : null
     const fiveMinutesAgo = Date.now() - 5 * 60 * 1000
-    const machineOnline = machine?.lastHeartbeatAt && machine.lastHeartbeatAt > fiveMinutesAgo
+    const machineOnline = lastHeartbeatAt !== null && lastHeartbeatAt > fiveMinutesAgo
 
     const session = await ctx.db
       .query("liveChatSessions")
@@ -889,3 +903,4 @@ export const generateMachineUploadUrl = action({
     return { uploadUrl }
   },
 })
+