diff --git a/server/prometheus-service.js b/server/prometheus-service.js
index af45f04..41ad658 100644
--- a/server/prometheus-service.js
+++ b/server/prometheus-service.js
@@ -391,25 +391,23 @@ function calculateTrafficFromHistory(values) {
 }
 
 /**
- * Get total traffic for the past 24h by fetching all points and integrating
+ * Get total traffic for the past 24h using Prometheus increase() for stability and accuracy
  */
 async function get24hTrafficSum(url) {
-  const now = Math.floor(Date.now() / 1000);
-  const start = now - 86400;
-  const step = 60; // 1-minute points for calculation
+  try {
+    const [rxResult, txResult] = await Promise.all([
+      query(url, 'sum(increase(node_network_receive_bytes_total{device!~"lo|veth.*|docker.*|br-.*"}[24h]))').catch(() => []),
+      query(url, 'sum(increase(node_network_transmit_bytes_total{device!~"lo|veth.*|docker.*|br-.*"}[24h]))').catch(() => [])
+    ]);
 
-  const [rxResult, txResult] = await Promise.all([
-    queryRange(url, 'sum(rate(node_network_receive_bytes_total{device!~"lo|veth.*|docker.*|br-.*"}[1m]))', start, now, step).catch(() => []),
-    queryRange(url, 'sum(rate(node_network_transmit_bytes_total{device!~"lo|veth.*|docker.*|br-.*"}[1m]))', start, now, step).catch(() => [])
-  ]);
+    const rx = rxResult.length > 0 ? parseFloat(rxResult[0].value[1]) : 0;
+    const tx = txResult.length > 0 ? parseFloat(txResult[0].value[1]) : 0;
 
-  const rxValues = rxResult.length > 0 ? rxResult[0].values : [];
-  const txValues = txResult.length > 0 ? txResult[0].values : [];
-
-  return {
-    rx: calculateTrafficFromHistory(rxValues),
-    tx: calculateTrafficFromHistory(txValues)
-  };
+    return { rx, tx };
+  } catch (err) {
+    console.error(`[Prometheus] get24hTrafficSum error:`, err.message);
+    return { rx: 0, tx: 0 };
+  }
 }
 
 /**
@@ -417,34 +415,28 @@ async function get24hTrafficSum(url) {
  */
 async function get24hServerTrafficSum(url, instance, job) {
   const node = resolveToken(instance);
-  const now = Math.floor(Date.now() / 1000);
-  const start = now - 86400;
-  const step = 60;
-
-  const rxExpr = `sum(rate(node_network_receive_bytes_total{instance="${node}",job="${job}",device!~'tap.*|veth.*|br.*|docker.*|virbr*|podman.*|lo.*|vmbr.*|fwbr.|ip.*|gre.*|virbr.*|vnet.*'}[1m]))`;
-  const txExpr = `sum(rate(node_network_transmit_bytes_total{instance="${node}",job="${job}",device!~'tap.*|veth.*|br.*|docker.*|virbr*|podman.*|lo.*|vmbr.*|fwbr.|ip.*|gre.*|virbr.*|vnet.*'}[1m]))`;
+  
+  const rxExpr = `sum(increase(node_network_receive_bytes_total{instance="${node}",job="${job}",device!~'tap.*|veth.*|br.*|docker.*|virbr*|podman.*|lo.*|vmbr.*|fwbr.|ip.*|gre.*|virbr.*|vnet.*'}[24h]))`;
+  const txExpr = `sum(increase(node_network_transmit_bytes_total{instance="${node}",job="${job}",device!~'tap.*|veth.*|br.*|docker.*|virbr*|podman.*|lo.*|vmbr.*|fwbr.|ip.*|gre.*|virbr.*|vnet.*'}[24h]))`;
 
   const [rxResult, txResult] = await Promise.all([
-    queryRange(url, rxExpr, start, now, step).catch(() => []),
-    queryRange(url, txExpr, start, now, step).catch(() => [])
+    query(url, rxExpr).catch(() => []),
+    query(url, txExpr).catch(() => [])
   ]);
 
-  const rxValues = rxResult.length > 0 ? rxResult[0].values : [];
-  const txValues = txResult.length > 0 ? txResult[0].values : [];
+  const rx = rxResult.length > 0 ? parseFloat(rxResult[0].value[1]) : 0;
+  const tx = txResult.length > 0 ? parseFloat(txResult[0].value[1]) : 0;
 
-  return {
-    rx: calculateTrafficFromHistory(rxValues),
-    tx: calculateTrafficFromHistory(txValues)
-  };
+  return { rx, tx };
 }
 
 /**
  * Get network traffic history (past 24h, 5-min intervals for chart)
  */
 async function getNetworkHistory(url) {
-  const now = Math.floor(Date.now() / 1000);
-  const start = now - 86400; // 24h ago
   const step = 300; // 5 minutes for better resolution on chart
+  const now = Math.floor(Date.now() / 1000 / step) * step; // Sync to step boundary
+  const start = now - 86400; // 24h ago
 
   const [rxResult, txResult] = await Promise.all([
     queryRange(url,
@@ -496,9 +488,9 @@ function mergeNetworkHistories(histories) {
  * Get CPU usage history (past 1h, 1-min intervals)
  */
 async function getCpuHistory(url) {
-  const now = Math.floor(Date.now() / 1000);
-  const start = now - 3600; // 1h ago
   const step = 60; // 1 minute
+  const now = Math.floor(Date.now() / 1000 / step) * step; // Sync to step boundary
+  const start = now - 3600; // 1h ago
 
   const result = await queryRange(url,
     '100 - (avg(rate(node_cpu_seconds_total{mode="idle"}[1m])) * 100)',