diff --git a/backend/src/db/migrate.js b/backend/src/db/migrate.js
index d2b5608..1cb047f 100644
--- a/backend/src/db/migrate.js
+++ b/backend/src/db/migrate.js
@@ -295,6 +295,18 @@ const migrate = async () => {
     ON CONFLICT (key) DO NOTHING
   `
 
+  // Mitra reachability — replaces the implicit `ping_interval * 3` grace
+  // window with an operator-facing "max heartbeat age" knob. The companion
+  // heartbeat cadence lives in env (MITRA_HEARTBEAT_CADENCE_SECONDS, default
+  // 30s). Default 45s keeps the same effective grace as the old 15s ping × 3.
+  // `mitra_ping_interval_seconds` is left in place (vestigial) — no live code
+  // path reads it anymore; safe to drop after one release.
+  await sql`
+    INSERT INTO app_config (key, value)
+    VALUES ('mitra_stale_after_seconds', '{"value": 45}')
+    ON CONFLICT (key) DO NOTHING
+  `
+
   // --- Phase 3.2: Mitra Request Activity Log ---
 
   await sql`
diff --git a/backend/src/routes/internal/config.routes.js b/backend/src/routes/internal/config.routes.js
index 14d3fc3..5ccdcb5 100644
--- a/backend/src/routes/internal/config.routes.js
+++ b/backend/src/routes/internal/config.routes.js
@@ -9,7 +9,7 @@ import {
   getFreeTrialConfig, setFreeTrialConfig,
   getExtensionTimeoutConfig, setExtensionTimeoutConfig,
   getEarlyEndConfig, setEarlyEndConfig,
-  getMitraPingConfig, setMitraPingConfig,
+  getMitraPingConfig, setMitraPingConfig, getMitraHeartbeatCadenceSeconds,
   getSensitivityConfig, setSensitivityConfig,
   getPaymentSessionTimeoutMinutes, setPaymentSessionTimeoutMinutes,
   getReturningChatConfirmationTimeoutSeconds, setReturningChatConfirmationTimeoutSeconds,
@@ -173,14 +173,23 @@ export const internalConfigRoutes = async (app) => {
   app.patch('/mitra-ping', {
     preHandler: [authenticate, attachCcUser, requirePermission('config', 'update')],
   }, async (request, reply) => {
-    const { require_ping, ping_interval_seconds } = request.body ?? {}
+    const { require_ping, stale_after_seconds } = request.body ?? {}
     if (require_ping !== undefined && typeof require_ping !== 'boolean') {
       return reply.code(422).send({ success: false, error: { code: 'VALIDATION_ERROR', message: 'require_ping must be a boolean' } })
     }
-    if (ping_interval_seconds !== undefined && (typeof ping_interval_seconds !== 'number' || ping_interval_seconds < 5)) {
-      return reply.code(422).send({ success: false, error: { code: 'VALIDATION_ERROR', message: 'ping_interval_seconds must be a number >= 5' } })
+    if (stale_after_seconds !== undefined) {
+      const cadence = getMitraHeartbeatCadenceSeconds()
+      if (typeof stale_after_seconds !== 'number' || stale_after_seconds < cadence) {
+        return reply.code(422).send({
+          success: false,
+          error: {
+            code: 'VALIDATION_ERROR',
+            message: `stale_after_seconds must be a number >= heartbeat cadence (${cadence}s)`,
+          },
+        })
+      }
     }
-    const config = await setMitraPingConfig({ require_ping, ping_interval_seconds })
+    const config = await setMitraPingConfig({ require_ping, stale_after_seconds })
     return reply.send({ success: true, data: config })
   })
 
diff --git a/backend/src/services/config.service.js b/backend/src/services/config.service.js
index 2b8e0d6..429152b 100644
--- a/backend/src/services/config.service.js
+++ b/backend/src/services/config.service.js
@@ -128,18 +128,38 @@ export const getEarlyEndConfig = async () => {
   }
 }
 
-// --- Phase 3.1: Mitra Ping Config ---
+// --- Mitra reachability config ---
+//
+// Two separate concerns, deliberately decoupled:
+//   - heartbeat_cadence_seconds: how often the mitra app sends a heartbeat.
+//     Fixed per backend deployment via the MITRA_HEARTBEAT_CADENCE_SECONDS
+//     env (default 30). The mitra app reads this from /api/mitra/status and
+//     uses it directly as its Timer.periodic interval.
+//   - stale_after_seconds: how long the backend tolerates silence before
+//     marking a mitra offline. DB-stored, CC-tunable. Must be >= the
+//     heartbeat cadence (CC PATCH validates this).
+//
+// `require_ping` stays as the master switch — when false, the auto-offline
+// sweep is skipped entirely and mitras stay online forever once they toggle.
+
+export const getMitraHeartbeatCadenceSeconds = () => {
+  const raw = process.env.MITRA_HEARTBEAT_CADENCE_SECONDS
+  if (!raw || raw.trim() === '') return 30
+  const parsed = Number.parseInt(raw, 10)
+  return Number.isFinite(parsed) && parsed >= 5 ? parsed : 30
+}
 
 export const getMitraPingConfig = async () => {
   const [requireRow] = await sql`SELECT value FROM app_config WHERE key = 'require_mitra_ping'`
-  const [intervalRow] = await sql`SELECT value FROM app_config WHERE key = 'mitra_ping_interval_seconds'`
+  const [staleRow] = await sql`SELECT value FROM app_config WHERE key = 'mitra_stale_after_seconds'`
   return {
     require_ping: requireRow?.value?.value ?? true,
-    ping_interval_seconds: intervalRow?.value?.value ?? 15,
+    stale_after_seconds: staleRow?.value?.value ?? 45,
+    heartbeat_cadence_seconds: getMitraHeartbeatCadenceSeconds(),
   }
 }
 
-export const setMitraPingConfig = async ({ require_ping, ping_interval_seconds }) => {
+export const setMitraPingConfig = async ({ require_ping, stale_after_seconds }) => {
   if (require_ping !== undefined) {
     await sql`
       INSERT INTO app_config (key, value, updated_at)
@@ -147,10 +167,10 @@ export const setMitraPingConfig = async ({ require_ping, ping_interval_seconds }
       ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value, updated_at = NOW()
     `
   }
-  if (ping_interval_seconds !== undefined) {
+  if (stale_after_seconds !== undefined) {
     await sql`
       INSERT INTO app_config (key, value, updated_at)
-      VALUES ('mitra_ping_interval_seconds', ${sql.json({ value: ping_interval_seconds })}, NOW())
+      VALUES ('mitra_stale_after_seconds', ${sql.json({ value: stale_after_seconds })}, NOW())
       ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value, updated_at = NOW()
     `
   }
diff --git a/backend/src/services/mitra-status.service.js b/backend/src/services/mitra-status.service.js
index 6cd0376..558deda 100644
--- a/backend/src/services/mitra-status.service.js
+++ b/backend/src/services/mitra-status.service.js
@@ -96,7 +96,9 @@ export const getStatus = async (mitraId) => {
   return {
     ...status,
     require_ping: pingConfig.require_ping,
-    ping_interval_seconds: pingConfig.ping_interval_seconds,
+    // The app reads this to set its Timer.periodic interval. Backend-fixed
+    // (via env), not operator-tunable.
+    heartbeat_cadence_seconds: pingConfig.heartbeat_cadence_seconds,
   }
 }
 
@@ -134,7 +136,12 @@ export const autoOfflineStaleMitras = async () => {
   // If ping is not required, skip the auto-offline sweep entirely
   if (!pingConfig.require_ping) return 0
 
-  const staleSeconds = pingConfig.ping_interval_seconds * 3
+  // stale_after_seconds is the operator-facing knob — what they set is what
+  // they get. No multiplier, no implicit "tolerate N missed heartbeats"
+  // contract baked in. The CC PATCH validates that the value is >= the env-
+  // driven heartbeat cadence so single missed pings can't flip a mitra
+  // offline.
+  const staleSeconds = pingConfig.stale_after_seconds
   const stale = await sql`
     UPDATE mitra_online_status
     SET is_online = false, last_offline_at = NOW(), updated_at = NOW()
diff --git a/control_center/src/pages/settings/SettingsPage.jsx b/control_center/src/pages/settings/SettingsPage.jsx
index 672b728..0797270 100644
--- a/control_center/src/pages/settings/SettingsPage.jsx
+++ b/control_center/src/pages/settings/SettingsPage.jsx
@@ -452,7 +452,7 @@ export default function SettingsPage() {
 
       <section style={{ marginBottom: 24 }}>
         <h2>Mitra Online Status (Ping)</h2>
-        <p>Konfigurasi apakah mitra harus mengirim ping (heartbeat) untuk tetap online.</p>
+        <p>Mitra dianggap online selama heartbeat terakhir berusia ≤ ambang batas. Cadence (frekuensi ping aplikasi) di-fix oleh server lewat env var.</p>
         <label style={{ display: 'flex', alignItems: 'center', gap: 8, marginBottom: 8 }}>
           <input
             type="checkbox"
@@ -465,21 +465,27 @@ export default function SettingsPage() {
         <p style={{ fontSize: 12, color: '#666', marginBottom: 8 }}>
           Jika dinonaktifkan, mitra akan tetap online tanpa perlu mengirim ping. QC bertanggung jawab atas kualitas layanan mitra.
         </p>
-        <div style={{ display: 'flex', alignItems: 'center', gap: 8 }}>
-          <label>Interval Ping:</label>
+        <div style={{ display: 'flex', alignItems: 'center', gap: 8, marginBottom: 6 }}>
+          <label>Ambang offline (heartbeat terakhir lebih lama dari):</label>
           <input
             type="number"
-            min="5"
-            value={mpData?.ping_interval_seconds ?? 15}
+            min={mpData?.heartbeat_cadence_seconds ?? 30}
+            value={mpData?.stale_after_seconds ?? 45}
             onChange={e => {
               const val = parseInt(e.target.value, 10)
-              if (val >= 5) mpMutation.mutate({ ping_interval_seconds: val })
+              const floor = mpData?.heartbeat_cadence_seconds ?? 30
+              if (Number.isFinite(val) && val >= floor) {
+                mpMutation.mutate({ stale_after_seconds: val })
+              }
             }}
             disabled={mpMutation.isPending}
             style={{ width: 80 }}
           />
           <span>detik</span>
         </div>
+        <p style={{ fontSize: 12, color: '#666', marginBottom: 0 }}>
+          Cadence ping mitra: <strong>{mpData?.heartbeat_cadence_seconds ?? 30} detik</strong> (server-set via MITRA_HEARTBEAT_CADENCE_SECONDS env). Nilai ambang minimum mengikuti cadence — tidak bisa lebih rendah.
+        </p>
         {mpMutation.isError && <p style={{ color: 'red' }}>Gagal menyimpan.</p>}
       </section>
 
diff --git a/mitra_app/lib/core/status/status_notifier.dart b/mitra_app/lib/core/status/status_notifier.dart
index 4d5efc2..b5f65e5 100644
--- a/mitra_app/lib/core/status/status_notifier.dart
+++ b/mitra_app/lib/core/status/status_notifier.dart
@@ -31,7 +31,11 @@ class StatusErrorData extends OnlineStatusData {
 class OnlineStatus extends _$OnlineStatus {
   Timer? _heartbeatTimer;
   bool _requirePing = true;
-  int _pingIntervalSeconds = 15;
+  // Heartbeat cadence is backend-fixed (MITRA_HEARTBEAT_CADENCE_SECONDS env,
+  // default 30s). Surfaced via /api/mitra/status. The CC-tunable
+  // mitra_stale_after_seconds is the offline threshold and lives entirely
+  // server-side — the app doesn't care, it just pings on a steady cadence.
+  int _heartbeatCadenceSeconds = 30;
 
   @override
   OnlineStatusData build() => const StatusInitialData();
@@ -41,7 +45,7 @@ class OnlineStatus extends _$OnlineStatus {
       final response = await ref.read(apiClientProvider).get('/api/mitra/status');
       final data = response['data'] as Map<String, dynamic>;
       _requirePing = data['require_ping'] as bool? ?? true;
-      _pingIntervalSeconds = data['ping_interval_seconds'] as int? ?? 15;
+      _heartbeatCadenceSeconds = data['heartbeat_cadence_seconds'] as int? ?? 30;
       state = StatusLoadedData(isOnline: data['is_online'] as bool);
     } catch (e) {
       state = const StatusLoadedData(isOnline: false);
@@ -83,7 +87,7 @@ class OnlineStatus extends _$OnlineStatus {
 
   void _startHeartbeat() {
     _stopHeartbeat();
-    _heartbeatTimer = Timer.periodic(Duration(seconds: _pingIntervalSeconds), (_) {
+    _heartbeatTimer = Timer.periodic(Duration(seconds: _heartbeatCadenceSeconds), (_) {
       _heartbeatTick();
     });
   }