diff --git a/src/main/java/com/ffii/fpsms/modules/common/SettingNames.java b/src/main/java/com/ffii/fpsms/modules/common/SettingNames.java
index 316b865..61cb2b7 100644
--- a/src/main/java/com/ffii/fpsms/modules/common/SettingNames.java
+++ b/src/main/java/com/ffii/fpsms/modules/common/SettingNames.java
@@ -26,6 +26,8 @@ public abstract class SettingNames {
   public static final String SCHEDULE_M18_PO = "SCHEDULE.m18.po";
 
   public static final String SCHEDULE_M18_DO1 = "SCHEDULE.m18.do1";
+  /** Saturday-only DO1 time (default 03:10). Mon–Fri & Sun use [SCHEDULE_M18_DO1] time via a second trigger. */
+  public static final String SCHEDULE_M18_DO1_SAT = "SCHEDULE.m18.do1.sat";
   public static final String SCHEDULE_M18_DO2 = "SCHEDULE.m18.do2";
 
   public static final String SCHEDULE_M18_MASTER = "SCHEDULE.m18.master";
diff --git a/src/main/java/com/ffii/fpsms/modules/common/scheduler/service/SchedulerService.kt b/src/main/java/com/ffii/fpsms/modules/common/scheduler/service/SchedulerService.kt
index 3fcc6ce..eacdf67 100644
--- a/src/main/java/com/ffii/fpsms/modules/common/scheduler/service/SchedulerService.kt
+++ b/src/main/java/com/ffii/fpsms/modules/common/scheduler/service/SchedulerService.kt
@@ -39,6 +39,8 @@ open class SchedulerService(
     @Value("\${scheduler.m18Units.enabled:true}") val m18UnitsSchedulerEnabled: Boolean,
 @Value("\${scheduler.m18Units.incrementalLookbackDays:7}") val m18UnitsIncrementalLookbackDays: Int,
 @Value("\${scheduler.inventoryLotExpiry.enabled:true}") val inventoryLotExpiryEnabled: Boolean,
+    /** When false (default), M18 PO / DO1 / DO2 / master-data cron jobs are not registered — use true in production only. */
+    @Value("\${scheduler.m18Sync.enabled:false}") val m18SyncEnabled: Boolean,
     val settingsService: SettingsService,
     /**
      * Lookback window for GRN code sync: rows with `created` from **start of (today − N days)** through **now**,
@@ -63,6 +65,8 @@ open class SchedulerService(
     var scheduledM18Po: ScheduledFuture<*>? = null
 
     var scheduledM18Do1: ScheduledFuture<*>? = null
+    /** Saturday DO1 run (same [getM18Dos1] as [scheduledM18Do1]). */
+    var scheduledM18Do1Sat: ScheduledFuture<*>? = null
     var scheduledM18Do2: ScheduledFuture<*>? = null
 
     @Volatile
@@ -110,6 +114,49 @@ open class SchedulerService(
         )
     }
 
+    /**
+     * Same second/minute/hour as [cronExpression] but only Mon–Fri and Sun (Saturday uses [SCHEDULE_M18_DO1_SAT]).
+     * Expects a 6-field cron.
+     */
+    private fun cronToMonFriSunSchedule(cronExpression: String): String {
+        val parts = cronExpression.trim().split(Regex("\\s+"))
+        if (parts.size != 6) {
+            return cronExpression
+        }
+        return "${parts[0]} ${parts[1]} ${parts[2]} ? * MON-FRI,SUN"
+    }
+
+    /**
+     * M18 DO1: [SCHEDULE_M18_DO1] applies Mon–Fri & Sun; [SCHEDULE_M18_DO1_SAT] is Saturday only (default 03:10).
+     */
+    fun scheduleM18Do1() {
+        scheduledM18Do1?.cancel(false)
+        scheduledM18Do1Sat?.cancel(false)
+        if (!m18SyncEnabled) {
+            scheduledM18Do1 = null
+            scheduledM18Do1Sat = null
+            logger.info("M18 DO1 schedulers disabled (scheduler.m18Sync.enabled=false)")
+            return
+        }
+
+        var cronMain = settingsService.findByName(SettingNames.SCHEDULE_M18_DO1).getOrNull()?.value ?: "0 10 19 * * *"
+        if (!isValidCronExpression(cronMain)) {
+            cronMain = "0 10 19 * * *"
+        }
+        val weekdaySunCron = cronToMonFriSunSchedule(cronMain)
+        val mainCron = if (isValidCronExpression(weekdaySunCron)) weekdaySunCron else cronMain
+
+        scheduledM18Do1 = taskScheduler.schedule({ getM18Dos1() }, CronTrigger(mainCron))
+
+        var cronSat = settingsService.findByName(SettingNames.SCHEDULE_M18_DO1_SAT).getOrNull()?.value ?: "0 10 3 ? * SAT"
+        if (!isValidCronExpression(cronSat)) {
+            cronSat = "0 10 3 ? * SAT"
+        }
+        scheduledM18Do1Sat = taskScheduler.schedule({ getM18Dos1() }, CronTrigger(cronSat))
+
+        logger.info("Scheduled M18 DO1: Mon-Fri,Sun -> {} | Saturday -> {}", mainCron, cronSat)
+    }
+
     // Init Scheduler
     @PostConstruct
     fun init() {
@@ -142,19 +189,33 @@ open class SchedulerService(
     }
 
     fun scheduleM18Po() {
-        commonSchedule(scheduledM18Po, SettingNames.SCHEDULE_M18_PO, ::getM18Po)
-    }
-
-    fun scheduleM18Do1() {
-        commonSchedule(scheduledM18Do1, SettingNames.SCHEDULE_M18_DO1, ::getM18Dos1)
+        if (!m18SyncEnabled) {
+            scheduledM18Po?.cancel(false)
+            scheduledM18Po = null
+            logger.info("M18 PO scheduler disabled (scheduler.m18Sync.enabled=false)")
+            return
+        }
+        scheduledM18Po = commonSchedule(scheduledM18Po, SettingNames.SCHEDULE_M18_PO, ::getM18Po)
     }
 
     fun scheduleM18Do2() {
-        commonSchedule(scheduledM18Do2, SettingNames.SCHEDULE_M18_DO2, ::getM18Dos2)
+        if (!m18SyncEnabled) {
+            scheduledM18Do2?.cancel(false)
+            scheduledM18Do2 = null
+            logger.info("M18 DO2 scheduler disabled (scheduler.m18Sync.enabled=false)")
+            return
+        }
+        scheduledM18Do2 = commonSchedule(scheduledM18Do2, SettingNames.SCHEDULE_M18_DO2, ::getM18Dos2)
     }
 
     fun scheduleM18MasterData() {
-        commonSchedule(scheduledM18Master, SettingNames.SCHEDULE_M18_MASTER, ::getM18MasterData)
+        if (!m18SyncEnabled) {
+            scheduledM18Master?.cancel(false)
+            scheduledM18Master = null
+            logger.info("M18 master-data scheduler disabled (scheduler.m18Sync.enabled=false)")
+            return
+        }
+        scheduledM18Master = commonSchedule(scheduledM18Master, SettingNames.SCHEDULE_M18_MASTER, ::getM18MasterData)
     }
 
     /**
diff --git a/src/main/resources/application-prod.yml b/src/main/resources/application-prod.yml
index 92fbf56..d9d9024 100644
--- a/src/main/resources/application-prod.yml
+++ b/src/main/resources/application-prod.yml
@@ -22,6 +22,8 @@ spring:
 
 
 scheduler:
+  m18Sync:
+    enabled: true
   m18Grn:
     createEnabled: true
   postCompletedDnGrn:
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
index 35b7124..f01703f 100644
--- a/src/main/resources/application.yml
+++ b/src/main/resources/application.yml
@@ -12,7 +12,10 @@ server:
 # PostCompletedDn GRN: runs daily at 00:01, processes all POs with receipt date = yesterday.
 # Set enabled: false to disable. Optional receiptDate: "yyyy-MM-dd" overrides for testing only.
 # m18Grn.createEnabled: M18 GRN PUT/create — false outside production so UAT/dev never posts GRNs.
+# m18Sync: M18 cron jobs for PO, DO1, DO2, master data — false outside production (manual /trigger/* still works).
 scheduler:
+  m18Sync:
+    enabled: false
   m18Grn:
     createEnabled: false
   postCompletedDnGrn:
diff --git a/src/main/resources/db/changelog/changes/20260401_do1_sat_setting/01_insert_do1_sat_scheduler.sql b/src/main/resources/db/changelog/changes/20260401_do1_sat_setting/01_insert_do1_sat_scheduler.sql
new file mode 100644
index 0000000..a1ef226
--- /dev/null
+++ b/src/main/resources/db/changelog/changes/20260401_do1_sat_setting/01_insert_do1_sat_scheduler.sql
@@ -0,0 +1,9 @@
+--liquibase formatted sql
+--changeset fpsms:20260401_do1_sat_setting
+
+INSERT INTO `fpsmsdb`.`settings` (`name`, `value`, `category`, `type`)
+SELECT 'SCHEDULE.m18.do1.sat', '0 10 3 ? * SAT', 'SCHEDULE', 'string'
+FROM DUAL
+WHERE NOT EXISTS (
+    SELECT 1 FROM `fpsmsdb`.`settings` WHERE `name` = 'SCHEDULE.m18.do1.sat'
+);