ModernStandbyGate disables the schedule on a machine that never sleeps (13.1.1.700)

[guitarnerdswe]

I ran into this after reinstalling Windows, and it took a while to pin down, so I'm posting the findings in case others hit the same thing.

Short version: on a machine where idle sleep is disabled, ModernStandbyGate treats the screen turning off as the machine entering Modern Standby, and disables the backup schedule for as long as the screen stays off. Scheduled backups never run at night; they run the next morning as missed backups.

Setup: ASUS Zenbook Duo UX8407AA, Windows 11 Pro (build 26200), Agent 13.1.1.700 (Free). On AC power at night, sleep and hibernate timeouts both set to Never. Only the display timeout is active, so the screen turns off after five minutes while the machine stays fully awake. Backups scheduled for 03:30 to a local USB SSD. This worked before the reinstall.

From Svc.VeeamEndpointBackup.log, the moment the screen turns off:

[13.09.2026 20:44:54.451] [ModernStandbyGate] ScreenOff -> Pause() + cancel gate.
[13.09.2026 20:44:54.452] [ModernStandbyGate][1] Suspend detected.
[13.09.2026 20:44:54.453] Warning (1) Modern Standby detected. Schedule is disabled

The schedule stays disabled all night. At 03:30 the hourly heartbeat prints the job and its next run time, but nothing starts. When the screen comes on in the morning, the stability gate runs its 150 seconds, "Resume detected" is logged, and the job runs as a missed backup.

The machine was never in Modern Standby that night. A powercfg sleepstudy report for the same session (20:44 to 08:14) shows "No CS Phase" at 100% and "System Idle" at 100%, so Connected Standby was never entered. The session metadata confirms StandbyTimeoutInSeconds = 0, HibernateTimeoutInSeconds = 0, IdleTimeoutSource = Disabled.

Display-off is the trigger for a transition into Modern Standby, but that transition doesn't happen when the idle sleep timeout is disabled. The gate seems to treat the trigger as the transition itself. On any platform reporting ConnectedStandby = true, that means a machine with sleep set to Never will never run a scheduled backup while the screen is off.

A question for anyone who knows the internals: does the gate check the active power scheme's idle sleep timeout before disabling the schedule? If it doesn't, adding that check looks straightforward - the value is readable through PowerReadACValue / PowerReadDCValue using GUID_SLEEP_SUBGROUP and GUID_STANDBY_TIMEOUT, and the Agent appears to read power schemes already, judging by the log line "[WakeupManager] Waitable timers are disabled in all power schemes". A lid close or user-initiated sleep would still enter Modern Standby, but those raise their own power notifications that the Agent already handles ("Catched PowerAction: Suspend"), so display-off alone doesn't seem like sufficient evidence that the system is going to sleep.

Workarounds, for anyone stuck on the same thing:

A blank screensaver instead of the display timeout. The screen stays "on" as far as Windows is concerned, so the gate never fires. Simplest fix, and it worked immediately. I moved away from it only because my monitors aren't dark enough at black for a dark room.

A scheduled script that moves the mouse from 03:25, which wakes the screen and lets the gate release the schedule before the job is due. The gate needs 150 seconds (60s fixed delay + 90s stable window), so five minutes of lead time is plenty. Worth noting that the movement has to look like real mouse input - SetCursorPos doesn't wake the display, and single-pixel jitter didn't either.

I reported this through the in-product form, but as a free user the ticket was closed unread, so I'm posting here instead. Has anyone else with sleep disabled seen the same behaviour?

Support ID: 08242166

[david.domask]

Hi guitarnerdswe, welcome to the forums.

Thanks for the detailed write-up; I checked our internal Support documentation and seems that Support has seen this before and it indeed seems to be a limitation on how Modern StandBy works and signals a sleep. I wasn't able to find the full logic written out, but based on what Support has seen, it's a similar situation where the machine reports sleep even though just the screen has been shut off.

Recommendation from Support is to enable the Missed Backup Schedule to ensure that such cases are caught.