Sync stalls when phone is not active.

I seem to be having a strange and very frustrating issue.

Syncthing downloads at 4MBps, yet as soon as you stop using the phone for 5 seconds it slows to a crawl and reaches 0.

It has nothing to do with the App itself or the screen being on or off.

As soon as I start scrolling my apps or gallery screen the sync resumes at full speed.

This makes syncthing basically unusable for me.

I was on Android 12 and thought it may be an OS bug, so I decided to update to Android 13. Unfortunately the issues is still there.

Its probably phone vendors battery optimization shenanigans, which effectively suspends the apps when the screen is off.

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I had this in the past, and yes, it’s the ROM your running. There should be a line in the adb log which is like "freezing app … syncthingandroid " when it goes to zero transfer. Switched mine to PixelExperience rom 12/12.1 and now 13 and all is fine.

I have tried all the following:

  1. Disable battery optimisation. (Unrestricted mode)
  2. Keep screen on for 10 minutes.
  3. Keep screen on while charging.
  4. CPU on Max/High Performance.
  5. Upgrade from Android 12 to 13.

No matter if the App is in the foreground or in the background, the screen will be on and after 5-10 seconds of no phone activity (not touching screen), the transfer will stall, once you touch the screen, the transfer will resume at max speed (4MBps+).

@Catfriend1 - It certainly sounds like some baked in CPU sleep/freeze beyond my control. I really hope I don’t have to install a custom ROM for this to work.

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Have you tried adjusting the options in Syncthing under Settings? (specifically “Run Conditions” and “Experimental”)

Some of them might be helpful.

What’s the make/model of your Android device?

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I’ve been having the same problem with a custom rom on android 13. It seems to have been solved by enabling the following option: ExperimentalKeep CPU active while running syncthing.

With your Android is local on the same LAN, try this :

When your Android shows offline in your other device, check if you can ping it: this will tell if Syncthing went asleep or if the WiFi went asleep.

No issue with these setting on A13 (and no experimental ST feature set)

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