Devices in a group should only do synchronised updates to a new main version

(solved in my case, see next post; but maybe still worth considering for upcoming main versions in case of incompatible protocols)

I have a sync group of 2 Windows PCs and an Android smartphone. When I installed Syncthing first, V0.11 was up to date, I loved it. One day I agreed to the update to V0.12 on one device, and though I had nodded away the “possible incompatibility” note, I didn’t expect it would result in mere ‘disconnected’ status on all devices, with not a trace of a helping message. I was unable to use Syncthing for several weeks and really felt relief, when I got V0.12 working again.

Now I noticed that (as the default setting?) on one PC the “auto update” mark was set, after again several days of, to me, unexplainable connection problems.

So I’d suggest that preferredly a synch group of devices should only do upgrades after they negotiated that each device has the new version ready on board; or at least the disconnected status display should be enhanced to show a version incompatibility note or the version of the remote device; and in this case, an easier update undo than to open the folder, delete syncthing.exe and rename syncthing.exe.old should be available. As I interpret the user statistics when new versions come up, my issue applies to several people.

I am puzzled now because I opened the Android app and it shows Syncthing v0.13.5, one PC shows v0.13.6 (proposes update to v0.13.7 now), the other PC shows v0.13.1 (also proposes update to v0.13.7), and they synchronise successfully. What I downloaded an installed, however, was v0.12.21 – which is unimportant. But it is important that after updates to v0.13.7 on the PCs, everything shows disconnected everywhere. Maybe it’s a Windows filewall issue this time (standard MS Windows 10 firewall, no other firewalls installed. Avast Free antivirus on one PC, MS Windows Defender on the other one), but really annoying.

SOLVED - though I have no idea why. I again allowed updates to the higher minor versions and the devices connect now. The only thing I can imagine is, that during the past 6 days of trouble, the devices were online at different times and thus had different chances and points of time to do their updates, and that it is a main version compatibility issue indeed.

Syncthing will never auto update to a new major / potentially incompatible version. Also syncthing now will give you an error message that another device cannot connect because of incompatible versions.