Sometimes windows don't get persisted on a Windows Update

[zadjii-msft]

v1.21

I've now had a couple days where I've gotten a Windows Update, and came back to the Terminal not quite in the right state as before:

• A few times, I've had the buffer restored, but to a previous day's state. As if the buffer didn't get persisted on shutdown, but on launch I did get the buffer from the previous shutdown.
• Today, I only had one of my two windows persisted across the reboot. The window that was persisted did have all it's buffers restored, but the other window was gone entirely.

I have a theory that this is somehow related to us not handling WM_ENDSESSION post-PMv3 quite right, but that's a guess, not a root cause.

[zadjii-msft]

Yea, again today, I got both windows back, but the buffer state was what it was the previous time I had quit the Terminal. So, whatever happened during the update meant that the Terminal didn't actually persist the buffer.

[lhecker]

I found that this tool can be used for shutdown tests:

C:\Program Files (x86)\Windows Kits\10\App Certification Kit\rmlogotest.exe

For instance:

& "C:\Program Files (x86)\Windows Kits\10\App Certification Kit\rmlogotest.exe" (ps -Name WindowsTerminal).Id

I couldn't reproduce any issues on the main branch, even with multiple windows that have multiple tabs, and no matter how I re-launched the app.

[lhecker]

tl;dr: handoff doesn't assign a SessionId!

I figured out how to reproduce multiple issues (probably even the issue):

• Launch
• (Register that version of WT as the default)
• Close all tabs (Ctrl+Shift+W)
• Bug: persistedWindowLayouts is non-empty
• Launch cmd/pwsh via handoff, but use the one that's not your default profile
• (Known) Bug: You got 2 windows now instead of 1 (this is a consequence of the previous bug)
• Close the tab with the default profile (= the extra window)
• Close window with the handoff'd non-default profile (= press red X)
• Bug: Buffer doesn't get persisted, and no SessionId gets stored

[zadjii-msft]

So yea here's the thing - defterm wasn't involved (to the best of my knowledge) in my scenario. I almost never open things via defterm anymore - pretty sure Stable is set as my defterm handler. Normally quitting the terminal will persist just fine - there's something specific about updates that makes the terminal not persist the current state of the buffer 🤷