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[PR #18869] [1.22] Fix teardown when 'allowHeadless' is enabled #31629

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opened 2026-01-31 09:48:30 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:48:30 +00:00
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Original Pull Request: https://github.com/microsoft/terminal/pull/18869

State: closed
Merged: Yes

Summary of the Pull Request

Fixes a bug where Monarch::_peasants would not be updated when the last window was closed and compatibility.allowHeadless was enabled.

Detailed Description of the Pull Request / Additional comments

The bug was originally caused by Monarch::_peasants still holding on to a reference to itself in the list. Normally, a Peasant was removed from the list via the WindowManager::SignalClose() (aka Monarch::SignalClose()) function. However, AppHost::_CloseRequested() would omit that call when the last window was closing.

Normally, that makes sense. It's the last window, so let's call AppHost::_quit() --> WindowManager::QuitAll() --> Monarch::QuitAll(), where we just call Peasant::Quit() on all the peasants and the monarch and we call it a day. Everything should be cleaned up and if we need a new session, we'll create a new Monarch anyways.

Problem is, when compatibility.allowHeadless is enabled, the WindowEmperor doesn't actually close! We want the WindowEmperor to stick around because that's the "headless" part we're allowing. See WindowEmperor::_decrementWindowCount(): bbd6427b08/src/cascadia/WindowsTerminal/WindowEmperor.cpp (L296-L308)

The fix here was to avoid the QuitAll() code path mentioned above if compatibility.allowHeadless is enabled. Just treat this as a normal teardown otherwise so that the WindowEmperor creates a new Monarch when we need it.

Validation Steps Performed

✅ The scenario from the bug works:

  • enable compatibility.allowHeadless
  • set windowingBehavior to useExisting
  • Open Terminal
  • Close the only open window
  • Attempting to open Terminal again should open a new window
    ✅ when all windows are closed, we still have the background process

Closes #18827

**Original Pull Request:** https://github.com/microsoft/terminal/pull/18869 **State:** closed **Merged:** Yes --- ## Summary of the Pull Request Fixes a bug where `Monarch::_peasants` would not be updated when the last window was closed and `compatibility.allowHeadless` was enabled. ## Detailed Description of the Pull Request / Additional comments The bug was originally caused by `Monarch::_peasants` still holding on to a reference to itself in the list. Normally, a `Peasant` was removed from the list via the `WindowManager::SignalClose()` (aka `Monarch::SignalClose()`) function. However, `AppHost::_CloseRequested()` would omit that call when the last window was closing. Normally, that makes sense. It's the last window, so let's call `AppHost::_quit()` --> `WindowManager::QuitAll()` --> `Monarch::QuitAll()`, where we just call `Peasant::Quit()` on all the peasants and the monarch and we call it a day. Everything should be cleaned up and if we need a new session, we'll create a new `Monarch` anyways. Problem is, when `compatibility.allowHeadless` is enabled, the `WindowEmperor` doesn't actually close! We want the `WindowEmperor` to stick around because that's the "headless" part we're allowing. See `WindowEmperor::_decrementWindowCount()`: https://github.com/microsoft/terminal/blob/bbd6427b0831a16dc65506b386f63e6c3b3567ad/src/cascadia/WindowsTerminal/WindowEmperor.cpp#L296-L308 The fix here was to avoid the `QuitAll()` code path mentioned above if `compatibility.allowHeadless` is enabled. Just treat this as a normal teardown otherwise so that the `WindowEmperor` creates a new `Monarch` when we need it. ## Validation Steps Performed ✅ The scenario from the bug works: - enable `compatibility.allowHeadless` - set `windowingBehavior` to `useExisting` - Open Terminal - Close the only open window - Attempting to open Terminal again should open a new window ✅ when all windows are closed, we still have the background process Closes #18827
claunia added the pull-request label 2026-01-31 09:48:30 +00:00
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Reference: starred/terminal#31629
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