How do I keep IntelliJ from closing my Editor Tabs automatically?

Question

Change the Tab Limit under the Tab Closing Policy settings.

Open your IntelliJ settings: Select File -> Settings -> Editor -> General -> Editor Tabs.

Look for Tab Closing Policy -> Tab Limit and change the value to a higher integer.

You can also select to either close non-modified files first or less frequently used files first once your tab limit has been reached.

Adding an answer to help anyone else with a similar problem. OSX+Catalina on JetBrains/PyCharm was having closing all tabs when I lost focus on the application. When I came back the "Synchronization" action happened (top right circle arrow spins) and all windows are reset (many closed as a result). My fix was to disable in the settings. Appearance & Behavior > System Settings > Disable everything under the "Synchronization" section. You may need to seek out other "sync" options in settings.

For recent versions on Mac, Configure Editor tabs is under

In the Editor --> General --> Editor Tabs, Under Closing Policy, change the Tab limit as per your requirement

If you need more than 100 tabs:

By default, the maximum number of open tabs that you can allow is limited to 100. If you want to increase that limit, press Ctrl+Shift+A or choose Help | Find Action from the main menu. In the popup that opens, start typing Registry, select the corresponding item and press Enter. In the Registry dialog, search for the ide.max.editor.tabs key and change its value.