Steps to reproduce: 1. Open a project and any Java file, write: String s = ""; 2. Now open somewhere a large text file. I'm using a 100KB html file. 3. Copy file contents into clipboard and paste into "" to get a 100KB string literal. Observed: StackOverflowException (see below) 4. Try to edit the file further, for example use Undo to remove the large string. Observed: IDEA is slow, a lot of CPU is used. Changes are not saved to disk . 5. Close IDEA, edit file manually to remove the large text, open IDEA and this file again. Observed: The large string is still there! After I manually pressed sync, it offered to load the updated file from disk, but slowness and CPU consumption remained after that. Speculation: it has something to do with the local history. I'm going to clear local caches to get IDEA into usable state again.