the pdf follows your typing, and the shortcuts do one thing each

[swimmingbrain]

From the HN thread:

Ctrl+S brings up the browser save as but also saves the document and recompiles. Ctrl+Enter puts in a new line and recompiles. Can click compile of course, but that's not efficient.

All three are real.

• Ctrl+Enter is also CodeMirror's "insert blank line", so both happened. CodeMirror doesn't see Mod+Enter anymore, same as Mod+/ and Mod+G before it.
• Ctrl+S on a document that was never saved (the welcome document everyone lands on now) went through save as and opened the file picker. Ctrl+S now saves when the file lives somewhere and compiles either way. The save button and Ctrl+Shift+S still ask where to put a new file.
• The landing page has claimed "the PDF updates while you type" all along and it never did. Now it does: a second after typing stops the document compiles on its own, and if one is running the next pass goes right after. An automatic compile never switches to the problems tab mid sentence and never repeats the missing file warnings, that only happens on a manual compile. An Auto button next to Compile turns it off for people who would rather press Ctrl+Enter, the choice is remembered.

Checked on the built site: the compile starts 1.0 s after typing stops, Ctrl+Enter leaves the text alone, Ctrl+S on the welcome document compiles with no dialog, and with Auto off typing does nothing.