How does the F-35 do short take-offs?

In the Harrier when you want to do a running short take-off, the nozzles are first facing backwards, you apply power and after a few moments you turn the nozzles downwards and the combined lift from wing and engine lift you off the ground.

But how is a short take-off done in the future FAV-35B?
# Option1 — Is the clutch engaged from engine start-up? That would mean the vertical thrust increases analog to horizontal thrust and at some point you would swivel the main nozzle downwards (which takes about three to four seconds) and lift off like a Harrier. But how is the thrust of the main engine and the cold liftfan each linear to the rpms coming from the main engine?
# or Option2 — is the clutch engaged after a couple of seconds of pure horizontal thrust? Since it takes about two seconds for the cold liftfan to spool up, the moment the vertical thrust sets in is somewhat fuzzy and then remains the fact that the liftfan develops vertical lift faster than the main nozzle swivels thru 90° (almost twice as fast).

Both options sound somewhat nasty. Or will the F-35 never lift off vertically?
Has anybody any information or ideas about how it’s done?