Update (0750ET): Here comes Reuters with the latest on the Musk-Twitter deal. Their three-sentence scooplet includes two notable details.

The first is that Musk and Twitter are indeed negotiating on the basis that his offer of $54.20/share (which would value the company at $43 billion).

The second is that the deal would preclude a "go-shop" provision (something we discussed below and for the first time earlier this month) allowing Twitter to solicit rival bids - although the company would still be allowed to take a rival offer if it pays the Musk group a break-up fee (agreements like these are pretty standard fare).