When does the beginning of your turn ends? Because I want to know if you can WEAPON RECONFIGURE and choose poison and work? I know you can do free actions at the beginning and end of your turn, but I'm not 100% sure when the beginning ends. Thanks

The beginning of the turn phase ends when you give the first non-free action (that doesn't specify it can be given during the beginning of the turn) of the turn.

The Weaponer can choose Poison and then use it.
On the next turn the Weaponer can use Poison and then choose another power.

General PG:

Turns
The “beginning of turn” ends with the first non-free action assigned to a character, unless that action specifically states that it can be given during the beginning of the turn.

Since Weapon Reconfigure is not activated by a non-free action, there is no way for it to end the beginning of the turn.

Thanks you both, I was assuming that, but wasn't 100%. Thanks again