When you action surge in 2024, is it legal to use the extra action first, so you can do something involving attacking first and casting a spell second?
I can't see any reason why you couldn't. Action Surge grants you another action, but doesn't impose any restriction on when you can use that action; there's nothing preventing you from using the additional action to attack, then your main action to cast a spell.
When you action surge in 2024, is it legal to use the extra action first, so you can do something involving attacking first and casting a spell second?
In the following order for example:
Why or why not?
Yes, there's zero stipulation about when you take the action, just that you can take an additional action.
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I can't see any reason why you couldn't. Action Surge grants you another action, but doesn't impose any restriction on when you can use that action; there's nothing preventing you from using the additional action to attack, then your main action to cast a spell.
While many use it after taking their main action, nothing prevent you from using it before instead.
The only drawback is that you might waste your action surge (after evaluating your main action, maybe you decide action surge is no longer required).