How would AI respond? Would they figure out where the shot came from and go investigate?
Yes. In 5e, when you attack, you reveal your position.
I see, so there is no "stealth roll" to remain hidden after attack from stealth in original rules? If so,than yes, I think it would be fair to give enemies "ping" to investigate even if character remained in stealth. Of course, if character hides when combat is in process 1) it should take full turn, so one cannot attack and hide on the same turn, 2) enemies should remember last seen location and investigate.
Nope, there isn't! This is said directly in the "Unseen Attackers and Targets" rules (PHB p 194-195), and also by implication in the Skulker feat: "When you are hidden from a creature and miss it with a ranged weapon attack, making the attack doesn't reveal your position" --> you ARE revealed if you
don't have the Skulker feat, even if you miss.
As for hiding during your same turn, I disagree. Per 5e RAW, only rogues can Hide as a Bonus Action. For everybody else, it costs an action. If e.g., a rogue attacks from stealth -> breaks line of sight -> hides again, they should be able to. This is intended, and is ~required for rogues to remain competitive dpr-wise. If a Fighter wants to Action Surge to attack -> break line of sight -> hide again, they should be able to.
Of course, in BG3, everyone can hide as a bonus action, which is too much imo. Under this implementation, I wouldn't care if Hide was restricted like that, but now we're fixing homebrew with more homebrew.
