huh what? Nathan never had plans to kill Caleb - he always had plans to "use" him, but there was never a plan to kill.

Kenny, perhaps I'm conflating two events. There is a conversation between Nathan and Caleb toward the very end where Nathan reveals the truth about everything. Then soon thereafter, he knocks out Caleb and heads off to kill Ava. I figured once done with her, he'd return to dispose of Caleb. Perhaps those are two separate events, but I thought they were connected. Why would Nathan allow Caleb to leave? Wouldn't Caleb act as a threat to Nathan's security, the intimate knowledge Caleb has about Nathan's AI projects? So perhaps I was wrong in making an assumption. I'll be curious if anyone else had that same sense.

yeah, i took that as a character expression. Nathan is all about control and ego. He wants to see himself as a "god", the genius inventor. He is hubris personified. He thought he had outwitted Ava and Caleb by bugging the room and spotting the "plan". But then Caleb reveals that he'd already done it all the night before. Nathan can't handle that he's not in control, not on top of everything - then his default reaction comes out - he tries to break what he cant control. Its the same thing he does to his AI - he's made potentially dozens of them (Ava is v9.4) and each time they dont do what Nathan wants, each time they cant be controlled of "programmed" into doing what he wants, he destroys them (well, overwrites them).