Live programming
Also: liveness, Bret Victor
Programming with an immediate, continuous connection between the code you write and the behaviour you see.
Live programming seeks to abolish the delay — and the leap of imagination — between editing code and seeing what it does. Instead of write → compile → run → imagine why it broke, the system shows you the consequences of every change as you make it, continuously.
The idea has deep roots — the REPL, Smalltalk's live image — but its sharpest modern statement is Bret Victor's 2012 talk "Inventing on Principle," where he argues that creators need an immediate connection to what they're creating, and demonstrates editors where changing a number instantly changes the running picture. His essay Learnable Programming extends the argument to how we teach.
Liveness is less a single technology than a principle you can apply everywhere: shrink the feedback loop until thought and result are nearly the same act.