An AI game character can sound convincing in one isolated exchange and still lose its identity across a branching scene.
The failure usually is not a single “bad line.” It is voice drift: the character becomes warmer, more knowledgeable, more verbose, or more compliant depending on how the player reaches the same narrative state.
A practical way to catch this is to test voice as a constrained system rather than as a vague feeling. I use a small matrix with four axes:
State — what the character knows, wants, and is allowed to reveal.
Intent — what the player is trying to do.
