I've had some funny conversations -- Me:"Why did you choose to do X to solve the problem?" ... It:"Oh I should totally not have done that, I'll do Y instead".
But it's far from being so unreliable that it's not useful.
As far as I understand, any reasoning tokens for previous answers are generally not kept in the context for follow-up questions, so the model can't even really introspect on its previous chain of thought.
It providing a different result is exactly because it's now looking at the existing solution and generating from there.
Not to get all philosophical but maybe justification is post-hoc even for humans.
I guess I should have used ‘completely trust’ instead of ‘trust’ in my original comment. I was referring to the subset of developers who call themselves vibe coders.