On the one hand, one obviously needs some technological leeway to write a fun novel set in the future.
On the other, if every roadblock is responded to by suspending scientific treatment, it doesn't seem like that's a good faith "hard" effort.
I think Ringworld is instructive. The Wikipedia article specifically calls out technical inaccuracies in the original... inaccuracies Niven specifically made an effort to patch up in later books.
So the count of intentional lapses seems as decent a proxy for hardness as anything else.
I would consider Ringworld to be borderline hard sci-fi, but precisely because it has some reasonably sounding explanation for his technomagic. E.g. the General Product hulls - them being a single macro-molecule is a reasonable pop-sci explanation for their properties, even if the book doesn't explain how such a molecule is made. Does that count as an intentional lapse?
On the one hand, one obviously needs some technological leeway to write a fun novel set in the future.
On the other, if every roadblock is responded to by suspending scientific treatment, it doesn't seem like that's a good faith "hard" effort.
I think Ringworld is instructive. The Wikipedia article specifically calls out technical inaccuracies in the original... inaccuracies Niven specifically made an effort to patch up in later books.
So the count of intentional lapses seems as decent a proxy for hardness as anything else.