Insofar means to the extent that. It limits a claim to exactly the part being agreed.
It always appears as insofar as, which is a three-word construction doing one job. The word is formal and legal, and contracts and judgments use it constantly, since insofar as the rule applies is agreeing only within a stated boundary. British English sometimes writes it as three words, in so far as, and both are accepted. To the extent that is the plainer alternative.
1adverbinsofarTo the extent or degree that.
“The clause applies insofar as the goods were faulty.”
in + so + far.
Etymology from Wiktionary, CC BY-SA