«حَتَّىٰ إِذَا جَاءُوهَا وَفُتِحَتْ أَبْوَابُهَا»
“Until, when they arrive there and its gates have been opened.” (al-Zumar 39:73, excerpt)
The arrival of the people of Paradise is framed by “idhā.” The presence of “wa” before “the gates were opened” invites grammatical analysis: it can be discussed in terms of circumstantial or conjunctive linkage and the relation to the answer of the temporal clause.
Compare the passage about the people of the Fire: “Ḥattā idhā jāʾūhā futiḥat abwābuhā” (al-Zumar 39:71, excerpt), where the conjunction is not expressed in the same position.
The contrast warrants attention but not dogmatic reduction of a debated syntactic question to one fixed explanation.