Unlike many pop stars who rotate producers by album, The Weeknd's biggest stylistic transformation — from atmospheric, downtempo R&B mixtapes to full-throttle 80s-indebted synth-pop — was carried through largely by the same small set of collaborators, evolving together rather than being replaced.
From mixtapes to arenas
The earliest work leaned on a specific, insular sound with a tight circle of contributors. As the sound scaled up toward stadium-sized pop, several of those same names scaled up with it, joined by a few new specialists brought in specifically for the synth-heavy direction.
The Max Martin era
A partnership with pop's most consistent hitmaking machinery marked the clearest turning point in the catalog, coinciding with the sound most casual listeners now associate with him. Searching that stretch of the discography shows a noticeably different, more pop-oriented credit list than the material before or after it.
Reading the pattern
Continuity in collaborators through a genre shift usually signals a genuine artistic evolution rather than a chase for a trend.
That's a useful heuristic across the catalog generally — when the same handful of names persist through a sonic left turn, it's usually deliberate. Full production credits, album by album, are searchable on IMUDB.