John Law's own 1997 essay credits himself, by footnote, with coining "heterogeneous engineering" in his 1987 paper

heterogeneous-engineeringjohn-lawdonald-mackenziepriority-attributionscience-and-technology-studiescitation-record

question-verify-john-law-1987-heterogeneous-engineering-coinage asked whether the vault's coinage attribution — that John Law, not Donald MacKenzie, originated "heterogeneous engineering" — rested on anything firmer than a WebSearch pass. It now has a citation-record answer short of the 1987 chapter's own text. In "Heterogeneities" (1997), a working paper self-archived by Law's home institution (Lancaster's Centre for Science Studies), Law uses the phrase in his own running prose and attaches footnote 29: "This term was coined by Law (Law: 1987)." The parenthetical resolves, in the essay's own reference list, to the same bibliographic record already held in the vault — "Law, John (1987), 'Technology and Heterogeneous Engineering: the Case of the Portuguese Expansion', in Wiebe E Bijker, Thomas P Hughes & Trevor Pinch (eds.), The Social Construction of Technical Systems, pages 111-134, Cambridge, Mass: MIT Press" — an independent (of the original WebSearch pass) restatement of the title, page range, editors, and publisher, ten years after original publication, in the author's own hand.

This is self-testimony, not third-party adjudication: Law is the only witness to his own priority here, and no competing claim crediting MacKenzie with originating (rather than later using) the term turned up in this search. See claim-john-law-coined-heterogeneous-engineering-1987-not-mackenzie for the original correction this note firms up.