Found by the package matrix re-run (#11723): fastify/inject throws … (reading 'once'). Reproduces 3/3 at 9e29f59 and on origin/main 9e05951.
On a CommonJS subclass of http.ServerResponse (built with http.ServerResponse.call(this, req) plus util.inherits), this.assignSocket(sock) does nothing, so this.connection stays undefined. The same code in a .ts file throws "not a ServerResponse" instead.
The 8-line repro is in RERUN-2026-09-30.md in #11723 (benchmarks/packages).
Found by the package matrix re-run (#11723):
fastify/injectthrows… (reading 'once'). Reproduces 3/3 at 9e29f59 and on origin/main 9e05951.On a CommonJS subclass of
http.ServerResponse(built withhttp.ServerResponse.call(this, req)plusutil.inherits),this.assignSocket(sock)does nothing, sothis.connectionstaysundefined. The same code in a.tsfile throws "not a ServerResponse" instead.The 8-line repro is in
RERUN-2026-09-30.mdin #11723 (benchmarks/packages).