sapper-dev-client loading over network and 404'ing #1789

Hey guys, I'm trying to migrate my big sapper project to webpack because I can't take rollup any longer and I've gotten it mostly done but am now running into this error:

manifest-client.mjs:40 GET http://localhost:3000/Users/sunnymittal/workspace/XXXX/node_modules/sapper/sapper-dev-client.js net::ERR_ABORTED 404 (Not Found)

When I start a brand new sapper/webpack/ts project, it works fine but as far as I can tell, there's nothing I'd be doing that would tell the file to be loaded over the network. Any help onthis would be greatly appreciated!