I don't use a proxy, but have limited or unreliable internet access.
I use a proxy when downloading Git repos.
I use a proxy to connect to the npm registry.
npm config get registry prints: default.
Note that I'm constantly switching between npm 2, 3, 4, and 5 via nvm, so if sharing the cache would collide, that might be a problem. Npm install browserify or npm install -save-dev browserify How can the CLI team reproduce the problem?