Don't co-install a React Native app and a web app in one npm workspace

The break

Making mobile an npm workspace alongside frontend and packages/core looked tidy — one install, shared @shadow-ai/core. Then Vercel's frontend build (a branch preview) failed:

Error: No prebuild or local build of @parcel/watcher found.
       Tried @parcel/watcher-linux-x64-glibc.
npm error workspace frontend@0.1.0 ... command sh -c next build ... exited 1

Why

Because mobile was a workspace, Vercel — installing the workspace root — pulled in the entire Expo / React Native / Metro dependency tree, including @parcel/watcher, a native module with no Linux prebuild for Vercel's build image. The web app never needed it; it leaked in purely because the mobile workspace was installed alongside the frontend.

The fix

mobile is no longer an npm workspace. The root workspaces is narrowed to ["packages/*", "frontend"]; mobile depends on the shared core through a file: link ("@shadow-ai/core": "file:../packages/core") and is installed on its own (cd mobile && npm install). So the root install — the thing Vercel runs — resolves only web-compatible deps, and the React Native native tree stays out of it.

The takeaway

A monorepo should only co-install, in one workspace root, the things that platform can build. A React Native / Expo app and a web app under the same workspace root means the web deploy installs RN's native modules — which have no Linux/serverless prebuilds — and breaks. Keep the cross-platform app out of the workspace and share code via a file: (or published) package.

Commit: cc48293. (Footnote: this killed one source of the @parcel/watcher break. The same error class later returned from a different dependency — next-intl — and took a different fix; see the four-binary Vercel saga.)