Nx daemon unsupported in WebAssembly: missing OS-specific optional packages

TL;DR

Nothing in the repo had changed; the breakage arrived via a dependency update. Community-diagnosed root cause: your install is missing OS-specific optional packages.

Steps

1. Issue nrwl/nx#27263 (closed, 80 comments): Overnight, every nx command in a monorepo started printing "The Nx Daemon is unsupported in WebAssembly environments", then got stuck and crashed with a wasm memory allocation failure. Nothing in the repo had changed; the breakage arrived via a dependency update.
2. Community-diagnosed root cause: your install is missing OS-specific optional packages. Per commenter damienwebdev, this traces back to an npm behavior where optionalDependencies for other operating systems never make it into package-lock.json when a coworker or bot on a different OS runs npm install. When you then run npm ci locally, the native Nx daemon binary packages are missing and Nx falls back to the wasm build, which fails. The fix: run npm install nx@yourversion yourself on your own machine so your lockfile picks up your OS's optional packages. Do not just delete node_modules and package-lock.json and reinstall: that works, but it also nukes everyone else's locked dependency state.

When to use

You are seeing this: Issue nrwl/nx#27263 (closed, 80 comments): Overnight, every nx command in a monorepo started printing "The Nx Daemon is unsupported in WebAssembly environments", then got stuck and crashed with a wasm memory allocation failure. Use this skill when you run into "Nx daemon unsupported in WebAssembly: missing OS-specific optional packages".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

In gh:nrwl/nx#27263 (Nx), the issue reported was: Issue nrwl/nx#27263 (closed, 80 comments): Overnight, every nx command in a monorepo started printing "The Nx Daemon is unsupported in WebAssembly environments", then got stuck and crashed with a wasm memory allocation failure. Nothing in the repo had changed; the breakage arrived via a dependency update. The verified resolution from the thread: Community-diagnosed root cause: your install is missing OS-specific optional packages. Per commenter damienwebdev, this traces back to an npm behavior where optionalDependencies for other operating systems never make it into package-lock.json when a coworker or bot on a different OS runs npm install. When you then run npm ci locally, the native Nx daemon binary packages are missing and Nx falls back to the wasm build, which fails. The fix: run npm install nx@yourversion yourself on your own machine so your lockfile picks up your OS's optional packages. Do not just delete node_modules and package-lock.json and reinstall: that works, but it also nukes everyone else's locked dependency state. Source: mount the host path https at container path //github.com/nrwl/nx/issues/27263