Nushell integration for Fast Node Manager (fnm), a fast and simple Node.js version manager. Automatically switches Node.js versions when you cd into a directory containing .nvmrc, .node-version, or package.json.

Based on this GitHub issue and fnm-nushell.

Requires fnm to be installed separately.

Copy or clone fnm.nu to a location of your choice and add the following to your Nushell config ($nu.config-path):

use /path/to/fnm.nu

It also works from $nu.user-autoload-dirs if you prefer autoloading.

All options are configured through $env.FNM_NU_CONFIG. Set it in your config.nu before use fnm.nu is evaluated. Every field is optional — defaults are applied for anything you omit.

$env.FNM_NU_CONFIG = {
    triggers: ['.nvmrc', '.node-version']  # files that trigger a version switch
    auto_install: true                      # install missing versions without prompting
    install_flags: ['--lts']                # extra flags passed to `fnm install`
    fallback_alias: 'default'               # optional stable PATH entry for non-shell processes
}

Configuration is re-read on every directory change, so you can update $env.FNM_NU_CONFIG at any time without restarting the shell.

fnm's multishell path is session-specific. If another tool copies your login environment into systemd (or similar), that path won't resolve for non-shell processes like IDEs or background services.

Setting fallback_alias to e.g. 'default' places that alias's bin directory in PATH below the multishell path. The active fnm version still takes precedence inside the shell, but non-shell consumers get a stable path to node, pnpm, and other tools.

The concrete use case that triggered adding this was Aspire launching ViteApp resources without env vars from the shell, and thus the install step failed when looking for pnpm. With fallback_alias: 'default', Aspire can find the default Node.js version even without the multishell path. So if you're playing around with Aspire and your dashboard yells at you that frontend couldn't start because "Missing command Required command 'pnpm' was not found on PATH or at the specified location" - there you go.

When you cd into a project that requires a Node.js version you don't have installed:

• auto_install: true — the version is installed and activated automatically.

• auto_install: false (default) — you see a message and an interactive prompt:

  fnm: Requested version v23.x.x is not currently installed
  Install it? [y/N]
  

  Answering y installs and activates the version. Answering anything else skips with a hint to run fnm install manually.