fnm env fails in Cursor agent shells (non-interactive zsh + sandboxed writes)

[kharandziuk]

Context

Cursor runs AI agent commands in a dedicated shell, not the integrated terminal. That shell sets CURSOR_AGENT=1, is non-interactive login zsh, and often runs inside a sandbox that only allows writes inside the workspace.

Projects pin Node via .nvmrc (e.g. 20.19.6). In a normal interactive terminal, fnm works as expected.

Setup

• OS: macOS
• Shell: zsh
• fnm: Homebrew (/opt/homebrew/bin/fnm)
• Interactive terminal (.zshrc):

  eval "$(fnm env --use-on-cd --shell zsh)"

• Agent shell (.zshenv, sourced on every zsh invocation):

  if [[ -n "$CURSOR_AGENT" ]]; then
    eval "$(fnm env)"
  fi

Problem

1. .zshrc is not sourced in the agent shell (interactive=no), so --use-on-cd never runs and .nvmrc is not applied automatically.

2. fnm env fails when initializing in the agent shell:

   error: Can't create the symlink for multishells at
   "/Users/local_admin/.local/state/fnm_multishells/<pid>_<ts>".
   Operation not permitted (os error 1)
   

   fnm creates a new multishell symlink on every shell start. The agent sandbox blocks writes under ~/.local/state/.

any idea how to fix it? or any workaround?