Auto Activation

New in version 2.1

devenv includes a built in shell hook that automatically activates your developer environment when you cd into a project directory. No external tools required.

Setup

Add one line to your shell configuration file:

BashZshFishNushell

~/.bashrc

eval "$(devenv hook bash)"

~/.zshrc

eval "$(devenv hook zsh)"

~/.config/fish/config.fish

devenv hook fish | source

config.nu

devenv hook nu | save --force ~/.cache/devenv/hook.nu
source ~/.cache/devenv/hook.nu

Setup via the NixOS, nix-darwin, or home-manager module

New in version 2.2

NixOS, nix-darwin, and home-manager users can import the flake modules that devenv ships, which install the package and source the shell hook for every shell you have enabled — no rc-file edits required.

Add devenv as a flake input:

flake.nix

{
  inputs.devenv.url = "github:cachix/devenv";
}

NixOSnix-darwinhome-manager

configuration.nix

{ inputs, ... }:
{
  imports = [ inputs.devenv.nixosModules.default ];

  programs.devenv.enable = true;
}

configuration.nix

{ inputs, ... }:
{
  imports = [ inputs.devenv.darwinModules.default ];

  programs.devenv.enable = true;
}

home.nix

{ inputs, ... }:
{
  imports = [ inputs.devenv.homeManagerModules.default ];

  programs.devenv.enable = true;
}

By default, every supported shell that you have enabled also gets the hook sourced. Disable an individual integration with:

programs.devenv.enableBashIntegration = false;
programs.devenv.enableZshIntegration = false;
programs.devenv.enableFishIntegration = false;
programs.devenv.enableNushellIntegration = false; # home-manager only

The exported hook scripts are also available directly under ${pkgs.devenv}/share/devenv/shell-integration/<shell>/hook.<ext> if you want to wire them up by hand.

Trusting a project

Before a project can auto activate, you need to explicitly trust it. This is a security measure that prevents untrusted projects from modifying your shell.

Navigate to the project directory and run:

$ cd ~/myproject
$ devenv allow
devenv: allowed /home/user/myproject

When you cd into the directory next time, devenv will automatically start a shell:

$ cd ~/myproject
(devenv) $

Revoking trust

To stop a project from auto activating:

$ cd ~/myproject
$ devenv revoke
devenv: revoked /home/user/myproject

How it works

The hook runs on every directory change and:

1. Walks up from the current directory looking for a devenv.yaml file.
2. Checks the trust database to verify the project was allowed.
3. If trusted, runs devenv shell in a subshell for that project.

If a project has not been trusted yet, you will see a message asking you to run devenv allow:

devenv: /home/user/myproject is not allowed. Run 'devenv allow' to trust this directory.

Note

The hook only detects projects that have a devenv.yaml file. Projects with only devenv.nix (without devenv.yaml) are not detected.

Automatic deactivation

When you cd out of the project directory (or any of its subdirectories), the devenv shell exits automatically and you return to your normal shell:

(devenv) $ cd ..
$

Re-entry protection

The hook will not nest environments. While inside a devenv shell, navigating into a subdirectory of the same project keeps the current shell. Only navigating outside the project triggers deactivation.

Comparison with direnv

Feature	devenv hook	direnv
External dependencies	None	Requires direnv
Setup	One line in shell config	direnv install + .envrc per project
Trust granularity	Per project directory	Per .envrc file
Environment application	Spawns a subshell	Modifies current shell in place
Unloading on exit	Subshell exits automatically	direnv unloads variables

Use devenv hook for a simple, dependency free setup. Use direnv if you prefer in place environment modification without a subshell.