Auto Activation

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

• Bash
• Zsh
• Fish
• Nushell

Add one line to your shell configuration file:

eval "$(devenv hook bash)"

~/.bashrc

Add one line to your shell configuration file:

eval "$(devenv hook zsh)"

~/.zshrc

Usually nothing to do — devenv installed via Nix ships a snippet that fish loads automatically. If it doesn’t load for you, add this instead:

devenv hook fish | source

~/.config/fish/config.fish

Usually nothing to do — devenv installed via Nix ships a snippet that nu loads automatically. If it doesn’t load for you, add this instead:

Run once, in Nu:

mkdir ($nu.default-config-dir | path join autoload)devenv hook nu | save --force ($nu.default-config-dir | path join autoload/devenv-hook.nu)

Terminal window

Passing arguments to devenv shell

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 allowdevenv: allowed /home/user/myproject

Terminal window

To activate one or more profiles whenever the project is entered, pass them when allowing it:

$ devenv --profile backend --profile observability allowdevenv: allowed /home/user/myproject with profile backend, observability

Terminal window

The selected profiles also apply to subsequent devenv commands in the project. An explicit --profile takes priority. Run plain devenv allow again to clear the saved profile selection without revoking trust.

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

$ cd ~/myproject(devenv) $

Terminal window

Revoking trust

To stop a project from auto activating:

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

Terminal window

How it works

The hook runs on every directory change and:

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.

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 ..$

Terminal window

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

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

Last updated Oct 08, 2026