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

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 and devenv.yaml has not changed since.
3. If trusted, runs devenv shell in a subshell for that project.

If devenv.yaml changes after you allow a project (for example, after pulling new changes), you will see a message asking you to run devenv allow again:

devenv: /home/user/myproject is not allowed or devenv.yaml has changed. 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 (devenv.yaml hash)	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.