.tool-versions: Same Versions in Dev and CI

Wed, 21 Oct 2026 00:00:00 -0400

Work on a few projects and you start collecting version managers. nvm for Node, SDKMAN for Java, pyenv for Python, tfenv for Terraform. Each one has its own install, its own setup in your shell, and its own file: .nvmrc, .sdkmanrc, .python-version, .terraform-version.

One manager per language doesn’t scale

They do their job. Node has had .nvmrc for years, so pinning a version isn’t the hard part. Keeping all those managers around is. Every new project can mean one more on every laptop, and CI has to be told the same versions again, in its own way.

direnv: Onboarding in One cd

Tue, 20 Oct 2026 10:00:00 -0400

Most of what I read these days is about something new. A new model, a new agent, a new way to not write code. Fine. This post goes back to basics: a small tool that has been around for years and quietly removed a whole category of onboarding problems at work.

The tool is direnv.

The problem

Every project needs an environment to run. Default config, like which Vault to talk to or the log level. And secrets, like a database password. Before, everyone kept a local .env with all of that copied in by hand. It worked on day one. Then a password was rotated or a default changed, and your copy was quietly out of date. And since that file was full of real values, it was always one .gitignore slip away from a commit.

Back to Basics on Alexis Couvreur

.tool-versions: Same Versions in Dev and CI

One manager per language doesn’t scale

direnv: Onboarding in One cd

The problem