devenv-setup

# devenv Setup ## When to use Use this skill when: - Creating a new `devenv.nix` configuration - Adding programming languages, services, or packages - Configuring processes, tasks, or git hooks - Setting up a reproducible developer environment ## Quick start Initialize a new project: ```shell devenv init ``` This creates `devenv.nix` and `devenv.yaml` in the current directory. For installation instructions, see [https://devenv.sh/getting-started/](https://devenv.sh/getting-started/). ## Configuration ### devenv.nix The main configuration file. Example: ```nix { pkgs, ... }: { packages = [ pkgs.git pkgs.curl ]; languages.rust.enable = true; services.postgres.enable = true; processes.server.exec = "cargo run"; } ``` ### devenv.yaml Defines inputs and imports: ```yaml inputs: nixpkgs: url: github:cachix/devenv-nixpkgs/rolling ``` ## Key features - **Languages**: `languages.<name>.enable = true;` — supports 50+ languages - **Services**: `services.<name>.enable = true;` — supports 100+ services (postgres, redis, etc.) - **Packages**: `packages = [ pkgs.<name> ];` — any package from nixpkgs - **Processes**: `processes.<name>.exec = "command";` — managed background processes - **Scripts**: `scripts.<name>.exec = "command";` — custom shell scripts - **Tasks**: `tasks.<name>.exec = "command";` — DAG-based task execution - **Git hooks**: `git-hooks.hooks.<name>.enable = true;` — pre-commit hooks - **Containers**: `containers."<name>" = { ... };` — OCI containers ## Ad-hoc environments Run commands in a temporary environment without creating files: ```shell devenv -O languages.rust.enable:bool true shell devenv -O languages.python.enable:bool true -O packages:pkgs "nodejs git" shell -- node --version ``` ## Commands - `devenv shell` — enter the development shell - `devenv up` — start all processes - `devenv test` — run tests - `devenv build` — build outputs - `devenv search <query>` — search for packages - `devenv update` — update all inputs - `devenv update <name>` — update a specific input ## MCP server devenv provides an MCP server with `search_packages` and `search_options` tools. Use it for looking up available packages and configuration options. ```shell devenv mcp # stdio mode devenv mcp --http # HTTP mode on port 8080 ``` To wire it up automatically in a project, add to `devenv.nix`: ```nix { # For Claude Code claude.code.mcpServers.devenv = { type = "stdio"; command = "devenv"; args = [ "mcp" ]; }; # For OpenCode opencode.mcp.devenv = { type = "local"; command = [ "devenv" "mcp" ]; }; } ``` A hosted instance is also available at `https://mcp.devenv.sh`. ## Reference - [Documentation](https://devenv.sh) - [Configuration options](https://devenv.sh/reference/options/) - [Source code](https://github.com/cachix/devenv) --- > Source: [cachix/devenv](https://github.com/cachix/devenv) — distributed by [TomeVault](https://tomevault.io). <!-- tomevault:4.0:skill_md:2026-06-28 -->