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Add a tembo.nix file to your repository root when your project needs tools that are not pre-installed in the sandbox. Tembo automatically detects the file and runs commands inside your Nix dev shell.

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Prerequisites

  • You have a repository connected to Tembo.
  • You know which system packages or language toolchains your project needs.

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Create tembo.nix

Create tembo.nix in your repository root with a default dev shell. Tembo uses devShells.x86_64-linux.default in the sandbox. 
{
  description = "Tembo Cloud VM Dependencies";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
      in {
        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            go
            rustc
            cargo
            jdk
          ];
        };
      }
    );
}
After you commit the file, new Tembo sessions use the dev shell automatically. Agents can then run commands that depend on those packages, such as go test, cargo test, or Java build tools.

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Add packages

Add packages to the packages list. For example, this dev shell adds PostgreSQL client tools and pkg-config for projects that compile native dependencies: 
{
  description = "Tembo Cloud VM Dependencies";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
      in {
        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            postgresql
            pkg-config
            openssl
          ];
        };
      }
    );
}

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Configure the shell

Use shellHook when the sandbox needs environment variables for local commands: 
{
  description = "Tembo Cloud VM Dependencies";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
      in {
        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            nodejs_22
            pnpm
          ];

          shellHook = ''
            export NODE_ENV=development
          '';
        };
      }
    );
}
Keep secrets out of tembo.nix. Add secrets through your sandbox environment variables instead.

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Tips

  • Keep tembo.nix focused on system packages and toolchains that your project needs.
  • Commit the file so Tembo can load it in every new session.
  • Use snapshots if installing dependencies still takes meaningful time at the start of each session.