Managing Flake Inputs

The stackpanel flake command group lets you manage your flake.nix inputs without editing the file by hand. It uses tree-sitter to parse Nix syntax, so comments, formatting, and whitespace are preserved.

Adding an Input

The most common operation is adding a new flake input. Pass the input name and URL:

stackpanel flake add-input sops-nix github:Mic92/sops-nix

This finds the inputs = { ... } block in your flake.nix, inserts the new input before the closing brace, and runs nix flake lock to fetch it. Your file goes from:

inputs = {
  nixpkgs.url = "...";
};

to:

inputs = {
  nixpkgs.url = "...";
  sops-nix.url = "github:Mic92/sops-nix";
  sops-nix.inputs.nixpkgs.follows = "nixpkgs";
};

By default, a nixpkgs.follows line is added so the new input shares your nixpkgs instead of pulling its own copy.

Skipping nixpkgs.follows

Some inputs don't have a nixpkgs dependency, or you want them to use their own. Pass --no-follows:

stackpanel flake add-input process-compose-flake \
  github:Platonic-Systems/process-compose-flake --no-follows

Adding an Import at the Same Time

If the input provides a Stackpanel module, you probably also need to add it to stackpanelImports in your flake outputs. Use --module-path to do both in one command:

stackpanel flake add-input my-module github:author/my-module \
  --module-path stackpanelModules.default

This inserts the input and adds inputs.my-module.stackpanelModules.default to your stackpanelImports list. The command detects whether stackpanelImports is defined anywhere in your flake (inside mkFlake, in the outputs function, etc.) and inserts into the right place.

Previewing Changes

To see what would change without actually writing the file, use --dry-run:

stackpanel flake add-input my-input github:someone/repo --dry-run

The modified flake.nix is printed to stdout. Nothing is written to disk and nix flake lock is not run.

Skipping the Lock Step

If you're adding several inputs at once and want to lock them all in one go afterward, pass --no-lock:

stackpanel flake add-input input-a github:a/a --no-lock
stackpanel flake add-input input-b github:b/b --no-lock
nix flake lock --update-input input-a --update-input input-b

Idempotent by Default

If the input already exists in your flake.nix, the command prints a warning and does nothing:

  Input 'sops-nix' already exists in flake.nix

If the input exists but you also passed --module-path and that import is missing, the import is still added. This makes the command safe to run repeatedly.

Safety

Before writing changes, the command:

1. Creates a flake.nix.bak backup
2. Writes the modified file
3. Runs nix flake lock --update-input <name>
4. If the lock fails, restores the backup automatically
5. If everything succeeds, deletes the backup

If you interrupt the process or something goes wrong, your original flake.nix is either untouched or recoverable from the .bak file.

Fixing Missing Module Inputs

When you enable an extension that requires a flake input you don't have, the MOTD warns you on shell entry:

  Module "process-compose" requires flake input "process-compose-flake"
  Fix: stackpanel flake add-input process-compose-flake github:Platonic-Systems/process-compose-flake

Copy-paste the fix command and re-enter your shell. See Flake Inputs for more on how extensions declare their input requirements.

Flags Reference

Next Steps

• Extension Flake Inputs for how extensions declare required inputs and the detection pipeline
• Packages & Scripts for adding tools and commands to your shell
• Shell Hooks & Files for running code on shell entry