`fetch-tree`-powered `nix-run`

[KiaraGrouwstra]

Is your feature request related to a problem?

it would be nice to have a convenient way to run programs from fetch-tree-accessible (potentially remote) repositories.

Proposed solution

a v2-cli-like command nix-run, functioning perhaps not unlike bash aliases like:

• drop-in nix-run for use like nix-run github:nixos/nixpkgs?ref=nixos-25.11#hello (i.e. arguments like nix run's): alias nix-run='run() { $(nix-instantiate --raw --impure --eval --expr "(import <nixpkgs> {}).lib.getExe (import (builtins.fetchTree \"$(cut -d "#" -f 1 <<< "$1")\").outPath { }).$(cut -d "#" -f 2 <<< "$1")"); }; run'
• version for use like nix-run github:nixos/nixpkgs?ref=nixos-25.11 hello (so args spaced): alias nix-run='run() { $(nix-instantiate --raw --impure --eval --expr "(import <nixpkgs> {}).lib.getExe (import (builtins.fetchTree \"$1\").outPath { }).$2"); }; run'

Alternative solutions

flakes

Additional context

• in my testing this could also work with nix registry
• while commands like nix-shell with say nix-shell -p hello might similarly use nixpkgs, in that case to build packages from, it's maybe another question whether it makes sense to depend on nixpkgs' lib.getExe within nix core. i'm not sure how that works for nix-shell - maybe a similar relation to the one taken there could work here as well. maybe. nix run seems prior art on getExe-like considerations.

Checklist

• checked latest Nix manual (source)
• checked open feature issues and pull requests for possible duplicates

---

Add 👍 to issues you find important.

[roberth]

nix run -f is pretty close, except lacking fetchTree.
I suppose something similar to the NIX_PATH=nixpkgs=flake:github:... feature could be done for CLI arguments, renaming flake: to the more accurate tree: while we're at it.

I personally wouldn't mind adding a new "old CLI" command, but we can do achieve this quite nicely in the new CLI as well, and that would have the benefit of furthering progress on the nix-command project.

nix run -f tree:github:nixos/nixpkgs?ref=nixos-25.11#hello