Unusable `users.users."foo".packages`

[lloeki]

Describe the bug

When users.users."foo".packages is set to a non-empty value, system-manager switch --flake fails with:

[2026-03-11T07:51:46Z INFO  system_manager_engine::register] Building new system-manager generation...
[2026-03-11T07:51:46Z INFO  system_manager_engine::register] Running nix build...
warning: Git tree '/home/ll/.config/system-manager' is dirty
error:
       … while calling the 'derivationStrict' builtin
         at <nix/derivation-internal.nix>:37:12:
           36|
           37|   strict = derivationStrict drvAttrs;
             |            ^
           38|

       … while evaluating derivation 'system-manager'
         whose name attribute is located at /nix/store/w2jcgb8c6yph72nsksa6zmc8qdna8ys4-source/pkgs/stdenv/generic/make-derivation.nix:536:13

       … while evaluating attribute 'buildCommand' of derivation 'system-manager'
         at /nix/store/w2jcgb8c6yph72nsksa6zmc8qdna8ys4-source/pkgs/build-support/trivial-builders/default.nix:80:17:
           79|         enableParallelBuilding = true;
           80|         inherit buildCommand name;
             |                 ^
           81|         passAsFile = [ "buildCommand" ] ++ (derivationArgs.passAsFile or [ ]);

       … while evaluating the option `environment.etc."profiles/per-user/ll".source':

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: attribute 'path' missing
       at /nix/store/gz424yag8ik0gmgngprbkqp66d4gb4k8-source/nix/modules/upstream/nixpkgs/users-groups.nix:930:22:
          929|             inherit (config.environment) pathsToLink extraOutputsToInstall;
          930|             inherit (config.system.path) ignoreCollisions postBuild;
             |                      ^
          931|           };
[2026-03-11T07:51:49Z ERROR system_manager] Nix build failed, see console output for details.

To Reproduce

Steps to reproduce the behavior:

1. add this to config:

   users.users."foo".packages = [pkgs.vim];
   

2. run system-manager switch --flake

Expected behavior

System build succeeds and vim is available in the user environment.

System information

$ nix run nixpkgs#nix-info -- -m
 - system: `"x86_64-linux"`
 - host os: `Linux 6.17.0-1012-oem, Ubuntu, 24.04.4 LTS (Noble Numbat), nobuild`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.33.3`
 - channels(root): `"nixpkgs"`
 - nixpkgs: `/nix/store/cpwpjm4w4nadpajf3fv9lwxkb0dypfgp-nixpkgs/nixpkgs`

$ system-manager --version
system-manager 1.0.0

Additional context

environment.systemPackages works fine.