I have my hosts setup like this:

    nixosConfigurations = {
      utm = import ./machines/utm.nix {};

I really don't get the example config:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  };
  outputs = { nixpkgs, ... }: {
    colmena = {
      meta = {
        nixpkgs = import nixpkgs {
          system = "x86_64-linux";
          overlays = [];
        };
      };

      host-a = { name, nodes, pkgs, ... }: {
        boot.isContainer = true;
        time.timeZone = nodes.host-b.config.time.timeZone;
      };
      host-b = {
        deployment = {
          targetHost = "somehost.tld";
          targetPort = 1234;
          targetUser = "luser";
        };
        boot.isContainer = true;
        time.timeZone = "America/Los_Angeles";
      };
    };
  };
}

No nixosConfigurations?

Urgh. That looks quite complicated.
Hoping this would work feels naiv now

      colema = {
        meta = {};
        utm = {
          deployment = {
            targetHost = "192.168.71.3";
            targetUser = "root";
          };
        };
        utm = self.nixosConfigurations.utm // {
          deployment = {
            targetHost = "192.168.71.3";
            targetUser = "root";
          };
        };
      };

Urgh. That looks quite complicated.
Hoping this would work feels naiv now

      colema = {
        meta = {};
        utm = self.nixosConfigurations.utm // {
          deployment = {
            targetHost = "192.168.71.3";
            targetUser = "root";
          };
        };
      };

In reply to @dmoonfire:matrix.org
I struggle a lot translating those two concepts. Mostly I use a lot if Just file to handle what I couldn't figure out on my own.

And trying to get home-manager into colmena took me months to puzzle out.

In reply to @hexa:lossy.network
but you can create nixosConfigurations and transform them into colmena outputs

take this slightly modified example from https://github.com/zhaofengli/colmena/blob/v0.4.0/src/nix/hive/tests/makehive-flake/flake.nix

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    colmena.url = "github:zhaofengli/colmena";
  };
  outputs = { nixpkgs, colmena, ... }: rec {
    colmenaHive = colmena.lib.makeHive {
      meta = {
        nixpkgs = import nixpkgs {
          system = "x86_64-linux";
        };
      };

      host-a = { name, nodes, pkgs, ... }: {
        boot.isContainer = true;
        time.timeZone = nodes.host-b.config.time.timeZone;
      };
      host-b = {
        deployment = {
          targetHost = "somehost.tld";
          targetPort = 1234;
          targetUser = "luser";
        };
        boot.isContainer = true;
        time.timeZone = "America/Los_Angeles";
      };
    };
    nixosConfigurations = colmenaHive.nodes;
  };
}

the diff to the upstream test is:

diff --git a/upstream-flake.nix b/flake.nix
index 11c7f62..a1f59d7 100644
--- a/upstream-flake.nix
+++ b/flake.nix
@@ -1,9 +1,9 @@
 {
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
-    colmena.url = "git+file://@repoPath@";
+    colmena.url = "github:zhaofengli/colmena";
   };
-  outputs = { nixpkgs, colmena, ... }: {
+  outputs = { nixpkgs, colmena, ... }: rec {
     colmenaHive = colmena.lib.makeHive {
       meta = {
         nixpkgs = import nixpkgs {
@@ -25,5 +25,6 @@
         time.timeZone = "America/Los_Angeles";
       };
     };
+    nixosConfigurations = colmenaHive.nodes;
   };
 }

you can then use nix v3 (unstable) cli and nixos-rebuild as you wish:

❯ nixos-rebuild --flake .#host-a build
building the system configuration...
trace: warning: system.stateVersion is not set, defaulting to 24.05. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.