Seems like I'm really close...

deployments/seattle/flake.nix

@@ -11,14 +11,26 @@
       # url = "git+ssh://fudo_git@git.fudo.org:2222/fudosys/NixOS.git?ref=nixops-flake";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    fudo-entities = {
+      url = "path:/state/fudo-entities";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
+    fudo-lib = {
+      url = "path:/state/fudo-lib";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
-  outputs = { self, nixpkgs, fudo-nixos, fudo-secrets, ... } @ inputs:
+  outputs = { self, nixpkgs, fudo-nixos, fudo-entities, fudo-secrets, ... } @ inputs:
     with nixpkgs.lib; {
       nixopsConfigurations.default = let
         deployment-hosts = filterAttrs
-          (hostname: hostOpts: hostOpts.domain == "sea.fudo.org")
-          fudo-nixos.fudoHosts;
+          (hostname: hostOpts:
+            hostOpts.domain == "sea.fudo.org" &&
+            hostOpts.nixos-system)
+          fudo-entities.entities.hosts;
 
         build-timestamp = self.sourceInfo.lastModified;
 
@@ -26,7 +38,7 @@
           inherit inputs build-timestamp;
         };
 
-        host-configs = mapAttrs host-gen-config deployment-hosts;
+        common-configs = mapAttrs host-gen-config deployment-hosts;
       in {
         inherit nixpkgs;
 
@@ -34,6 +46,6 @@
           description = "Seattle NixOps network";
           enableRollback = true;
         };
-      } // host-configs;
+      } // common-configs;
     };
 }