diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 3a76b1ea..243d2f11 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -106,11 +106,6 @@ jobs:
     runs-on: ubuntu-latest
     needs:
       - build-repo
-    strategy:
-      matrix:
-        ghc:
-          - ghc8107
-          - ghc926
 
     steps:
       - name: Install Nix
@@ -133,7 +128,7 @@ jobs:
           name: built-repo
           path: _repo
 
-      - name: Build a smoke-test package
+      - name: Build checks
         # The > is the "YAML folded string" marker, which replaces 
         # newlines with spaces, since the usual bash idiom of \ 
         # doesn't work for some reason
@@ -141,14 +136,13 @@ jobs:
         # See https://github.com/nixbuild/feedback/issues/14 for
         # why some of these options are here
         run: >
-          nix build 
+          nix flake check 
           -L 
           --override-input CHaP path:_repo 
           --eval-store auto 
           --store ssh-ng://eu.nixbuild.net 
           --max-jobs 2
           --builders ""
-          .#hydraJobs.${{matrix.ghc}}.plutus-core-1-1-1-0.x86_64-linux  
 
   deploy-check:
     runs-on: ubuntu-latest
diff --git a/builder/default.nix b/builder/default.nix
index 1e583e37..6a071fd2 100644
--- a/builder/default.nix
+++ b/builder/default.nix
@@ -2,15 +2,25 @@
 compiler-nix-name:
 let
   inherit (pkgs) lib;
+  inherit (pkgs.haskell-nix) haskellLib;
 
+  # [ { name = "foo"; version = "X.Y.Z"; }, { name = "foo"; version = "P.Q.R"; } ]
   chap-package-list =
-    builtins.filter (lib.strings.hasPrefix "plutus-core") (
-      builtins.map (p: "${p.pkg-name}-${p.pkg-version}")
-        (builtins.fromJSON (builtins.readFile "${CHaP}/foliage/packages.json")));
+      builtins.map (p: { name = p.pkg-name; version = p.pkg-version; })
+        (builtins.fromJSON (builtins.readFile "${CHaP}/foliage/packages.json"));
 
-  build-chap-package = package-id:
+  # { "foo" : [ "X.Y.Z" "P.Q.R" ], ... }
+  chap-package-attrs = 
+    let 
+      # { "foo" = [{ name = "foo"; version = "X.Y.Z"; }, { name = "foo"; version = "P.Q.R"; }]; ... }
+      grouped = lib.groupBy (m: m.name) chap-package-list;
+      # { "foo" : [ "X.Y.Z" "P.Q.R" ], ... }
+      simplified = lib.mapAttrs (name: metas: builtins.map (m: m.version) metas) grouped;
+    in simplified;
+
+  chap-package-components = package-name: package-version:
     let
-      package-name = (builtins.parseDrvName package-id).name;
+      package-id = "${package-name}-${package-version}";
 
       # No need to set index-state:
       # - haskell.nix will automatically use the latest known one for hackage
@@ -46,16 +56,10 @@ let
         }];
 
       };
-
-    in
-    pkgs.releaseTools.aggregate {
-      name = package-id;
-      constituents = lib.collect lib.isDerivation {
-        inherit (project.hsPkgs.${package-name}) components checks;
-      };
-    };
-
+      pkg = project.hsPkgs.${package-name};
+      components = haskellLib.getAllComponents pkg;
+    # Not an ideal name here, would be nice to use something simpler
+    in lib.recurseIntoAttrs (builtins.listToAttrs (builtins.map (c: lib.nameValuePair c.name c) components));
 in
-lib.attrsets.mapAttrs' (name: lib.attrsets.nameValuePair (builtins.replaceStrings [ "." ] [ "-" ] name)) (
-  lib.attrsets.genAttrs chap-package-list build-chap-package
-)
+# { foo = { X.Y.Z = <components>; P.Q.R = <components>; }; ... }
+lib.recurseIntoAttrs (lib.mapAttrs (name: versions: lib.recurseIntoAttrs (lib.genAttrs versions (version: chap-package-components name version))) chap-package-attrs)
diff --git a/flake.nix b/flake.nix
index 9a5f07fd..784f7eb5 100644
--- a/flake.nix
+++ b/flake.nix
@@ -34,18 +34,29 @@
   };
 
   outputs = { self, nixpkgs, flake-utils, foliage, haskell-nix, CHaP, iohk-nix, ... }:
-    flake-utils.lib.eachDefaultSystem
+    let 
+      compilers = [ "ghc8107" "ghc926" ];
+      smokeTestPackages = [ 
+        "cardano-node" 
+        "cardano-cli" 
+        "cardano-api" 
+        "plutus-core" 
+        ];
+    # The foliage flake only works on this system, so we are stuck with it too
+    in flake-utils.lib.eachSystem [ "x86_64-linux" ]
       (system:
-        let pkgs = import nixpkgs {
-          inherit system;
-          inherit (haskell-nix) config;
-          overlays = [
-            haskell-nix.overlay
-            iohk-nix.overlays.crypto
-          ];
-        };
+        let 
+          pkgs = import nixpkgs {
+            inherit system;
+            inherit (haskell-nix) config;
+            overlays = [
+              haskell-nix.overlay
+              iohk-nix.overlays.crypto
+            ];
+          };
+          inherit (pkgs) lib;
         in
-        {
+        rec {
           devShells.default = with pkgs; mkShellNoCC {
             name = "cardano-haskell-packages";
             buildInputs = [
@@ -58,13 +69,27 @@
             ];
           };
 
-          hydraJobs =
+          # { ghc8107 = { foo = { X.Y.Z = <components>; ... }; ...}; ... }
+          haskellPackages = 
             let
-              inherit (pkgs) lib;
               builder = import ./builder { inherit pkgs CHaP; };
-              compilers = [ "ghc8107" "ghc926" ];
             in
-            lib.attrsets.genAttrs compilers builder;
+            lib.recurseIntoAttrs (lib.genAttrs compilers builder);
+
+          # A nested tree of derivations containing all the smoke test packages for all the compiler versions
+          smokeTestDerivations = lib.genAttrs compilers (compiler: 
+            let 
+              # The latest version in the set (attrValues sorts by key). Remove the 'recurseForDerivations' here otherwise
+              # we get that!
+              latest = versionToValue: lib.last (lib.attrValues (builtins.removeAttrs versionToValue ["recurseForDerivations"]));
+              compilerPkgs = builtins.getAttr compiler haskellPackages;
+              smokeTestPkgs = lib.recurseIntoAttrs (lib.genAttrs smokeTestPackages (pkgname: latest (builtins.getAttr pkgname compilerPkgs)));
+            in smokeTestPkgs);
+
+          # The standard checks: build all the smoke test packages
+          checks = flake-utils.lib.flattenTree smokeTestDerivations;
+
+          hydraJobs = checks;
         });
 
   nixConfig = {
@@ -82,5 +107,6 @@
       "loony-tools:pr9m4BkM/5/eSTZlkQyRt57Jz7OMBxNSUiMC4FkcNfk="
       "nixbuild.net/smart.contracts@iohk.io-1:s2PhQXWwsZo1y5IxFcx2D/i2yfvgtEnRBOZavlA8Bog="
     ];
+    allow-import-from-derivation = true;
   };
 }