diff --git a/default.nix b/default.nix
index 49e2c31bb..977ae387f 100644
--- a/default.nix
+++ b/default.nix
@@ -2,4 +2,6 @@
 let
   sane-nix-files = import ./pkgs/by-name/sane-nix-files/package.nix { };
 in
-  import "${sane-nix-files}/impure.nix" args
+  import "${sane-nix-files}/impure.nix" ({
+    localSystem = builtins.currentSystem;
+  } // args)
diff --git a/impure.nix b/impure.nix
index 05f2cc61e..adf38a016 100644
--- a/impure.nix
+++ b/impure.nix
@@ -4,7 +4,7 @@
 # race conditions or eval failures.
 #
 # see default.nix for a wrapper around this with better purity guarantees.
-{ }:
+{ localSystem }:
 let
   mkPkgs = branch: args: (
     (import ./pkgs/by-name/nixpkgs-bootstrap/${branch}.nix {}).override args
@@ -12,9 +12,9 @@ let
   pkgs = mkPkgs "master" {};
   inherit (pkgs) lib;
 
-  evalHost = { name, system, branch ? "master", variant ? null }:
+  evalHost = { name, localSystem, system, branch ? "master", variant ? null }:
   let
-    pkgs = mkPkgs branch { inherit system; };
+    pkgs = mkPkgs branch { inherit localSystem system; };
   in pkgs.nixos [
     (import ./hosts/instantiate.nix { hostName = name; inherit variant; })
     (import ./modules)
@@ -49,19 +49,53 @@ let
     "${args.name}-min-staging" = mkFlavoredHost (args // { variant = "min"; branch = "staging"; });
   };
 
-  hosts = builtins.foldl' (acc: host: acc // mkHost host) {} [
-    # real hosts:
-    { name = "crappy"; system = "armv7l-linux";  }
-    { name = "desko";  system = "x86_64-linux";  }
-    { name = "lappy";  system = "x86_64-linux";  }
-    { name = "moby";   system = "aarch64-linux"; }
-    { name = "servo";  system = "x86_64-linux";  }
+  # this exists to unify my kernel configs across different platforms.
+  # ordinarily, certain kernel config options are derived by nixpkgs using the `system` parameter,
+  # via <repo:nixos/nixpkgs:lib/systems/platforms.nix>.
+  # but i want these a little more normalized, which is possible either here, or
+  # by assigning `boot.kernelPackages`.
+  #
+  # TODO: maybe just call `lib.platforms.elaborate`, and patch whatever i care about on top that?
+  elaborate = system: {
+    inherit system;
+    linux-kernel.name = "unknown";  #< i'm 90% sure this doesn't impact anything
+    linux-kernel.baseConfig = "defconfig";
+    linux-kernel.DTB = system != "x86_64-linux";  #< x86_64 doesn't even know how to compile device trees
+    linux-kernel.autoModules = true;
+    # build all features as modules where possible, especially because
+    # 1. some bootloaders fail on large payloads and this allows the kernel/initrd to be smaller.
+    # 2. building as module means i can override that module very cheaply as i develop.
+    linux-kernel.preferBuiltin = false;
+    # `target` support matrix:
+    # Image:     aarch64:yes (nixpkgs defaule)       x86_64:no
+    # Image.gz:  aarch64:yes, if capable bootloader  x86_64:no
+    # zImage     aarch64:no                          x86_64:yes
+    # bzImage    aarch64:no                          x86_64:yes (nixpkgs default)
+    # vmlinux    aarch64:?                           x86_64:no?
+    # vmlinuz    aarch64:?                           x86_64:?
+    # uImage     aarch64:bootloader?                 x86_64:probably not
+    linux-kernel.target = if system == "x86_64-linux" then "bzImage" else "Image";
+  };
+  # elaborate = system: system;
 
-    { name = "rescue"; system = "x86_64-linux";  }
-    # pseudo hosts used for debugging
-    { name = "baseline-x86_64";  system = "x86_64-linux";  }
-    { name = "baseline-aarch64";  system = "aarch64-linux";  }
-  ];
+  hosts = builtins.foldl'
+    # XXX: i `elaborate` localSystem the same as i do `system` because otherwise nixpkgs
+    # sees they're (slightly) different and forces everything down the (expensive) cross-compilation path.
+    (acc: host: acc // mkHost ({ localSystem = elaborate localSystem; } // host))
+    {}
+    [
+      # real hosts:
+      # { name = "crappy"; system = "armv7l-linux";  }
+      { name = "desko";  system = elaborate "x86_64-linux";  }
+      { name = "lappy";  system = elaborate "x86_64-linux";  }
+      { name = "moby";   system = elaborate "aarch64-linux"; }
+      { name = "servo";  system = elaborate "x86_64-linux";  }
+
+      { name = "rescue"; system = elaborate "x86_64-linux";  }
+      # pseudo hosts used for debugging
+      { name = "baseline-x86_64";  system = elaborate "x86_64-linux";  }
+      { name = "baseline-aarch64";  system = elaborate "aarch64-linux";  }
+    ];
 
   # subAttrNames :: AttrSet -> [ String ]
   # returns the names of all items in `attrs` which are themselves attrsets.