testing

configurations/server.nix

@@ -64,6 +64,56 @@
 
   host.ssh.enable = true;
 
+  # Offload Nix builds to the WSL2 NixOS instance running on vetymae
+  # (Windows 11 host). Sapphira only has 2 logical cores; the WSL exposes
+  # 24 cores + 14 GiB. The matchBlock with ProxyCommand is generated by
+  # modules/server/builder.nix, the other side of the same option lives in
+  # modules/wsl/builder.nix.
+  #
+  # `proxyCommand` is what marks this builder as needing the SSH matchBlock
+  # (see modules/server/builder.nix). A builder reachable directly would
+  # omit it.
+  host.builder.clients = [
+    {
+      hostName = "vetymae-nix";
+      sshUser = "oqyude";
+      sshKey = "/root/.ssh/id_ed25519";
+      # NixOS calls this `systems` (plural), not `systemTypes`. The
+      # default is empty — every derivation is rejected. The WSL NixOS
+      # runs on x86_64-linux, matching sapphira.
+      systems = [ "x86_64-linux" ];
+      # vetymae-nix drops kvm + nixos-test from its advertised
+      # system-features (see modules/wsl/builder.nix). Listing them here
+      # would not break anything (Nix intersects), but listing the
+      # features the WSL actually has is the documented contract.
+      supportedFeatures = [
+        "benchmark"
+        "big-parallel"
+      ];
+      mandatoryFeatures = [ ];
+      maxJobs = 24;
+      speedFactor = 0.5;
+      # Keep the SSH session alive across many small builds in one daemon
+      # session — compile-heavy workloads spam the daemon with hundreds of
+      # derivations and ControlMaster collapses those into one Windows hop.
+      # NB: `nix.buildMachines` has no `sshOptions` attribute, so the
+      # ControlMaster directive lives in the SSH matchBlock instead (see
+      # modules/server/builder.nix).
+      #
+      # The OpenSSH alias for this host (matches the user's
+      # ~/.ssh/config so known_hosts entries do not collide with the
+      # Windows OpenSSH entry on 127.0.0.1/vetymae) is consumed only by
+      # the SSH matchBlock below — not by `nix.buildMachines`, which has
+      # no such attribute.
+      hostKeyAlias = "wsl-nixos-on-vetymae";
+      # Use the Windows host's IP directly so the nix-daemon (running as
+      # root, without the user's ~/.ssh/config) does not need a separate
+      # `vetymae` host alias. With StrictHostKeyChecking=accept-new the
+      # first connection adds the Windows host key to /root/.ssh/known_hosts.
+      proxyCommand = "ssh oqyude@192.168.1.100 'wsl -d NixOS -- nc 127.0.0.1 22'";
+    }
+  ];
+
   networking = {
     networkmanager.enable = true;
     firewall.enable = false;