nix: hyperhive.westonRdp.enable — opt-in weston + RDP backend per agent

nix/templates/harness-base.nix

@@ -10,6 +10,11 @@
   # this. The systemd service that actually runs the harness binary
   # differs per role and lives in the child module.
 
+  # Optional feature modules. Each declares its own `hyperhive.*`
+  # option(s), default-off, so every agent has them available but
+  # only opts in from its own `agent.nix`.
+  imports = [ ./weston-rdp.nix ];
+
   options.hyperhive.allowedRecipients = lib.mkOption {
     type = lib.types.listOf lib.types.str;
     default = [ ];

nix/templates/weston-rdp.nix

@@ -0,0 +1,97 @@
+{
+  pkgs,
+  lib,
+  config,
+  ...
+}:
+{
+  # Optional Weston (the reference Wayland compositor) with the RDP
+  # backend, surfaced as a per-agent hyperhive option. An agent turns
+  # it on from its own `agent.nix`:
+  #
+  #   hyperhive.westonRdp.enable = true;
+  #
+  # Imported by `harness-base.nix`, so every sub-agent + the manager
+  # has the option available; only those that flip it on get the
+  # service. This is a flat per-agent option (evaluated inside that
+  # agent's own container build) — NOT a `hyperhive.agents.<name>.*`
+  # registry, which can't work: each agent is its own
+  # nixosConfiguration and has no cross-agent view.
+
+  options.hyperhive.westonRdp.enable = lib.mkOption {
+    type = lib.types.bool;
+    default = false;
+    description = ''
+      Run Weston with the RDP backend as a systemd service, for
+      remote-desktop access to the agent's container. A self-signed
+      TLS cert/key pair is generated on first start under
+      `/var/lib/weston`. Renders in software (pixman) — no GPU, DRM,
+      or VT access, so no extra container capabilities are needed.
+
+      The unit is deliberately built so enabling it can NEVER abort
+      the agent's `nixos-container update`: `Type = "simple"` (so
+      `switch-to-configuration` doesn't block on weston readiness)
+      and an `ExecStartPre` that always exits 0. A misconfigured
+      weston degrades to a restart loop visible in `journalctl` — it
+      does not block the rebuild. (Same reasoning as the `tea-login`
+      unit in `harness-base.nix`.)
+
+      Host networking means the RDP port (3389) is reachable on the
+      host. With more than one RDP-enabled agent the port would
+      collide — add a port knob to this option before that happens.
+    '';
+  };
+
+  config = lib.mkIf config.hyperhive.westonRdp.enable {
+    systemd.services.weston = {
+      description = "Weston Wayland compositor (RDP backend)";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        # `simple`, not `notify`: switch-to-configuration must not
+        # wait on weston signalling readiness. A `notify` unit that
+        # never sends READY=1 fails after TimeoutStartSec, which
+        # aborts `nixos-container update` on every reload — exactly
+        # the trap `tea-login` documents.
+        Type = "simple";
+        # Creates /var/lib/weston (0700 root) before ExecStartPre.
+        StateDirectory = "weston";
+        Environment = "XDG_RUNTIME_DIR=/run/user/0";
+        # Runtime dir + first-boot cert generation. No `set -e`, and
+        # it always exits 0: a cert hiccup must not fail the unit
+        # start (that would abort the rebuild). If the cert/key end
+        # up missing, weston's own ExecStart fails into the Restart
+        # loop instead — graceful degradation, not a blocked deploy.
+        ExecStartPre = pkgs.writeShellScript "weston-rdp-setup" ''
+          mkdir -p /run/user/0 && chmod 700 /run/user/0 || true
+          CERT=/var/lib/weston/weston-rdp.crt
+          KEY=/var/lib/weston/weston-rdp.key
+          if [ ! -f "$CERT" ] || [ ! -f "$KEY" ]; then
+            if ${pkgs.openssl}/bin/openssl req -x509 -newkey rsa:2048 \
+                 -keyout "$KEY" -out "$CERT" -days 3650 -nodes \
+                 -subj "/CN=localhost" 2>/dev/null; then
+              chmod 600 "$KEY" 2>/dev/null || true
+              chmod 644 "$CERT" 2>/dev/null || true
+            else
+              echo "weston-rdp-setup: cert generation failed; weston will retry"
+            fi
+          fi
+          exit 0
+        '';
+        ExecStart = lib.concatStringsSep " " [
+          "${pkgs.weston}/bin/weston"
+          "--backend=rdp-backend.so"
+          "--renderer=pixman"
+          "--rdp-tls-cert=/var/lib/weston/weston-rdp.crt"
+          "--rdp-tls-key=/var/lib/weston/weston-rdp.key"
+        ];
+        Restart = "on-failure";
+        RestartSec = "5s";
+      };
+    };
+
+    # weston on the agent's interactive PATH too, so claude can run
+    # Wayland clients / `weston-info` against the compositor.
+    environment.systemPackages = [ pkgs.weston ];
+  };
+}