feat: setup mcp-nixos

Author: stackptr

hosts/glyph/services/default.nix

@@ -61,11 +61,16 @@
   };
 
   services.basic-memory.enable = true;
+  services.mcp-nixos.enable = true;
   services.mcpjungle = {
     enable = true;
     servers.basic-memory = {
       url = "http://127.0.0.1:8091/mcp";
       description = "Knowledge management with markdown files";
     };
+    servers.mcp-nixos = {
+      url = "http://127.0.0.1:8092/mcp";
+      description = "NixOS options, packages, and Home Manager search";
+    };
   };
 }

modules/home/development.nix

@@ -58,6 +58,9 @@ in {
               "Bash(git branch *)"
               "Bash(gh api:*)"
               "Bash(mkdir *)"
+              "Bash(journalctl:*)"
+              "Bash(systemctl list-jobs:*)"
+              "Bash(systemctl status:*)"
               "Bash(* --version)"
               "Bash(* --help *)"
               "WebFetch(domain:raw.githubusercontent.com)"

modules/nixos/llm/default.nix

@@ -1,6 +1,7 @@
 {
   imports = [
     ./basic-memory.nix
+    ./mcp-nixos.nix
     ./mcpjungle.nix
   ];
 }

modules/nixos/llm/mcp-nixos.nix

@@ -0,0 +1,81 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}: let
+  cfg = config.services.mcp-nixos;
+
+  startScript = pkgs.writeShellScript "mcp-nixos-start" ''
+    exec ${lib.getExe pkgs.uv} run --with mcp-nixos python -c "
+    from mcp_nixos.server import mcp
+    mcp.run(transport='streamable-http', port=${toString cfg.port}, host='${cfg.host}')
+    "
+  '';
+in {
+  options.services.mcp-nixos = {
+    enable = lib.mkEnableOption "MCP NixOS server";
+
+    port = lib.mkOption {
+      type = lib.types.port;
+      default = 8092;
+      description = "Port for the streamable HTTP transport.";
+    };
+
+    host = lib.mkOption {
+      type = lib.types.str;
+      default = "127.0.0.1";
+      description = "Address to bind the HTTP server to.";
+    };
+
+    openFirewall = lib.mkEnableOption "opening firewall ports for MCP NixOS";
+  };
+
+  config = lib.mkIf cfg.enable {
+    users.users.mcp-nixos = {
+      isSystemUser = true;
+      group = "mcp-nixos";
+      home = "/var/lib/mcp-nixos";
+    };
+    users.groups.mcp-nixos = {};
+
+    systemd.services.mcp-nixos = {
+      description = "MCP NixOS Server";
+      after = ["network-online.target"];
+      wants = ["network-online.target"];
+      wantedBy = ["multi-user.target"];
+
+      environment = {
+        HOME = "/var/lib/mcp-nixos";
+        UV_CACHE_DIR = "/var/lib/mcp-nixos/.cache/uv";
+      };
+
+      serviceConfig = {
+        ExecStart = "${startScript}";
+        User = "mcp-nixos";
+        Group = "mcp-nixos";
+        WorkingDirectory = "/var/lib/mcp-nixos";
+        StateDirectory = "mcp-nixos";
+        Restart = "on-failure";
+        RestartSec = 5;
+
+        # Hardening
+        NoNewPrivileges = true;
+        PrivateDevices = true;
+        PrivateTmp = true;
+        ProtectHome = "tmpfs";
+        BindPaths = ["/var/lib/mcp-nixos"];
+        ProtectSystem = "strict";
+        ReadWritePaths = ["/var/lib/mcp-nixos"];
+        ProtectKernelTunables = true;
+        ProtectKernelModules = true;
+        ProtectControlGroups = true;
+        RestrictSUIDSGID = true;
+      };
+    };
+
+    programs.nix-ld.enable = true;
+
+    networking.firewall.allowedTCPPorts = lib.mkIf cfg.openFirewall [cfg.port];
+  };
+}

modules/nixos/llm/mcpjungle.nix

@@ -82,12 +82,33 @@ in {
         Type = "oneshot";
         RemainAfterExit = true;
       };
+      path = [pkgs.curl];
       script = let
         registry = "http://127.0.0.1:${toString cfg.port}";
         bin = lib.getExe cfg.package;
         registrations = lib.concatStringsSep "\n" (lib.mapAttrsToList (name: server: ''
-            if ! ${bin} list servers --registry ${registry} 2>/dev/null | grep -q '${name}'; then
+            if ${bin} list servers --registry ${registry} 2>/dev/null | grep -q '${name}'; then
+              echo "${name} already registered, skipping."
+            else
+
+            # Wait for server to be reachable before registering
+            ready=false
+            for i in $(seq 1 30); do
+              http_code=$(curl -s -o /dev/null -w '%{http_code}' "${server.url}" 2>/dev/null)
+              if [ "$http_code" != "000" ]; then
+                ready=true
+                break
+              fi
+              echo "Waiting for ${name} at ${server.url} (attempt $i/30)..."
+              sleep 2
+            done
+
+            if [ "$ready" = true ]; then
               ${bin} register --name '${name}' --description '${server.description}' --url '${server.url}' --registry ${registry}
+            else
+              echo "WARNING: ${name} at ${server.url} not reachable after 60s, skipping registration."
+            fi
+
             fi
           '')
           cfg.servers);