diff --git a/configuration.nix b/configuration.nix
index 48980b2..a181410 100644
--- a/configuration.nix
+++ b/configuration.nix
@@ -19,6 +19,7 @@
     ./modules/secureboot.nix
     ./modules/no-rgb.nix
     ./modules/security.nix
+    ./modules/arr-init.nix
 
     ./services/postgresql.nix
     ./services/jellyfin.nix
@@ -38,6 +39,7 @@
     ./services/arr/bazarr.nix
     ./services/arr/jellyseerr.nix
     ./services/arr/recyclarr.nix
+    ./services/arr/init.nix
 
     ./services/soulseek.nix
 
diff --git a/flake.nix b/flake.nix
index e49a82b..ca46157 100644
--- a/flake.nix
+++ b/flake.nix
@@ -221,6 +221,11 @@
         recyclarr = {
           dataDir = services_dir + "/recyclarr";
         };
+
+        media = {
+          moviesDir = torrents_path + "/media/movies";
+          tvDir = torrents_path + "/media/tv";
+        };
         };
       };
 
diff --git a/modules/arr-init.nix b/modules/arr-init.nix
new file mode 100644
index 0000000..774e276
--- /dev/null
+++ b/modules/arr-init.nix
@@ -0,0 +1,218 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.services.arrInit;
+
+  downloadClientModule = lib.types.submodule {
+    options = {
+      name = lib.mkOption {
+        type = lib.types.str;
+        description = "Display name of the download client (e.g. \"qBittorrent\").";
+        example = "qBittorrent";
+      };
+
+      implementation = lib.mkOption {
+        type = lib.types.str;
+        description = "Implementation identifier for the Servarr API.";
+        example = "QBittorrent";
+      };
+
+      configContract = lib.mkOption {
+        type = lib.types.str;
+        description = "Config contract identifier for the Servarr API.";
+        example = "QBittorrentSettings";
+      };
+
+      protocol = lib.mkOption {
+        type = lib.types.enum [
+          "torrent"
+          "usenet"
+        ];
+        default = "torrent";
+        description = "Download protocol type.";
+      };
+
+      fields = lib.mkOption {
+        type = lib.types.attrsOf lib.types.anything;
+        default = { };
+        description = ''
+          Flat key/value pairs for the download client configuration.
+          These are converted to the API's [{name, value}] array format.
+        '';
+        example = {
+          host = "192.168.15.1";
+          port = 6011;
+          useSsl = false;
+          tvCategory = "tvshows";
+        };
+      };
+    };
+  };
+
+  instanceModule = lib.types.submodule {
+    options = {
+      enable = lib.mkEnableOption "Servarr application API initialization";
+
+      serviceName = lib.mkOption {
+        type = lib.types.str;
+        description = "Name of the systemd service this init depends on.";
+        example = "sonarr";
+      };
+
+      dataDir = lib.mkOption {
+        type = lib.types.str;
+        description = "Path to the application data directory containing config.xml.";
+        example = "/var/lib/sonarr";
+      };
+
+      port = lib.mkOption {
+        type = lib.types.port;
+        description = "API port of the Servarr application.";
+        example = 8989;
+      };
+
+      apiVersion = lib.mkOption {
+        type = lib.types.str;
+        default = "v3";
+        description = "API version string used in the base URL.";
+      };
+
+      downloadClients = lib.mkOption {
+        type = lib.types.listOf downloadClientModule;
+        default = [ ];
+        description = "List of download clients to configure via the API.";
+      };
+
+      rootFolders = lib.mkOption {
+        type = lib.types.listOf lib.types.str;
+        default = [ ];
+        description = "List of root folder paths to configure via the API.";
+        example = [
+          "/media/tv"
+          "/media/movies"
+        ];
+      };
+    };
+  };
+
+  curl = "${pkgs.curl}/bin/curl";
+  jq = "${pkgs.jq}/bin/jq";
+  grep = "${pkgs.gnugrep}/bin/grep";
+
+  mkDownloadClientPayload =
+    dc:
+    builtins.toJSON {
+      enable = true;
+      protocol = dc.protocol;
+      priority = 1;
+      name = dc.name;
+      implementation = dc.implementation;
+      configContract = dc.configContract;
+      fields = lib.mapAttrsToList (n: v: {
+        name = n;
+        value = v;
+      }) dc.fields;
+      tags = [ ];
+    };
+
+  mkDownloadClientSection = dc: ''
+    # Download client: ${dc.name}
+    echo "Checking download client '${dc.name}'..."
+    EXISTING_DC=$(${curl} -sf "$BASE_URL/downloadclient" -H "X-Api-Key: $API_KEY")
+    if echo "$EXISTING_DC" | ${jq} -e --arg name ${lib.escapeShellArg dc.name} '.[] | select(.name == $name)' > /dev/null 2>&1; then
+      echo "Download client '${dc.name}' already exists, skipping"
+    else
+      echo "Adding download client '${dc.name}'..."
+      ${curl} -sf -X POST "$BASE_URL/downloadclient?forceSave=true" \
+        -H "X-Api-Key: $API_KEY" \
+        -H "Content-Type: application/json" \
+        -d ${lib.escapeShellArg (mkDownloadClientPayload dc)}
+      echo "Download client '${dc.name}' added"
+    fi
+  '';
+
+  mkRootFolderSection = path: ''
+    # Root folder: ${path}
+    echo "Checking root folder '${path}'..."
+    EXISTING_RF=$(${curl} -sf "$BASE_URL/rootfolder" -H "X-Api-Key: $API_KEY")
+    if echo "$EXISTING_RF" | ${jq} -e --arg path ${lib.escapeShellArg path} '.[] | select(.path == $path)' > /dev/null 2>&1; then
+      echo "Root folder '${path}' already exists, skipping"
+    else
+      echo "Adding root folder '${path}'..."
+      ${curl} -sf -X POST "$BASE_URL/rootfolder" \
+        -H "X-Api-Key: $API_KEY" \
+        -H "Content-Type: application/json" \
+        -d ${lib.escapeShellArg (builtins.toJSON { inherit path; })}
+      echo "Root folder '${path}' added"
+    fi
+  '';
+
+  mkInitScript =
+    name: inst:
+    pkgs.writeShellScript "${name}-init" ''
+      set -euo pipefail
+
+      CONFIG_XML="${inst.dataDir}/config.xml"
+
+      if [ ! -f "$CONFIG_XML" ]; then
+        echo "Config file $CONFIG_XML not found, skipping ${name} init"
+        exit 0
+      fi
+
+      API_KEY=$(${grep} -oP '(?<=<ApiKey>)[^<]+' "$CONFIG_XML")
+      BASE_URL="http://localhost:${builtins.toString inst.port}/api/${inst.apiVersion}"
+
+      # Wait for API to become available
+      echo "Waiting for ${name} API..."
+      for i in $(seq 1 90); do
+        if ${curl} -sf "$BASE_URL/system/status" -H "X-Api-Key: $API_KEY" > /dev/null 2>&1; then
+          echo "${name} API is ready"
+          break
+        fi
+        if [ "$i" -eq 90 ]; then
+          echo "${name} API not available after 90 seconds" >&2
+          exit 1
+        fi
+        sleep 1
+      done
+
+      ${lib.concatMapStringsSep "\n" mkDownloadClientSection inst.downloadClients}
+      ${lib.concatMapStringsSep "\n" mkRootFolderSection inst.rootFolders}
+
+      echo "${name} init complete"
+    '';
+
+  enabledInstances = lib.filterAttrs (_: inst: inst.enable) cfg;
+in
+{
+  options.services.arrInit = lib.mkOption {
+    type = lib.types.attrsOf instanceModule;
+    default = { };
+    description = ''
+      Attribute set of Servarr application instances to initialize via their APIs.
+      Each instance generates a systemd oneshot service that idempotently configures
+      download clients and root folders.
+    '';
+  };
+
+  config = lib.mkIf (enabledInstances != { }) {
+    systemd.services = lib.mapAttrs' (
+      name: inst:
+      lib.nameValuePair "${inst.serviceName}-init" {
+        description = "Initialize ${name} API connections";
+        after = [ "${inst.serviceName}.service" ];
+        requires = [ "${inst.serviceName}.service" ];
+        wantedBy = [ "multi-user.target" ];
+        serviceConfig = {
+          Type = "oneshot";
+          RemainAfterExit = true;
+          ExecStart = "${mkInitScript name inst}";
+        };
+      }
+    ) enabledInstances;
+  };
+}
diff --git a/services/arr/init.nix b/services/arr/init.nix
new file mode 100644
index 0000000..05b7849
--- /dev/null
+++ b/services/arr/init.nix
@@ -0,0 +1,46 @@
+{ config, service_configs, ... }:
+{
+  services.arrInit = {
+    sonarr = {
+      enable = true;
+      serviceName = "sonarr";
+      port = service_configs.ports.sonarr;
+      dataDir = service_configs.sonarr.dataDir;
+      rootFolders = [ service_configs.media.tvDir ];
+      downloadClients = [
+        {
+          name = "qBittorrent";
+          implementation = "QBittorrent";
+          configContract = "QBittorrentSettings";
+          fields = {
+            host = config.vpnNamespaces.wg.namespaceAddress;
+            port = service_configs.ports.torrent;
+            useSsl = false;
+            tvCategory = "tvshows";
+          };
+        }
+      ];
+    };
+
+    radarr = {
+      enable = true;
+      serviceName = "radarr";
+      port = service_configs.ports.radarr;
+      dataDir = service_configs.radarr.dataDir;
+      rootFolders = [ service_configs.media.moviesDir ];
+      downloadClients = [
+        {
+          name = "qBittorrent";
+          implementation = "QBittorrent";
+          configContract = "QBittorrentSettings";
+          fields = {
+            host = config.vpnNamespaces.wg.namespaceAddress;
+            port = service_configs.ports.torrent;
+            useSsl = false;
+            movieCategory = "movies";
+          };
+        }
+      ];
+    };
+  };
+}
diff --git a/tests/arr-init.nix b/tests/arr-init.nix
new file mode 100644
index 0000000..50dc0d6
--- /dev/null
+++ b/tests/arr-init.nix
@@ -0,0 +1,265 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  testPkgs = pkgs.appendOverlays [ (import ../modules/overlays.nix) ];
+in
+testPkgs.testers.runNixOSTest {
+  name = "arr-init";
+
+  nodes.machine =
+    { pkgs, ... }:
+    {
+      imports = [
+        ../modules/arr-init.nix
+      ];
+
+      system.stateVersion = config.system.stateVersion;
+
+      virtualisation.memorySize = 2048;
+
+      environment.systemPackages = with pkgs; [
+        curl
+        jq
+        gnugrep
+      ];
+
+      systemd.services.mock-qbittorrent =
+        let
+          mockQbitScript = pkgs.writeScript "mock-qbittorrent.py" ''
+            import json
+            from http.server import HTTPServer, BaseHTTPRequestHandler
+            from urllib.parse import parse_qs, urlparse
+
+
+            CATEGORIES = {
+                "tv": {"name": "tv", "savePath": "/downloads"},
+                "movies": {"name": "movies", "savePath": "/downloads"},
+            }
+
+
+            class QBitMock(BaseHTTPRequestHandler):
+                def _respond(self, code=200, body=b"Ok.", content_type="text/plain"):
+                    self.send_response(code)
+                    self.send_header("Content-Type", content_type)
+                    self.send_header("Set-Cookie", "SID=mock_session_id; Path=/")
+                    self.end_headers()
+                    self.wfile.write(body if isinstance(body, bytes) else body.encode())
+
+                def do_GET(self):
+                    path = self.path.split("?")[0]
+                    if path == "/api/v2/app/webapiVersion":
+                        self._respond(body=b"2.9.3")
+                    elif path == "/api/v2/app/version":
+                        self._respond(body=b"v5.0.0")
+                    elif path == "/api/v2/torrents/info":
+                        self._respond(body=b"[]", content_type="application/json")
+                    elif path == "/api/v2/torrents/categories":
+                        body = json.dumps(CATEGORIES).encode()
+                        self._respond(body=body, content_type="application/json")
+                    elif path == "/api/v2/app/preferences":
+                        body = json.dumps({"save_path": "/tmp"}).encode()
+                        self._respond(body=body, content_type="application/json")
+                    else:
+                        self._respond()
+
+                def do_POST(self):
+                    content_length = int(self.headers.get("Content-Length", 0))
+                    body = self.rfile.read(content_length).decode()
+                    path = urlparse(self.path).path
+                    query = parse_qs(urlparse(self.path).query)
+                    form = parse_qs(body)
+                    params = {**query, **form}
+                    if path == "/api/v2/torrents/createCategory":
+                        name = params.get("category", [""])[0]
+                        save_path = params.get("savePath", params.get("save_path", [""]))[0] or "/downloads"
+                        if name:
+                            CATEGORIES[name] = {"name": name, "savePath": save_path}
+                    if path in ["/api/v2/torrents/editCategory", "/api/v2/torrents/removeCategory"]:
+                        self._respond()
+                        return
+                    self._respond()
+
+                def log_message(self, format, *args):
+                    pass
+
+
+            HTTPServer(("0.0.0.0", 6011), QBitMock).serve_forever()
+          '';
+        in
+        {
+          description = "Mock qBittorrent API";
+          wantedBy = [ "multi-user.target" ];
+          before = [
+            "sonarr-init.service"
+            "radarr-init.service"
+          ];
+          serviceConfig = {
+            ExecStart = "${pkgs.python3}/bin/python3 ${mockQbitScript}";
+            Type = "simple";
+          };
+        };
+
+      systemd.tmpfiles.rules = [
+        "d /media/tv 0755 sonarr sonarr -"
+        "d /media/movies 0755 radarr radarr -"
+      ];
+
+      services.sonarr = {
+        enable = true;
+        dataDir = "/var/lib/sonarr/.config/NzbDrone";
+        settings.server.port = lib.mkDefault 8989;
+      };
+
+      services.radarr = {
+        enable = true;
+        dataDir = "/var/lib/radarr/.config/Radarr";
+        settings.server.port = lib.mkDefault 7878;
+      };
+
+      services.arrInit.sonarr = {
+        enable = true;
+        serviceName = "sonarr";
+        dataDir = "/var/lib/sonarr/.config/NzbDrone";
+        port = 8989;
+        downloadClients = [
+          {
+            name = "qBittorrent";
+            implementation = "QBittorrent";
+            configContract = "QBittorrentSettings";
+            protocol = "torrent";
+            fields = {
+              host = "127.0.0.1";
+              port = 6011;
+              useSsl = false;
+              tvCategory = "tv";
+            };
+          }
+        ];
+        rootFolders = [ "/media/tv" ];
+      };
+
+      services.arrInit.radarr = {
+        enable = true;
+        serviceName = "radarr";
+        dataDir = "/var/lib/radarr/.config/Radarr";
+        port = 7878;
+        downloadClients = [
+          {
+            name = "qBittorrent";
+            implementation = "QBittorrent";
+            configContract = "QBittorrentSettings";
+            protocol = "torrent";
+            fields = {
+              host = "127.0.0.1";
+              port = 6011;
+              useSsl = false;
+              movieCategory = "movies";
+            };
+          }
+        ];
+        rootFolders = [ "/media/movies" ];
+      };
+    };
+
+  testScript = ''
+    start_all()
+
+    # Wait for services to start
+    machine.wait_for_unit("mock-qbittorrent.service")
+    machine.wait_until_succeeds("curl -sf http://localhost:6011/api/v2/app/version", timeout=30)
+    machine.wait_for_unit("sonarr.service")
+    machine.wait_for_unit("radarr.service")
+
+    # Wait for Sonarr API to be ready (config.xml is auto-generated on first start)
+    machine.wait_until_succeeds(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/sonarr/.config/NzbDrone/config.xml) && "
+        "curl -sf http://localhost:8989/api/v3/system/status -H \"X-Api-Key: $API_KEY\"",
+        timeout=120,
+    )
+
+    # Wait for Radarr API to be ready
+    machine.wait_until_succeeds(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/radarr/.config/Radarr/config.xml) && "
+        "curl -sf http://localhost:7878/api/v3/system/status -H \"X-Api-Key: $API_KEY\"",
+        timeout=120,
+    )
+
+    # Ensure init services run after config.xml exists
+    machine.succeed("systemctl restart sonarr-init.service")
+    machine.succeed("systemctl restart radarr-init.service")
+    machine.wait_for_unit("sonarr-init.service")
+    machine.wait_for_unit("radarr-init.service")
+
+    # Wait for init services to complete
+    machine.wait_for_unit("sonarr-init.service")
+    machine.wait_for_unit("radarr-init.service")
+
+    # Verify Sonarr download clients
+    machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/sonarr/.config/NzbDrone/config.xml) && "
+        "curl -sf http://localhost:8989/api/v3/downloadclient -H \"X-Api-Key: $API_KEY\" | "
+        "jq -e '.[] | select(.name == \"qBittorrent\")'"
+    )
+
+    # Verify Sonarr root folders
+    machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/sonarr/.config/NzbDrone/config.xml) && "
+        "curl -sf http://localhost:8989/api/v3/rootfolder -H \"X-Api-Key: $API_KEY\" | "
+        "jq -e '.[] | select(.path == \"/media/tv\")'"
+    )
+
+    # Verify Radarr download clients
+    machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/radarr/.config/Radarr/config.xml) && "
+        "curl -sf http://localhost:7878/api/v3/downloadclient -H \"X-Api-Key: $API_KEY\" | "
+        "jq -e '.[] | select(.name == \"qBittorrent\")'"
+    )
+
+    # Verify Radarr root folders
+    machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/radarr/.config/Radarr/config.xml) && "
+        "curl -sf http://localhost:7878/api/v3/rootfolder -H \"X-Api-Key: $API_KEY\" | "
+        "jq -e '.[] | select(.path == \"/media/movies\")'"
+    )
+
+    # Idempotency test: restart init services and verify no duplicate entries
+    machine.succeed("systemctl restart sonarr-init.service")
+    machine.succeed("systemctl restart radarr-init.service")
+
+    # Verify Sonarr still has exactly 1 download client
+    result = machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/sonarr/.config/NzbDrone/config.xml) && "
+        "curl -sf http://localhost:8989/api/v3/downloadclient -H \"X-Api-Key: $API_KEY\" | "
+        "jq '. | length'"
+    ).strip()
+    assert result == "1", f"Expected 1 Sonarr download client, got {result}"
+
+    # Verify Sonarr still has exactly 1 root folder
+    result = machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/sonarr/.config/NzbDrone/config.xml) && "
+        "curl -sf http://localhost:8989/api/v3/rootfolder -H \"X-Api-Key: $API_KEY\" | "
+        "jq '. | length'"
+    ).strip()
+    assert result == "1", f"Expected 1 Sonarr root folder, got {result}"
+
+    # Verify Radarr still has exactly 1 download client
+    result = machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/radarr/.config/Radarr/config.xml) && "
+        "curl -sf http://localhost:7878/api/v3/downloadclient -H \"X-Api-Key: $API_KEY\" | "
+        "jq '. | length'"
+    ).strip()
+    assert result == "1", f"Expected 1 Radarr download client, got {result}"
+
+    # Verify Radarr still has exactly 1 root folder
+    result = machine.succeed(
+        "API_KEY=$(grep -oP '(?<=<ApiKey>)[^<]+' /var/lib/radarr/.config/Radarr/config.xml) && "
+        "curl -sf http://localhost:7878/api/v3/rootfolder -H \"X-Api-Key: $API_KEY\" | "
+        "jq '. | length'"
+    ).strip()
+    assert result == "1", f"Expected 1 Radarr root folder, got {result}"
+  '';
+}
diff --git a/tests/tests.nix b/tests/tests.nix
index f7a2e93..8c3504b 100644
--- a/tests/tests.nix
+++ b/tests/tests.nix
@@ -22,3 +22,6 @@ in
   fail2banImmichTest = handleTest ./fail2ban-immich.nix;
   fail2banJellyfinTest = handleTest ./fail2ban-jellyfin.nix;
 }
+
+  # arr tests
+  arrInitTest = handleTest ./arr-init.nix;