diff --git a/lib/membership/membership.ex b/lib/membership/membership.ex
index 7fa35dc..72be69b 100644
--- a/lib/membership/membership.ex
+++ b/lib/membership/membership.ex
@@ -836,7 +836,10 @@ defmodule Mv.Membership do
     - `{:ok, rejected_request}` - Rejected JoinRequest
     - `{:error, error}` - Status error or authorization error
   """
-  @spec reject_join_request(String.t(), keyword()) :: {:ok, JoinRequest.t()} | {:error, term()}
+  @spec reject_join_request(String.t(), keyword()) ::
+          {:ok, JoinRequest.t()}
+          | {:ok, JoinRequest.t(), [Ash.Notifier.Notification.t()]}
+          | {:error, term()}
   def reject_join_request(id, opts \\ []) do
     actor = Keyword.get(opts, :actor)
 
diff --git a/lib/mv/authorization/permission_sets.ex b/lib/mv/authorization/permission_sets.ex
index 3ffae93..ae84cdb 100644
--- a/lib/mv/authorization/permission_sets.ex
+++ b/lib/mv/authorization/permission_sets.ex
@@ -43,6 +43,7 @@ defmodule Mv.Authorization.PermissionSets do
   pattern matches and map lookups with no database queries or external calls.
   """
 
+  @type permission_set_name :: :own_data | :read_only | :normal_user | :admin
   @type scope :: :own | :linked | :all
   @type action :: :read | :create | :update | :destroy
 
@@ -88,7 +89,7 @@ defmodule Mv.Authorization.PermissionSets do
       iex> PermissionSets.all_permission_sets()
       [:own_data, :read_only, :normal_user, :admin]
   """
-  @spec all_permission_sets() :: [atom()]
+  @spec all_permission_sets() :: [permission_set_name(), ...]
   def all_permission_sets do
     [:own_data, :read_only, :normal_user, :admin]
   end
@@ -107,7 +108,7 @@ defmodule Mv.Authorization.PermissionSets do
       iex> PermissionSets.get_permissions(:invalid)
       ** (ArgumentError) invalid permission set: :invalid. Must be one of: [:own_data, :read_only, :normal_user, :admin]
   """
-  @spec get_permissions(atom()) :: permission_set()
+  @spec get_permissions(permission_set_name()) :: permission_set()
 
   def get_permissions(set) when set not in [:own_data, :read_only, :normal_user, :admin] do
     raise ArgumentError,
diff --git a/lib/mv/config.ex b/lib/mv/config.ex
index 870d1d3..f198191 100644
--- a/lib/mv/config.ex
+++ b/lib/mv/config.ex
@@ -409,7 +409,7 @@ defmodule Mv.Config do
   @doc """
   Returns the OIDC groups claim name (default "groups"). ENV first, then Settings.
   """
-  @spec oidc_groups_claim() :: String.t() | nil
+  @spec oidc_groups_claim() :: String.t()
   def oidc_groups_claim do
     case env_or_setting("OIDC_GROUPS_CLAIM", :oidc_groups_claim) do
       nil -> "groups"
@@ -492,7 +492,7 @@ defmodule Mv.Config do
   - ENV-only mode (`SMTP_HOST` set): read from ENV `SMTP_PORT`
   - Settings mode: read from Settings only
   """
-  @spec smtp_port() :: non_neg_integer() | nil
+  @spec smtp_port() :: pos_integer() | nil
   def smtp_port do
     if smtp_env_mode?() do
       parse_smtp_port_env(System.get_env("SMTP_PORT"))
@@ -638,9 +638,15 @@ defmodule Mv.Config do
   """
   @spec mail_from_name() :: String.t()
   def mail_from_name do
-    case System.get_env("MAIL_FROM_NAME") do
-      nil -> get_from_settings(:smtp_from_name) || "Mila"
-      value -> trim_nil(value) || "Mila"
+    name =
+      case System.get_env("MAIL_FROM_NAME") do
+        nil -> get_from_settings(:smtp_from_name)
+        value -> trim_nil(value)
+      end
+
+    case name do
+      nil -> "Mila"
+      name -> name
     end
   end
 
diff --git a/lib/mv/helpers/system_actor.ex b/lib/mv/helpers/system_actor.ex
index 8cd93d2..7b86a3c 100644
--- a/lib/mv/helpers/system_actor.ex
+++ b/lib/mv/helpers/system_actor.ex
@@ -225,7 +225,10 @@ defmodule Mv.Helpers.SystemActor do
   # This allows configuration via SYSTEM_ACTOR_EMAIL env var
   @spec system_user_email_config() :: String.t()
   defp system_user_email_config do
-    System.get_env("SYSTEM_ACTOR_EMAIL") || "system@mila.local"
+    case System.get_env("SYSTEM_ACTOR_EMAIL") do
+      nil -> "system@mila.local"
+      email -> email
+    end
   end
 
   # Loads the system actor from the database
@@ -257,7 +260,7 @@ defmodule Mv.Helpers.SystemActor do
   end
 
   # Handles database error when loading system user
-  @spec handle_system_user_error(term()) :: Mv.Accounts.User.t() | no_return()
+  @spec handle_system_user_error({:error, Ash.Error.t()}) :: Mv.Accounts.User.t() | no_return()
   defp handle_system_user_error(error) do
     case load_admin_user_fallback() do
       {:ok, admin_user} ->
@@ -393,15 +396,18 @@ defmodule Mv.Helpers.SystemActor do
     # 1. Only creates system user with known email
     # 2. Only called during system actor initialization (bootstrap)
     # 3. Once created, all subsequent operations use proper authorization
-    Accounts.create_user!(%{email: system_user_email_config()},
-      upsert?: true,
-      upsert_identity: :unique_email,
-      authorize?: false
-    )
-    |> Ash.Changeset.for_update(:update_internal, %{})
-    |> Ash.Changeset.manage_relationship(:role, admin_role, type: :append_and_remove)
-    |> Ash.update!(authorize?: false)
-    |> Ash.load!(:role, domain: Mv.Accounts, authorize?: false)
+    user =
+      Accounts.create_user!(%{email: system_user_email_config()},
+        upsert?: true,
+        upsert_identity: :unique_email,
+        authorize?: false
+      )
+      |> Ash.Changeset.for_update(:update_internal, %{})
+      |> Ash.Changeset.manage_relationship(:role, admin_role, type: :append_and_remove)
+      |> Ash.update!(authorize?: false)
+      |> Ash.load!(:role, domain: Mv.Accounts, authorize?: false)
+
+    %Accounts.User{} = user
   end
 
   # Finds a user by email address
diff --git a/lib/mv/membership/import/csv_parser.ex b/lib/mv/membership/import/csv_parser.ex
index 2de75ee..142450f 100644
--- a/lib/mv/membership/import/csv_parser.ex
+++ b/lib/mv/membership/import/csv_parser.ex
@@ -100,7 +100,8 @@ defmodule Mv.Membership.Import.CsvParser do
     |> String.replace("\r", "\n")
   end
 
-  @spec get_parser(String.t()) :: module()
+  @spec get_parser(String.t()) ::
+          Mv.Membership.Import.CsvParserSemicolon | Mv.Membership.Import.CsvParserComma
   defp get_parser(";"), do: Mv.Membership.Import.CsvParserSemicolon
   defp get_parser(","), do: Mv.Membership.Import.CsvParserComma
   defp get_parser(_), do: Mv.Membership.Import.CsvParserSemicolon
@@ -116,7 +117,10 @@ defmodule Mv.Membership.Import.CsvParser do
     if semicolon_score >= comma_score, do: ";", else: ","
   end
 
-  @spec header_field_count(module(), binary()) :: non_neg_integer()
+  @spec header_field_count(
+          Mv.Membership.Import.CsvParserSemicolon | Mv.Membership.Import.CsvParserComma,
+          binary()
+        ) :: non_neg_integer()
   defp header_field_count(parser, header_record) do
     case parse_single_record(parser, header_record, nil) do
       {:ok, fields} -> Enum.count(fields, &(String.trim(&1) != ""))
diff --git a/lib/mv/membership/member_export.ex b/lib/mv/membership/member_export.ex
index 16341c4..d96c82f 100644
--- a/lib/mv/membership/member_export.ex
+++ b/lib/mv/membership/member_export.ex
@@ -16,6 +16,21 @@ defmodule Mv.Membership.MemberExport do
   alias MvWeb.MemberLive.Index
   alias MvWeb.MemberLive.Index.MembershipFeeStatus
 
+  @typedoc "Validated export parameters produced by `parse_params/1`."
+  @type parsed_params :: %{
+          selected_ids: [String.t()],
+          member_fields: [String.t()],
+          selectable_member_fields: [String.t()],
+          computed_fields: [String.t()],
+          custom_field_ids: [String.t()],
+          query: String.t() | nil,
+          sort_field: String.t() | nil,
+          sort_order: String.t() | nil,
+          show_current_cycle: boolean(),
+          cycle_status_filter: :paid | :unpaid | nil,
+          boolean_filters: %{optional(String.t()) => boolean()}
+        }
+
   @member_fields_allowlist (Mv.Constants.member_fields() |> Enum.map(&Atom.to_string/1)) ++
                              ["membership_fee_type", "membership_fee_status", "groups"]
   @computed_export_fields ["membership_fee_status"]
@@ -305,7 +320,7 @@ defmodule Mv.Membership.MemberExport do
   :computed_fields, :custom_field_ids, :query, :sort_field, :sort_order,
   :show_current_cycle, :cycle_status_filter, :boolean_filters.
   """
-  @spec parse_params(map()) :: map()
+  @spec parse_params(map()) :: parsed_params()
   def parse_params(params) do
     # DB fields come from "member_fields"
     raw_member_fields = extract_list(params, "member_fields")
diff --git a/lib/mv/membership/members_csv.ex b/lib/mv/membership/members_csv.ex
index 6331893..0a19810 100644
--- a/lib/mv/membership/members_csv.ex
+++ b/lib/mv/membership/members_csv.ex
@@ -21,7 +21,7 @@ defmodule Mv.Membership.MembersCSV do
   Returns iodata suitable for `IO.iodata_to_binary/1` or sending as response body.
   RFC 4180 escaping and formula-injection safe_cell are applied.
   """
-  @spec export([struct() | map()], [map()]) :: iodata()
+  @spec export([struct() | map()], [map()]) :: [iodata()] | Enumerable.t()
   def export(members, columns) when is_list(members) do
     header = build_header(columns)
     rows = Enum.map(members, fn member -> build_row(member, columns) end)
diff --git a/lib/mv/membership_fees/cycle_generation_job.ex b/lib/mv/membership_fees/cycle_generation_job.ex
index 71a3158..b38886c 100644
--- a/lib/mv/membership_fees/cycle_generation_job.ex
+++ b/lib/mv/membership_fees/cycle_generation_job.ex
@@ -58,7 +58,7 @@ defmodule Mv.MembershipFees.CycleGenerationJob do
       {:ok, %{success: 45, failed: 0, total: 45}}
 
   """
-  @spec run() :: {:ok, map()} | {:error, term()}
+  @spec run() :: {:ok, CycleGenerator.results_summary()} | {:error, Ash.Error.t()}
   def run do
     Logger.info("Starting membership fee cycle generation job")
     start_time = System.monotonic_time(:millisecond)
@@ -98,7 +98,7 @@ defmodule Mv.MembershipFees.CycleGenerationJob do
       Mv.MembershipFees.CycleGenerationJob.run(batch_size: 5)
 
   """
-  @spec run(keyword()) :: {:ok, map()} | {:error, term()}
+  @spec run(keyword()) :: {:ok, CycleGenerator.results_summary()} | {:error, Ash.Error.t()}
   def run(opts) when is_list(opts) do
     Logger.info("Starting membership fee cycle generation job with opts: #{inspect(opts)}")
     start_time = System.monotonic_time(:millisecond)
@@ -135,7 +135,7 @@ defmodule Mv.MembershipFees.CycleGenerationJob do
     - `{:error, reason}` - Error with reason
 
   """
-  @spec pending_members_count() :: {:ok, non_neg_integer()} | {:error, term()}
+  @spec pending_members_count() :: {:ok, non_neg_integer()} | {:error, Ash.Error.t()}
   def pending_members_count do
     today = Date.utc_today()
 
@@ -166,7 +166,7 @@ defmodule Mv.MembershipFees.CycleGenerationJob do
     - `{:error, reason}` - Error with reason
 
   """
-  @spec run_for_member(String.t()) :: {:ok, [map()]} | {:error, term()}
+  @spec run_for_member(String.t()) :: CycleGenerator.generate_result()
   def run_for_member(member_id) when is_binary(member_id) do
     Logger.info("Generating cycles for member #{member_id}")
     CycleGenerator.generate_cycles_for_member(member_id)
diff --git a/lib/mv/membership_fees/cycle_generator.ex b/lib/mv/membership_fees/cycle_generator.ex
index 8f1bc7c..4014d80 100644
--- a/lib/mv/membership_fees/cycle_generator.ex
+++ b/lib/mv/membership_fees/cycle_generator.ex
@@ -1,4 +1,11 @@
 defmodule Mv.MembershipFees.CycleGenerator do
+  @typedoc "Aggregate counts returned by a batch cycle-generation run."
+  @type results_summary :: %{
+          success: non_neg_integer(),
+          failed: non_neg_integer(),
+          total: non_neg_integer()
+        }
+
   @moduledoc """
   Module for generating membership fee cycles for members.
 
@@ -159,7 +166,8 @@ defmodule Mv.MembershipFees.CycleGenerator do
     - `{:error, reason}` - Error with reason
 
   """
-  @spec generate_cycles_for_all_members(keyword()) :: {:ok, map()} | {:error, term()}
+  @spec generate_cycles_for_all_members(keyword()) ::
+          {:ok, results_summary()} | {:error, Ash.Error.t()}
   def generate_cycles_for_all_members(opts \\ []) do
     today = Keyword.get(opts, :today, Date.utc_today())
     batch_size = Keyword.get(opts, :batch_size, 10)
diff --git a/lib/mv/vereinfacht/client.ex b/lib/mv/vereinfacht/client.ex
index 3cbba71..6a81c46 100644
--- a/lib/mv/vereinfacht/client.ex
+++ b/lib/mv/vereinfacht/client.ex
@@ -8,6 +8,12 @@ defmodule Mv.Vereinfacht.Client do
   """
   require Logger
 
+  @typedoc "Error reasons returned by Vereinfacht API calls."
+  @type error_reason ::
+          :not_configured
+          | {:request_failed, map()}
+          | {:http, non_neg_integer(), :html_response | binary()}
+
   @content_type "application/vnd.api+json"
 
   @doc """
@@ -31,7 +37,7 @@ defmodule Mv.Vereinfacht.Client do
       {:error, :not_configured}
   """
   @spec test_connection(String.t() | nil, String.t() | nil, String.t() | nil) ::
-          {:ok, :connected} | {:error, term()}
+          {:ok, :connected} | {:error, error_reason()}
   def test_connection(api_url, api_key, club_id) do
     if blank?(api_url) or blank?(api_key) or blank?(club_id) do
       {:error, :not_configured}
@@ -230,7 +236,7 @@ defmodule Mv.Vereinfacht.Client do
 
   Returns the full response body (decoded JSON) for debugging/display.
   """
-  @spec get_contact(String.t()) :: {:ok, map()} | {:error, term()}
+  @spec get_contact(String.t()) :: {:ok, map()} | {:error, error_reason()}
   def get_contact(contact_id) when is_binary(contact_id) do
     fetch_contact(contact_id, [])
   end
diff --git a/lib/mv/vereinfacht/vereinfacht.ex b/lib/mv/vereinfacht/vereinfacht.ex
index 83492b7..4d58f8d 100644
--- a/lib/mv/vereinfacht/vereinfacht.ex
+++ b/lib/mv/vereinfacht/vereinfacht.ex
@@ -26,7 +26,7 @@ defmodule Mv.Vereinfacht do
   - `{:error, {:http, status, message}}` – API returned an error (e.g. 401, 403)
   - `{:error, {:request_failed, reason}}` – network/transport error
   """
-  @spec test_connection() :: {:ok, :connected} | {:error, term()}
+  @spec test_connection() :: {:ok, :connected} | {:error, Mv.Vereinfacht.Client.error_reason()}
   def test_connection do
     Client.test_connection(
       Mv.Config.vereinfacht_api_url(),
diff --git a/lib/mv_web/live/member_live/index/field_visibility.ex b/lib/mv_web/live/member_live/index/field_visibility.ex
index df20d25..52ebe86 100644
--- a/lib/mv_web/live/member_live/index/field_visibility.ex
+++ b/lib/mv_web/live/member_live/index/field_visibility.ex
@@ -190,7 +190,7 @@ defmodule MvWeb.MemberLive.Index.FieldVisibility do
   These fields are not in the database; they must not be used for Ash query
   select/sort. Use this to filter sort options and validate sort_field.
   """
-  @spec computed_member_fields() :: [atom()]
+  @spec computed_member_fields() :: [:membership_fee_status | :membership_fee_type | :groups, ...]
   def computed_member_fields, do: @pseudo_member_fields
 
   @doc """
diff --git a/lib/mv_web/live/membership_fee_type_live/form.ex b/lib/mv_web/live/membership_fee_type_live/form.ex
index bfdfa2d..ebaa977 100644
--- a/lib/mv_web/live/membership_fee_type_live/form.ex
+++ b/lib/mv_web/live/membership_fee_type_live/form.ex
@@ -341,7 +341,7 @@ defmodule MvWeb.MembershipFeeTypeLive.Form do
     end
   end
 
-  @spec notify_parent(any()) :: any()
+  @spec notify_parent(any()) :: {module(), any()}
   defp notify_parent(msg), do: send(self(), {__MODULE__, msg})
 
   @spec assign_form(Phoenix.LiveView.Socket.t()) :: Phoenix.LiveView.Socket.t()
diff --git a/lib/mv_web/live/role_live/form.ex b/lib/mv_web/live/role_live/form.ex
index 51f5cac..eb672da 100644
--- a/lib/mv_web/live/role_live/form.ex
+++ b/lib/mv_web/live/role_live/form.ex
@@ -186,7 +186,7 @@ defmodule MvWeb.RoleLive.Form do
     end
   end
 
-  @spec notify_parent(any()) :: any()
+  @spec notify_parent(any()) :: {module(), any()}
   defp notify_parent(msg), do: send(self(), {__MODULE__, msg})
 
   @spec assign_form(Phoenix.LiveView.Socket.t()) :: Phoenix.LiveView.Socket.t()
diff --git a/lib/mv_web/live/user_live/form.ex b/lib/mv_web/live/user_live/form.ex
index 4a26078..35ce1fe 100644
--- a/lib/mv_web/live/user_live/form.ex
+++ b/lib/mv_web/live/user_live/form.ex
@@ -775,7 +775,7 @@ defmodule MvWeb.UserLive.Form do
      )}
   end
 
-  @spec notify_parent(any()) :: any()
+  @spec notify_parent(any()) :: {module(), any()}
   defp notify_parent(msg), do: send(self(), {__MODULE__, msg})
 
   # Helper to ignore keyboard events when dropdown is closed
@@ -913,7 +913,7 @@ defmodule MvWeb.UserLive.Form do
     MemberResource.filter_by_email_match(members, user_email_str)
   end
 
-  @spec load_roles(any()) :: [Mv.Authorization.Role.t()]
+  @spec load_roles(any()) :: [Mv.Authorization.Role.t()] | Ash.Page.page()
   defp load_roles(actor) do
     case Authorization.list_roles(actor: actor) do
       {:ok, roles} -> roles
diff --git a/lib/mv_web/live_helpers.ex b/lib/mv_web/live_helpers.ex
index 4206aa6..ebf51e2 100644
--- a/lib/mv_web/live_helpers.ex
+++ b/lib/mv_web/live_helpers.ex
@@ -145,7 +145,10 @@ defmodule MvWeb.LiveHelpers do
       end
   """
   @spec submit_form(AshPhoenix.Form.t(), map(), Mv.Accounts.User.t() | nil) ::
-          {:ok, Ash.Resource.t()} | {:error, AshPhoenix.Form.t()}
+          {:ok, Ash.Resource.record() | nil | [Ash.Notifier.Notification.t()]}
+          | {:ok, Ash.Resource.record(), [Ash.Notifier.Notification.t()]}
+          | :ok
+          | {:error, AshPhoenix.Form.t()}
   def submit_form(form, params, actor) do
     AshPhoenix.Form.submit(form, params: params, action_opts: ash_actor_opts(actor))
   end
diff --git a/lib/mv_web/translations/field_types.ex b/lib/mv_web/translations/field_types.ex
index 969f20b..1580b99 100644
--- a/lib/mv_web/translations/field_types.ex
+++ b/lib/mv_web/translations/field_types.ex
@@ -12,7 +12,9 @@ defmodule MvWeb.Translations.FieldTypes do
   """
   use Gettext, backend: MvWeb.Gettext
 
-  @spec label(atom()) :: String.t()
+  @type field_type :: :string | :integer | :boolean | :date | :email
+
+  @spec label(field_type()) :: String.t()
   def label(:string), do: gettext("Text")
   def label(:integer), do: gettext("Number")
   def label(:boolean), do: gettext("Yes/No-Selection")