diff --git a/.dialyzer_ignore.exs b/.dialyzer_ignore.exs
new file mode 100644
index 0000000..da2329f
--- /dev/null
+++ b/.dialyzer_ignore.exs
@@ -0,0 +1,3 @@
+[
+  {"lib/phoenix/router.ex", :pattern_match, 402}
+]
diff --git a/lib/matrix_server.ex b/lib/matrix_server.ex
index 676905e..97d7bcc 100644
--- a/lib/matrix_server.ex
+++ b/lib/matrix_server.ex
@@ -1,39 +1,33 @@
 defmodule MatrixServer do
   alias MatrixServer.EncodableMap
 
+  @random_string_alphabet Enum.into(?a..?z, []) ++ Enum.into(?A..?Z, [])
+
+  @spec get_mxid(String.t()) :: String.t()
   def get_mxid(localpart) when is_binary(localpart) do
     "@#{localpart}:#{server_name()}"
   end
 
+  @spec server_name() :: String.t()
   def server_name do
     Application.get_env(:matrix_server, :server_name)
   end
 
-  def maybe_update_map(map, old_key, new_key) do
-    maybe_update_map(map, old_key, new_key, &Function.identity/1)
-  end
-
-  def maybe_update_map(map, old_key, new_key, fun) when is_map_key(map, old_key) do
-    value = Map.fetch!(map, old_key)
-
-    map
-    |> Map.put(new_key, fun.(value))
-    |> Map.delete(old_key)
-  end
-
-  def maybe_update_map(map, _, _, _), do: map
-
+  @spec localpart_regex() :: Regex.t()
   def localpart_regex, do: ~r/^([a-z0-9\._=\/])+$/
 
-  @alphabet Enum.into(?a..?z, []) ++ Enum.into(?A..?Z, [])
-  def random_string(length), do: random_string(length, @alphabet)
+  @spec random_string(pos_integer()) :: String.t()
+  def random_string(length), do: random_string(length, @random_string_alphabet)
 
+  @spec random_string(pos_integer(), Enum.t()) :: String.t()
   def random_string(length, alphabet) when length >= 1 do
     for _ <- 1..length, into: "", do: <<Enum.random(alphabet)>>
   end
 
+  @spec default_room_version() :: String.t()
   def default_room_version, do: "7"
 
+  @spec get_domain(String.t()) :: String.t() | nil
   def get_domain(id) do
     case String.split(id, ":", parts: 2) do
       [_, server_name] -> server_name
@@ -42,6 +36,7 @@ defmodule MatrixServer do
   end
 
   # TODO Eventually move to regex with named captures.
+  @spec get_localpart(String.t()) :: String.t() | nil
   def get_localpart(id) do
     with [part, _] <- String.split(id, ":", parts: 2),
          {_, localpart} <- String.split_at(part, 1) do
@@ -52,6 +47,7 @@ defmodule MatrixServer do
   end
 
   # https://elixirforum.com/t/22709/9
+  @spec has_duplicates?(list()) :: boolean()
   def has_duplicates?(list) do
     list
     |> Enum.reduce_while(%MapSet{}, fn x, acc ->
@@ -61,6 +57,7 @@ defmodule MatrixServer do
   end
 
   # https://matrix.org/docs/spec/appendices#unpadded-base64
+  @spec encode_unpadded_base64(String.t()) :: String.t()
   def encode_unpadded_base64(data) do
     data
     |> Base.encode64()
@@ -68,12 +65,14 @@ defmodule MatrixServer do
   end
 
   # Decode (possibly unpadded) base64.
+  @spec decode_base64(String.t()) :: {:ok, String.t()} | :error
   def decode_base64(data) when is_binary(data) do
     rem = rem(String.length(data), 4)
     padded_data = if rem > 0, do: data <> String.duplicate("=", 4 - rem), else: data
     Base.decode64(padded_data)
   end
 
+  @spec encode_canonical_json(map()) :: {:ok, String.t()} | {:error, Jason.EncodeError.t()}
   def encode_canonical_json(object) do
     object
     |> EncodableMap.from_map()
@@ -81,6 +80,7 @@ defmodule MatrixServer do
   end
 
   # https://stackoverflow.com/questions/41523762/41671211
+  @spec to_serializable_map(struct()) :: map()
   def to_serializable_map(struct) do
     association_fields = struct.__struct__.__schema__(:associations)
     waste_fields = association_fields ++ [:__meta__]
@@ -90,6 +90,7 @@ defmodule MatrixServer do
     |> Map.drop(waste_fields)
   end
 
+  @spec serialize_and_encode(struct()) :: {:ok, String.t()} | {:error, Jason.EncodeError.t()}
   def serialize_and_encode(struct) do
     # TODO: handle nil values in struct?
     struct
@@ -97,6 +98,7 @@ defmodule MatrixServer do
     |> encode_canonical_json()
   end
 
+  @spec add_signature(map(), String.t(), String.t()) :: map()
   def add_signature(object, key_id, sig) when not is_map_key(object, :signatures) do
     Map.put(object, :signatures, %{MatrixServer.server_name() => %{key_id => sig}})
   end
@@ -108,6 +110,7 @@ defmodule MatrixServer do
     %{object | signatures: new_sigs}
   end
 
+  @spec validate_change_simple(Ecto.Changeset.t(), atom(), (term() -> boolean())) :: Ecto.Changeset.t()
   def validate_change_simple(changeset, field, func) do
     augmented_func = fn _, val ->
       if func.(val), do: [], else: [{field, "invalid"}]
@@ -118,6 +121,7 @@ defmodule MatrixServer do
 
   # Returns a Boolean whether the signature is valid.
   # Also returns false on ArgumentError.
+  @spec sign_verify(binary(), String.t(), binary()) :: boolean()
   def sign_verify(sig, text, key) do
     try do
       :enacl.sign_verify_detached(sig, text, key)
@@ -126,6 +130,7 @@ defmodule MatrixServer do
     end
   end
 
+  @spec min_datetime(DateTime.t(), DateTime.t()) :: DateTime.t()
   def min_datetime(datetime1, datetime2) do
     if DateTime.compare(datetime1, datetime2) == :gt do
       datetime2
@@ -134,6 +139,7 @@ defmodule MatrixServer do
     end
   end
 
+  @spec encode_url_safe_base64(String.t()) :: String.t()
   def encode_url_safe_base64(data) do
     data
     |> encode_unpadded_base64()
diff --git a/lib/matrix_server/key_server.ex b/lib/matrix_server/key_server.ex
index 00076bd..39b4e07 100644
--- a/lib/matrix_server/key_server.ex
+++ b/lib/matrix_server/key_server.ex
@@ -10,10 +10,12 @@ defmodule MatrixServer.KeyServer do
     GenServer.start_link(__MODULE__, opts, name: __MODULE__)
   end
 
+  @spec sign_object(map()) :: {:ok, String.t(), String.t()} | :error
   def sign_object(object) do
     GenServer.call(__MODULE__, {:sign_object, object})
   end
 
+  @spec get_own_signing_keys() :: list({String.t(), binary()})
   def get_own_signing_keys() do
     GenServer.call(__MODULE__, :get_own_signing_keys)
   end
@@ -41,6 +43,7 @@ defmodule MatrixServer.KeyServer do
   end
 
   # https://blog.swwomm.com/2020/09/elixir-ed25519-signatures-with-enacl.html
+  @spec sign_object(map(), binary()) :: {:ok, String.t()} | {:error, Jason.EncodeError.t()}
   defp sign_object(object, private_key) do
     object = Map.drop(object, [:signatures, :unsigned])
 
@@ -55,7 +58,8 @@ defmodule MatrixServer.KeyServer do
   end
 
   # TODO: not sure if there is a better way to do this...
-  def read_keys do
+  @spec read_keys() :: {binary(), binary()}
+  defp read_keys do
     raw_priv_key =
       Application.get_env(:matrix_server, :private_key_file)
       |> File.read!()
diff --git a/lib/matrix_server/quick_check.ex b/lib/matrix_server/quick_check.ex
deleted file mode 100644
index 8507d01..0000000
--- a/lib/matrix_server/quick_check.ex
+++ /dev/null
@@ -1,14 +0,0 @@
-defmodule MatrixServer.QuickCheck do
-  import Ecto.Query
-
-  alias MatrixServer.{Repo, Room, Account, RoomServer}
-  alias MatrixServerWeb.Client.Request.CreateRoom
-
-  def create_room(name \\ nil, topic \\ nil) do
-    account = Repo.one!(from a in Account, limit: 1)
-    input = %CreateRoom{name: name, topic: topic}
-    %Room{id: room_id} = Repo.insert!(Room.create_changeset(input))
-    {:ok, pid} = RoomServer.get_room_server(room_id)
-    RoomServer.create_room(pid, account, input)
-  end
-end
diff --git a/lib/matrix_server/room_server.ex b/lib/matrix_server/room_server.ex
index 9c33749..25a7cd6 100644
--- a/lib/matrix_server/room_server.ex
+++ b/lib/matrix_server/room_server.ex
@@ -20,6 +20,7 @@ defmodule MatrixServer.RoomServer do
 
   # Get room server pid, or spin one up for the room.
   # If the room does not exist, return an error.
+  @spec get_room_server(String.t()) :: {:error, :not_found} | DynamicSupervisor.on_start_child()
   def get_room_server(room_id) do
     case Repo.one(from r in Room, where: r.id == ^room_id) do
       nil ->
@@ -42,10 +43,12 @@ defmodule MatrixServer.RoomServer do
     end
   end
 
+  @spec create_room(pid(), MatrixServer.Account.t(), MatrixServerWeb.Client.Request.CreateRoom.t()) :: {:ok, String.t()} | {:error, atom()}
   def create_room(pid, account, input) do
     GenServer.call(pid, {:create_room, account, input})
   end
 
+  @spec server_in_room(pid(), String.t()) :: boolean()
   def server_in_room(pid, domain) do
     GenServer.call(pid, {:server_in_room, domain})
   end
diff --git a/lib/matrix_server/schema/account.ex b/lib/matrix_server/schema/account.ex
index 42aea28..a62fa93 100644
--- a/lib/matrix_server/schema/account.ex
+++ b/lib/matrix_server/schema/account.ex
@@ -7,6 +7,10 @@ defmodule MatrixServer.Account do
   alias MatrixServerWeb.Client.Request.{Register, Login}
   alias Ecto.Multi
 
+  @type t :: %__MODULE__{
+    password_hash: String.t()
+  }
+
   @max_mxid_length 255
 
   @primary_key {:localpart, :string, []}
diff --git a/lib/matrix_server/schema/room.ex b/lib/matrix_server/schema/room.ex
index fc30728..fbb898b 100644
--- a/lib/matrix_server/schema/room.ex
+++ b/lib/matrix_server/schema/room.ex
@@ -7,6 +7,12 @@ defmodule MatrixServer.Room do
   alias MatrixServer.{Repo, Room, Event, Alias, RoomServer}
   alias MatrixServerWeb.Client.Request.CreateRoom
 
+  @type t :: %__MODULE__{
+    visibility: :public | :private,
+    state: list(list(String.t())),
+    forward_extremities: list(String.t())
+  }
+
   @primary_key {:id, :string, []}
   schema "rooms" do
     field :visibility, Ecto.Enum, values: [:public, :private]
diff --git a/lib/matrix_server/state_resolution/authorization.ex b/lib/matrix_server/state_resolution/authorization.ex
index 854ab18..317828b 100644
--- a/lib/matrix_server/state_resolution/authorization.ex
+++ b/lib/matrix_server/state_resolution/authorization.ex
@@ -129,8 +129,10 @@ defmodule MatrixServer.StateResolution.Authorization do
   end
 
   defp _authorized?(%Event{type: "m.room.third_party_invite", sender: sender}, state_set) do
+    power_levels = get_power_levels(state_set)
     # Check rule: 7.1
-    has_power_level(sender, state_set, :invite)
+
+    has_power_level(sender, power_levels, :invite)
   end
 
   defp _authorized?(%Event{state_key: state_key, sender: sender} = event, state_set) do
@@ -202,8 +204,10 @@ defmodule MatrixServer.StateResolution.Authorization do
   defp get_action_power_level(:invite, _), do: 50
   defp get_action_power_level(:ban, %{"ban" => pl}), do: pl
   defp get_action_power_level(:ban, _), do: 50
-  defp get_action_power_level(:redact, %{"redact" => pl}), do: pl
-  defp get_action_power_level(:redact, _), do: 50
+  # defp get_action_power_level(:redact, %{"redact" => pl}), do: pl
+  # defp get_action_power_level(:redact, _), do: 50
+  # defp get_action_power_level(:kick, %{"kick" => pl}), do: pl
+  # defp get_action_power_level(:kick, _), do: 50
 
   defp get_action_power_level({:event, %Event{type: type}}, %{"events" => events})
        when is_map_key(events, type),
diff --git a/lib/matrix_server_web/client/request/create_room.ex b/lib/matrix_server_web/client/request/create_room.ex
index b8e7402..d37d129 100644
--- a/lib/matrix_server_web/client/request/create_room.ex
+++ b/lib/matrix_server_web/client/request/create_room.ex
@@ -5,6 +5,16 @@ defmodule MatrixServerWeb.Client.Request.CreateRoom do
 
   alias Ecto.Changeset
 
+  @type t :: %__MODULE__{
+    visibility: String.t(),
+    room_alias_name: String.t(),
+    name: String.t(),
+    topic: String.t(),
+    invite: list(String.t()),
+    room_version: String.t(),
+    preset: String.t()
+  }
+
   @primary_key false
   embedded_schema do
     field :visibility, :string
diff --git a/mix.exs b/mix.exs
index 0848f5f..3493cca 100644
--- a/mix.exs
+++ b/mix.exs
@@ -10,7 +10,8 @@ defmodule MatrixServer.MixProject do
       compilers: [:phoenix] ++ Mix.compilers(),
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),
-      deps: deps()
+      deps: deps(),
+      dialyzer: [plt_add_deps: :app_tree]
     ]
   end
 
@@ -46,7 +47,8 @@ defmodule MatrixServer.MixProject do
       {:ex_machina, "~> 2.7", only: :test},
       {:enacl, "~> 1.2"},
       {:tesla, "~> 1.4"},
-      {:finch, "~> 0.8.1"}
+      {:finch, "~> 0.8.1"},
+      {:dialyxir, "~> 1.1", only: [:dev], runtime: false}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index 129829d..7576533 100644
--- a/mix.lock
+++ b/mix.lock
@@ -9,10 +9,12 @@
   "cowlib": {:hex, :cowlib, "2.11.0", "0b9ff9c346629256c42ebe1eeb769a83c6cb771a6ee5960bd110ab0b9b872063", [:make, :rebar3], [], "hexpm", "2b3e9da0b21c4565751a6d4901c20d1b4cc25cbb7fd50d91d2ab6dd287bc86a9"},
   "db_connection": {:hex, :db_connection, "2.4.0", "d04b1b73795dae60cead94189f1b8a51cc9e1f911c234cc23074017c43c031e5", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "ad416c21ad9f61b3103d254a71b63696ecadb6a917b36f563921e0de00d7d7c8"},
   "decimal": {:hex, :decimal, "2.0.0", "a78296e617b0f5dd4c6caf57c714431347912ffb1d0842e998e9792b5642d697", [:mix], [], "hexpm", "34666e9c55dea81013e77d9d87370fe6cb6291d1ef32f46a1600230b1d44f577"},
+  "dialyxir": {:hex, :dialyxir, "1.1.0", "c5aab0d6e71e5522e77beff7ba9e08f8e02bad90dfbeffae60eaf0cb47e29488", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "07ea8e49c45f15264ebe6d5b93799d4dd56a44036cf42d0ad9c960bc266c0b9a"},
   "ecto": {:hex, :ecto, "3.6.2", "efdf52acfc4ce29249bab5417415bd50abd62db7b0603b8bab0d7b996548c2bc", [:mix], [{:decimal, "~> 1.6 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "efad6dfb04e6f986b8a3047822b0f826d9affe8e4ebdd2aeedbfcb14fd48884e"},
   "ecto_sql": {:hex, :ecto_sql, "3.6.2", "9526b5f691701a5181427634c30655ac33d11e17e4069eff3ae1176c764e0ba3", [:mix], [{:db_connection, "~> 2.2", [hex: :db_connection, repo: "hexpm", optional: false]}, {:ecto, "~> 3.6.2", [hex: :ecto, repo: "hexpm", optional: false]}, {:myxql, "~> 0.4.0 or ~> 0.5.0", [hex: :myxql, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.15.0 or ~> 1.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:tds, "~> 2.1.1", [hex: :tds, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "5ec9d7e6f742ea39b63aceaea9ac1d1773d574ea40df5a53ef8afbd9242fdb6b"},
   "elixir_make": {:hex, :elixir_make, "0.6.2", "7dffacd77dec4c37b39af867cedaabb0b59f6a871f89722c25b28fcd4bd70530", [:mix], [], "hexpm", "03e49eadda22526a7e5279d53321d1cced6552f344ba4e03e619063de75348d9"},
   "enacl": {:hex, :enacl, "1.2.1", "7776480b9b3d42a51d66dbbcbf17fa3d79285b3d2adcb4d5b5bd0b70f0ef1949", [:rebar3], [], "hexpm", "67bbbeddd2564dc899a3dcbc3765cd6ad71629134f1e500a50ec071f0f75e552"},
+  "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
   "ex_machina": {:hex, :ex_machina, "2.7.0", "b792cc3127fd0680fecdb6299235b4727a4944a09ff0fa904cc639272cd92dc7", [:mix], [{:ecto, "~> 2.2 or ~> 3.0", [hex: :ecto, repo: "hexpm", optional: true]}, {:ecto_sql, "~> 3.0", [hex: :ecto_sql, repo: "hexpm", optional: true]}], "hexpm", "419aa7a39bde11894c87a615c4ecaa52d8f107bbdd81d810465186f783245bf8"},
   "finch": {:hex, :finch, "0.8.1", "761e39640c98d12c9ac7aa15b4d0732205669b20055e26bcc8da7ce826070fdc", [:mix], [{:castore, "~> 0.1", [hex: :castore, repo: "hexpm", optional: false]}, {:mint, "~> 1.3", [hex: :mint, repo: "hexpm", optional: false]}, {:nimble_options, "~> 0.3.5", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:nimble_pool, "~> 0.2", [hex: :nimble_pool, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "bc80f759f701dd56793f4edfaa6dc6480707c23046fde3a98c9887b164924cad"},
   "jason": {:hex, :jason, "1.2.2", "ba43e3f2709fd1aa1dce90aaabfd039d000469c05c56f0b8e31978e03fa39052", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "18a228f5f0058ee183f29f9eae0805c6e59d61c3b006760668d8d18ff0d12179"},
diff --git a/priv/repo/seeds.exs b/priv/repo/seeds.exs
index 4e7c0ae..a5fada9 100644
--- a/priv/repo/seeds.exs
+++ b/priv/repo/seeds.exs
@@ -40,14 +40,16 @@ room =
     visibility: :public
   })
 
-Repo.insert!(
-  Event.create_room(room, alice, "v1")
-  |> Map.put(:origin_server_ts, timestamp.(0))
-  |> Map.put(:event_id, "create")
-)
+create_room =
+  Repo.insert!(
+    Event.create_room(room, alice, "v1", false)
+    |> Map.put(:origin_server_ts, timestamp.(0))
+    |> Event.post_process()
+    |> elem(1)
+  )
 
 Repo.insert!(
-  Event.join(room, alice)
+  Event.join(room, alice, false)
   |> Map.put(:prev_events, ["create"])
   |> Map.put(:auth_events, ["create"])
   |> Map.put(:origin_server_ts, timestamp.(1))
@@ -56,6 +58,7 @@ Repo.insert!(
 
 Repo.insert!(
   Event.join(room, bob)
+  |> elem(1)
   |> Map.put(:prev_events, ["join_alice"])
   |> Map.put(:auth_events, ["create"])
   |> Map.put(:origin_server_ts, timestamp.(2))
@@ -64,13 +67,14 @@ Repo.insert!(
 
 Repo.insert!(
   Event.join(room, charlie)
+  |> elem(1)
   |> Map.put(:prev_events, ["join_bob"])
   |> Map.put(:auth_events, ["create"])
   |> Map.put(:origin_server_ts, timestamp.(3))
   |> Map.put(:event_id, "join_charlie")
 )
 
-%Event{content: content} = event = Event.power_levels(room, alice)
+%Event{content: content} = event = Event.power_levels(room, alice) |> elem(1)
 event = %Event{event | content: %{content | "users" => %{"alice" => 100, "bob" => 100}}}
 
 Repo.insert!(
@@ -81,7 +85,7 @@ Repo.insert!(
   |> Map.put(:event_id, "a")
 )
 
-%Event{content: content} = event = Event.power_levels(room, bob)
+%Event{content: content} = event = Event.power_levels(room, bob) |> elem(1)
 
 event = %Event{
   event
@@ -98,6 +102,7 @@ Repo.insert!(
 
 Repo.insert!(
   Event.topic(room, alice, "sneed")
+  |> elem(1)
   |> Map.put(:prev_events, ["a"])
   |> Map.put(:auth_events, ["create", "join_alice", "a"])
   |> Map.put(:origin_server_ts, timestamp.(5))