diff --git a/CHANGELOG.md b/CHANGELOG.md
index ba9cfb8..7f77ba1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+# Unreleased
+* Add all missing type annotations (Filip Hoffmann)
+
 # v1.0.1 (21/12/2025)
 * Update README.md (Filip Hoffmann)
 * Update grom.version/0 (Filip Hoffmann)
diff --git a/flake.lock b/flake.lock
index 62a32e6..b69ce9b 100644
--- a/flake.lock
+++ b/flake.lock
@@ -5,11 +5,11 @@
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1765001337,
-        "narHash": "sha256-6Pex/7RZ84UPdsdPfAL38W/r8Oe8zPVV1GkborQxWnU=",
+        "lastModified": 1766297333,
+        "narHash": "sha256-WZ3W65CieAGdQrpbF44svpmhb60pDmurY8PM+3aelaY=",
         "owner": "Comamoca",
         "repo": "gleam-overlay",
-        "rev": "2486a97a5f5d93685d9dfade21ec3dc545ad4fa7",
+        "rev": "1e34374044150257a16f207aa9ec451172ab5415",
         "type": "github"
       },
       "original": {
@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1754725699,
-        "narHash": "sha256-iAcj9T/Y+3DBy2J0N+yF9XQQQ8IEb5swLFzs23CdP88=",
+        "lastModified": 1765186076,
+        "narHash": "sha256-hM20uyap1a0M9d344I692r+ik4gTMyj60cQWO+hAYP8=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "85dbfc7aaf52ecb755f87e577ddbe6dbbdbc1054",
+        "rev": "addf7cf5f383a3101ecfba091b98d0a1263dc9b8",
         "type": "github"
       },
       "original": {
@@ -36,11 +36,11 @@
     },
     "nixpkgs_2": {
       "locked": {
-        "lastModified": 1764950072,
-        "narHash": "sha256-BmPWzogsG2GsXZtlT+MTcAWeDK5hkbGRZTeZNW42fwA=",
+        "lastModified": 1766070988,
+        "narHash": "sha256-G/WVghka6c4bAzMhTwT2vjLccg/awmHkdKSd2JrycLc=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "f61125a668a320878494449750330ca58b78c557",
+        "rev": "c6245e83d836d0433170a16eb185cefe0572f8b8",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 49f4b8c..0cc5451 100644
--- a/flake.nix
+++ b/flake.nix
@@ -23,7 +23,7 @@
     devShells = forAllSystems (pkgs: {
       default = pkgs.mkShellNoCC {
         buildInputs = with pkgs; [
-          pkgs.gleam.bin.latest
+          pkgs.gleam.bin.nightly
           rebar3
           beamPackages.erlang
         ];
diff --git a/src/grom.gleam b/src/grom.gleam
index bf1363c..545d253 100644
--- a/src/grom.gleam
+++ b/src/grom.gleam
@@ -26,6 +26,6 @@ pub type Error {
 
 // FUNCTIONS -------------------------------------------------------------------
 
-pub fn version() {
+pub fn version() -> String {
   "v1.0.2"
 }
diff --git a/src/grom/channel.gleam b/src/grom/channel.gleam
index 59c1af8..a4b9840 100644
--- a/src/grom/channel.gleam
+++ b/src/grom/channel.gleam
@@ -480,7 +480,7 @@ pub fn text_decoder() -> decode.Decoder(Channel) {
 }
 
 @internal
-pub fn dm_decoder() {
+pub fn dm_decoder() -> decode.Decoder(Channel) {
   use id <- decode.field("id", decode.string)
   use last_message_id <- decode.field(
     "last_message_id",
diff --git a/src/grom/command.gleam b/src/grom/command.gleam
index 892f819..33ce2f1 100644
--- a/src/grom/command.gleam
+++ b/src/grom/command.gleam
@@ -2317,11 +2317,15 @@ pub fn new_create_global_slash_command(
   )
 }
 
-pub fn new_create_global_user_command(named name: String) {
+pub fn new_create_global_user_command(
+  named name: String,
+) -> CreateGlobalUserCommand {
   CreateGlobalUserCommand(name, None, None, None, None, False)
 }
 
-pub fn new_create_global_message_command(named name: String) {
+pub fn new_create_global_message_command(
+  named name: String,
+) -> CreateGlobalMessageCommand {
   CreateGlobalMessageCommand(name, None, None, None, None, False)
 }
 
diff --git a/src/grom/component/section.gleam b/src/grom/component/section.gleam
index 4260d9d..7bfd96e 100644
--- a/src/grom/component/section.gleam
+++ b/src/grom/component/section.gleam
@@ -53,7 +53,7 @@ pub fn component_decoder() -> decode.Decoder(Component) {
 }
 
 @internal
-pub fn accessory_decoder() {
+pub fn accessory_decoder() -> decode.Decoder(Accessory) {
   use type_ <- decode.field("type", decode.int)
   case type_ {
     2 -> {
diff --git a/src/grom/component/user_select.gleam b/src/grom/component/user_select.gleam
index 388ac45..d8a095c 100644
--- a/src/grom/component/user_select.gleam
+++ b/src/grom/component/user_select.gleam
@@ -111,7 +111,7 @@ pub fn to_json(user_select: UserSelect) -> Json {
 }
 
 @internal
-pub fn default_value_to_json(default_value: DefaultValue) {
+pub fn default_value_to_json(default_value: DefaultValue) -> Json {
   json.object([
     #("id", json.string(default_value.id)),
     #("type", json.string("user")),
diff --git a/src/grom/gateway.gleam b/src/grom/gateway.gleam
index 469efab..9218065 100644
--- a/src/grom/gateway.gleam
+++ b/src/grom/gateway.gleam
@@ -2385,7 +2385,10 @@ fn try_resume(connection_state: Connection(user_state)) -> Nil {
   }
 }
 
-fn resume(connection_state: Connection(user_state), resuming_info: ResumingInfo) {
+fn resume(
+  connection_state: Connection(user_state),
+  resuming_info: ResumingInfo,
+) -> Nil {
   let request_url =
     resuming_info.resume_gateway_url
     |> string.replace(each: "wss://", with: "https://")
@@ -2500,6 +2503,9 @@ fn reconnect(connection_state: Connection(user_state)) -> Nil {
 fn on_connection_manager_message(
   current: Option(Subject(stratus.InternalMessage(UserMessage(user_state)))),
   message: ConnectionManagerMessage(user_state),
+) -> actor.Next(
+  Option(Subject(stratus.InternalMessage(UserMessage(user_state)))),
+  a,
 ) {
   case current {
     Some(manager) -> {
@@ -2551,7 +2557,7 @@ pub fn identify_with_presence(
 pub fn update_presence(
   connection_state: Connection(user_state),
   using message: UpdatePresenceMessage,
-) {
+) -> Nil {
   process.send(
     connection_state.manager,
     SendUserMessage(StartPresenceUpdate(message)),
@@ -2561,7 +2567,7 @@ pub fn update_presence(
 pub fn update_voice_state(
   connection_state: Connection(user_state),
   using message: UpdateVoiceStateMessage,
-) {
+) -> Nil {
   process.send(
     connection_state.manager,
     SendUserMessage(StartVoiceStateUpdate(message)),
@@ -2571,7 +2577,7 @@ pub fn update_voice_state(
 pub fn request_guild_members(
   connection_state: Connection(user_state),
   using message: RequestGuildMembersMessage,
-) {
+) -> Nil {
   process.send(
     connection_state.manager,
     SendUserMessage(StartGuildMembersRequest(message)),
@@ -2581,7 +2587,7 @@ pub fn request_guild_members(
 pub fn request_soundboard_sounds(
   connection_state: Connection(user_state),
   for guild_ids: List(String),
-) {
+) -> Nil {
   process.send(
     connection_state.manager,
     SendUserMessage(StartSoundboardSoundsRequest(guild_ids)),
@@ -2659,7 +2665,7 @@ fn on_start_guild_members_request(
   connection_state: Connection(user_state),
   connection: stratus.Connection,
   msg: RequestGuildMembersMessage,
-) {
+) -> stratus.Next(Connection(user_state), a) {
   let send_result =
     msg
     |> request_guild_members_message_to_json
@@ -2677,7 +2683,7 @@ fn on_start_voice_state_update(
   connection_state: Connection(user_state),
   connection: stratus.Connection,
   msg: UpdateVoiceStateMessage,
-) {
+) -> stratus.Next(Connection(user_state), a) {
   let send_result =
     msg
     |> update_voice_state_message_to_json
@@ -2787,7 +2793,10 @@ fn on_reconnect_request(
   stratus.stop()
 }
 
-fn send_error(err: grom.Error, connection_state: Connection(user_state)) {
+fn send_error(
+  err: grom.Error,
+  connection_state: Connection(user_state),
+) -> stratus.Next(Connection(user_state), a) {
   let next =
     connection_state.event_handler(
       connection_state.user_state,
@@ -3125,7 +3134,7 @@ type HeartbeatCount {
 fn start_heartbeats(
   every interval: Duration,
   send_to connection_manager: Subject(ConnectionManagerMessage(user_state)),
-) {
+) -> Result(actor.Started(Subject(HeartbeatManagerMessage)), grom.Error) {
   let initial_wait =
     interval
     |> duration.to_seconds
@@ -3165,7 +3174,7 @@ fn start_heartbeats(
 fn on_heartbeat_manager_message(
   current: HeartbeatState(user_state),
   message: HeartbeatManagerMessage,
-) {
+) -> actor.Next(HeartbeatState(user_state), a) {
   case message {
     HeartbeatSent ->
       actor.continue(
@@ -3236,4 +3245,4 @@ fn check_heartbeat_equality(
 }
 
 // sounds better
-const heartbeat_jitter = float.random
+const heartbeat_jitter: fn() -> Float = float.random
diff --git a/src/grom/guild/integration.gleam b/src/grom/guild/integration.gleam
index feb3beb..542c8b6 100644
--- a/src/grom/guild/integration.gleam
+++ b/src/grom/guild/integration.gleam
@@ -171,7 +171,7 @@ pub fn application_decoder() -> decode.Decoder(Application) {
 }
 
 @internal
-pub fn expire_behavior_decoder() {
+pub fn expire_behavior_decoder() -> decode.Decoder(ExpireBehavior) {
   use variant <- decode.then(decode.int)
   case variant {
     0 -> decode.success(RemoveRole)
diff --git a/src/grom/guild_member.gleam b/src/grom/guild_member.gleam
index fe207a3..8121ffb 100644
--- a/src/grom/guild_member.gleam
+++ b/src/grom/guild_member.gleam
@@ -62,7 +62,7 @@ pub type Modify {
 // FLAGS -----------------------------------------------------------------------
 
 @internal
-pub fn bits_member_flags() {
+pub fn bits_member_flags() -> List(#(Int, Flag)) {
   [
     #(int.bitwise_shift_left(1, 0), DidRejoin),
     #(int.bitwise_shift_left(1, 1), CompletedOnboarding),
diff --git a/src/grom/interaction.gleam b/src/grom/interaction.gleam
index 3a8c84d..926e9b1 100644
--- a/src/grom/interaction.gleam
+++ b/src/grom/interaction.gleam
@@ -1297,7 +1297,7 @@ pub fn response_message_to_json(message: ResponseMessage) -> Json {
 }
 
 @internal
-pub fn modal_response_to_json(modal: ModalResponse) {
+pub fn modal_response_to_json(modal: ModalResponse) -> Json {
   json.object([
     #("custom_id", json.string(modal.custom_id)),
     #("title", json.string(modal.title)),
@@ -1306,7 +1306,7 @@ pub fn modal_response_to_json(modal: ModalResponse) {
 }
 
 @internal
-pub fn modify_original_response_to_json(modify: ModifyOriginalResponse) {
+pub fn modify_original_response_to_json(modify: ModifyOriginalResponse) -> Json {
   [
     modification.to_json(modify.content, "content", json.string),
     modification.to_json(modify.embeds, "embeds", json.array(_, embed.to_json)),
diff --git a/src/grom/internal/rest.gleam b/src/grom/internal/rest.gleam
index 744622d..b4e795a 100644
--- a/src/grom/internal/rest.gleam
+++ b/src/grom/internal/rest.gleam
@@ -16,9 +16,9 @@ import status_code
 
 // CONSTANTS -------------------------------------------------------------------
 
-const discord_url = "discord.com"
+const discord_url: String = "discord.com"
 
-const discord_api_path = "api/v10"
+const discord_api_path: String = "api/v10"
 
 // INTERNAL FUNCTIONS ----------------------------------------------------------