diff --git a/src/Net/LockstepClient.ts b/src/Net/LockstepClient.ts
index 002f2db..ad22e97 100644
--- a/src/Net/LockstepClient.ts
+++ b/src/Net/LockstepClient.ts
@@ -7,10 +7,29 @@ import pipe from "callbag-pipe";
 import { INPUT_FREQUENCY, LockstepProcessor, LockstepState } from "../Ecs/Lockstep";
 
 export const enum MessageTypes {
+    /**
+     * Reserved, likely for transient messages that wouldn't make sense appearing in a replay
+     */
     META = 0,
+    /**
+     * From server: initialize client state / load new level, plus informing client of their "controller number"
+     * From client: (op only) force a new game state, likely loading a level
+     */
     SET_STATE = 1,
+    /**
+     * From server: array of canonical inputs for a frame
+     * From client: input for their controller for the next frame (TBD: strategy for handling late inputs)
+     */
     INPUT = 2,
+    /**
+     * From server: issue request for the current game state, with a cookie to identify the response
+     * From client: serialized game state, with the cookie of the request
+     */
     GET_STATE = 3,
+    /**
+     * For liveness checks / latency estimate. Echos a cookie.
+     * May be refactored into one of the above messages.
+     */
     PING = 4
 }
 
@@ -18,11 +37,17 @@ export type Packet<TypeId, Payload> = { t: TypeId } & Payload;
 
 export type ClientMessage<Input, State> =
     | Packet<MessageTypes.SET_STATE, { s: Partial<State> }>
-    | Packet<MessageTypes.INPUT, { i: Input }>;
+    | Packet<MessageTypes.INPUT, { i: Input }>
+    | Packet<MessageTypes.GET_STATE, { c: number, s: State }>
+    | Packet<MessageTypes.PING, { z: number }>
+;
 
 export type ServerMessage<Input, State> =
     | Packet<MessageTypes.SET_STATE, { s: Partial<State> }>
-    | Packet<MessageTypes.INPUT, { i: Input }>;
+    | Packet<MessageTypes.INPUT, { i: Input }>
+    | Packet<MessageTypes.GET_STATE, { c: number }>
+    | Packet<MessageTypes.PING, { z: number }>
+;
 
 export type Server<Input, State> = Callbag<ClientMessage<Input, State>, ServerMessage<Input, State>>;