diff --git a/packages/mnswpr/core/session/session.d.ts b/packages/mnswpr/core/session/session.d.ts
index 8dff90f..1a62f76 100644
--- a/packages/mnswpr/core/session/session.d.ts
+++ b/packages/mnswpr/core/session/session.d.ts
@@ -6,6 +6,7 @@
  * Future home: @cozy-games/game-session.
  *
  * @typedef {{ init: Function, apply: Function, status: Function, project: Function, serialize?: Function, deserialize?: Function, toMoveEvent?: Function }} Rules
+ * @typedef {import('../minesweeper/rules.js').MoveEvent} MoveEvent
  */
 export class GameSession {
     /**
@@ -56,8 +57,8 @@ export class GameSession {
     }>;
     _t0: number;
     _tEnd: number;
-    /** @type {Set<(event: object) => void>} */
-    _moveHandlers: Set<(event: object) => void>;
+    /** @type {Set<(event: MoveEvent) => void>} */
+    _moveHandlers: Set<(event: MoveEvent) => void>;
     _seq: number;
     /**
      * Subscribe to typed move-events — one per effective move (reveal / flag /
@@ -65,10 +66,10 @@ export class GameSession {
      * unsubscribe function. Pure in-process pub/sub: no DOM, no rendering. Requires
      * the rules to implement `toMoveEvent`.
      *
-     * @param {(event: object) => void} handler
+     * @param {(event: MoveEvent) => void} handler
      * @returns {() => void} unsubscribe
      */
-    onMove(handler: (event: object) => void): () => void;
+    onMove(handler: (event: MoveEvent) => void): () => void;
     /**
      * Apply a move: stamp it, fold it through the rules, and return the projected
      * view + events + authoritative elapsed time.
@@ -79,8 +80,8 @@ export class GameSession {
         view: any;
         time: number;
     };
-    /** @param {object} event */
-    _emitMove(event: object): void;
+    /** @param {MoveEvent} event */
+    _emitMove(event: MoveEvent): void;
     status(): any;
     view(): any;
     log(): {
@@ -136,3 +137,11 @@ export type Rules = {
     deserialize?: Function;
     toMoveEvent?: Function;
 };
+/**
+ * Layer 1 — owns lifecycle, the (injected) clock, and the move log; delegates all
+ * game meaning to an injected `rules` object. This is where timing authority
+ * lives: on the client `clock` is `Date.now` (cosmetic); on a server it is the
+ * server's clock (authoritative). The session never calls a wall clock itself.
+ * Future home:
+ */
+export type MoveEvent = import("../minesweeper/rules.js").MoveEvent;
diff --git a/packages/mnswpr/core/session/session.js b/packages/mnswpr/core/session/session.js
index c4ee5f0..13c7b44 100644
--- a/packages/mnswpr/core/session/session.js
+++ b/packages/mnswpr/core/session/session.js
@@ -8,6 +8,7 @@
  * Future home: @cozy-games/game-session.
  *
  * @typedef {{ init: Function, apply: Function, status: Function, project: Function, serialize?: Function, deserialize?: Function, toMoveEvent?: Function }} Rules
+ * @typedef {import('../minesweeper/rules.js').MoveEvent} MoveEvent
  */
 export class GameSession {
   /**
@@ -30,7 +31,7 @@ export class GameSession {
     // Move-event emission: subscribers + a monotonic sequence counter (last seq
     // assigned; 0 = none yet). Seq is part of the snapshot so it keeps rising
     // across a resume rather than restarting.
-    /** @type {Set<(event: object) => void>} */
+    /** @type {Set<(event: MoveEvent) => void>} */
     this._moveHandlers = new Set()
     this._seq = 0
   }
@@ -41,7 +42,7 @@ export class GameSession {
    * unsubscribe function. Pure in-process pub/sub: no DOM, no rendering. Requires
    * the rules to implement `toMoveEvent`.
    *
-   * @param {(event: object) => void} handler
+   * @param {(event: MoveEvent) => void} handler
    * @returns {() => void} unsubscribe
    */
   onMove(handler) {
@@ -75,7 +76,7 @@ export class GameSession {
     return { events, view: this.rules.project(state), time: this.elapsed() }
   }
 
-  /** @param {object} event */
+  /** @param {MoveEvent} event */
   _emitMove(event) {
     for (const handler of this._moveHandlers) handler(event)
   }
diff --git a/packages/mnswpr/package.json b/packages/mnswpr/package.json
index ae3fb34..5900ff8 100644
--- a/packages/mnswpr/package.json
+++ b/packages/mnswpr/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@cozy-games/mnswpr",
-  "version": "0.5.3",
+  "version": "0.5.4",
   "description": "Classic Minesweeper browser game",
   "author": "Ayo",
   "type": "module",