diff --git a/backend/app/socketio/game_namespace.py b/backend/app/socketio/game_namespace.py
index 20d27f3..8cd37b8 100644
--- a/backend/app/socketio/game_namespace.py
+++ b/backend/app/socketio/game_namespace.py
@@ -177,6 +177,20 @@ class GameNamespaceHandler:
                 response["turn_timeout_seconds"] = result.turn_timeout_seconds
                 response["turn_deadline"] = result.turn_deadline
 
+            # Emit game:state event to the client
+            if result.visible_state:
+                await sio.emit(
+                    "game:state",
+                    {
+                        "game_id": game_id,
+                        "state": response["state"],
+                        "is_your_turn": response["is_your_turn"],
+                        "game_over": response["game_over"],
+                    },
+                    to=sid,
+                    namespace="/game",
+                )
+
             logger.info(f"Player {user_id} joined game {game_id}")
             return response
 
diff --git a/frontend/src/api/client.ts b/frontend/src/api/client.ts
index a219526..16bef31 100644
--- a/frontend/src/api/client.ts
+++ b/frontend/src/api/client.ts
@@ -43,7 +43,20 @@ async function parseErrorResponse(response: Response): Promise<ApiError> {
 
   try {
     const data: ErrorResponse = await response.json()
-    detail = data.detail || data.message
+
+    // Handle Pydantic validation errors (422) - detail is an array
+    if (Array.isArray(data.detail)) {
+      // Extract error messages from validation error array
+      detail = data.detail
+        .map((err: any) => {
+          const field = err.loc ? err.loc.join('.') : 'unknown'
+          return `${field}: ${err.msg || 'Invalid value'}`
+        })
+        .join('; ')
+    } else {
+      detail = data.detail || data.message
+    }
+
     code = data.code
   } catch {
     // Response body is not JSON or empty
diff --git a/frontend/src/api/types.ts b/frontend/src/api/types.ts
index 607d98e..57ca69a 100644
--- a/frontend/src/api/types.ts
+++ b/frontend/src/api/types.ts
@@ -92,9 +92,10 @@ export interface PaginatedResponse<T> {
 
 /**
  * Backend error response shape.
+ * For validation errors (422), detail is an array of validation error objects.
  */
 export interface ErrorResponse {
-  detail?: string
+  detail?: string | Array<{ loc: string[]; msg: string; type: string }>
   message?: string
   code?: string
 }