diff --git a/contracts/v1/collaboration-session-response.json b/contracts/v1/collaboration-session-response.json
index ab80da5..3554364 100644
--- a/contracts/v1/collaboration-session-response.json
+++ b/contracts/v1/collaboration-session-response.json
@@ -14,10 +14,26 @@
         "properties": {
           "user_id": { "type": "string" },
           "user_display_name": { "type": ["string", "null"] },
+          "user_login": { "type": ["string", "null"] },
           "slot_id": { "type": ["string", "null"] },
-          "is_live": { "type": ["boolean", "null"] }
+          "is_live": { "type": ["boolean", "null"] },
+          "volume": { "type": ["integer", "null"], "minimum": 0, "maximum": 100 },
+          "assigned_at": { "type": ["string", "null"], "format": "date-time" },
+          "audio_settings": { "$ref": "#/$defs/media_settings" },
+          "video_settings": { "$ref": "#/$defs/media_settings" }
         }
       }
     }
+  },
+  "$defs": {
+    "media_settings": {
+      "type": ["object", "null"],
+      "additionalProperties": false,
+      "properties": {
+        "is_host_enabled": { "type": ["boolean", "null"] },
+        "is_guest_enabled": { "type": ["boolean", "null"] },
+        "is_available": { "type": ["boolean", "null"] }
+      }
+    }
   }
 }
diff --git a/fixtures/v1/collaboration-session.response.json b/fixtures/v1/collaboration-session.response.json
index 2c6d83c..6ac7a54 100644
--- a/fixtures/v1/collaboration-session.response.json
+++ b/fixtures/v1/collaboration-session.response.json
@@ -1,4 +1,24 @@
 {
   "id": "guest-star-session-1",
-  "guests": []
+  "guests": [
+    {
+      "user_id": "123456",
+      "user_display_name": "GuestOne",
+      "user_login": "guestone",
+      "slot_id": "1",
+      "is_live": true,
+      "volume": 85,
+      "assigned_at": "2026-10-25T12:01:00Z",
+      "audio_settings": {
+        "is_host_enabled": true,
+        "is_guest_enabled": true,
+        "is_available": true
+      },
+      "video_settings": {
+        "is_host_enabled": true,
+        "is_guest_enabled": false,
+        "is_available": true
+      }
+    }
+  ]
 }