From 7844dfcc12e7f95d424daf10ef32b3e21efed2a7 Mon Sep 17 00:00:00 2001
From: lebaudantoine <lebaud.antoine131@gmail.com>
Date: Sat, 5 Sep 2026 00:25:22 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=93=88(frontend)=20track=20missing=20lobb?=
 =?UTF-8?q?y=20participant=20on=20accept/reject?=
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When a moderator accepts or rejects a lobby entry that no longer
exists, emit a tracking event so we can measure how often it
happens.

This signal will help tune the lobby polling interval: too many
"not found" events means the moderator side is working from a stale
list. Keep raising the error to the client on top of tracking it,
so the frontend still surfaces the issue (its current handling of
this case is still incomplete).
---
 CHANGELOG.md                                  |  1 +
 .../features/participants/api/enterRoom.ts    | 25 +++++++++++++------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7d978995..319b8b18 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project adheres to
 - ✨(backend) add Traefik support via configurable media-auth url header #1649
 - ✨(backend) update a room's attributes from the external API
 - 🔊(backend) log request duration in Gunicorn workers
+- 📈(frontend) track missing lobby participant on accept/reject
 
 ### Changed
 
diff --git a/src/frontend/src/features/participants/api/enterRoom.ts b/src/frontend/src/features/participants/api/enterRoom.ts
index 2c8c618a..80d70d3a 100644
--- a/src/frontend/src/features/participants/api/enterRoom.ts
+++ b/src/frontend/src/features/participants/api/enterRoom.ts
@@ -1,5 +1,6 @@
 import { ApiError } from '@/api/ApiError'
 import { fetchApi } from '@/api/fetchApi'
+import { captureEvent } from '@/features/analytics/telemetry'
 import { useMutation, type UseMutationOptions } from '@tanstack/react-query'
 
 export interface EnterRoomParams {
@@ -17,13 +18,23 @@ export const enterRoom = async ({
   allowEntry,
   participantId,
 }: EnterRoomParams): Promise<EnterRoomResponse> => {
-  return await fetchApi<EnterRoomResponse>(`/rooms/${roomId}/enter/`, {
-    method: 'POST',
-    body: JSON.stringify({
-      participant_id: participantId,
-      allow_entry: allowEntry,
-    }),
-  })
+  try {
+    return await fetchApi<EnterRoomResponse>(`/rooms/${roomId}/enter/`, {
+      method: 'POST',
+      body: JSON.stringify({
+        participant_id: participantId,
+        allow_entry: allowEntry,
+      }),
+    })
+  } catch (error) {
+    if (error instanceof ApiError && error.statusCode === 404) {
+      captureEvent('lobby_entry_participant_gone', {
+        room_id: roomId,
+        allow_entry: allowEntry,
+      })
+    }
+    throw error
+  }
 }
 
 export function useEnterRoom(