diff --git a/src/client/HostLobbyModal.ts b/src/client/HostLobbyModal.ts
index c086354e62..6bca2ca8c8 100644
--- a/src/client/HostLobbyModal.ts
+++ b/src/client/HostLobbyModal.ts
@@ -655,6 +655,7 @@ export class HostLobbyModal extends BaseModal {
             detail: {
               gameID: this.lobbyId,
               clientID: this.lobbyCreatorClientID,
+              source: "host",
             } as JoinLobbyEvent,
             bubbles: true,
             composed: true,
diff --git a/src/client/JoinLobbyModal.ts b/src/client/JoinLobbyModal.ts
index 7cd330d644..0f1c5e2da7 100644
--- a/src/client/JoinLobbyModal.ts
+++ b/src/client/JoinLobbyModal.ts
@@ -336,6 +336,7 @@ export class JoinLobbyModal extends BaseModal {
         detail: {
           gameID: lobbyId,
           clientID: this.currentClientID,
+          source: "public",
         } as JoinLobbyEvent,
         bubbles: true,
         composed: true,
@@ -776,6 +777,7 @@ export class JoinLobbyModal extends BaseModal {
           detail: {
             gameID: lobbyId,
             clientID: this.currentClientID,
+            source: "private",
           } as JoinLobbyEvent,
           bubbles: true,
           composed: true,
@@ -834,6 +836,7 @@ export class JoinLobbyModal extends BaseModal {
           gameID: lobbyId,
           gameRecord: parsed.data,
           clientID: this.currentClientID,
+          source: "private",
         } as JoinLobbyEvent,
         bubbles: true,
         composed: true,
diff --git a/src/client/Matchmaking.ts b/src/client/Matchmaking.ts
index 4e53ea6abd..3fa4af738c 100644
--- a/src/client/Matchmaking.ts
+++ b/src/client/Matchmaking.ts
@@ -231,6 +231,7 @@ export class MatchmakingModal extends BaseModal {
         detail: {
           gameID: this.gameID,
           clientID: getClientIDForGame(this.gameID),
+          source: "matchmaking",
         } as JoinLobbyEvent,
         bubbles: true,
         composed: true,
diff --git a/src/client/SinglePlayerModal.ts b/src/client/SinglePlayerModal.ts
index 7a10f21aae..1623d996e6 100644
--- a/src/client/SinglePlayerModal.ts
+++ b/src/client/SinglePlayerModal.ts
@@ -967,6 +967,7 @@ export class SinglePlayerModal extends BaseModal {
             },
             lobbyCreatedAt: Date.now(), // ms; server should be authoritative in MP
           },
+          source: "singleplayer",
         } satisfies JoinLobbyEvent,
         bubbles: true,
         composed: true,