diff --git a/src/matrix/calls/callEventTypes.ts b/src/matrix/calls/callEventTypes.ts
index a0eb986c..879d0c11 100644
--- a/src/matrix/calls/callEventTypes.ts
+++ b/src/matrix/calls/callEventTypes.ts
@@ -22,11 +22,17 @@ export enum EventType {
 // TODO: Change to "sdp_stream_metadata" when MSC3077 is merged
 export const SDPStreamMetadataKey = "org.matrix.msc3077.sdp_stream_metadata";
 
+export interface FocusConfig {
+    user_id: string,
+    device_id: string
+}
+
 export interface CallDeviceMembership {
     device_id: string,
     session_id: string,
     ["expires_ts"]?: number,
     feeds?: Array<{purpose: string}>
+    ["m.foci.active"]?: Array<FocusConfig>
 }
 
 export interface CallMembership {
diff --git a/src/matrix/calls/group/GroupCall.ts b/src/matrix/calls/group/GroupCall.ts
index e0099f4e..16f09dd2 100644
--- a/src/matrix/calls/group/GroupCall.ts
+++ b/src/matrix/calls/group/GroupCall.ts
@@ -145,6 +145,15 @@ export class GroupCall extends EventEmitter<{change: never}> {
         return !!this.callContent?.["m.terminated"];
     }
 
+    get usesFoci(): boolean {
+        for (const member of this._members.values()) {
+            if (member.usesFoci) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     get duration(): number | undefined {
         if (typeof this.startTime === "number") {
             return (this.options.clock.now() - this.startTime);
diff --git a/src/matrix/calls/group/Member.ts b/src/matrix/calls/group/Member.ts
index e097804c..ab99c6b8 100644
--- a/src/matrix/calls/group/Member.ts
+++ b/src/matrix/calls/group/Member.ts
@@ -117,6 +117,11 @@ export class Member {
         return this.errorBoundary.error;
     }
 
+    get usesFoci(): boolean {
+        const activeFoci = this.callDeviceMembership["m.foci.active"];
+        return Array.isArray(activeFoci) && activeFoci.length > 0;
+    }
+
     private _renewExpireTimeout(log: ILogItem) {
         this.expireTimeout?.dispose();
         this.expireTimeout = undefined;