presence: "who's here" — online devices in the room, with names

Presence chirps now carry the friendly device name, and the engine tracks the
present set as Peers (id/name/source/room). New Engine.present() -> [Peer]
exposes who's online in the room across any network. Both apps poll it and show
a green-dot row of online devices above the feed.

The present set already powered prefer-direct's coverage check; this enriches it
with names and surfaces it. Verified live on macOS: an agent in the room shows
as "● Patrick's NAS".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/src/lib.rs

@@ -92,10 +92,9 @@ type Receipts = Arc<Mutex<Vec<(Receipt, Instant)>>>;
 /// by `from`. Written by the RTC/LAN transports, read by `send` to decide whether
 /// the relay is still needed.
 type DirectSet = Arc<Mutex<HashSet<String>>>;
-/// Peers currently in the room, by `from`, last-seen via presence chirps. Lets
-/// `send` know the full audience so it only suppresses the relay when *every*
-/// present peer is directly reachable.
-type PresentSet = Arc<Mutex<HashMap<String, Instant>>>;
+/// Peers currently in the room, by `from`, with their Peer info and last-seen
+/// (via presence chirps). Drives both `send`'s coverage check and `present()`.
+type PresentSet = Arc<Mutex<HashMap<String, (Peer, Instant)>>>;
 
 /// Short content fingerprint — a receipt carries this, never the clipboard text,
 /// so acks can't leak content (sender matches by computing the same fingerprint).
@@ -112,7 +111,7 @@ fn directly_covered(direct: &DirectSet, present: &PresentSet) -> bool {
     let d = direct.lock().unwrap();
     let now = Instant::now();
     let mut p = present.lock().unwrap();
-    p.retain(|_, t| now.duration_since(*t) < Duration::from_secs(20));
+    p.retain(|_, (_, t)| now.duration_since(*t) < Duration::from_secs(20));
     !p.is_empty() && p.keys().all(|x| d.contains(x))
 }
 
@@ -234,6 +233,15 @@ impl Engine {
         map.values().map(|(p, _)| p.clone()).collect()
     }
 
+    /// Devices currently in your room (online via presence chirps), across any
+    /// network — for a "who's here" indicator. Pruned after 20s unseen.
+    pub fn present(&self) -> Vec<Peer> {
+        let now = Instant::now();
+        let mut p = self.present.lock().unwrap();
+        p.retain(|_, (_, t)| now.duration_since(*t) < Duration::from_secs(20));
+        p.values().map(|(peer, _)| peer.clone()).collect()
+    }
+
     /// Begin streaming on every transport. Idempotent while already running.
     pub fn start(&self, handler: Box<dyn MessageHandler>) {
         if self.running.swap(true, Ordering::SeqCst) {

core/src/rtc.rs

@@ -138,7 +138,9 @@ impl RtcTransport {
     async fn post_presence(&self) {
         self.post(json!({
             "type": "presence", "role": self.cfg.source,
-            "from": self.cfg.from, "room": self.cfg.room,
+            "from": self.cfg.from, "source": self.cfg.source,
+            "text": self.cfg.name, // friendly name for the "who's here" list
+            "room": self.cfg.room,
         }))
         .await;
     }
@@ -415,11 +417,24 @@ impl RtcTransport {
         }
         match v["type"].as_str().unwrap_or("") {
             "presence" => {
-                // Track who's in the room so send() knows the full audience.
-                self.present
-                    .lock()
-                    .unwrap()
-                    .insert(from.to_string(), Instant::now());
+                // Track who's in the room (with their name) for send()'s coverage
+                // check and the engine's present() "who's here" list.
+                let name = v["text"].as_str().filter(|s| !s.is_empty()).unwrap_or(from);
+                let source = v["source"].as_str().unwrap_or("").to_string();
+                let room = v["room"].as_str().unwrap_or("").to_string();
+                self.present.lock().unwrap().insert(
+                    from.to_string(),
+                    (
+                        crate::Peer {
+                            id: from.to_string(),
+                            name: name.to_string(),
+                            source,
+                            room,
+                            account: String::new(),
+                        },
+                        Instant::now(),
+                    ),
+                );
                 // Deterministic initiator: the smaller id offers.
                 if self.cfg.from.as_str() < from {
                     self.initiate_offer(from).await;

ios/MacTetherApp/Sources/ContentView.swift

@@ -8,6 +8,10 @@ struct ContentView: View {
         VStack(spacing: 0) {
             toolbar
             Divider()
+            if store.connected && !store.present.isEmpty {
+                presenceRow
+                Divider()
+            }
             if store.connected && !store.nearby.isEmpty {
                 nearbyStrip
                 Divider()
@@ -38,6 +42,22 @@ struct ContentView: View {
         .padding(.horizontal, 14).padding(.vertical, 5)
     }
 
+    // MARK: - Presence ("who's here")
+
+    private var presenceRow: some View {
+        HStack(spacing: 12) {
+            ForEach(store.present, id: \.id) { peer in
+                HStack(spacing: 5) {
+                    Circle().fill(.green).frame(width: 7, height: 7)
+                    Image(systemName: sourceIcon(peer.source)).font(.caption2)
+                    Text(peer.name).font(.caption).foregroundStyle(.secondary).lineLimit(1)
+                }
+            }
+            Spacer()
+        }
+        .padding(.horizontal, 14).padding(.vertical, 5)
+    }
+
     // MARK: - Nearby devices (AirDrop-style picker)
 
     private var nearbyStrip: some View {

ios/MacTetherApp/Sources/MacTetherStore.swift

@@ -26,6 +26,7 @@ final class MacTetherStore {
     }()
     var feed: [FeedItem] = []
     var nearby: [Peer] = []   // tether devices on the LAN, for the picker
+    var present: [Peer] = []   // devices online in the room ("who's here")
     var receipts: [Receipt] = []   // delivery acks — "seen by <device>"
     var connected = false
     var lastError: String?
@@ -69,6 +70,7 @@ final class MacTetherStore {
                 try? await Task.sleep(for: .seconds(2))
                 guard let self, let engine = self.engine else { continue }
                 self.nearby = engine.nearby().sorted { $0.name < $1.name }
+                self.present = engine.present().sorted { $0.name < $1.name }
                 self.receipts = engine.receipts()
             }
         }

ios/TetherApp/Sources/RoomView.swift

@@ -9,6 +9,10 @@ struct RoomView: View {
             VStack(spacing: 0) {
                 connectionBar
                 Divider()
+                if store.connected && !store.present.isEmpty {
+                    presenceRow
+                    Divider()
+                }
                 if store.connected && !store.nearby.isEmpty {
                     nearbyStrip
                     Divider()
@@ -58,6 +62,23 @@ struct RoomView: View {
         .padding()
     }
 
+    // MARK: - Presence ("who's here")
+
+    private var presenceRow: some View {
+        ScrollView(.horizontal, showsIndicators: false) {
+            HStack(spacing: 12) {
+                ForEach(store.present, id: \.id) { peer in
+                    HStack(spacing: 5) {
+                        Circle().fill(.green).frame(width: 7, height: 7)
+                        Image(systemName: sourceIcon(peer.source)).font(.caption2)
+                        Text(peer.name).font(.caption).foregroundStyle(.secondary).lineLimit(1)
+                    }
+                }
+            }
+            .padding(.horizontal, 14).padding(.vertical, 5)
+        }
+    }
+
     // MARK: - Nearby devices (AirDrop-style picker)
 
     private var nearbyStrip: some View {

ios/TetherApp/Sources/TetherStore.swift

@@ -31,6 +31,7 @@ final class TetherStore {
     }()
     var feed: [FeedItem] = []
     var nearby: [Peer] = []   // tether devices on the LAN (empty on iOS w/o multicast entitlement)
+    var present: [Peer] = []   // devices online in the room ("who's here")
     var receipts: [Receipt] = []   // delivery acks — "seen by <device>"
     var connected = false
     var lastError: String?
@@ -68,6 +69,7 @@ final class TetherStore {
                 try? await Task.sleep(for: .seconds(2))
                 guard let self, let engine = self.engine else { continue }
                 self.nearby = engine.nearby().sorted { $0.name < $1.name }
+                self.present = engine.present().sorted { $0.name < $1.name }
                 self.receipts = engine.receipts()
             }
         }