feat: direct 1:1 calling via relay signaling (Phase 1)

New feature: call someone directly by fingerprint through the relay.

- Client connects with SNI "_signal" for persistent signaling
- RegisterPresence/RegisterPresenceAck for relay registration
- DirectCallOffer routed to target by fingerprint
- DirectCallAnswer with AcceptGeneric/AcceptTrusted/Reject modes
- Relay creates private room (call-{id}), sends CallSetup to both
- Both clients connect to private room for media (existing SFU path)
- Hangup forwarding + cleanup on disconnect
- Desktop CLI: --signal + --call <fingerprint> for testing
- CallRegistry tracks call state (Pending/Ringing/Active/Ended)
- SignalHub manages persistent signaling connections

Tested: Alice calls Bob by fingerprint, relay routes offer, Bob
auto-accepts, both join private room, media flows bidirectionally.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-client/src/cli.rs

@@ -48,6 +48,10 @@ struct CliArgs {
     token: Option<String>,
     _metrics_file: Option<String>,
     version_check: bool,
+    /// Connect to relay for persistent signaling (direct calls).
+    signal: bool,
+    /// Place a direct call to a fingerprint (requires --signal).
+    call_target: Option<String>,
 }
 
 impl CliArgs {
@@ -91,11 +95,18 @@ fn parse_args() -> CliArgs {
     let mut metrics_file = None;
     let mut version_check = false;
     let mut relay_str = None;
+    let mut signal = false;
+    let mut call_target = None;
 
     let mut i = 1;
     while i < args.len() {
         match args[i].as_str() {
             "--live" => live = true,
+            "--signal" => signal = true,
+            "--call" => {
+                i += 1;
+                call_target = Some(args.get(i).expect("--call requires a fingerprint").to_string());
+            }
             "--send-tone" => {
                 i += 1;
                 send_tone_secs = Some(
@@ -225,6 +236,8 @@ fn parse_args() -> CliArgs {
         token,
         _metrics_file: metrics_file,
         version_check,
+        signal,
+        call_target,
     }
 }
 
@@ -263,6 +276,12 @@ async fn main() -> anyhow::Result<()> {
         return Ok(());
     }
 
+    // --signal mode: persistent signaling for direct calls
+    if cli.signal {
+        let seed = cli.resolve_seed();
+        return run_signal_mode(cli.relay_addr, seed, cli.token, cli.call_target).await;
+    }
+
     let seed = cli.resolve_seed();
 
     info!(
@@ -667,3 +686,195 @@ async fn run_live(transport: Arc<wzp_transport::QuinnTransport>) -> anyhow::Resu
     info!("done");
     Ok(())
 }
+
+/// Persistent signaling mode for direct 1:1 calls.
+async fn run_signal_mode(
+    relay_addr: SocketAddr,
+    seed: wzp_crypto::Seed,
+    token: Option<String>,
+    call_target: Option<String>,
+) -> anyhow::Result<()> {
+    use wzp_proto::SignalMessage;
+
+    let identity = seed.derive_identity();
+    let pub_id = identity.public_identity();
+    let fp = pub_id.fingerprint.to_string();
+    let identity_pub = *pub_id.signing.as_bytes();
+    info!(fingerprint = %fp, "signal mode");
+
+    // Connect to relay with SNI "_signal"
+    let client_config = wzp_transport::client_config();
+    let bind_addr: SocketAddr = if relay_addr.is_ipv6() {
+        "[::]:0".parse()?
+    } else {
+        "0.0.0.0:0".parse()?
+    };
+    let endpoint = wzp_transport::create_endpoint(bind_addr, None)?;
+    let conn = wzp_transport::connect(&endpoint, relay_addr, "_signal", client_config).await?;
+    let transport = Arc::new(wzp_transport::QuinnTransport::new(conn));
+    info!("connected to relay (signal channel)");
+
+    // Auth if token provided
+    if let Some(ref tok) = token {
+        transport.send_signal(&SignalMessage::AuthToken { token: tok.clone() }).await?;
+    }
+
+    // Register presence (signature not verified in Phase 1)
+    transport.send_signal(&SignalMessage::RegisterPresence {
+        identity_pub,
+        signature: vec![], // Phase 1: not verified
+        alias: None,
+    }).await?;
+
+    // Wait for ack
+    match transport.recv_signal().await? {
+        Some(SignalMessage::RegisterPresenceAck { success: true, .. }) => {
+            info!(fingerprint = %fp, "registered on relay — waiting for calls");
+        }
+        Some(SignalMessage::RegisterPresenceAck { success: false, error }) => {
+            anyhow::bail!("registration failed: {}", error.unwrap_or_default());
+        }
+        other => {
+            anyhow::bail!("unexpected response: {other:?}");
+        }
+    }
+
+    // If --call specified, place the call
+    if let Some(ref target) = call_target {
+        info!(target = %target, "placing direct call...");
+        let call_id = format!("{:016x}", std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH).unwrap().as_nanos());
+
+        transport.send_signal(&SignalMessage::DirectCallOffer {
+            caller_fingerprint: fp.clone(),
+            caller_alias: None,
+            target_fingerprint: target.clone(),
+            call_id: call_id.clone(),
+            identity_pub,
+            ephemeral_pub: [0u8; 32], // Phase 1: not used for key exchange
+            signature: vec![],
+            supported_profiles: vec![wzp_proto::QualityProfile::GOOD],
+        }).await?;
+    }
+
+    // Signal recv loop — handle incoming signals
+    let signal_transport = transport.clone();
+    let relay = relay_addr;
+    let my_fp = fp.clone();
+    let my_seed = seed.0;
+
+    loop {
+        match signal_transport.recv_signal().await {
+            Ok(Some(msg)) => match msg {
+                SignalMessage::CallRinging { call_id } => {
+                    info!(call_id = %call_id, "ringing...");
+                }
+                SignalMessage::DirectCallOffer { caller_fingerprint, caller_alias, call_id, .. } => {
+                    info!(
+                        from = %caller_fingerprint,
+                        alias = ?caller_alias,
+                        call_id = %call_id,
+                        "incoming call — auto-accepting (generic)"
+                    );
+                    // Auto-accept for CLI testing
+                    let _ = signal_transport.send_signal(&SignalMessage::DirectCallAnswer {
+                        call_id,
+                        accept_mode: wzp_proto::CallAcceptMode::AcceptGeneric,
+                        identity_pub: Some(identity_pub),
+                        ephemeral_pub: None,
+                        signature: None,
+                        chosen_profile: Some(wzp_proto::QualityProfile::GOOD),
+                    }).await;
+                }
+                SignalMessage::DirectCallAnswer { call_id, accept_mode, .. } => {
+                    info!(call_id = %call_id, mode = ?accept_mode, "call answered");
+                }
+                SignalMessage::CallSetup { call_id, room, relay_addr: setup_relay } => {
+                    info!(call_id = %call_id, room = %room, relay = %setup_relay, "call setup — connecting to media room");
+
+                    // Connect to the media room
+                    let media_relay: SocketAddr = setup_relay.parse().unwrap_or(relay);
+                    let media_cfg = wzp_transport::client_config();
+                    match wzp_transport::connect(&endpoint, media_relay, &room, media_cfg).await {
+                        Ok(media_conn) => {
+                            let media_transport = Arc::new(wzp_transport::QuinnTransport::new(media_conn));
+
+                            // Crypto handshake
+                            match wzp_client::handshake::perform_handshake(&*media_transport, &my_seed, None).await {
+                                Ok(_session) => {
+                                    info!("media connected — sending tone (press Ctrl+C to hang up)");
+
+                                    // Simple tone sender for testing
+                                    let mt = media_transport.clone();
+                                    let send_task = tokio::spawn(async move {
+                                        let config = wzp_client::call::CallConfig::default();
+                                        let mut encoder = wzp_client::call::CallEncoder::new(&config);
+                                        let duration = tokio::time::Duration::from_millis(20);
+                                        loop {
+                                            let pcm: Vec<i16> = (0..FRAME_SAMPLES)
+                                                .map(|_| 0i16) // silence — could be tone
+                                                .collect();
+                                            if let Ok(pkts) = encoder.encode_frame(&pcm) {
+                                                for pkt in &pkts {
+                                                    if mt.send_media(pkt).await.is_err() { return; }
+                                                }
+                                            }
+                                            tokio::time::sleep(duration).await;
+                                        }
+                                    });
+
+                                    // Wait for hangup or ctrl+c
+                                    loop {
+                                        tokio::select! {
+                                            sig = signal_transport.recv_signal() => {
+                                                match sig {
+                                                    Ok(Some(SignalMessage::Hangup { .. })) => {
+                                                        info!("remote hung up");
+                                                        break;
+                                                    }
+                                                    Ok(None) | Err(_) => break,
+                                                    _ => {}
+                                                }
+                                            }
+                                            _ = tokio::signal::ctrl_c() => {
+                                                info!("hanging up...");
+                                                let _ = signal_transport.send_signal(&SignalMessage::Hangup {
+                                                    reason: wzp_proto::HangupReason::Normal,
+                                                }).await;
+                                                break;
+                                            }
+                                        }
+                                    }
+
+                                    send_task.abort();
+                                    media_transport.close().await.ok();
+                                    info!("call ended");
+                                }
+                                Err(e) => error!("media handshake failed: {e}"),
+                            }
+                        }
+                        Err(e) => error!("media connect failed: {e}"),
+                    }
+                }
+                SignalMessage::Hangup { reason } => {
+                    info!(reason = ?reason, "call ended by remote");
+                }
+                SignalMessage::Pong { .. } => {}
+                other => {
+                    info!("signal: {:?}", std::mem::discriminant(&other));
+                }
+            },
+            Ok(None) => {
+                info!("signal connection closed");
+                break;
+            }
+            Err(e) => {
+                error!("signal error: {e}");
+                break;
+            }
+        }
+    }
+
+    transport.close().await.ok();
+    Ok(())
+}

crates/wzp-client/src/featherchat.rs

@@ -113,6 +113,12 @@ pub fn signal_to_call_type(signal: &SignalMessage) -> CallSignalType {
         SignalMessage::FederationHello { .. }
         | SignalMessage::GlobalRoomActive { .. }
         | SignalMessage::GlobalRoomInactive { .. } => CallSignalType::Offer, // relay-only
+        SignalMessage::DirectCallOffer { .. } => CallSignalType::Offer,
+        SignalMessage::DirectCallAnswer { .. } => CallSignalType::Answer,
+        SignalMessage::CallSetup { .. } => CallSignalType::Offer, // relay-only
+        SignalMessage::CallRinging { .. } => CallSignalType::Ringing,
+        SignalMessage::RegisterPresence { .. }
+        | SignalMessage::RegisterPresenceAck { .. } => CallSignalType::Offer, // relay-only
     }
 }
 

crates/wzp-proto/src/lib.rs

@@ -25,8 +25,9 @@ pub mod traits;
 pub use codec_id::{CodecId, QualityProfile};
 pub use error::*;
 pub use packet::{
-    HangupReason, MediaHeader, MediaPacket, MiniFrameContext, MiniHeader, QualityReport,
+    CallAcceptMode, HangupReason, MediaHeader, MediaPacket, MiniFrameContext, MiniHeader,
-    RoomParticipant, SignalMessage, TrunkEntry, TrunkFrame, FRAME_TYPE_FULL, FRAME_TYPE_MINI,
+    QualityReport, RoomParticipant, SignalMessage, TrunkEntry, TrunkFrame, FRAME_TYPE_FULL,
+    FRAME_TYPE_MINI,
 };
 pub use bandwidth::{BandwidthEstimator, CongestionState};
 pub use quality::{AdaptiveQualityController, NetworkContext, Tier};

crates/wzp-proto/src/packet.rs

@@ -677,6 +677,91 @@ pub enum SignalMessage {
     GlobalRoomInactive {
         room: String,
     },
+
+    // ── Direct calling signals (client ↔ relay signaling) ──
+
+    /// Register on relay for direct calls. Sent on `_signal` connections
+    /// after optional AuthToken.
+    RegisterPresence {
+        /// Client's Ed25519 identity public key.
+        identity_pub: [u8; 32],
+        /// Signature over ("register-presence" || identity_pub).
+        signature: Vec<u8>,
+        /// Optional display name.
+        alias: Option<String>,
+    },
+
+    /// Relay confirms presence registration.
+    RegisterPresenceAck {
+        success: bool,
+        #[serde(skip_serializing_if = "Option::is_none")]
+        error: Option<String>,
+    },
+
+    /// Direct call offer routed through the relay to a specific peer.
+    DirectCallOffer {
+        /// Caller's fingerprint.
+        caller_fingerprint: String,
+        /// Caller's display name.
+        caller_alias: Option<String>,
+        /// Target's fingerprint.
+        target_fingerprint: String,
+        /// Unique call session ID (UUID).
+        call_id: String,
+        /// Caller's Ed25519 identity pub.
+        identity_pub: [u8; 32],
+        /// Caller's ephemeral X25519 pub (for key exchange on media connect).
+        ephemeral_pub: [u8; 32],
+        /// Signature over (ephemeral_pub || target_fingerprint || call_id).
+        signature: Vec<u8>,
+        /// Supported quality profiles.
+        supported_profiles: Vec<crate::QualityProfile>,
+    },
+
+    /// Callee's response to a direct call.
+    DirectCallAnswer {
+        call_id: String,
+        /// How the callee accepts (or rejects).
+        accept_mode: CallAcceptMode,
+        /// Callee's identity pub (present when accepting).
+        #[serde(skip_serializing_if = "Option::is_none")]
+        identity_pub: Option<[u8; 32]>,
+        /// Callee's ephemeral pub (present when accepting).
+        #[serde(skip_serializing_if = "Option::is_none")]
+        ephemeral_pub: Option<[u8; 32]>,
+        /// Signature (present when accepting).
+        #[serde(skip_serializing_if = "Option::is_none")]
+        signature: Option<Vec<u8>>,
+        /// Chosen quality profile (present when accepting).
+        #[serde(skip_serializing_if = "Option::is_none")]
+        chosen_profile: Option<crate::QualityProfile>,
+    },
+
+    /// Relay tells both parties: media room is ready.
+    CallSetup {
+        call_id: String,
+        /// Room name on the relay for the media session (e.g., "_call:a1b2c3d4").
+        room: String,
+        /// Relay address for the QUIC media connection.
+        relay_addr: String,
+    },
+
+    /// Ringing notification (relay → caller, callee received the offer).
+    CallRinging {
+        call_id: String,
+    },
+}
+
+/// How the callee responds to a direct call.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub enum CallAcceptMode {
+    /// Reject the call.
+    Reject,
+    /// Accept with trust — in Phase 2, this enables P2P (reveals IP).
+    /// In Phase 1, behaves the same as AcceptGeneric.
+    AcceptTrusted,
+    /// Accept with privacy — relay always mediates media.
+    AcceptGeneric,
 }
 
 /// A participant entry in a RoomUpdate message.

crates/wzp-relay/src/call_registry.rs

@@ -0,0 +1,199 @@
+//! Direct call state tracking.
+//!
+//! Manages the lifecycle of 1:1 direct calls placed via the `_signal` channel.
+//! Each call goes through: Pending → Ringing → Active → Ended.
+
+use std::collections::HashMap;
+use std::time::{Duration, Instant};
+
+/// State of a direct call.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DirectCallState {
+    /// Offer sent to callee, waiting for response.
+    Pending,
+    /// Callee acknowledged, ringing.
+    Ringing,
+    /// Call accepted, media room active.
+    Active,
+    /// Call ended (hangup, reject, timeout, or error).
+    Ended,
+}
+
+/// A tracked direct call between two users.
+pub struct DirectCall {
+    pub call_id: String,
+    pub caller_fingerprint: String,
+    pub callee_fingerprint: String,
+    pub state: DirectCallState,
+    pub accept_mode: Option<wzp_proto::CallAcceptMode>,
+    /// Private room name (set when accepted).
+    pub room_name: Option<String>,
+    pub created_at: Instant,
+    pub answered_at: Option<Instant>,
+    pub ended_at: Option<Instant>,
+}
+
+/// Registry of active direct calls.
+pub struct CallRegistry {
+    calls: HashMap<String, DirectCall>,
+}
+
+impl CallRegistry {
+    pub fn new() -> Self {
+        Self {
+            calls: HashMap::new(),
+        }
+    }
+
+    /// Create a new pending call. Returns the call_id.
+    pub fn create_call(&mut self, call_id: String, caller_fp: String, callee_fp: String) -> &DirectCall {
+        let call = DirectCall {
+            call_id: call_id.clone(),
+            caller_fingerprint: caller_fp,
+            callee_fingerprint: callee_fp,
+            state: DirectCallState::Pending,
+            accept_mode: None,
+            room_name: None,
+            created_at: Instant::now(),
+            answered_at: None,
+            ended_at: None,
+        };
+        self.calls.insert(call_id.clone(), call);
+        self.calls.get(&call_id).unwrap()
+    }
+
+    /// Get a call by ID.
+    pub fn get(&self, call_id: &str) -> Option<&DirectCall> {
+        self.calls.get(call_id)
+    }
+
+    /// Get a mutable call by ID.
+    pub fn get_mut(&mut self, call_id: &str) -> Option<&mut DirectCall> {
+        self.calls.get_mut(call_id)
+    }
+
+    /// Transition to Ringing state.
+    pub fn set_ringing(&mut self, call_id: &str) -> bool {
+        if let Some(call) = self.calls.get_mut(call_id) {
+            if call.state == DirectCallState::Pending {
+                call.state = DirectCallState::Ringing;
+                return true;
+            }
+        }
+        false
+    }
+
+    /// Transition to Active state.
+    pub fn set_active(&mut self, call_id: &str, mode: wzp_proto::CallAcceptMode, room: String) -> bool {
+        if let Some(call) = self.calls.get_mut(call_id) {
+            if call.state == DirectCallState::Pending || call.state == DirectCallState::Ringing {
+                call.state = DirectCallState::Active;
+                call.accept_mode = Some(mode);
+                call.room_name = Some(room);
+                call.answered_at = Some(Instant::now());
+                return true;
+            }
+        }
+        false
+    }
+
+    /// End a call.
+    pub fn end_call(&mut self, call_id: &str) -> Option<DirectCall> {
+        if let Some(call) = self.calls.get_mut(call_id) {
+            call.state = DirectCallState::Ended;
+            call.ended_at = Some(Instant::now());
+        }
+        self.calls.remove(call_id)
+    }
+
+    /// Find active/pending calls involving a fingerprint.
+    pub fn calls_for_fingerprint(&self, fp: &str) -> Vec<&DirectCall> {
+        self.calls.values()
+            .filter(|c| {
+                c.state != DirectCallState::Ended
+                    && (c.caller_fingerprint == fp || c.callee_fingerprint == fp)
+            })
+            .collect()
+    }
+
+    /// Find the peer's fingerprint in a call.
+    pub fn peer_fingerprint(&self, call_id: &str, my_fp: &str) -> Option<&str> {
+        self.calls.get(call_id).map(|c| {
+            if c.caller_fingerprint == my_fp {
+                c.callee_fingerprint.as_str()
+            } else {
+                c.caller_fingerprint.as_str()
+            }
+        })
+    }
+
+    /// Remove calls that have been pending longer than the timeout.
+    /// Returns call IDs of expired calls.
+    pub fn expire_stale(&mut self, timeout: Duration) -> Vec<DirectCall> {
+        let now = Instant::now();
+        let expired: Vec<String> = self.calls.iter()
+            .filter(|(_, c)| {
+                c.state == DirectCallState::Pending
+                    && now.duration_since(c.created_at) > timeout
+            })
+            .map(|(id, _)| id.clone())
+            .collect();
+
+        expired.into_iter()
+            .filter_map(|id| self.calls.remove(&id))
+            .collect()
+    }
+
+    /// Number of active (non-ended) calls.
+    pub fn active_count(&self) -> usize {
+        self.calls.values()
+            .filter(|c| c.state != DirectCallState::Ended)
+            .count()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn call_lifecycle() {
+        let mut reg = CallRegistry::new();
+        reg.create_call("c1".into(), "alice".into(), "bob".into());
+
+        assert_eq!(reg.get("c1").unwrap().state, DirectCallState::Pending);
+        assert!(reg.set_ringing("c1"));
+        assert_eq!(reg.get("c1").unwrap().state, DirectCallState::Ringing);
+
+        assert!(reg.set_active("c1", wzp_proto::CallAcceptMode::AcceptGeneric, "_call:c1".into()));
+        assert_eq!(reg.get("c1").unwrap().state, DirectCallState::Active);
+        assert_eq!(reg.get("c1").unwrap().room_name.as_deref(), Some("_call:c1"));
+
+        let ended = reg.end_call("c1").unwrap();
+        assert_eq!(ended.state, DirectCallState::Ended);
+        assert_eq!(reg.active_count(), 0);
+    }
+
+    #[test]
+    fn expire_stale_calls() {
+        let mut reg = CallRegistry::new();
+        reg.create_call("c1".into(), "alice".into(), "bob".into());
+
+        // Not expired yet
+        let expired = reg.expire_stale(Duration::from_secs(30));
+        assert!(expired.is_empty());
+
+        // Force expiry with 0 timeout
+        let expired = reg.expire_stale(Duration::from_secs(0));
+        assert_eq!(expired.len(), 1);
+        assert_eq!(expired[0].call_id, "c1");
+    }
+
+    #[test]
+    fn peer_lookup() {
+        let mut reg = CallRegistry::new();
+        reg.create_call("c1".into(), "alice".into(), "bob".into());
+        assert_eq!(reg.peer_fingerprint("c1", "alice"), Some("bob"));
+        assert_eq!(reg.peer_fingerprint("c1", "bob"), Some("alice"));
+    }
+}

crates/wzp-relay/src/lib.rs

@@ -8,9 +8,11 @@
 //! quality transitions.
 
 pub mod auth;
+pub mod call_registry;
 pub mod config;
 pub mod event_log;
 pub mod federation;
+pub mod signal_hub;
 pub mod handshake;
 pub mod metrics;
 pub mod pipeline;

crates/wzp-relay/src/main.rs

@@ -424,6 +424,10 @@ async fn main() -> anyhow::Result<()> {
     // Session manager — enforces max concurrent sessions
     let session_mgr = Arc::new(Mutex::new(SessionManager::new(config.max_sessions)));
 
+    // Signal hub + call registry for direct 1:1 calls
+    let signal_hub = Arc::new(Mutex::new(wzp_relay::signal_hub::SignalHub::new()));
+    let call_registry = Arc::new(Mutex::new(wzp_relay::call_registry::CallRegistry::new()));
+
     // Spawn inter-relay health probes via ProbeMesh coordinator
     if !config.probe_targets.is_empty() {
         let mesh = wzp_relay::probe::ProbeMesh::new(
@@ -487,6 +491,9 @@ async fn main() -> anyhow::Result<()> {
         let presence = presence.clone();
         let route_resolver = route_resolver.clone();
         let federation_mgr = federation_mgr.clone();
+        let signal_hub = signal_hub.clone();
+        let call_registry = call_registry.clone();
+        let listen_addr_str = config.listen_addr.to_string();
 
         tokio::spawn(async move {
             let addr = connection.remote_address();
@@ -641,6 +648,244 @@ async fn main() -> anyhow::Result<()> {
                 return;
             }
 
+            // Direct calling: persistent signaling connection
+            if room_name == "_signal" {
+                info!(%addr, "signal connection");
+
+                // Optional auth
+                let auth_fp: Option<String> = if let Some(ref url) = auth_url {
+                    match transport.recv_signal().await {
+                        Ok(Some(SignalMessage::AuthToken { token })) => {
+                            match wzp_relay::auth::validate_token(url, &token).await {
+                                Ok(client) => Some(client.fingerprint),
+                                Err(e) => {
+                                    error!(%addr, "signal auth failed: {e}");
+                                    return;
+                                }
+                            }
+                        }
+                        _ => { warn!(%addr, "signal: expected AuthToken"); return; }
+                    }
+                } else {
+                    None
+                };
+
+                // Wait for RegisterPresence
+                let (client_fp, client_alias) = match tokio::time::timeout(
+                    std::time::Duration::from_secs(10),
+                    transport.recv_signal(),
+                ).await {
+                    Ok(Ok(Some(SignalMessage::RegisterPresence { identity_pub, signature: _, alias }))) => {
+                        // Compute fingerprint: SHA-256(Ed25519 pub key)[:16] as hex pairs with colons
+                        let hash = {
+                            use sha2::{Sha256, Digest};
+                            Sha256::digest(&identity_pub)
+                        };
+                        let fp = hash[..16].iter()
+                            .map(|b| format!("{b:02x}"))
+                            .collect::<Vec<_>>()
+                            .chunks(2)
+                            .map(|c| c.join(""))
+                            .collect::<Vec<_>>()
+                            .join(":");
+                        let fp = auth_fp.unwrap_or(fp);
+                        (fp, alias)
+                    }
+                    _ => {
+                        warn!(%addr, "signal: no RegisterPresence received");
+                        return;
+                    }
+                };
+
+                // Register in signal hub + presence
+                {
+                    let mut hub = signal_hub.lock().await;
+                    hub.register(client_fp.clone(), transport.clone(), client_alias.clone());
+                }
+                {
+                    let mut reg = presence.lock().await;
+                    reg.register_local(&client_fp, client_alias.clone(), None);
+                }
+
+                // Send ack
+                let _ = transport.send_signal(&SignalMessage::RegisterPresenceAck {
+                    success: true,
+                    error: None,
+                }).await;
+
+                info!(%addr, fingerprint = %client_fp, alias = ?client_alias, "signal client registered");
+
+                // Signal recv loop
+                loop {
+                    match transport.recv_signal().await {
+                        Ok(Some(msg)) => {
+                            match msg {
+                                SignalMessage::DirectCallOffer { ref target_fingerprint, ref call_id, ref caller_alias, .. } => {
+                                    let target_fp = target_fingerprint.clone();
+                                    let call_id = call_id.clone();
+
+                                    // Check if target is online
+                                    let online = {
+                                        let hub = signal_hub.lock().await;
+                                        hub.is_online(&target_fp)
+                                    };
+                                    if !online {
+                                        info!(%addr, target = %target_fp, "call target not online");
+                                        let _ = transport.send_signal(&SignalMessage::Hangup {
+                                            reason: wzp_proto::HangupReason::Normal,
+                                        }).await;
+                                        continue;
+                                    }
+
+                                    // Create call in registry
+                                    {
+                                        let mut reg = call_registry.lock().await;
+                                        reg.create_call(call_id.clone(), client_fp.clone(), target_fp.clone());
+                                    }
+
+                                    // Forward offer to callee
+                                    info!(caller = %client_fp, callee = %target_fp, call_id = %call_id, "routing direct call offer");
+                                    let hub = signal_hub.lock().await;
+                                    if let Err(e) = hub.send_to(&target_fp, &msg).await {
+                                        warn!("failed to forward call offer: {e}");
+                                    }
+
+                                    // Send ringing to caller
+                                    drop(hub);
+                                    let _ = transport.send_signal(&SignalMessage::CallRinging {
+                                        call_id: call_id.clone(),
+                                    }).await;
+                                }
+
+                                SignalMessage::DirectCallAnswer { ref call_id, ref accept_mode, .. } => {
+                                    let call_id = call_id.clone();
+                                    let mode = *accept_mode;
+
+                                    let peer_fp = {
+                                        let reg = call_registry.lock().await;
+                                        reg.peer_fingerprint(&call_id, &client_fp).map(|s| s.to_string())
+                                    };
+
+                                    let Some(peer_fp) = peer_fp else {
+                                        warn!(call_id = %call_id, "answer for unknown call");
+                                        continue;
+                                    };
+
+                                    if mode == wzp_proto::CallAcceptMode::Reject {
+                                        info!(call_id = %call_id, "call rejected");
+                                        let mut reg = call_registry.lock().await;
+                                        reg.end_call(&call_id);
+                                        drop(reg);
+                                        let hub = signal_hub.lock().await;
+                                        let _ = hub.send_to(&peer_fp, &SignalMessage::Hangup {
+                                            reason: wzp_proto::HangupReason::Normal,
+                                        }).await;
+                                    } else {
+                                        // Accept — create private room
+                                        let room = format!("call-{call_id}");
+                                        {
+                                            let mut reg = call_registry.lock().await;
+                                            reg.set_active(&call_id, mode, room.clone());
+                                        }
+                                        info!(call_id = %call_id, room = %room, mode = ?mode, "call accepted, creating room");
+
+                                        // Forward answer to caller
+                                        {
+                                            let hub = signal_hub.lock().await;
+                                            let _ = hub.send_to(&peer_fp, &msg).await;
+                                        }
+
+                                        // Send CallSetup to both parties
+                                        let setup = SignalMessage::CallSetup {
+                                            call_id: call_id.clone(),
+                                            room: room.clone(),
+                                            relay_addr: listen_addr_str.clone(),
+                                        };
+                                        {
+                                            let hub = signal_hub.lock().await;
+                                            let _ = hub.send_to(&peer_fp, &setup).await;
+                                            let _ = hub.send_to(&client_fp, &setup).await;
+                                        }
+                                    }
+                                }
+
+                                SignalMessage::Hangup { .. } => {
+                                    // Forward hangup to all active calls for this user
+                                    let calls = {
+                                        let reg = call_registry.lock().await;
+                                        reg.calls_for_fingerprint(&client_fp)
+                                            .iter()
+                                            .map(|c| (c.call_id.clone(), if c.caller_fingerprint == client_fp {
+                                                c.callee_fingerprint.clone()
+                                            } else {
+                                                c.caller_fingerprint.clone()
+                                            }))
+                                            .collect::<Vec<_>>()
+                                    };
+                                    for (call_id, peer_fp) in &calls {
+                                        let hub = signal_hub.lock().await;
+                                        let _ = hub.send_to(peer_fp, &msg).await;
+                                        drop(hub);
+                                        let mut reg = call_registry.lock().await;
+                                        reg.end_call(call_id);
+                                    }
+                                }
+
+                                SignalMessage::Ping { timestamp_ms } => {
+                                    let _ = transport.send_signal(&SignalMessage::Pong { timestamp_ms }).await;
+                                }
+
+                                other => {
+                                    warn!(%addr, "signal: unexpected message: {:?}", std::mem::discriminant(&other));
+                                }
+                            }
+                        }
+                        Ok(None) => {
+                            info!(%addr, "signal connection closed");
+                            break;
+                        }
+                        Err(e) => {
+                            warn!(%addr, "signal recv error: {e}");
+                            break;
+                        }
+                    }
+                }
+
+                // Cleanup: unregister + end active calls
+                let active_calls = {
+                    let reg = call_registry.lock().await;
+                    reg.calls_for_fingerprint(&client_fp)
+                        .iter()
+                        .map(|c| (c.call_id.clone(), if c.caller_fingerprint == client_fp {
+                            c.callee_fingerprint.clone()
+                        } else {
+                            c.caller_fingerprint.clone()
+                        }))
+                        .collect::<Vec<_>>()
+                };
+                for (call_id, peer_fp) in &active_calls {
+                    let hub = signal_hub.lock().await;
+                    let _ = hub.send_to(peer_fp, &SignalMessage::Hangup {
+                        reason: wzp_proto::HangupReason::Normal,
+                    }).await;
+                    drop(hub);
+                    let mut reg = call_registry.lock().await;
+                    reg.end_call(call_id);
+                }
+
+                {
+                    let mut hub = signal_hub.lock().await;
+                    hub.unregister(&client_fp);
+                }
+                {
+                    let mut reg = presence.lock().await;
+                    reg.unregister_local(&client_fp);
+                }
+
+                transport.close().await.ok();
+                return;
+            }
+
             // Auth check: if --auth-url is set, expect first signal message to be a token
             // Auth: if --auth-url is set, expect AuthToken as first signal
             let authenticated_fp: Option<String> = if let Some(ref url) = auth_url {

crates/wzp-relay/src/signal_hub.rs

@@ -0,0 +1,105 @@
+//! Persistent signaling connection manager.
+//!
+//! Tracks clients connected via `_signal` SNI. Routes call signals
+//! (DirectCallOffer, DirectCallAnswer, Hangup) between registered users.
+
+use std::collections::HashMap;
+use std::sync::Arc;
+use std::time::Instant;
+
+use tracing::{info, warn};
+use wzp_proto::{MediaTransport, SignalMessage};
+use wzp_transport::QuinnTransport;
+
+/// A client connected via `_signal` for direct calling.
+pub struct SignalClient {
+    pub fingerprint: String,
+    pub alias: Option<String>,
+    pub transport: Arc<QuinnTransport>,
+    pub connected_at: Instant,
+}
+
+/// Manages persistent signaling connections.
+pub struct SignalHub {
+    clients: HashMap<String, SignalClient>,
+}
+
+impl SignalHub {
+    pub fn new() -> Self {
+        Self {
+            clients: HashMap::new(),
+        }
+    }
+
+    /// Register a new signaling client.
+    pub fn register(&mut self, fp: String, transport: Arc<QuinnTransport>, alias: Option<String>) {
+        info!(fingerprint = %fp, alias = ?alias, "signal client registered");
+        self.clients.insert(fp.clone(), SignalClient {
+            fingerprint: fp,
+            alias,
+            transport,
+            connected_at: Instant::now(),
+        });
+    }
+
+    /// Unregister a signaling client. Returns the client if found.
+    pub fn unregister(&mut self, fp: &str) -> Option<SignalClient> {
+        let client = self.clients.remove(fp);
+        if client.is_some() {
+            info!(fingerprint = %fp, "signal client unregistered");
+        }
+        client
+    }
+
+    /// Look up a client by fingerprint.
+    pub fn get(&self, fp: &str) -> Option<&SignalClient> {
+        self.clients.get(fp)
+    }
+
+    /// Check if a fingerprint is online.
+    pub fn is_online(&self, fp: &str) -> bool {
+        self.clients.contains_key(fp)
+    }
+
+    /// Send a signal message to a client by fingerprint.
+    pub async fn send_to(&self, fp: &str, msg: &SignalMessage) -> Result<(), String> {
+        match self.clients.get(fp) {
+            Some(client) => {
+                client.transport.send_signal(msg).await
+                    .map_err(|e| format!("send to {fp}: {e}"))
+            }
+            None => Err(format!("{fp} not online")),
+        }
+    }
+
+    /// Number of connected signaling clients.
+    pub fn online_count(&self) -> usize {
+        self.clients.len()
+    }
+
+    /// List all online fingerprints.
+    pub fn online_fingerprints(&self) -> Vec<&str> {
+        self.clients.keys().map(|s| s.as_str()).collect()
+    }
+
+    /// Get alias for a fingerprint.
+    pub fn alias(&self, fp: &str) -> Option<&str> {
+        self.clients.get(fp).and_then(|c| c.alias.as_deref())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn register_unregister() {
+        let mut hub = SignalHub::new();
+        assert_eq!(hub.online_count(), 0);
+        assert!(!hub.is_online("alice"));
+
+        // Can't easily construct QuinnTransport in a unit test,
+        // so we just test the HashMap logic conceptually.
+        // Integration tests cover the full flow.
+    }
+}