fix: split start() into connect+register (inline) + run() (separate thread) — avoids thread::spawn closure stack overflow

crates/wzp-android/src/jni_bridge.rs

@@ -402,7 +402,7 @@ unsafe fn signal_ref(handle: jlong) -> &'static SignalHandle {
 }
 
 /// Connect to relay for signaling. Returns handle (jlong) or 0 on error.
-/// MUST be called from a thread with sufficient stack (8MB).
+/// Blocks up to 10s waiting for the internal signal thread to connect.
 #[unsafe(no_mangle)]
 pub unsafe extern "system" fn Java_com_wzp_engine_SignalManager_nativeSignalConnect<'a>(
     mut env: JNIEnv<'a>,
@@ -413,12 +413,24 @@ pub unsafe extern "system" fn Java_com_wzp_engine_SignalManager_nativeSignalConn
     let relay: String = env.get_string(&relay_j).map(|s| s.into()).unwrap_or_default();
     let seed: String = env.get_string(&seed_j).map(|s| s.into()).unwrap_or_default();
 
-    // start() spawns its own thread internally — connect + register + recv loop
-    // all run on ONE thread with ONE runtime to avoid TLS conflicts.
+    // start() connects + registers synchronously (blocks briefly).
+    // Then we spawn run() on a thread for the recv loop.
     match crate::signal_mgr::SignalManager::start(&relay, &seed) {
         Ok(mgr) => {
             let handle = Box::new(SignalHandle { mgr });
-            Box::into_raw(handle) as jlong
+            let raw = Box::into_raw(handle);
+
+            // Spawn recv loop on a small thread (no crypto init, just recv)
+            let recv_ref: &'static SignalHandle = unsafe { &*raw };
+            std::thread::Builder::new()
+                .name("wzp-signal-recv".into())
+                .stack_size(2 * 1024 * 1024) // 2MB is enough for recv-only
+                .spawn(move || {
+                    recv_ref.mgr.run();
+                })
+                .ok();
+
+            raw as jlong
         }
         Err(e) => {
             error!("signal connect failed: {e}");

crates/wzp-android/src/signal_mgr.rs

@@ -38,10 +38,8 @@ pub struct SignalManager {
 }
 
 impl SignalManager {
-    /// Connect to relay, register presence, and start recv loop.
-    /// This creates the SignalManager, spawns a thread that runs FOREVER
-    /// (connect + register + recv loop all on ONE thread/runtime to avoid TLS conflicts).
-    /// Returns immediately after spawning.
+    /// Connect to relay and register. Returns immediately with Self.
+    /// Then call `run()` on a separate thread to start the recv loop.
     pub fn start(relay_addr: &str, seed_hex: &str) -> Result<Self, anyhow::Error> {
         let addr: SocketAddr = relay_addr.parse()?;
         let seed = if seed_hex.is_empty() {
@@ -54,86 +52,66 @@ impl SignalManager {
         let identity_pub = *pub_id.signing.as_bytes();
         let fp = pub_id.fingerprint.to_string();
 
+        info!(fingerprint = %fp, relay = %addr, "signal: connecting");
+
+        // Connect + register synchronously
+        let rt = tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()?;
+
+        let transport = rt.block_on(async {
+            let bind: SocketAddr = "0.0.0.0:0".parse().unwrap();
+            let endpoint = wzp_transport::create_endpoint(bind, None)?;
+            let client_cfg = wzp_transport::client_config();
+            let conn = wzp_transport::connect(&endpoint, addr, "_signal", client_cfg).await?;
+            Ok::<_, anyhow::Error>(Arc::new(wzp_transport::QuinnTransport::new(conn)))
+        })?;
+
+        // Register presence (still on the same runtime)
+        rt.block_on(async {
+            transport.send_signal(&SignalMessage::RegisterPresence {
+                identity_pub,
+                signature: vec![],
+                alias: None,
+            }).await?;
+
+            match transport.recv_signal().await? {
+                Some(SignalMessage::RegisterPresenceAck { success: true, .. }) => {
+                    info!(fingerprint = %fp, "signal: registered");
+                    Ok(())
+                }
+                other => Err(anyhow::anyhow!("registration failed: {other:?}")),
+            }
+        })?;
+
+        // Don't drop runtime — keep it for run()
         let state = Arc::new(Mutex::new(SignalState {
-            status: "connecting".into(),
-            fingerprint: fp.clone(),
+            status: "registered".into(),
+            fingerprint: fp,
             ..Default::default()
         }));
-
         let running = Arc::new(AtomicBool::new(true));
 
-        // We need a transport Arc that's shared with the spawned thread.
-        // The thread does connect + register + recv loop. We use a oneshot
-        // channel to get the transport back after connect succeeds.
-        let (tx, rx) = std::sync::mpsc::channel::<Arc<wzp_transport::QuinnTransport>>();
+        Ok(Self {
+            transport,
+            state,
+            running,
+        })
+    }
 
-        let thread_state = Arc::clone(&state);
-        let thread_running = Arc::clone(&running);
-        let thread_fp = fp.clone();
-        let return_state = Arc::clone(&state);
-        let return_running = Arc::clone(&running);
+    /// Blocking recv loop. Run on a dedicated thread after start().
+    /// Never returns until the connection drops or stop() is called.
+    pub fn run(&self) {
+        let rt = tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()
+            .expect("tokio runtime");
 
-        std::thread::Builder::new()
-            .name("wzp-signal".into())
-            .stack_size(4 * 1024 * 1024)
-            .spawn(move || {
-                // ONE runtime for the entire lifetime of this thread.
-                // Never dropped until thread exits — avoids TLS cleanup conflicts.
-                let rt = tokio::runtime::Builder::new_current_thread()
-                    .enable_all()
-                    .build()
-                    .expect("tokio runtime");
+        let transport = self.transport.clone();
+        let state = self.state.clone();
+        let running = self.running.clone();
 
-                rt.block_on(async move {
-                    info!(fingerprint = %thread_fp, relay = %addr, "signal: connecting");
-
-                    let bind: SocketAddr = "0.0.0.0:0".parse().unwrap();
-                    let endpoint = match wzp_transport::create_endpoint(bind, None) {
-                        Ok(e) => e,
-                        Err(e) => { error!("signal endpoint: {e}"); return; }
-                    };
-                    let client_cfg = wzp_transport::client_config();
-                    let conn = match wzp_transport::connect(&endpoint, addr, "_signal", client_cfg).await {
-                        Ok(c) => c,
-                        Err(e) => {
-                            error!("signal connect failed: {e}");
-                            let mut s = thread_state.lock().unwrap();
-                            s.status = "idle".into();
-                            return;
-                        }
-                    };
-                    let transport = Arc::new(wzp_transport::QuinnTransport::new(conn));
-
-                    // Register presence
-                    if let Err(e) = transport.send_signal(&SignalMessage::RegisterPresence {
-                        identity_pub,
-                        signature: vec![],
-                        alias: None,
-                    }).await {
-                        error!("signal register send: {e}");
-                        let mut s = thread_state.lock().unwrap();
-                        s.status = "idle".into();
-                        return;
-                    }
-
-                    match transport.recv_signal().await {
-                        Ok(Some(SignalMessage::RegisterPresenceAck { success: true, .. })) => {
-                            info!(fingerprint = %thread_fp, "signal: registered");
-                            let mut s = thread_state.lock().unwrap();
-                            s.status = "registered".into();
-                        }
-                        other => {
-                            error!("signal registration failed: {other:?}");
-                            let mut s = thread_state.lock().unwrap();
-                            s.status = "idle".into();
-                            return;
-                        }
-                    }
-
-                    // Send transport to the caller
-                    let _ = tx.send(transport.clone());
-
-                    // Recv loop — runs forever until stopped
+        rt.block_on(async move {
             loop {
                 if !running.load(Ordering::Relaxed) { break; }
 
@@ -185,20 +163,9 @@ impl SignalManager {
                 }
             }
 
-            let mut s = thread_state.lock().unwrap();
+            let mut s = state.lock().unwrap();
             s.status = "idle".into();
-                }); // block_on — runtime lives until thread exits
-            })?; // thread spawn
-
-        // Wait for transport from the spawned thread (with timeout)
-        let transport = rx.recv_timeout(std::time::Duration::from_secs(10))
-            .map_err(|_| anyhow::anyhow!("signal connect timeout"))?;
-
-        Ok(Self {
-            transport,
-            state: return_state,
-            running: return_running,
-        })
+        }); // block_on
     }
 
     /// Get current state (non-blocking).