diff --git a/crates/wasm-actor/tests/wasm_actor.rs b/crates/wasm-actor/tests/wasm_actor.rs
index 7f0230d..afa613f 100644
--- a/crates/wasm-actor/tests/wasm_actor.rs
+++ b/crates/wasm-actor/tests/wasm_actor.rs
@@ -1,6 +1,6 @@
 use swactor::actor::{ActorAddress, ActorInterface};
 use swactor::runtime::{Ctx, Runtime, RuntimeConfig};
-use swactor_wasm_actor::{ByteMessage, SharedEngine, WasmActorBuilder, WasmActorError};
+use swactor_wasm_actor::{ByteMessage, SharedEngine, WasmActor, WasmActorBuilder, WasmActorError};
 
 use proptest::prelude::*;
 
@@ -3912,3 +3912,71 @@ fn echo_processes_500_sequential_messages() {
     // all 500 messages should fit. Verify all echoed correctly.
     assert_eq!(received_count, 500, "all 500 messages should echo");
 }
+
+// ── Mass spawn and stop: 100 WASM actors ────────────────────────────────────
+
+#[test]
+fn mass_spawn_and_stop_100_actors() {
+    let engine = SharedEngine::new().unwrap();
+    let wasm_bytes = guest_wasm("silent");
+    let rt = Runtime::new(RuntimeConfig::default());
+
+    let mut addrs = Vec::new();
+    for _ in 0..100 {
+        let actor = WasmActorBuilder::new(engine.clone(), wasm_bytes.clone())
+            .build().unwrap();
+        addrs.push(rt.spawn(actor).unwrap());
+    }
+    rt.tick();
+
+    for addr in &addrs {
+        rt.stop_actor(*addr).unwrap();
+    }
+    rt.tick();
+    rt.tick();
+
+    for addr in &addrs {
+        assert!(rt.send_to(*addr, ByteMessage(vec![1])).is_err());
+    }
+}
+
+// ── Echo to stopping actor: send silently fails ─────────────────────────────
+
+#[test]
+fn echo_to_stopping_actor_silently_fails() {
+    let engine = SharedEngine::new().unwrap();
+    let wasm_bytes = guest_wasm("echo");
+
+    let actor_a = WasmActorBuilder::new(engine.clone(), wasm_bytes.clone()).build().unwrap();
+    let actor_b = WasmActorBuilder::new(engine, wasm_bytes).build().unwrap();
+
+    let rt = Runtime::new(RuntimeConfig::default());
+    let addr_a = rt.spawn(actor_a).unwrap();
+    let addr_b = rt.spawn(actor_b).unwrap();
+    rt.tick();
+
+    rt.send_to(addr_a, framed_msg(&addr_b, b"to-dying-b")).unwrap();
+    rt.stop_actor(addr_b).unwrap();
+    rt.tick(); // A echoes to B (stopping) — silently fails
+    rt.tick();
+
+    // A should still be alive
+    let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+    rt.send_to(addr_a, framed_msg(inbox.addr(), b"still-alive")).unwrap();
+    rt.tick();
+    assert!(inbox.try_recv().is_some(), "actor A should survive");
+}
+
+// ── Compile-time trait checks ───────────────────────────────────────────────
+
+#[test]
+fn shared_engine_is_send_and_sync() {
+    fn assert_send_sync<T: Send + Sync>() {}
+    assert_send_sync::<SharedEngine>();
+}
+
+#[test]
+fn wasm_actor_is_send() {
+    fn assert_send<T: Send>() {}
+    assert_send::<WasmActor>();
+}