diff --git a/crates/wasm-actor/tests/wasm_actor.rs b/crates/wasm-actor/tests/wasm_actor.rs
index 4dcbf5f..94807f7 100644
--- a/crates/wasm-actor/tests/wasm_actor.rs
+++ b/crates/wasm-actor/tests/wasm_actor.rs
@@ -11988,4 +11988,130 @@ fn heterogeneous_wat_actors_on_same_runtime() {
     // One is "hello", other is [0x42]
     assert!(msgs.iter().any(|m| m == b"hello"));
     assert!(msgs.iter().any(|m| m == &[0x42]));
+}
+
+// ── Cycle 84 ─────────────────────────────────────────────────────────────────
+
+// Guest inverts bit pattern: i32.xor with 0xFFFFFFFF on 4-byte chunks
+#[test]
+fn guest_inverts_i32_pattern() {
+    let wat = r#"(module
+        (import "swactor" "send" (func $send (param i32 i32 i32)))
+        (memory (export "memory") 1)
+        (func (export "alloc") (param $len i32) (result i32) i32.const 1024)
+        (func (export "handle") (param $ptr i32) (param $len i32)
+            (local $i i32)
+            ;; Need at least 36 bytes (32 addr + 4 payload)
+            (if (i32.lt_u (local.get $len) (i32.const 36)) (then return))
+            ;; XOR 4 bytes at ptr+32 with 0xFFFFFFFF
+            (i32.store (i32.add (local.get $ptr) (i32.const 32))
+                (i32.xor
+                    (i32.load (i32.add (local.get $ptr) (i32.const 32)))
+                    (i32.const -1)))
+            (call $send
+                (local.get $ptr)
+                (i32.add (local.get $ptr) (i32.const 32))
+                (i32.const 4))
+        )
+    )"#;
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wat::parse_str(wat).unwrap())
+        .build().unwrap();
+    let rt = Runtime::new(RuntimeConfig::default());
+    let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+    let addr = rt.spawn(actor).unwrap();
+
+    rt.send_to(addr, framed_msg(inbox.addr(), &[0x12, 0x34, 0x56, 0x78])).unwrap();
+    rt.tick();
+
+    let resp = inbox.try_recv().expect("inverted pattern");
+    assert_eq!(resp.0, vec![0xED, 0xCB, 0xA9, 0x87]);
+}
+
+// Native actor that spawns WASM and sends to it
+struct NativeWasmSpawner2 {
+    engine: SharedEngine,
+    inbox_addr: ActorAddress,
+}
+impl ActorInterface for NativeWasmSpawner2 {
+    type Incoming = ByteMessage;
+    type Response = ();
+    fn handle(&mut self, ctx: &Ctx, _msg: ByteMessage) {
+        let actor = WasmActorBuilder::new(self.engine.clone(), guest_wasm("echo"))
+            .build().unwrap();
+        let wasm_addr = ctx.spawn(actor).unwrap();
+        let _ = ctx.send(wasm_addr, framed_msg(&self.inbox_addr, b"spawned-inline"));
+    }
+}
+
+#[test]
+fn native_spawns_wasm_and_sends_in_handler() {
+    let engine = SharedEngine::new().unwrap();
+    let rt = Runtime::new(RuntimeConfig::default());
+    let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+
+    let spawner = NativeWasmSpawner2 {
+        engine,
+        inbox_addr: *inbox.addr(),
+    };
+    let s_addr = rt.spawn(spawner).unwrap();
+    rt.send_to(s_addr, ByteMessage(vec![])).unwrap();
+    rt.tick(); // spawner spawns WASM + sends to it
+    rt.tick(); // WASM echo processes message
+    rt.tick(); // ensure delivery
+
+    let resp = inbox.try_recv().expect("spawned WASM should echo");
+    assert_eq!(resp.0, b"spawned-inline");
+}
+
+// Guest with nested loop computing factorial(5) = 120
+#[test]
+fn guest_factorial_loop() {
+    let wat = r#"(module
+        (memory (export "memory") 1)
+        (func (export "alloc") (param $len i32) (result i32) i32.const 1024)
+        (func (export "handle") (param $ptr i32) (param $len i32)
+            (local $result i32)
+            (local $n i32)
+            (local.set $result (i32.const 1))
+            (local.set $n (i32.const 5))
+            (block $exit
+                (loop $loop
+                    (br_if $exit (i32.le_u (local.get $n) (i32.const 1)))
+                    (local.set $result (i32.mul (local.get $result) (local.get $n)))
+                    (local.set $n (i32.sub (local.get $n) (i32.const 1)))
+                    (br $loop)
+                )
+            )
+            (i32.store (local.get $ptr) (local.get $result))
+        )
+    )"#;
+    let engine = SharedEngine::new().unwrap();
+    let actor = WasmActorBuilder::new(engine, wat::parse_str(wat).unwrap())
+        .build().unwrap();
+    let rt = Runtime::new(RuntimeConfig::default());
+    let addr = rt.spawn(actor).unwrap();
+    rt.send_to(addr, ByteMessage(vec![0u8; 4])).unwrap();
+    rt.tick();
+}
+
+// Verify echo determinism: same input always produces same output
+#[test]
+fn echo_determinism_ten_runs() {
+    let engine = SharedEngine::new().unwrap();
+    let payload = b"deterministic-test-payload";
+
+    let mut outputs = Vec::new();
+    for _ in 0..10 {
+        let actor = WasmActorBuilder::new(engine.clone(), guest_wasm("echo")).build().unwrap();
+        let rt = Runtime::new(RuntimeConfig::default());
+        let inbox = rt.new_inbox::<ByteMessage>().unwrap();
+        let addr = rt.spawn(actor).unwrap();
+        rt.send_to(addr, framed_msg(inbox.addr(), payload)).unwrap();
+        rt.tick();
+        outputs.push(inbox.try_recv().unwrap().0);
+    }
+
+    assert!(outputs.iter().all(|o| o == &outputs[0]),
+        "all 10 runs should produce identical output");
 }
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