diff --git a/include/async_mqtt5/detail/async_mutex.hpp b/include/async_mqtt5/detail/async_mutex.hpp
index 659f63c..b9e6515 100644
--- a/include/async_mqtt5/detail/async_mutex.hpp
+++ b/include/async_mqtt5/detail/async_mutex.hpp
@@ -28,20 +28,20 @@ private:
 	// Handler with assigned tracking executor.
 	// Objects of this type are type-erased by any_completion_handler
 	// and stored in the waiting queue.
-	template <typename Handler>
+	template <typename Handler, typename Executor>
 	class tracked_op {
-		tracking_type<Handler> _executor;
-		std::decay_t<Handler> _handler;
+		tracking_type<Handler, Executor> _executor;
+		Handler _handler;
 	public:
-		tracked_op(Handler&& h) :
-			_executor(tracking_executor(h)),
+		tracked_op(Handler&& h, const Executor& ex) :
+			_executor(tracking_executor(h, ex)),
 			_handler(std::move(h))
 		{}
 
 		tracked_op(tracked_op&&) noexcept = default;
 		tracked_op(const tracked_op&) = delete;
 
-		using executor_type = tracking_type<Handler>;
+		using executor_type = tracking_type<Handler, Executor>;
 		executor_type get_executor() const noexcept {
 			return _executor;
 		}
@@ -186,7 +186,7 @@ private:
 	// to asio::post to avoid recursion.
 	void execute_or_queue(auto handler) noexcept {
 		std::unique_lock l { _thread_mutex };
-		tracked_op h { std::move(handler) };
+		tracked_op h { std::move(handler), _ex };
 		if (_locked.load(std::memory_order_relaxed)) {
 			_waiting.emplace_back(std::move(h));
 			auto slot = _waiting.back().get_cancellation_slot();
diff --git a/include/async_mqtt5/detail/async_traits.hpp b/include/async_mqtt5/detail/async_traits.hpp
index 0741f71..76b065d 100644
--- a/include/async_mqtt5/detail/async_traits.hpp
+++ b/include/async_mqtt5/detail/async_traits.hpp
@@ -27,18 +27,19 @@ void assign_tls_sni(const authority_path& ap, TlsContext& ctx, TlsStream& s);
 
 namespace detail {
 
-template <typename Handler>
-auto tracking_executor(const Handler& handler) {
+template <typename Handler, typename DfltExecutor>
+auto tracking_executor(const Handler& handler, const DfltExecutor& ex) {
 	return asio::prefer(
-		asio::get_associated_executor(handler),
+		asio::get_associated_executor(handler, ex),
 		asio::execution::outstanding_work.tracked
 	);
 }
 
-template <typename Handler>
-using tracking_type = std::decay_t<
-	decltype(tracking_executor(std::declval<Handler>()))
->;
+template <typename Handler, typename DfltExecutor>
+using tracking_type = typename asio::prefer_result<
+	asio::associated_executor_t<Handler, DfltExecutor>,
+	asio::execution::outstanding_work_t::tracked_t
+>::type;
 
 template <typename T, typename B>
 concept has_async_write = requires(T a) {
diff --git a/include/async_mqtt5/detail/cancellable_handler.hpp b/include/async_mqtt5/detail/cancellable_handler.hpp
index 0f8f7be..02b072f 100644
--- a/include/async_mqtt5/detail/cancellable_handler.hpp
+++ b/include/async_mqtt5/detail/cancellable_handler.hpp
@@ -21,19 +21,19 @@ template <
 >
 class cancellable_handler {
 	struct op_state {
-		std::decay_t<Handler> _handler;
-		tracking_type<Handler> _handler_ex;
+		Handler _handler;
+		tracking_type<Handler, Executor> _handler_ex;
 		cancellable_handler* _owner;
 
-		op_state(Handler&& handler, cancellable_handler* owner) :
-			_handler(std::move(handler)),
-			_handler_ex(tracking_executor(_handler)),
+		op_state(
+			Handler&& handler, const Executor& ex, cancellable_handler* owner
+		) : _handler(std::move(handler)),
+			_handler_ex(tracking_executor(_handler, ex)),
 			_owner(owner)
 		{}
 
-		void cancel_op(asio::cancellation_type_t ct) {
-			if (ct != asio::cancellation_type_t::none)
-				_owner->cancel();
+		void cancel_op() {
+			_owner->cancel();
 		}
 	};
 
@@ -46,16 +46,16 @@ class cancellable_handler {
 		{}
 
 		void operator()(asio::cancellation_type_t type) {
-			auto op = [](
-				std::weak_ptr<op_state> wptr,
-				asio::cancellation_type_t type
-			) {
+			if ((type & asio::cancellation_type_t::terminal) ==
+				asio::cancellation_type_t::none)
+				return;
+			auto op = [wptr = _state_weak_ptr]() {
 				if (auto state = wptr.lock())
-					state->cancel_op(type);
+					state->cancel_op();
 			};
 			asio::dispatch(
 				_executor,
-				asio::prepend(std::move(op), _state_weak_ptr, type)
+				std::move(op)
 			);
 		}
 	};
@@ -67,12 +67,12 @@ public:
 	cancellable_handler(Handler&& handler, const Executor& ex) {
 		auto alloc = asio::get_associated_allocator(handler);
 		_state = std::allocate_shared<op_state>(
-			alloc, std::move(handler),this
+			alloc, std::move(handler), ex, this
 		);
-		_executor = ex;
 		auto slot = asio::get_associated_cancellation_slot(_state->_handler);
 		if (slot.is_connected())
 			slot.template emplace<cancel_proxy>(_state, ex);
+		_executor = ex;
 	}
 
 	cancellable_handler(cancellable_handler&& other) noexcept :
@@ -102,8 +102,9 @@ public:
 		if (empty()) return;
 
 		auto h = std::move(_state->_handler);
-		_state.reset();
 		asio::get_associated_cancellation_slot(h).clear();
+		auto handler_ex = std::move(_state->_handler_ex);
+		_state.reset();
 
 		auto op = std::apply([&h](auto... args) {
 			return asio::prepend(
@@ -111,7 +112,7 @@ public:
 			);
 		}, CancelArgs {});
 
-		asio::dispatch(std::move(_executor), std::move(op));
+		asio::dispatch(handler_ex, std::move(op));
 	}
 
 	template <typename... Args>
@@ -119,11 +120,12 @@ public:
 		if (empty()) return;
 
 		auto h = std::move(_state->_handler);
-		_state.reset();
 		asio::get_associated_cancellation_slot(h).clear();
+		auto handler_ex = std::move(_state->_handler_ex);
+		_state.reset();
 
 		asio::dispatch(
-			std::move(_executor),
+			handler_ex,
 			asio::prepend(std::move(h), std::forward<Args>(args)...)
 		);
 	}
@@ -133,14 +135,14 @@ public:
 		if (empty()) return;
 
 		auto h = std::move(_state->_handler);
-		_state.reset();
 		asio::get_associated_cancellation_slot(h).clear();
+		auto handler_ex = std::move(_state->_handler_ex);
+		_state.reset();
 
 		asio::post(
-			std::move(_executor),
+			_executor,
 			asio::prepend(std::move(h), std::forward<Args>(args)...)
 		);
-
 	}
 
 };
diff --git a/include/async_mqtt5/impl/assemble_op.hpp b/include/async_mqtt5/impl/assemble_op.hpp
index 4dedb8a..4e5133c 100644
--- a/include/async_mqtt5/impl/assemble_op.hpp
+++ b/include/async_mqtt5/impl/assemble_op.hpp
@@ -54,7 +54,7 @@ class assemble_op {
 	static constexpr size_t max_packet_size = 65536;
 
 	client_service& _svc;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 
 	std::string& _read_buff;
 	data_span& _data_span;
diff --git a/include/async_mqtt5/impl/connect_op.hpp b/include/async_mqtt5/impl/connect_op.hpp
index ed98e96..50af454 100644
--- a/include/async_mqtt5/impl/connect_op.hpp
+++ b/include/async_mqtt5/impl/connect_op.hpp
@@ -43,7 +43,7 @@ class connect_op {
 
 	Stream& _stream;
 	mqtt_context& _ctx;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 	std::unique_ptr<std::string> _buffer_ptr;
 
 	using endpoint = asio::ip::tcp::endpoint;
diff --git a/include/async_mqtt5/impl/disconnect_op.hpp b/include/async_mqtt5/impl/disconnect_op.hpp
index 6dbf389..53a61a2 100644
--- a/include/async_mqtt5/impl/disconnect_op.hpp
+++ b/include/async_mqtt5/impl/disconnect_op.hpp
@@ -9,6 +9,7 @@
 
 #include <async_mqtt5/detail/control_packet.hpp>
 #include <async_mqtt5/detail/internal_types.hpp>
+#include <async_mqtt5/detail/cancellable_handler.hpp>
 
 #include <async_mqtt5/impl/internal/codecs/message_encoders.hpp>
 
@@ -28,7 +29,10 @@ class disconnect_op {
 
 	std::shared_ptr<client_service> _svc_ptr;
 	DisconnectContext _context;
-	std::decay_t<Handler> _handler;
+	cancellable_handler<
+		Handler,
+		typename ClientService::executor_type
+	> _handler;
 
 public:
 	disconnect_op(
@@ -37,7 +41,7 @@ public:
 	) :
 		_svc_ptr(svc_ptr),
 		_context(std::move(context)),
-		_handler(std::move(handler))
+		_handler(std::move(handler), get_executor())
 	{}
 
 	disconnect_op(disconnect_op&&) noexcept = default;
@@ -103,10 +107,7 @@ public:
 
 private:
 	void complete(error_code ec) {
-		asio::dispatch(
-			get_executor(),
-			asio::prepend(std::move(_handler), ec)
-		);
+		_handler.complete(ec);
 	}
 };
 
diff --git a/include/async_mqtt5/impl/endpoints.hpp b/include/async_mqtt5/impl/endpoints.hpp
index f2c65af..4749624 100644
--- a/include/async_mqtt5/impl/endpoints.hpp
+++ b/include/async_mqtt5/impl/endpoints.hpp
@@ -26,7 +26,7 @@ class resolve_op {
 	struct on_resolve {};
 
 	Owner& _owner;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 
 public:
 	resolve_op(
diff --git a/include/async_mqtt5/impl/publish_send_op.hpp b/include/async_mqtt5/impl/publish_send_op.hpp
index 2b7f19d..c18fc39 100644
--- a/include/async_mqtt5/impl/publish_send_op.hpp
+++ b/include/async_mqtt5/impl/publish_send_op.hpp
@@ -142,6 +142,12 @@ public:
 	}
 
 	void send_publish(control_packet<allocator_type> publish) {
+		if (_handler.empty()) { // already cancelled
+			if constexpr (qos_type != qos_e::at_most_once)
+				_svc_ptr->free_pid(publish.packet_id());
+			return;
+		}
+
 		const auto& wire_data = publish.wire_data();
 		_svc_ptr->async_send(
 			wire_data,
diff --git a/include/async_mqtt5/impl/read_op.hpp b/include/async_mqtt5/impl/read_op.hpp
index dfff235..21fc938 100644
--- a/include/async_mqtt5/impl/read_op.hpp
+++ b/include/async_mqtt5/impl/read_op.hpp
@@ -19,7 +19,7 @@ class read_op {
 	struct on_reconnect {};
 
 	Owner& _owner;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 
 public:
 	read_op(Owner& owner, Handler&& handler) :
diff --git a/include/async_mqtt5/impl/reconnect_op.hpp b/include/async_mqtt5/impl/reconnect_op.hpp
index c567f78..9e383c1 100644
--- a/include/async_mqtt5/impl/reconnect_op.hpp
+++ b/include/async_mqtt5/impl/reconnect_op.hpp
@@ -27,7 +27,7 @@ class reconnect_op {
 	struct on_backoff {};
 
 	Owner& _owner;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 	std::unique_ptr<std::string> _buffer_ptr;
 
 	using endpoint = asio::ip::tcp::endpoint;
diff --git a/include/async_mqtt5/impl/subscribe_op.hpp b/include/async_mqtt5/impl/subscribe_op.hpp
index d8c2dc4..c7cf733 100644
--- a/include/async_mqtt5/impl/subscribe_op.hpp
+++ b/include/async_mqtt5/impl/subscribe_op.hpp
@@ -71,6 +71,9 @@ public:
 	}
 
 	void send_subscribe(control_packet<allocator_type> subscribe) {
+		if (_handler.empty()) // already cancelled
+			return _svc_ptr->free_pid(subscribe.packet_id());
+
 		const auto& wire_data = subscribe.wire_data();
 		_svc_ptr->async_send(
 			wire_data,
diff --git a/include/async_mqtt5/impl/unsubscribe_op.hpp b/include/async_mqtt5/impl/unsubscribe_op.hpp
index 573e2a9..c5d891f 100644
--- a/include/async_mqtt5/impl/unsubscribe_op.hpp
+++ b/include/async_mqtt5/impl/unsubscribe_op.hpp
@@ -71,6 +71,9 @@ public:
 	}
 
 	void send_unsubscribe(control_packet<allocator_type> unsubscribe) {
+		if (_handler.empty()) // already cancelled
+			return _svc_ptr->free_pid(unsubscribe.packet_id());
+
 		const auto& wire_data = unsubscribe.wire_data();
 		_svc_ptr->async_send(
 			wire_data,
diff --git a/include/async_mqtt5/impl/write_op.hpp b/include/async_mqtt5/impl/write_op.hpp
index 37e1785..5492b5e 100644
--- a/include/async_mqtt5/impl/write_op.hpp
+++ b/include/async_mqtt5/impl/write_op.hpp
@@ -15,7 +15,7 @@ class write_op {
 	struct on_reconnect {};
 
 	Owner& _owner;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 
 public:
 	write_op(
diff --git a/test/unit/include/test_common/test_stream.hpp b/test/unit/include/test_common/test_stream.hpp
index fc352db..83effef 100644
--- a/test/unit/include/test_common/test_stream.hpp
+++ b/test/unit/include/test_common/test_stream.hpp
@@ -94,7 +94,7 @@ template <typename Handler>
 class read_op {
 	struct on_read {};
 	std::shared_ptr<test_stream_impl> _stream_impl;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 
 public:
 	read_op(
@@ -155,7 +155,7 @@ class write_op {
 	struct on_write {};
 
 	std::shared_ptr<test_stream_impl> _stream_impl;
-	std::decay_t<Handler> _handler;
+	Handler _handler;
 
 public:
 	write_op(