diff --git a/src/lib/dataman_client/DatamanClient.cpp b/src/lib/dataman_client/DatamanClient.cpp
index a263f00a45..1ba9673f0f 100644
--- a/src/lib/dataman_client/DatamanClient.cpp
+++ b/src/lib/dataman_client/DatamanClient.cpp
@@ -64,14 +64,27 @@ DatamanClient::DatamanClient()
 		_fds.fd = _dataman_response_sub;
 		_fds.events = POLLIN;
 
-#if !(defined(ENABLE_LOCKSTEP_SCHEDULER) && defined(__PX4_WINDOWS))
+#if defined(ENABLE_LOCKSTEP_SCHEDULER) && defined(__PX4_WINDOWS)
+		// Windows lockstep build only: defer client-ID acquisition
+		// until the first sync/async call, because hrt_absolute_time()
+		// is not yet advancing when the constructor runs and the
+		// GET_ID round-trip would stall startup.
+		(void)response;
+#else
+		hrt_abstime timestamp = hrt_absolute_time();
 
-		// Acquire the client ID eagerly on POSIX (Linux/macOS) and
-		// non-lockstep builds. Only the Windows-lockstep build defers
-		// it, because hrt_absolute_time() is not yet advancing when
-		// the constructor runs there and the GET_ID round-trip would
-		// stall startup.
-		if (!updateClientId(1000_ms)) {
+		dataman_request_s request;
+		request.timestamp = timestamp;
+		request.request_type = DM_GET_ID;
+		request.client_id = CLIENT_ID_NOT_SET;
+
+		bool success = syncHandler(request, response, timestamp, 1000_ms);
+
+		if (success && (response.client_id > CLIENT_ID_NOT_SET)) {
+
+			_client_id = response.client_id;
+
+		} else {
 			PX4_ERR("Failed to get client ID!");
 		}
 
@@ -91,47 +104,29 @@ DatamanClient::~DatamanClient()
 bool DatamanClient::syncHandler(const dataman_request_s &request, dataman_response_s &response,
 				const hrt_abstime &start_time, hrt_abstime timeout)
 {
-	bool response_received = false;
-	int32_t ret = 0;
 #if defined(ENABLE_LOCKSTEP_SCHEDULER) && defined(__PX4_WINDOWS)
+	// Windows lockstep: hrt_absolute_time() does not advance until the
+	// shim attaches to the simulator clock, so use the OS monotonic
+	// clock here and poll the orb queue with a short usleep instead of
+	// px4_poll(), which blocks against the lockstep scheduler.
 	(void)start_time;
+	bool response_received = false;
 	const hrt_abstime sync_start_time = dataman_wall_time_us();
 	hrt_abstime last_request_time = sync_start_time;
 	hrt_abstime time_elapsed = 0;
 	const unsigned max_iterations = (timeout / 1000) + 1;
 	unsigned iterations = 0;
-#else
-	hrt_abstime time_elapsed = hrt_elapsed_time(&start_time);
-#endif
+
 	perf_begin(_sync_perf);
 	_dataman_request_pub.publish(request);
 
 	while (!response_received && (time_elapsed < timeout)) {
-#if defined(ENABLE_LOCKSTEP_SCHEDULER) && defined(__PX4_WINDOWS)
-
 		if (++iterations > max_iterations) {
 			break;
 		}
 
 		bool updated = false;
 		orb_check(_dataman_response_sub, &updated);
-#else
-		uint32_t timeout_ms = 100;
-		ret = px4_poll(&_fds, 1, timeout_ms);
-
-		if (ret < 0) {
-			PX4_ERR("px4_poll returned error: %" PRIu32, ret);
-			break;
-
-		}
-
-		bool updated = false;
-
-		if (ret > 0) {
-			orb_check(_dataman_response_sub, &updated);
-		}
-
-#endif
 
 		if (updated) {
 			orb_copy(ORB_ID(dataman_response), _dataman_response_sub, &response);
@@ -155,7 +150,6 @@ bool DatamanClient::syncHandler(const dataman_request_s &request, dataman_respon
 			}
 		}
 
-#if defined(ENABLE_LOCKSTEP_SCHEDULER) && defined(__PX4_WINDOWS)
 		const hrt_abstime now = dataman_wall_time_us();
 
 		if (now - last_request_time >= 100_ms) {
@@ -164,20 +158,67 @@ bool DatamanClient::syncHandler(const dataman_request_s &request, dataman_respon
 		}
 
 		system_usleep(1000);
-#else
+		time_elapsed = dataman_wall_time_us() - sync_start_time;
+	}
+
+	perf_end(_sync_perf);
+
+	if (!response_received) {
+		PX4_ERR("timeout after %" PRIu32 " ms!", static_cast<uint32_t>(timeout / 1000));
+	}
+
+	return response_received;
+
+#else
+	bool response_received = false;
+	int32_t ret = 0;
+	hrt_abstime time_elapsed = hrt_elapsed_time(&start_time);
+	perf_begin(_sync_perf);
+	_dataman_request_pub.publish(request);
+
+	while (!response_received && (time_elapsed < timeout)) {
+
+		uint32_t timeout_ms = 100;
+		ret = px4_poll(&_fds, 1, timeout_ms);
+
+		if (ret < 0) {
+			PX4_ERR("px4_poll returned error: %" PRIu32, ret);
+			break;
+
+		} else if (ret == 0) {
 
-		if (ret == 0) {
 			// No response received, send new request
 			_dataman_request_pub.publish(request);
+
+		} else {
+
+			bool updated = false;
+			orb_check(_dataman_response_sub, &updated);
+
+			if (updated) {
+				orb_copy(ORB_ID(dataman_response), _dataman_response_sub, &response);
+
+				if (response.client_id == request.client_id) {
+
+					if ((response.request_type == request.request_type) &&
+					    (response.item == request.item) &&
+					    (response.index == request.index)) {
+						response_received = true;
+						break;
+					}
+
+				} else if (request.client_id == CLIENT_ID_NOT_SET) {
+
+					// validate timestamp from response.data
+					if (0 == memcmp(&(request.timestamp), &(response.data), sizeof(hrt_abstime))) {
+						response_received = true;
+						break;
+					}
+				}
+			}
 		}
 
-#endif
-
-#if defined(ENABLE_LOCKSTEP_SCHEDULER) && defined(__PX4_WINDOWS)
-		time_elapsed = dataman_wall_time_us() - sync_start_time;
-#else
 		time_elapsed = hrt_elapsed_time(&start_time);
-#endif
 	}
 
 	perf_end(_sync_perf);
@@ -187,6 +228,7 @@ bool DatamanClient::syncHandler(const dataman_request_s &request, dataman_respon
 	}
 
 	return response_received;
+#endif
 }
 
 bool DatamanClient::updateClientId(hrt_abstime timeout)