diff --git a/src/daemon/xmrig_manager.cpp b/src/daemon/xmrig_manager.cpp
index 0ef57c7..1235e76 100644
--- a/src/daemon/xmrig_manager.cpp
+++ b/src/daemon/xmrig_manager.cpp
@@ -356,12 +356,6 @@ void XmrigManager::stop(int wait_ms) {
         // Try graceful termination first
         TerminateProcess(process_handle_, 0);
         WaitForSingleObject(process_handle_, wait_ms);
-        CloseHandle(process_handle_);
-        process_handle_ = nullptr;
-    }
-    if (stdout_read_) {
-        CloseHandle(stdout_read_);
-        stdout_read_ = nullptr;
     }
 #else
     if (process_pid_ > 0) {
@@ -386,15 +380,29 @@ void XmrigManager::stop(int wait_ms) {
         }
         process_pid_ = 0;
     }
+#endif
+
+    if (monitor_thread_.joinable())
+        monitor_thread_.join();
+
+    // Close the pipe only after the monitor thread has finished with it (it
+    // drains stdout); closing earlier let read() hit a closed/reused fd.
+#ifdef _WIN32
+    if (process_handle_) {
+        CloseHandle(process_handle_);
+        process_handle_ = nullptr;
+    }
+    if (stdout_read_) {
+        CloseHandle(stdout_read_);
+        stdout_read_ = nullptr;
+    }
+#else
     if (stdout_fd_ >= 0) {
         close(stdout_fd_);
         stdout_fd_ = -1;
     }
 #endif
 
-    if (monitor_thread_.joinable())
-        monitor_thread_.join();
-
     state_ = State::Stopped;
     DEBUG_LOGF("[INFO] XmrigManager: stopped\n");
 }
@@ -475,6 +483,7 @@ double XmrigManager::getMemoryUsageMB() const {
 }
 
 void XmrigManager::drainOutput() {
+    std::lock_guard<std::mutex> io_lk(io_mutex_);
     if (!stdout_read_) return;
     char buf[4096];
     DWORD avail = 0;
@@ -565,7 +574,7 @@ double XmrigManager::getMemoryUsageMB() const {
 #ifdef __APPLE__
     // macOS: use ps to read RSS for xmrig process
     char cmd[128];
-    snprintf(cmd, sizeof(cmd), "ps -o rss= -p %d 2>/dev/null", process_pid_);
+    snprintf(cmd, sizeof(cmd), "ps -o rss= -p %d 2>/dev/null", (int)process_pid_.load(std::memory_order_relaxed));
     FILE* fp = popen(cmd, "r");
     if (!fp) return 0.0;
     char line[64];
@@ -578,7 +587,7 @@ double XmrigManager::getMemoryUsageMB() const {
     return mb;
 #else
     char path[64];
-    snprintf(path, sizeof(path), "/proc/%d/statm", process_pid_);
+    snprintf(path, sizeof(path), "/proc/%d/statm", (int)process_pid_.load(std::memory_order_relaxed));
     FILE* fp = fopen(path, "r");
     if (!fp) return 0.0;
     long dummy = 0, pages = 0;
@@ -592,6 +601,7 @@ double XmrigManager::getMemoryUsageMB() const {
 }
 
 void XmrigManager::drainOutput() {
+    std::lock_guard<std::mutex> io_lk(io_mutex_);
     if (stdout_fd_ < 0) return;
     char buf[4096];
     while (true) {
@@ -702,9 +712,8 @@ void XmrigManager::monitorProcess() {
 // ============================================================================
 
 void XmrigManager::pollStats() {
-    // No-op on UI thread — stats are fetched by the monitor thread.
-    // Just drain stdout so log lines stay fresh.
-    drainOutput();
+    // No-op on UI thread — stats and the stdout drain both run on the monitor
+    // thread (a second reader here raced stop() closing the fd).
 }
 
 void XmrigManager::fetchStatsHttp() {
diff --git a/src/daemon/xmrig_manager.h b/src/daemon/xmrig_manager.h
index 03c3014..cc240c5 100644
--- a/src/daemon/xmrig_manager.h
+++ b/src/daemon/xmrig_manager.h
@@ -177,12 +177,13 @@ private:
 
     // Process handles
 #ifdef _WIN32
-    HANDLE process_handle_ = nullptr;
-    HANDLE stdout_read_    = nullptr;
+    std::atomic<HANDLE> process_handle_{nullptr};
+    std::atomic<HANDLE> stdout_read_{nullptr};
 #else
-    pid_t process_pid_     = 0;
-    int   stdout_fd_       = -1;
+    std::atomic<pid_t> process_pid_{0};
+    std::atomic<int>   stdout_fd_{-1};
 #endif
+    std::mutex io_mutex_;   // serializes drainOutput(); lock order io_mutex_ -> output_mutex_
 
     std::thread monitor_thread_;
     std::atomic<bool> should_stop_{false};