diff --git a/core/src/drivers/plugins/native/ethercat/CMakeLists.txt b/core/src/drivers/plugins/native/ethercat/CMakeLists.txt
index 40e5d57..5126f2b 100644
--- a/core/src/drivers/plugins/native/ethercat/CMakeLists.txt
+++ b/core/src/drivers/plugins/native/ethercat/CMakeLists.txt
@@ -60,8 +60,21 @@ target_compile_options(soem PUBLIC\n\
 # HAVE_U_INT*_T tells bundled bittypes.h to skip its typedefs --\n\
 # MSYS2 POSIX headers (sys/types.h) already provide these types and\n\
 # use different underlying types on LP64 (long vs long long for 64-bit).\n\
+#\n\
+# __USE_W32_SOCKETS tells MSYS2 / Cygwin's POSIX headers\n\
+# (\`sys/select.h\`, \`sys/unistd.h\`) NOT to declare their own \`select\`\n\
+# and \`gethostname\` — the Win32 \`winsock2.h\` declarations (which the\n\
+# bundled wpcap headers pull in transitively) are the ones we want\n\
+# to use.  Without this, any TU that includes both a POSIX header\n\
+# (e.g. \`<signal.h>\` in ethercat_plugin.c, which transitively pulls\n\
+# in sys/select.h) AND a SOEM/wpcap header (which pulls in\n\
+# winsock2.h) gets a redeclaration error because the two libcs\n\
+# disagree on the signature ( \`struct timeval *\` vs \`const TIMEVAL *\`,\n\
+# \`size_t\` vs \`int\`).  Marking the macro PUBLIC propagates it to\n\
+# every target linking against soem (notably ethercat_plugin).\n\
 target_compile_definitions(soem PUBLIC\n\
   WIN32\n\
+  __USE_W32_SOCKETS\n\
   HAVE_U_INT8_T\n\
   HAVE_U_INT16_T\n\
   HAVE_U_INT32_T\n\
diff --git a/core/src/plc_app/image_tables.cpp b/core/src/plc_app/image_tables.cpp
index de41933..d2805d8 100644
--- a/core/src/plc_app/image_tables.cpp
+++ b/core/src/plc_app/image_tables.cpp
@@ -93,7 +93,16 @@ namespace {
     {
         pthread_mutexattr_t attr;
         if (pthread_mutexattr_init(&attr) != 0) return -1;
+        // Priority inheritance is a POSIX optional feature.  MSYS2/Cygwin
+        // pthread on Windows doesn't ship it (PTHREAD_PRIO_INHERIT is
+        // undefined, pthread_mutexattr_setprotocol is unavailable).
+        // Windows has no real-time scheduling anyway, so the PI protocol
+        // would be a no-op even if it linked — fall back to a plain
+        // recursive mutex.
+#if !defined(__CYGWIN__) && !defined(__MSYS__) && \
+    defined(_POSIX_THREAD_PRIO_INHERIT) && _POSIX_THREAD_PRIO_INHERIT > 0
         pthread_mutexattr_setprotocol(&attr, PTHREAD_PRIO_INHERIT);
+#endif
         pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
         int rc = pthread_mutex_init(m, &attr);
         pthread_mutexattr_destroy(&attr);
diff --git a/core/src/plc_app/plc_state_manager.cpp b/core/src/plc_app/plc_state_manager.cpp
index fce8eb3..c77116a 100644
--- a/core/src/plc_app/plc_state_manager.cpp
+++ b/core/src/plc_app/plc_state_manager.cpp
@@ -140,6 +140,13 @@ static void *plc_task_thread(void *arg)
 
     if (ctx->cpu_affinity_mask != 0)
     {
+        // CPU affinity uses `cpu_set_t` / `CPU_ZERO` / `CPU_SETSIZE` /
+        // `pthread_setaffinity_np` — all Linux extensions to `<sched.h>`,
+        // not present on MSYS2/Cygwin/Windows.  Skip silently when
+        // building for a non-Linux host: Windows doesn't expose
+        // SCHED_FIFO either, so any "pin to CPU" guarantee would already
+        // be unachievable there.
+#if !defined(__CYGWIN__) && !defined(__MSYS__) && defined(__linux__)
         cpu_set_t cs;
         CPU_ZERO(&cs);
         for (int cpu = 0; cpu < 64 && cpu < CPU_SETSIZE; ++cpu)
@@ -151,6 +158,10 @@ static void *plc_task_thread(void *arg)
             log_warn("[task %s] pthread_setaffinity_np failed: %s",
                      ctx->name, strerror(errno));
         }
+#else
+        log_info("[task %s] CPU affinity requested but unsupported on this platform",
+                 ctx->name);
+#endif
     }
 
     if (sigsetjmp(ctx->crash_jmp, 1) != 0)