diff --git a/src/mcp/mcp.c b/src/mcp/mcp.c
index bdfdae8..cdcf2bb 100644
--- a/src/mcp/mcp.c
+++ b/src/mcp/mcp.c
@@ -2389,16 +2389,21 @@ int cbm_mcp_server_run(cbm_mcp_server_t *srv, FILE *in, FILE *out) {
             continue;
         }
 #else
-        struct pollfd pfd = {.fd = fd, .events = POLLIN};
-        int pr = poll(&pfd, 1, STORE_IDLE_TIMEOUT_S * 1000);
-
-        if (pr < 0) {
-            break; /* error or signal */
-        }
-        if (pr == 0) {
-            /* Timeout — evict idle store to free resources */
-            cbm_mcp_server_evict_idle(srv, STORE_IDLE_TIMEOUT_S);
-            continue;
+#ifdef __GLIBC__
+        int has_buffered = (in->_IO_read_ptr < in->_IO_read_end);
+#else
+        /* macOS / BSD: use __srget-style check.
+         * fp->_r is the count of unread bytes in the buffer. */
+        int has_buffered = (in->_r > 0);
+#endif
+        if (!has_buffered) {
+            struct pollfd pfd = {.fd = fd, .events = POLLIN};
+            int pr = poll(&pfd, 1, STORE_IDLE_TIMEOUT_S * 1000);
+            if (pr < 0) break;
+            if (pr == 0) {
+                cbm_mcp_server_evict_idle(srv, STORE_IDLE_TIMEOUT_S);
+                continue;
+            }
         }
 #endif