diff --git a/utils/markdown_to_image.py b/utils/markdown_to_image.py
index 1737ae8..e3b107b 100644
--- a/utils/markdown_to_image.py
+++ b/utils/markdown_to_image.py
@@ -39,15 +39,40 @@ async def safe_close_browser(browser, timeout: float = 4.0) -> None:
         try:
             parent = psutil.Process(browser.process.pid)
             children = parent.children(recursive=True)
-            for child in children:
+
+            # 3.1 try graceful terminate first
+            for proc in children:
                 try:
-                    child.kill()
-                except psutil.NoSuchProcess:
+                    proc.terminate()
+                except (psutil.NoSuchProcess, psutil.AccessDenied, psutil.ZombieProcess):
                     pass
-            parent.kill()
-            # 可选：等待一小会儿确认退出
-            psutil.wait_procs([parent] + children, timeout=3)
-            logger.debug("process tree killed")
+            try:
+                parent.terminate()
+            except (psutil.NoSuchProcess, psutil.AccessDenied, psutil.ZombieProcess):
+                pass
+
+            # 3.2 wait briefly, then force kill
+            try:
+                gone, alive = psutil.wait_procs([parent] + children, timeout=2)
+            except Exception:
+                gone, alive = [], [parent] + children
+
+            for proc in alive:
+                try:
+                    proc.kill()
+                except (psutil.NoSuchProcess, psutil.AccessDenied, psutil.ZombieProcess):
+                    pass
+
+            # 3.3 final wait and report
+            try:
+                gone, alive = psutil.wait_procs([parent] + children, timeout=3)
+            except Exception:
+                alive = []
+
+            if alive:
+                logger.warning(f"process still alive after kill: {[p.pid for p in alive]}")
+            else:
+                logger.debug("process tree terminated")
         except (psutil.NoSuchProcess, Exception) as e:
             logger.warning(f"force kill failed: {e}")