Use a separate process to call webbrowser open,

redirecting output at the OS level to avoid stdout contamination #257

src/serena/agent.py

@@ -2,7 +2,7 @@
 The Serena Model Context Protocol (MCP) Server
 """
 
-import contextlib
+import multiprocessing
 import os
 import platform
 import sys
@@ -273,11 +273,10 @@ class SerenaAgent:
             Logger.root.addHandler(dashboard_log_handler)
             self._dashboard_thread, port = SerenaDashboardAPI(dashboard_log_handler, tool_names).run_in_thread()
             if self.serena_config.web_dashboard_open_on_launch:
-                # open the dashboard URL in the default web browser, making sure to redirect output,
-                # as this can print to stdout (contaminating the MCP server stream)
-                with open(os.devnull, "w") as fnull:
-                    with contextlib.redirect_stdout(fnull), contextlib.redirect_stderr(fnull):
-                        webbrowser.open(f"http://localhost:{port}/dashboard/index.html")
+                # open the dashboard URL in the default web browser (using a separate process to control
+                # output redirection)
+                process = multiprocessing.Process(target=self._open_dashboard, args=(port,))
+                process.start()
 
         # log fundamental information
         log.info(f"Starting Serena server (version={serena_version()}, process id={os.getpid()}, parent process id={os.getppid()})")
@@ -326,6 +325,18 @@ class SerenaAgent:
                     "You should now pass either --project <project_name> or --project <project_root>."
                 )
 
+    @staticmethod
+    def _open_dashboard(port: int) -> None:
+        # Redirect stdout and stderr file descriptors to /dev/null,
+        # making sure that nothing can be written to stdout/stderr, even by subprocesses
+        null_fd = os.open(os.devnull, os.O_WRONLY)
+        os.dup2(null_fd, sys.stdout.fileno())
+        os.dup2(null_fd, sys.stderr.fileno())
+        os.close(null_fd)
+
+        # open the dashboard URL in the default web browser
+        webbrowser.open(f"http://localhost:{port}/dashboard/index.html")
+
     def get_project_root(self) -> str:
         """
         :return: the root directory of the active project (if any); raises a ValueError if there is no active project