diff --git a/hermes_cli/web_server.py b/hermes_cli/web_server.py
index f1d14ebf48b..fb5f7ca12d3 100644
--- a/hermes_cli/web_server.py
+++ b/hermes_cli/web_server.py
@@ -4432,11 +4432,33 @@ def start_server(
     if open_browser:
         import webbrowser
 
-        def _open():
-            time.sleep(1.0)
-            webbrowser.open(f"http://{host}:{port}")
+        # On headless Linux (no DISPLAY or WAYLAND_DISPLAY) some registered
+        # browsers are TUI programs (links, lynx, www-browser) that try to
+        # take over the terminal.  That can send SIGHUP to the server process
+        # and cause an immediate exit even though uvicorn bound successfully.
+        # Skip the auto-open attempt on headless systems and let the user
+        # open the URL manually.  macOS and Windows are always considered
+        # display-capable.
+        _has_display = (
+            sys.platform != "linux"
+            or bool(os.environ.get("DISPLAY"))
+            or bool(os.environ.get("WAYLAND_DISPLAY"))
+        )
 
-        threading.Thread(target=_open, daemon=True).start()
+        if _has_display:
+            def _open():
+                try:
+                    time.sleep(1.0)
+                    webbrowser.open(f"http://{host}:{port}")
+                except Exception:
+                    pass
+
+            threading.Thread(target=_open, daemon=True).start()
+        else:
+            _log.debug(
+                "Skipping browser-open: no DISPLAY or WAYLAND_DISPLAY detected "
+                "(headless Linux). Pass --no-open to suppress this detection."
+            )
 
     print(f"  Hermes Web UI → http://{host}:{port}")
     uvicorn.run(app, host=host, port=port, log_level="warning")