diff --git a/agent_v0/agent_v1/ui/chat_window.py b/agent_v0/agent_v1/ui/chat_window.py
index bb9805970..422b6cc31 100644
--- a/agent_v0/agent_v1/ui/chat_window.py
+++ b/agent_v0/agent_v1/ui/chat_window.py
@@ -5,6 +5,9 @@ Fenetre de chat Lea integree au systray — version tkinter native.
 Remplace l'approche Edge browser par une vraie fenetre tkinter integree.
 Design professionnel, theme clair, ancree en bas a droite de l'ecran.
 Tourne dans son propre thread daemon pour ne pas bloquer pystray.
+
+Le runtime Python embedded Windows ne contient pas toujours Tcl/Tk. Dans ce
+cas, le menu "Discuter avec Lea" ouvre le chat DGX dans le navigateur.
 """
 
 import logging
@@ -13,6 +16,8 @@ import math
 import threading
 import time
 from datetime import datetime
+from pathlib import Path
+from urllib.parse import urlparse
 from typing import Any, Callable, Dict, Optional
 
 logger = logging.getLogger(__name__)
@@ -219,7 +224,10 @@ class ChatWindow:
 
     def toggle(self) -> None:
         """Afficher/masquer la fenetre de chat."""
-        if self._destroyed or self._root is None:
+        if self._destroyed:
+            return
+        if self._root is None:
+            self._open_browser_fallback()
             return
         if self._visible:
             self.hide()
@@ -228,7 +236,10 @@ class ChatWindow:
 
     def show(self) -> None:
         """Afficher la fenetre."""
-        if self._destroyed or self._root is None:
+        if self._destroyed:
+            return
+        if self._root is None:
+            self._open_browser_fallback()
             return
         self._root.after(0, self._do_show)
 
@@ -257,6 +268,79 @@ class ChatWindow:
         """Mettre a jour le client serveur (appele si cree apres la fenetre)."""
         self._server_client = server_client
 
+    def _chat_url(self) -> str:
+        """Retourne l'URL web du chat, derivee de la config serveur."""
+        configured_url = self._chat_url_from_server_url(self._configured_server_url())
+        if self._server_client is not None:
+            chat_base = getattr(self._server_client, "_chat_base", None)
+            if chat_base:
+                chat_base = str(chat_base).rstrip("/")
+                if not self._is_local_url(chat_base):
+                    return chat_base
+                if configured_url:
+                    return configured_url
+
+        if configured_url:
+            return configured_url
+
+        host = (self._server_host or "localhost").strip()
+        if host.startswith(("http://", "https://")):
+            parsed = urlparse(host)
+            scheme = parsed.scheme or "http"
+            hostname = parsed.hostname or "localhost"
+            return f"{scheme}://{hostname}:{self._chat_port}"
+
+        return f"http://{host}:{self._chat_port}"
+
+    @staticmethod
+    def _is_local_url(url: str) -> bool:
+        try:
+            host = urlparse(url).hostname
+        except Exception:
+            return False
+        return host in {"localhost", "127.0.0.1", "::1"}
+
+    def _chat_url_from_server_url(self, server_url: Optional[str]) -> Optional[str]:
+        if not server_url:
+            return None
+        try:
+            parsed = urlparse(server_url.strip())
+        except Exception:
+            return None
+        if not parsed.hostname or parsed.hostname in {"localhost", "127.0.0.1", "::1"}:
+            return None
+        scheme = parsed.scheme or "http"
+        return f"{scheme}://{parsed.hostname}:{self._chat_port}"
+
+    def _configured_server_url(self) -> Optional[str]:
+        env_url = os.environ.get("RPA_SERVER_URL", "").strip()
+        if env_url:
+            return env_url
+
+        try:
+            # Installed layout: <app>/agent_v1/ui/chat_window.py.
+            for parent in Path(__file__).resolve().parents:
+                cfg = parent / "config.txt"
+                if cfg.exists():
+                    for line in cfg.read_text(encoding="utf-8", errors="ignore").splitlines():
+                        if line.startswith("RPA_SERVER_URL="):
+                            return line.split("=", 1)[1].strip()
+        except Exception:
+            logger.debug("Lecture config.txt pour chat_url impossible", exc_info=True)
+        return None
+
+    def _open_browser_fallback(self) -> None:
+        """Fallback POC quand tkinter est absent du Python embedded."""
+        url = self._chat_url()
+        try:
+            import webbrowser
+            if webbrowser.open(url, new=1):
+                logger.info("ChatWindow indisponible, chat ouvert dans le navigateur: %s", url)
+            else:
+                logger.warning("ChatWindow indisponible, ouverture navigateur refusee: %s", url)
+        except Exception as exc:
+            logger.error("Impossible d'ouvrir le chat dans le navigateur (%s): %s", url, exc)
+
     def _on_shared_state_change(self, state) -> None:
         """Callback appele quand l'etat partage change (depuis le systray ou ailleurs).