fix(ai): entetes navigateur pour le repli web_search (Bing/DDG, BUG-051)

backend/tools/web.py

@@ -54,6 +54,18 @@ BROWSER_UA = (
     "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 "
     "(KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
 )
+# A minimal UA is not enough: Bing serves decoy SERPs (unrelated results) to
+# requests missing the usual browser navigation headers.
+BROWSER_HEADERS = {
+    "User-Agent": BROWSER_UA,
+    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8",
+    "Accept-Language": "fr-CA,fr;q=0.9,en-US;q=0.8,en;q=0.7",
+    "Sec-Fetch-Dest": "document",
+    "Sec-Fetch-Mode": "navigate",
+    "Sec-Fetch-Site": "none",
+    "Sec-Fetch-User": "?1",
+    "Upgrade-Insecure-Requests": "1",
+}
 MAX_FETCH_BYTES = 1_500_000
 MAX_TEXT_CHARS = 20_000
 
@@ -209,7 +221,7 @@ def _search_duckduckgo(
     resp = httpx.get(
         "https://html.duckduckgo.com/html/",
         params={"q": query, **({"kl": params.language} if params.language else {})},
-        headers={"User-Agent": BROWSER_UA, "Accept": "text/html,application/xhtml+xml"},
+        headers=BROWSER_HEADERS,
         timeout=WEB_TIMEOUT,
         follow_redirects=False,
     )
@@ -251,7 +263,7 @@ def _search_bing(
     resp = httpx.get(
         "https://www.bing.com/search",
         params={"q": query, **({"setlang": params.language} if params.language else {})},
-        headers={"User-Agent": BROWSER_UA, "Accept": "text/html,application/xhtml+xml"},
+        headers=BROWSER_HEADERS,
         timeout=WEB_TIMEOUT,
         follow_redirects=False,
     )