diff --git a/backend/api/competitors.py b/backend/api/competitors.py
index 02504fd..2acb113 100644
--- a/backend/api/competitors.py
+++ b/backend/api/competitors.py
@@ -280,17 +280,18 @@ async def test_proxy_config(
     if not (proxy_util.is_enabled(cfg) and cfg['password']):
         raise HTTPException(status_code=400, detail="Proxy host, username and password must be saved first.")
 
-    proxy_url = proxy_util.httpx_proxy_url(cfg, proxy_util.new_session_id())
-
     import httpx
+    proxy = proxy_util.httpx_proxy(cfg, proxy_util.new_session_id())
+
     try:
-        async with httpx.AsyncClient(proxy=proxy_url, timeout=40.0) as client:
+        async with httpx.AsyncClient(proxy=proxy, timeout=40.0) as client:
             resp = await client.get("https://ipinfo.io/json")
             resp.raise_for_status()
             data = resp.json()
     except Exception as e:
-        logger.warning(f"Proxy test failed: {e}")
-        raise HTTPException(status_code=502, detail=f"Proxy test failed: {e}")
+        detail = repr(e) or str(e) or type(e).__name__
+        logger.warning(f"Proxy test failed: {detail}")
+        raise HTTPException(status_code=400, detail=f"Proxy test failed: {detail}")
 
     return {
         'ok': True,
diff --git a/backend/services/proxy.py b/backend/services/proxy.py
index b9313bc..336a71b 100644
--- a/backend/services/proxy.py
+++ b/backend/services/proxy.py
@@ -129,8 +129,9 @@ def httpx_proxy_url(cfg: dict, session_id: Optional[str] = None) -> Optional[str
     """Proxy URL for httpx.AsyncClient(proxy=...). None when disabled."""
     if not is_enabled(cfg):
         return None
+    from urllib.parse import quote
     user, pwd = _build_auth(cfg, session_id)
-    return f"http://{user}:{pwd}@{cfg['host']}:{cfg['port']}"
+    return f"http://{quote(user, safe='')}:{quote(pwd, safe='')}@{cfg['host']}:{cfg['port']}"
 
 
 def direct_httpx_proxy(db):