diff --git a/backend/main.py b/backend/main.py
index ee507f0..4940397 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -1036,7 +1036,7 @@ def _normalize_mcp_servers(raw: Any) -> Dict[str, Dict[str, Any]]:
     rows: Dict[str, Dict[str, Any]] = {}
     for server_name, server_cfg in raw.items():
         name = str(server_name or "").strip()
-        if not name or not _MCP_SERVER_NAME_RE.match(name):
+        if not name or not _MCP_SERVER_NAME_RE.fullmatch(name):
             continue
         if not isinstance(server_cfg, dict):
             continue
@@ -1074,6 +1074,44 @@ def _normalize_mcp_servers(raw: Any) -> Dict[str, Dict[str, Any]]:
     return rows
 
 
+def _merge_mcp_servers_preserving_extras(
+    current_raw: Any,
+    normalized: Dict[str, Dict[str, Any]],
+) -> Dict[str, Dict[str, Any]]:
+    """Preserve unknown per-server fields already present in config.json.
+
+    Dashboard only edits a subset of MCP fields (type/url/headers/toolTimeout).
+    Some MCP providers may rely on additional keys; dropping them can break startup.
+    """
+    current_map = current_raw if isinstance(current_raw, dict) else {}
+    merged: Dict[str, Dict[str, Any]] = {}
+    for name, normalized_cfg in normalized.items():
+        base = current_map.get(name)
+        base_cfg = dict(base) if isinstance(base, dict) else {}
+        next_cfg = dict(base_cfg)
+        next_cfg.update(normalized_cfg)
+        merged[name] = next_cfg
+    return merged
+
+
+def _sanitize_mcp_servers_in_config_data(config_data: Dict[str, Any]) -> Dict[str, Dict[str, Any]]:
+    """Normalize tools.mcpServers and drop hidden invalid entries safely.
+
+    Returns the sanitized mcpServers map written into config_data["tools"]["mcpServers"].
+    """
+    if not isinstance(config_data, dict):
+        return {}
+    tools_cfg = config_data.get("tools")
+    if not isinstance(tools_cfg, dict):
+        tools_cfg = {}
+    current_raw = tools_cfg.get("mcpServers")
+    normalized = _normalize_mcp_servers(current_raw)
+    merged = _merge_mcp_servers_preserving_extras(current_raw, normalized)
+    tools_cfg["mcpServers"] = merged
+    config_data["tools"] = tools_cfg
+    return merged
+
+
 def _probe_mcp_server(cfg: Dict[str, Any], bot_id: Optional[str] = None) -> Dict[str, Any]:
     transport_type = str(cfg.get("type") or "streamableHttp").strip()
     if transport_type not in {"streamableHttp", "sse"}:
@@ -1397,7 +1435,9 @@ def _probe_mcp_server_for_start(cfg: Dict[str, Any], image_tag: str) -> Dict[str
 
 def _preflight_mcp_servers_for_start(bot_id: str, image_tag: str) -> List[str]:
     config_data = _read_bot_config(bot_id)
-    tools_cfg = config_data.get("tools") if isinstance(config_data, dict) else {}
+    if not isinstance(config_data, dict):
+        return []
+    tools_cfg = config_data.get("tools")
     if not isinstance(tools_cfg, dict):
         return []
     mcp_servers = _normalize_mcp_servers(tools_cfg.get("mcpServers"))
@@ -2401,6 +2441,16 @@ async def start_bot(bot_id: str, session: Session = Depends(get_session)):
     if not bot:
         raise HTTPException(status_code=404, detail="Bot not found")
     _sync_workspace_channels(session, bot_id)
+    mcp_preflight_failures = _preflight_mcp_servers_for_start(bot_id, image_tag=bot.image_tag)
+    if mcp_preflight_failures:
+        bot.docker_status = "STOPPED"
+        session.add(bot)
+        session.commit()
+        _invalidate_bot_detail_cache(bot_id)
+        raise HTTPException(
+            status_code=400,
+            detail="MCP precheck failed: " + " | ".join(mcp_preflight_failures[:5]),
+        )
 
     runtime_snapshot = _read_bot_runtime_snapshot(bot)
     env_params = _read_env_store(bot_id)
@@ -2566,15 +2616,18 @@ def update_bot_mcp_config(bot_id: str, payload: BotMcpConfigUpdateRequest, sessi
     tools_cfg = config_data.get("tools")
     if not isinstance(tools_cfg, dict):
         tools_cfg = {}
-    mcp_servers = _normalize_mcp_servers(payload.mcp_servers or {})
-    tools_cfg["mcpServers"] = mcp_servers
+    normalized_mcp_servers = _normalize_mcp_servers(payload.mcp_servers or {})
+    current_mcp_servers = tools_cfg.get("mcpServers")
+    merged_mcp_servers = _merge_mcp_servers_preserving_extras(current_mcp_servers, normalized_mcp_servers)
+    tools_cfg["mcpServers"] = merged_mcp_servers
     config_data["tools"] = tools_cfg
+    sanitized_after_save = _sanitize_mcp_servers_in_config_data(config_data)
     _write_bot_config(bot_id, config_data)
     _invalidate_bot_detail_cache(bot_id)
     return {
         "status": "updated",
         "bot_id": bot_id,
-        "mcp_servers": mcp_servers,
+        "mcp_servers": _normalize_mcp_servers(sanitized_after_save),
         "locked_servers": [],
         "restart_required": True,
     }