fix ACP mcpServers payload (#1735)

* fix ACP mcpServers payload

* Handle invalid ACP MCP config

backend/packages/harness/deerflow/tools/builtins/invoke_acp_agent_tool.py

@@ -57,6 +57,42 @@ def _build_mcp_servers() -> dict[str, dict[str, Any]]:
     return build_servers_config(ExtensionsConfig.from_file())
 
 
+def _build_acp_mcp_servers() -> list[dict[str, Any]]:
+    """Build ACP ``mcpServers`` payload for ``new_session``.
+
+    The ACP client expects a list of server objects, while DeerFlow's MCP helper
+    returns a name -> config mapping for the LangChain MCP adapter. This helper
+    converts the enabled servers into the ACP wire format.
+    """
+    from deerflow.config.extensions_config import ExtensionsConfig
+
+    extensions_config = ExtensionsConfig.from_file()
+    enabled_servers = extensions_config.get_enabled_mcp_servers()
+
+    mcp_servers: list[dict[str, Any]] = []
+    for name, server_config in enabled_servers.items():
+        transport_type = server_config.type or "stdio"
+        payload: dict[str, Any] = {"name": name, "type": transport_type}
+
+        if transport_type == "stdio":
+            if not server_config.command:
+                raise ValueError(f"MCP server '{name}' with stdio transport requires 'command' field")
+            payload["command"] = server_config.command
+            payload["args"] = server_config.args
+            payload["env"] = [{"name": key, "value": value} for key, value in server_config.env.items()]
+        elif transport_type in ("http", "sse"):
+            if not server_config.url:
+                raise ValueError(f"MCP server '{name}' with {transport_type} transport requires 'url' field")
+            payload["url"] = server_config.url
+            payload["headers"] = [{"name": key, "value": value} for key, value in server_config.headers.items()]
+        else:
+            raise ValueError(f"MCP server '{name}' has unsupported transport type: {transport_type}")
+
+        mcp_servers.append(payload)
+
+    return mcp_servers
+
+
 def _build_permission_response(options: list[Any], *, auto_approve: bool) -> Any:
     """Build an ACP permission response.
 
@@ -173,7 +209,15 @@ def build_invoke_acp_agent_tool(agents: dict) -> BaseTool:
         cmd = agent_config.command
         args = agent_config.args or []
         physical_cwd = _get_work_dir(thread_id)
-        mcp_servers = _build_mcp_servers()
+        try:
+            mcp_servers = _build_acp_mcp_servers()
+        except ValueError as exc:
+            logger.warning(
+                "Invalid MCP server configuration for ACP agent '%s'; continuing without MCP servers: %s",
+                agent,
+                exc,
+            )
+            mcp_servers = []
         agent_env: dict[str, str] | None = None
         if agent_config.env:
             agent_env = {k: (os.environ.get(v[1:], "") if v.startswith("$") else v) for k, v in agent_config.env.items()}