diff --git a/src/backend/base/langflow/api/v2/mcp.py b/src/backend/base/langflow/api/v2/mcp.py
index 2dc79af3e1..91ee1f892b 100644
--- a/src/backend/base/langflow/api/v2/mcp.py
+++ b/src/backend/base/langflow/api/v2/mcp.py
@@ -40,6 +40,46 @@ def is_mcp_servers_locked(settings: object) -> bool:
return getattr(settings, "mcp_servers_locked", False) is True
+def _enforce_immutable_server_name(server_name: str, server_config: dict) -> dict:
+ """Enforce that the server name is owned by the URL path, not the request body.
+
+ ``server_name`` is the immutable identifier for an MCP server: it is both the
+ storage key and the POST/PATCH URL path segment. Because :class:`MCPServerConfig`
+ permits extra fields (``extra="allow"``), a ``name`` in the request body would
+ otherwise be silently persisted as stray config data and — on PATCH — echoed back
+ in the 200 response, falsely implying that a rename succeeded.
+
+ A body ``name`` that disagrees with the URL is rejected with 422 so the constraint
+ is explicit. A redundant but matching ``name`` is dropped so it never pollutes the
+ stored config.
+
+ Args:
+ server_name: The server name from the URL path (the canonical identifier).
+ server_config: The request body dumped to a dict.
+
+ Returns:
+ A config dict with any ``name`` key removed.
+
+ Raises:
+ HTTPException: 422 when ``name`` is present and differs from ``server_name``.
+ """
+ if "name" not in server_config:
+ return server_config
+
+ body_name = server_config["name"]
+ if body_name != server_name:
+ raise HTTPException(
+ status_code=422,
+ detail=(
+ f"Server name is immutable and is determined by the URL path "
+ f"('{server_name}'); it cannot be set or changed via the request body "
+ f"(got '{body_name}'). To rename a server, delete it and create a new one."
+ ),
+ )
+ # Matching name is redundant — drop it so it isn't persisted as stray config.
+ return {key: value for key, value in server_config.items() if key != "name"}
+
+
async def upload_server_config(
server_config: dict,
current_user: CurrentActiveUser,
@@ -353,7 +393,7 @@ async def add_server(
return await update_server(
server_name,
- server_config.model_dump(exclude_unset=True),
+ _enforce_immutable_server_name(server_name, server_config.model_dump(exclude_unset=True)),
current_user,
session,
storage_service,
@@ -380,7 +420,7 @@ async def update_server_endpoint(
return await update_server(
server_name,
- server_config.model_dump(exclude_unset=True),
+ _enforce_immutable_server_name(server_name, server_config.model_dump(exclude_unset=True)),
current_user,
session,
storage_service,
diff --git a/src/backend/tests/unit/api/v2/test_mcp_servers_file.py b/src/backend/tests/unit/api/v2/test_mcp_servers_file.py
index 80fb98fef1..a95ea0bdeb 100644
--- a/src/backend/tests/unit/api/v2/test_mcp_servers_file.py
+++ b/src/backend/tests/unit/api/v2/test_mcp_servers_file.py
@@ -4,7 +4,7 @@ from types import SimpleNamespace
from typing import TYPE_CHECKING
import pytest
-from fastapi import UploadFile
+from fastapi import HTTPException, UploadFile
# Module under test
from langflow.api.v2.files import upload_user_file
@@ -239,3 +239,122 @@ async def test_concurrent_update_server_should_not_lose_servers(
assert "server_a" in config_state["mcpServers"], "server_a was lost due to concurrent update_server race condition"
assert "server_b" in config_state["mcpServers"], "server_b was lost due to concurrent update_server race condition"
assert "server_c" in config_state["mcpServers"], "server_c was lost due to concurrent update_server race condition"
+
+
+def test_enforce_immutable_server_name_rejects_mismatch():
+ """A body name that differs from the URL name is an explicit 422, not a silent no-op."""
+ from langflow.api.v2.mcp import _enforce_immutable_server_name
+
+ with pytest.raises(HTTPException) as exc_info:
+ _enforce_immutable_server_name("old-name", {"name": "new-name", "url": "http://localhost:9000"})
+
+ assert exc_info.value.status_code == 422
+ # The message names both the URL identifier and the rejected body value.
+ assert "old-name" in exc_info.value.detail
+ assert "new-name" in exc_info.value.detail
+
+
+def test_enforce_immutable_server_name_strips_matching_name():
+ """A redundant matching name is dropped so it never pollutes the stored config."""
+ from langflow.api.v2.mcp import _enforce_immutable_server_name
+
+ cleaned = _enforce_immutable_server_name("srv", {"name": "srv", "command": "npx", "args": ["-y", "x"]})
+
+ assert cleaned == {"command": "npx", "args": ["-y", "x"]}
+ assert "name" not in cleaned
+
+
+def test_enforce_immutable_server_name_passthrough_without_name():
+ """Configs without a name field are returned unchanged."""
+ from langflow.api.v2.mcp import _enforce_immutable_server_name
+
+ config = {"command": "npx", "args": ["-y", "x"]}
+
+ assert _enforce_immutable_server_name("srv", config) == config
+
+
+@pytest.mark.asyncio
+async def test_patch_server_rejects_name_change(session, storage_service, settings_service, current_user):
+ """PATCH with a body name different from the URL must 422 instead of silently no-op'ing.
+
+ Regression: MCPServerConfig allows extra fields, so a ``name`` in the PATCH body was
+ persisted as stray config and echoed in the 200 response, falsely implying a rename
+ succeeded while the server stayed keyed under the original (URL) name.
+ """
+ from unittest.mock import AsyncMock, patch
+
+ from langflow.api.v2.mcp import update_server_endpoint
+ from langflow.api.v2.schemas import MCPServerConfig
+
+ body = MCPServerConfig(name="new-name", url="http://localhost:9000")
+
+ with (
+ patch("langflow.api.v2.mcp.update_server", new=AsyncMock()) as mock_update,
+ pytest.raises(HTTPException) as exc_info,
+ ):
+ await update_server_endpoint(
+ server_name="old-name",
+ server_config=body,
+ current_user=current_user,
+ session=session,
+ storage_service=storage_service,
+ settings_service=settings_service,
+ )
+
+ assert exc_info.value.status_code == 422
+ mock_update.assert_not_called() # guard fires before any write/upsert
+
+
+@pytest.mark.asyncio
+async def test_patch_server_strips_matching_name_before_persist(
+ session, storage_service, settings_service, current_user
+):
+ """A PATCH body that echoes the URL name must not persist ``name`` as stray config."""
+ from unittest.mock import AsyncMock, patch
+
+ from langflow.api.v2.mcp import update_server_endpoint
+ from langflow.api.v2.schemas import MCPServerConfig
+
+ body = MCPServerConfig(name="srv", url="http://localhost:9000")
+
+ with patch("langflow.api.v2.mcp.update_server", new=AsyncMock(return_value={"ok": True})) as mock_update:
+ await update_server_endpoint(
+ server_name="srv",
+ server_config=body,
+ current_user=current_user,
+ session=session,
+ storage_service=storage_service,
+ settings_service=settings_service,
+ )
+
+ # update_server is called positionally as (server_name, server_config_dict, ...).
+ persisted_config = mock_update.call_args.args[1]
+ assert persisted_config == {"url": "http://localhost:9000"}
+ assert "name" not in persisted_config
+
+
+@pytest.mark.asyncio
+async def test_post_server_rejects_name_mismatch(session, storage_service, settings_service, current_user):
+ """POST with a body name different from the URL must 422 (same guard as PATCH)."""
+ from unittest.mock import AsyncMock, patch
+
+ from langflow.api.v2.mcp import add_server
+ from langflow.api.v2.schemas import MCPServerConfig
+
+ body = MCPServerConfig(name="different", url="http://localhost:9000")
+
+ with (
+ patch("langflow.api.v2.mcp.update_server", new=AsyncMock()) as mock_update,
+ pytest.raises(HTTPException) as exc_info,
+ ):
+ await add_server(
+ server_name="intended-name",
+ server_config=body,
+ current_user=current_user,
+ session=session,
+ storage_service=storage_service,
+ settings_service=settings_service,
+ )
+
+ assert exc_info.value.status_code == 422
+ mock_update.assert_not_called()
diff --git a/src/frontend/src/modals/addMcpServerModal/__tests__/addMcpServerModal.test.tsx b/src/frontend/src/modals/addMcpServerModal/__tests__/addMcpServerModal.test.tsx
index 2adb39ec28..f12f4d9083 100644
--- a/src/frontend/src/modals/addMcpServerModal/__tests__/addMcpServerModal.test.tsx
+++ b/src/frontend/src/modals/addMcpServerModal/__tests__/addMcpServerModal.test.tsx
@@ -5,6 +5,7 @@ import type { MCPServerType } from "@/types/mcp";
import AddMcpServerModal from "..";
const mockPatchMCPServer = jest.fn();
+const mockAddMCPServer = jest.fn();
const mockSetQueryData = jest.fn();
jest.mock("nanoid", () => ({
@@ -23,7 +24,7 @@ jest.mock("@tanstack/react-query", () => ({
jest.mock("@/controllers/API/queries/mcp/use-add-mcp-server", () => ({
useAddMCPServer: () => ({
- mutateAsync: jest.fn(),
+ mutateAsync: mockAddMCPServer,
isPending: false,
}),
}));
@@ -66,16 +67,19 @@ jest.mock("@/components/ui/input", () => ({
onChange,
"data-testid": dataTestId,
placeholder,
+ disabled,
}: {
value?: string;
onChange?: (event: { target: { value: string } }) => void;
"data-testid"?: string;
placeholder?: string;
+ disabled?: boolean;
}) => (
onChange?.({ target: { value: event.target.value } })
}
@@ -203,6 +207,7 @@ describe("AddMcpServerModal", () => {
beforeEach(() => {
jest.clearAllMocks();
mockPatchMCPServer.mockResolvedValue(undefined);
+ mockAddMCPServer.mockResolvedValue(undefined);
});
it("sends empty headers and env when deleting the last remaining HTTP entries", async () => {
@@ -233,4 +238,68 @@ describe("AddMcpServerModal", () => {
env: {},
});
});
+
+ it("locks the HTTP server name field when editing an existing server", () => {
+ const initialData: MCPServerType = {
+ name: "my-server",
+ url: "http://host/sse",
+ };
+
+ render(
+ ,
+ );
+
+ // The name is the server's immutable identifier, so it cannot be edited.
+ expect(screen.getByTestId("http-name-input")).toBeDisabled();
+ });
+
+ it("locks the STDIO server name field when editing an existing server", () => {
+ const initialData: MCPServerType = {
+ name: "my-server",
+ command: "uvx",
+ args: ["mcp-server"],
+ };
+
+ render(
+ ,
+ );
+
+ expect(screen.getByTestId("stdio-name-input")).toBeDisabled();
+ });
+
+ it("patches the original server name when editing, instead of creating a duplicate", async () => {
+ const user = userEvent.setup();
+ const initialData: MCPServerType = {
+ name: "my-server",
+ command: "uvx",
+ args: ["mcp-server"],
+ };
+
+ render(
+ ,
+ );
+
+ // The name field is locked, so the update targets the original record.
+ await user.click(screen.getByTestId("add-mcp-server-button"));
+
+ expect(mockPatchMCPServer).toHaveBeenCalledTimes(1);
+ expect(mockPatchMCPServer).toHaveBeenCalledWith(
+ expect.objectContaining({ name: "my-server" }),
+ );
+ // The create (add) flow must never fire during an edit — that is what
+ // produced the duplicate server.
+ expect(mockAddMCPServer).not.toHaveBeenCalled();
+ });
});
diff --git a/src/frontend/src/modals/addMcpServerModal/index.tsx b/src/frontend/src/modals/addMcpServerModal/index.tsx
index b7907c5e27..d19e8e689a 100644
--- a/src/frontend/src/modals/addMcpServerModal/index.tsx
+++ b/src/frontend/src/modals/addMcpServerModal/index.tsx
@@ -181,11 +181,18 @@ export default function AddMcpServerModal({
setError(t("mcp.modal.errorDuplicateEnvKeys"));
return;
}
- const name = parseString(stdioName, [
- "mcp_name_case",
- "no_blank",
- "lowercase",
- ]).slice(0, MAX_MCP_SERVER_NAME_LENGTH);
+ // The server name is the immutable identifier: it is the storage key and
+ // the URL path PATCH targets. When editing, always reuse the original
+ // name so the update hits the existing record. Re-deriving it from the
+ // input would let a name change retarget the request and create a
+ // duplicate server instead of updating the original.
+ const name = initialData
+ ? initialData.name
+ : parseString(stdioName, [
+ "mcp_name_case",
+ "no_blank",
+ "lowercase",
+ ]).slice(0, MAX_MCP_SERVER_NAME_LENGTH);
const argsPayload = buildArgsPayload(stdioArgs, initialData?.args);
const envPayload = buildKeyPairPayload(stdioEnv, initialData?.env);
try {
@@ -233,11 +240,18 @@ export default function AddMcpServerModal({
setError(t("mcp.modal.errorDuplicateHeaders"));
return;
}
- const name = parseString(httpName, [
- "mcp_name_case",
- "no_blank",
- "lowercase",
- ]).slice(0, MAX_MCP_SERVER_NAME_LENGTH);
+ // The server name is the immutable identifier: it is the storage key and
+ // the URL path PATCH targets. When editing, always reuse the original
+ // name so the update hits the existing record. Re-deriving it from the
+ // input would let a name change retarget the request and create a
+ // duplicate server instead of updating the original.
+ const name = initialData
+ ? initialData.name
+ : parseString(httpName, [
+ "mcp_name_case",
+ "no_blank",
+ "lowercase",
+ ]).slice(0, MAX_MCP_SERVER_NAME_LENGTH);
const envPayload = buildKeyPairPayload(httpEnv, initialData?.env);
const headersPayload = buildKeyPairPayload(
httpHeaders,
@@ -432,7 +446,7 @@ export default function AddMcpServerModal({
onChange={(e) => setStdioName(e.target.value)}
placeholder={t("mcp.modal.placeholderServerName")}
data-testid="stdio-name-input"
- disabled={isPending}
+ disabled={isPending || !!initialData}
/>