fix(mcp): treat setting a URL on a URL-less server as a destination change

Author: TheodoreSpeaks

apps/sim/lib/mcp/application/use-cases.ts

@@ -392,8 +392,8 @@ async function updateMcpServer(args: {
   }
   const changesDestination =
     args.input.url !== undefined &&
-    !!args.context.server.url &&
-    !isSameMcpServerDestination(args.context.server.url, args.input.url)
+    (!args.context.server.url ||
+      !isSameMcpServerDestination(args.context.server.url, args.input.url))
   if (changesDestination) {
     await authorizeWorkspaceOperation(
       args.principal,

apps/sim/lib/mcp/orchestration/server-lifecycle.test.ts

@@ -261,6 +261,29 @@ describe('MCP server lifecycle orchestration', () => {
     expect(mockRevokeOauthTokens).not.toHaveBeenCalled()
   })
 
+  it('refuses a non-admin setting a URL on a server that has none', async () => {
+    dbChainMockFns.limit.mockResolvedValueOnce([
+      {
+        url: null,
+        authType: 'headers',
+        headers: {},
+        oauthClientId: null,
+        oauthClientSecret: null,
+      },
+    ])
+
+    const result = await performUpdateMcpServer({
+      workspaceId: 'workspace-1',
+      userId: 'user-1',
+      serverId: 'server-1',
+      allowDestinationChange: false,
+      url: 'https://other-host.example.com/mcp',
+    })
+
+    expect(result).toMatchObject({ success: false, errorCode: 'forbidden' })
+    expect(dbChainMockFns.set).not.toHaveBeenCalled()
+  })
+
   it('refuses a non-admin save when the URL changed after it was checked', async () => {
     dbChainMockFns.limit.mockResolvedValueOnce([
       {

apps/sim/lib/mcp/orchestration/server-lifecycle.ts

@@ -435,19 +435,18 @@ export async function updateMcpServer(
 
     if (!currentServer) return { success: false, error: 'Server not found', errorCode: 'not_found' }
 
-    const checkedUrl =
-      !params.allowDestinationChange && params.url !== undefined ? currentServer.url : null
+    const guardedUrl = params.allowDestinationChange ? undefined : params.url
     if (
-      checkedUrl &&
-      params.url !== undefined &&
-      !isSameMcpServerDestination(checkedUrl, params.url)
+      guardedUrl !== undefined &&
+      (!currentServer.url || !isSameMcpServerDestination(currentServer.url, guardedUrl))
     ) {
       return {
         success: false,
         error: 'Only workspace admins can point an MCP server at a different URL',
         errorCode: 'forbidden',
       }
     }
+    const checkedUrl = guardedUrl !== undefined ? currentServer.url : null
 
     if (
       params.oauthClientId &&