OAuth token response validation is too strict

[aritma-hengro]

I've got a MCP server that is protected using EntraID. I have set up a client id and secret in the OAuth section of the mcp server registration. All seems to work until token response is returned to LibreChat.

I get the following error in the log:

2025-10-03 11:05:35 error: [MCPOAuth] Failed to complete OAuth flow
2025-10-03 11:05:35 error: [MCP OAuth] OAuth callback error [
  {
    "code": "invalid_type",
    "expected": "number",
    "received": "string",
    "path": [
      "expires_in"
    ],
    "message": "Expected number, received string"
  }
]
2025-10-03 11:05:36 error: Error in OAuth authentication: Unknown error`

I've done some digging and the token response does indeed set the "expires_in" as a string, since this is Microsoft I will not presume to suggest that they are not following the oauth standard so that leads me to think that LibreChat is a tad too strict on the format of the token response.

Here is an abbreviated example of a token response from Entra ID:

{
  "token_type":"Bearer",
  "scope":"manage",
  "expires_in":"5250",
  "ext_expires_in":"5250",
  "expires_on":"1759495112",
  "not_before":"1759489561",
  "resource":"api://some-test-mcp-server",
  "access_token":"eyJ0e.....Y2WwQ"
}