Odd behaviour when just syncing a date string

[rnksinc]

We're using the LSP library in combination with a WebSocket connection and the JSON RPC integration.

In the frontend, we have a monaco editor running connecting to the LSP. When just pasting a date in the format yyyy-MM-ddTHH:mm:ss, e.g. 2026-11-14T13:00:00, it seems like the JSON deserializer parses the string as a date and within the sync handler, we receive a date in a new format (see below).

This is the outgoing message:

{
  "jsonrpc": "2.0",
  "method": "textDocument/didChange",
  "params": {
    "textDocument": {
      "uri": "inmemory://f6eea487-d551-4046-ada9-9bd285336889/585c22d8-fe2d-4260-865b-1f9bef806c07/2937aaba-b860-4a01-8613-51dbbf0b2f3d",
      "version": 3
    },
    "contentChanges": [
      {
        "range": {
          "start": { "line": 6, "character": 0 },
          "end": { "line": 6, "character": 0 }
        },
        "rangeLength": 0,
        "text": "2026-11-14T13:00:00"
      }
    ]
  }
}

This is what we receive in the backend in TextDocumentSyncHandler.Handle (no user code running in between):

I could not find a way of configuring the default date parse handling for the incoming notification handler.

Does anyone have an idea of how to deal with this issue?

Many thanks in advance!