The Robustness Principal and internal APIs
I wrote (the first version of) the LambdaMOO FileIO patch a long time ago, but I didn’t use it for very long and haven’t been the maintainer for a long time.
The link I had to the current version is dead.
toaststunt is a LambdaMOO fork which includes what appears to bea modern version of FileIO. I have not used it.