A link to the web map saved before it went flat now opens correctly. It used to open a three-dimensional view that had already been switched off - with nothing drawn in it and no button to leave it.
The ground around spawn is made out to 2500 blocks in every direction, so the map is filled in and walking somewhere new no longer waits for the world to be built.
Nothing is added to your game, and your client connects exactly as it did.
The full list of changes
01A view lives in the link
The web map stopped drawing in three dimensions, which took most of its size on disk with it. Switching the two three-dimensional views off removed their buttons from the interface - but the view itself is written into the address, and the map's own reader falls back to the three-dimensional one for anything it does not recognise.
So a link saved or sent before that change went on opening a view that no longer existed: nothing drawn in it, and no control left to leave it. It was not a cookie and it would not have healed by itself - the same link would have done the same thing to whoever it was sent to, for ever.
The map now reads which views the server actually offers and corrects the address in place, keeping the spot you were looking at.
02A setting the server used to erase
Which dimensions the web map draws is written in a file beside the world. The mod rewrites that file whenever it reads it, on purpose, so that a setting added later can be found there rather than guessed at - and a key the mod did not know about was dropped on the way through.
So switching the Nether off the map held only until the next restart. Nothing failed and nothing was written to a log; the map would simply have come back. The mod carries the key now, and a check refuses to let the two halves drift apart again.
03Ground made ahead of arrival
Ninety-nine thousand chunks around spawn, out to 2500 blocks. It changes nothing about the world itself - the same ground, generated the same way, at a different hour.
Making it is the one job that has actually brought this server down, by filling memory faster than chunks could be written back out. It now works in short stretches and rests between them, which keeps memory clear and saves its place as it goes - so an interruption costs minutes rather than the whole run.