Connect (UCI) engine(s) with GUI over network

[hgm]

Even if one would compress positions using FEN from last irreversible move - that's still not enough and UCI still has to send all the moves since that position.

This is actually what the UCCI protocol prescribes. Bad consequence is that most engine authors do not reserve space for more than 100 ply in their input buffer, so that the engines crash if you play them under a draw rule like 30-moves-not-counting-checks-and-evasions, which could prolong the game beyond 50 irreversible moves.

[mar]

This is actually what the UCCI protocol prescribes. Bad consequence is that most engine authors do not reserve space for more than 100 ply in their input buffer, so that the engines crash if you play them under a draw rule like 30-moves-not-counting-checks-and-evasions, which could prolong the game beyond 50 irreversible moves.

Arena obviously doesn't do that. It sends position startpos and all the moves over and over again.
As for input buffer, I thought everyone clears it anyaway whenever the engine encounters an irreversible move.

[hgm]

I could imagine that some engines just read and buffer the entire input line before they even start parsing to discover that it is a position/move command.

In UCI it is indeed not usual to attempt shortening the line by using FENs; Polyglot and UCI2WB don't do that either.