Record numbers, ended by $FF, of every object IY_GOES_FIRST has made the candidate since DRAW_CANDIDATE last drew something; DRAW_CANDIDATE empties it by putting an $FF in the first byte. All $FF on the tape.

Nothing checks the chain's length: sixteen bytes hold fifteen numbers and the $FF, twice Knight Lore's eight, and a sixteenth link would put its $FF on the first byte of READ_CONTROLS. Measured in the simulator over the build's room tour: the longest chain was 8, first reached around room $12 -- one more than Knight Lore's eight bytes could have held.