0RB1LB_1LA1RB
0RB1LB_1LA1RB (bbch) is the Beeping Booping Busy Beaver champion for BBBB(2), pseudoquasihalting after 18 steps. It was discovered and reported by Charlie Reams in October 2026, correcting an off-by-1 error in previous work.[1] This is proven to be the champion for this state and symbol count.[2]
With boop transition A1 and beep transition A0, the machine boops at steps 6, 13, 18, ...; the first interval contains a single beep (therefore emitting a 1), and all later intervals contain no beeps (therefore emitting 0 infinitely thereafter). So, in the BBBB interpretation, it outputs an infinite stream of zeroes beyond this point and the first zero is emitted at transition 18, so BBBB(M) = 18.