BUILD_OK
buffer_size=100 words, ptr=90, length-at-ptr=50
SHIPPED: OOB READ — first out-of-bounds word index = 100 (buffer holds 0..99); reads run to buffer[90+50]=buffer[140]
FIXED:   rejected (ERR_PARAM) — OOB prevented
OFF-BY-ONE (buffer_size == ptr == 90): SHIPPED ACCEPTS and reads buffer[90] (reads length at buffer[90] — one word past end)
OFF-BY-ONE: FIXED rejects
rc=0