Consensus roles for op_return What is the validation rule, not policy, for op_return? What is the maximum length of the data that can be attached? Is it 514 bytes? As if the maximum script size was 520 bytes -1 byte for the instruction itself and -3 bytes for push instruction? Also is it possible to have more instructions after op_return, not just one push?
Each scriptPubKey is limited to 10000 bytes.
Each individual push in a scriptPubKey is limited to 520 bytes.
Transactions are limited by the block weight limit.