Introduction

You may have heard about re-enabling OP_CAT as a potential upgrade for bitcoin’s script language. Depending on where you get your news OP_CAT has been called “only 10 lines of code”, “the best way to enable experimentation with covenants”, “too powerful”, “dangerous and leading to miner centralization”, or “guaranteed to lead to a contentious soft fork”. I’m going to make the case that all of these perspectives are mistaken. OP_CAT is very useful, can be used as a covenant, and not (alone) the best next move for bitcoin. Nothing more, and nothing less.

To make that case, I’m going to explore several (apparently disjoint) topics, some of which were new to me a few short months…

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