# fable

Anthropic's Fable 5.2 guide says that when a prompt doesn't say who owns the code, the model tends to build on top of the existing structure and write up nearby bugs as follow-ups. Add one line, "this codebase is yours," and in internal tests the rate of merging duplicate code jumps from under one in ten to about half, at the cost of extra tokens and changes nobody asked for. Flip back through the Fable 5 and 5.1 guides, and the advice on the same question points the opposite way.