>When questioned later, Claude honestly admits to having forgotten the peanut rule.

Claude doesn't "admit" anything.

It got a new prompt (the question "why did you do that? didn't you know the peanut rule?" etc) and churned out some more generated text that fits well with it and looks like an admission/apology.

Reading a truncated version of the file is a red herring. Claude could just as well have included peanuts after reading the whole file too. Just less likely.

>Why did Claude deceive me? Because it was acting in a very humanlike manner.

More likely because it was acting in a very "machine that reads text input and does a inference and spits out some response, with an RNG thrown in the mix, that statistically fits the prompt" way.