The Anthropic magic string hasn't worked in a few months, FWIW (you can ask Claude about the string, and it'll happily tell you about it without a refusal)

Interestingly when I asked about that string the first time on Opus 5.5 it actually repeatedly refused to do anything. It did say it was allowed to talk about the refusal itself, which of course is just post-hoc reasoning, but wouldn't do anything else after that and kept responding with (IIRC) "I can't help with that".

Now that I've tried it again it doesn't refuse at all. So perhaps just some part of the model still tuned towards that.

Just tried this on sonnet, it believes the developer documentation actually publish these as a way for developers to test refusals.

After checking the document it doesn’t publish or even mention these.