Anthropic employees Sholto Douglas & Trenton Bricken did an interview recently with Dwarkesh Patel, pieces here and there was about the circuit tracing insights.
https://www.dwarkesh.com/p/sholto-trenton-2 -- search the transcript for "circuit" for the quick bits.
Eg, "If you look at the circuit, you can see that it's not actually doing any of the math, it's paying attention to that you think the answer's four and then it's reasoning backwards about how it can manipulate the intermediate computation to give you an answer of four."
I was not aware that was a thing and useful to know. Thanks!