“Leaking Muse’s Charter, Meta’s model spec” by vigji

LessWrong (30+ Karma) · Oct 29, 2026 · 13m

TL;DR: Meta's open-weights model Muse Spark Open often mentions a "Charter" in its chain of thought. By eliciting it piece by piece, I reconstructed a large part of that document from the CoT. You can explore the reconstruction here, with passages linked to the transcripts that produced them.

Note: everything below is reconstructed from model outputs, not from a leaked document, and relatively unpolished. Take it with a grain of salt.

Thanks to James Hindmarch for his comments on an earlier draft of this post.

While interacting with the recently released Muse Spark Open, I noticed frequent…