Encrypted reasoning traces are portable plaintext you're publishing.

arXiv 2608.09867 finds encrypted chain-of-thought blocks move across sessions, users, and models, and carried recoverable PII and credentials into public repositories. Providers pushed reasoning state to the client to avoid storing it server-side, which quietly made it your liability. Treat any vendor-opaque blob in a transcript as secret material before you log, commit, or ship it to a trace store.