The /debug skill now explicitly supports enabling debug logging mid-session. When debug logging was off, invoking /debug turns it on and shows a message that nothing prior was captured. Users are instructed to reproduce the issue, then re-read the log.
Evidence
Debug logging toggle (search for "## Debug Logging Just Enabled")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
How sure we are
One source agreesOne thing we can check says the same as this entry.
Anthropic's release notes agreeUpdated /debug to toggle debug logging on mid-session, since debug logs are no longer written by default