Desktop Code tab: Claude spawns cascades of sessions nobody asked for (46 in one day, 25 started by other sessions)

After a recent Claude Code desktop update, the model proposes and starts a new session for every follow-up it notices (start_session own_initiative, hand_off_to_session). Each session it starts gets the same instructions and starts sessions of its own.

One working day (2026-10-15), one repo: 46 sessions with activity, 25 started by another session, chains up to 4 levels deep (a spreadsheet request → diagnosis → fix → fix → fix). At 23:30 a 4th-level session was still opening a new workstream nobody requested.

Impact: I lose track of what is being changed, where and why; worktrees and branches multiply; tokens go to unrequested work; reviewing what is safe to ship becomes a job of its own.

Expected:

• never start or propose a session unless the user explicitly asks;
• a follow-up is a line in the reply, not a card or a running session;
• sessions started by sessions never start more;
• a setting to turn this off. There is no such setting today.

Environment: Claude desktop app, Windows 11, Code tab, Opus 5.5.