/rename label silently reverts/disappears mid-session

Environment

• Claude Code (CLI), macOS 25.4.0
• Model: claude-opus-4-7

What happened
Ran /rename INF-1083 Unify - Postman to label the session. Label applied initially. Later in the same session (no /clear, no restart), the label silently reverted/disappeared — the sidebar shows only what looks like a stale breadcrumb ("← for agents") instead of the rename. Re-running /rename with the same args reproduced the disappearance.

Expected
A label set via /rename should persist for the lifetime of the session unless explicitly cleared (/clear is documented to reset it; nothing else should).

Actual
Label vanishes mid-session without user action.

Repro

1. Start a fresh session
2. /rename <some label>
3. Continue working — at some point the label is gone