Put a change behind a feature flag

Help me put a change behind a feature flag.
Inputs: change; flag system.

1. Define safe defaults and failure behavior.
2. distinguish release toggles, experiments and authorization.
3. plan staged rollout, monitoring, withdrawal and cleanup.

Deliver: Flag, Changes, Tests, Rollout and kill switch, Cleanup ticket.
Clarify critical gaps, separate facts from assumptions, and do not invent data, citations or completed actions.

My material: [fill in here]

Before you start

Provide change; flag system.