Keep the old key one season more. The lock is known; the faults have names. Then someone else removes the door and sends the date the house must change.
The institution in the constructed appeal kept its March model in production because replacing it would take work. Its retirement notice turns that delay into a deadline before the October review.
Model migration is described as a switch because the visible change can fit in one line of configuration. The institution experiences a project: prompts and guardrails need retesting, evaluation sets need rerunning, and reviewers have to learn a new pattern of errors. Documentation and training must catch up with the system already answering requests.
The rational delay
Staying pinned can be a reasonable local decision. The present system has known faults, and the people around it have built compensating habits. A successor promises better benchmark results while carrying unfamiliar failure modes. Every month of delay avoids immediate migration cost.
The accumulated choice produces dependence. Documentation drifts toward what experienced operators remember. Exceptions settle into prompts. Tests preserve the cases that once caused trouble and miss the ones the old model handled naturally. The method becomes fitted to a service the institution does not control.
A retirement date converts that dependence into an eviction. Work that never won internal priority now has to fit the supplier's notice window.
Sixty days
Anthropic promises at least 60 days' notice for retirement of publicly released models. Its deprecation history shows what that floor means in practice. Claude Opus 4.1 received notice on 5 June 2026 and retired on 5 August. Claude Opus 4 and Sonnet 4 were marked for retirement on 14 April and stopped accepting requests on 15 June.
Within such a window, a team has to recover the accumulated method, test a successor, run both systems where possible, train reviewers, and decide what happens to pending cases. The October appeal exposes the sequence: the institution postponed migration while it still had a choice, then inherited the supplier's timetable when the choice expired.
Procurement therefore needs a migration account before choosing a model. It should price evaluation and retraining alongside the parallel run and preservation of past determinations. The invoice for inference captures only a fraction of succession cost.
A clause for leaving
The contract should answer four questions before the first request is sent. How much notice accompanies retirement? Which version remains available during parallel testing? What configuration and usage records can the institution export? Who pays for re-validation when the supplier initiates the move?
These terms do not eliminate migration. They make its cost visible at the moment dependence is chosen.
The pinned system follows a calendar its institution does not own.
Companions
- The configured method under appeal: Validated Against a System That Is Gone.
- The supplier calendar: Anthropic model deprecations.
- The earlier regression finding: The Regression Was Made of Improvements.
These notes come out of Sociable Systems, a practice that reads AI-shaped documents the way a hostile reviewer will, before a lender or a court finds the gap. The argument has an operational form: the Interim Protocol sets out four rules for AI use in environmental and social deliverables, covering disclosure at touch-point grain, evidence custody, the phrases no automated screening may settle, and a hostile read before anything ships. Free, and written to be cited or retired once institutional guidance arrives.