Legacy period: the window between warning and removal
A legacy period is a named window between a warning and a removal: existing customers keep using a model, new ones cannot adopt it, and a date is set for the end. One platform in this register publishes one, in months or in days depending on the model, on the model card itself. As of 2026-09-22.
| What the window provides | Where it can fail a production |
|---|---|
| A stated length, before anything is scheduled | Length can vary per model with no rule published |
| Continued access for existing customers | Access can end after a stated period of disuse |
| A date for the end | Removal is then global, with no fallback region |
| A middle condition, rather than on or off | New adoption stops immediately, so tests get harder |
Inclusion rule. Read from the lifecycle documentation of the one platform in this register that publishes such a window. Order. What the window provides first, then its sharp edges.
1A middle condition is what makes a removal plannable
Available and gone are the only two conditions a model has from outside unless somebody names a third. A legacy window is that third, and everything a production can usefully do happens inside it.
It also concentrates the sharp clauses. The one window published in this register contains a sentence allowing access to end after a fortnight of disuse, which is shorter than the window by an order of magnitude.
2Closing the door to new adoption has a cost
Once a model is in a legacy window, a team cannot start using it, which sounds obviously right and complicates testing. A production comparing the legacy model against its successor may find it cannot set up a clean comparison.
So the window is most useful to teams already on the model and least useful to teams deciding whether to move. That asymmetry is worth knowing before a window opens.
3A length with no rule behind it
Where the published figure is six months for some models and forty-five days for others, with the choice made on the model card, a reader cannot compute their runway from the policy alone.
The policy is then a promise to state a figure rather than a promise about its size. Both readings are honest and only the second one lets a production plan before choosing a model.
A definition rather than a dated entry: no line above is a vendor statement. Where this word turns up in a real notice, the wording and the date are on the inactivity clause reading. Nearby terms: Sunset, Advance notice, General availability.