The model is deprecated but has no retirement date yet

What you're actually looking at

A model id is marked deprecated, still works, and carries no published retirement date — which puts it in a genuinely different state from a model that's deprecated with a known cutover date already on the calendar. Requests against it succeed today. That's not the same as a guarantee about tomorrow, and treating "no date announced yet" as "no date coming" is the mistake this page exists to head off.

Why "no date yet" isn't the same as "safe long-term"

Deprecation without an announced retirement date usually means exactly what it says: the retirement is coming, and the specific date hasn't been set or published yet, not that this model is exempt from the retirement process other deprecated ids have already gone through. Once a retirement date is announced for a model in this state, the runway between announcement and actual cutover is not necessarily long — it's the same clock every other deprecated model has run on, just one that hasn't started counting down publicly yet.

Why this is worse to build against than an already-scheduled retirement

A model with a known retirement date at least gives you a concrete deadline to plan a migration around. A model deprecated with no date at all gives you no deadline, which paradoxically makes it easier to deprioritise — there's no ticking clock forcing the migration onto a roadmap, right up until a date does get announced and the runway is suddenly much shorter than anyone planned for.

What happened the last time a model sat in this state

This page was first written about Opus 4 and Sonnet 4, both deprecated with no date announced. Both now have one — in the past. Anthropic set their retirement date, the notice period ran, and requests to both ids on the Claude API now fail; the lifecycle table records the deprecation and retirement dates side by side. The "no date yet" state lasted exactly until it didn't, which is the whole argument of this page made concrete.

Today the deprecated-without-a-date row belongs to Mythos Preview, and every active model now carries a published "not sooner than" floor — the earliest date it can retire. Those floors make planning easier than it used to be; they do not make a deprecated id safer to keep.

The fix

Treat any deprecated model id — dated or not — as something you're actively migrating off, not something you're monitoring for a date to appear. Start the move to its current-generation successor now rather than waiting for an announcement that only shortens your available runway once it lands. Check using a retired model id for what actually happens once that date does arrive and passes, and pick the target model from the reference index rather than guessing at a successor.