claude-sonnet-4-0 — pricing, context window and limits

Deprecated, with no retirement date announced yet

This model is marked deprecated, and unlike some other deprecated ids in this lineup, no retirement date has been published for it at all. That's worth treating as an active migration target regardless — see the model is deprecated but has no retirement date yet for why "no date yet" is not the same thing as "safe to keep building against long-term."

No effort parameter on this generation

Like the other models from this era of the lineup, this one has no effort parameter — thinking control here runs through the older budget-based mechanism, which doesn't carry forward directly onto its documented successor's effort-level system. See migrating off budget_tokens to the effort parameter for how to approach that specific transition.

What to actually do about it

Migrate to Sonnet 5 rather than waiting for a retirement date to force the issue — the runway between an eventual announcement and actual cutover is not guaranteed to be generous, and starting the migration now avoids being caught by a compressed timeline later.

Auditing where this id might still be hiding

A model this far back in the lineup is more likely to be buried in an older integration nobody's touched recently than in active, closely-watched code — worth an explicit audit across your codebase for this specific id rather than assuming it would have surfaced on its own by now if it were still in use somewhere.

Related

See claude-sonnet-5 for the documented successor's full specification.