The model ID you're calling has been retired

The error

A request that has worked for months suddenly starts failing with no code change on your end at all — the model id it targets has been retired, and the API stops accepting it past that date. This is one of the few errors on this list that isn't caused by anything in your request; it's caused by time passing.

Why this catches teams by surprise

Retirements are announced ahead of time, with a notice period Anthropic commits to for publicly released models, but an announcement is easy to lose track of by the time the date arrives — especially for a model that was working fine and never prompted anyone to look for news. Code that pins a model id directly, rather than routing through configuration someone actively maintains, has no way to notice a retirement coming. It keeps working until the date passes, and then it doesn't.

What "retired" means, and where it doesn't apply

Deprecation is the warning period; retirement is the id no longer answering. Anthropic's model-deprecations page records each retirement as executed, so check it rather than your own last observation — this site's lifecycle table mirrors it with the dates.

One nuance catches people: those dates apply where Anthropic runs the service itself — its API, Claude Platform on AWS and Microsoft Foundry. The partner clouds, Amazon Bedrock and Google Cloud, retire models on their own timetables, so a model gone from the Claude API can still be listed on either. A request that still succeeds through a partner cloud is not evidence the id is alive on the first-party API, and it is not a schedule you control.

The fix

Migrate to the current model in the same tier. Every retired model on this site names its successor on its own reference page, and the move is rarely a drop-in replacement given how much shifts between generations on pricing, cache minimums, thinking defaults and effort support. Treat it as a real migration rather than a one-line id swap: see what actually changed from Opus 4.6 to Opus 5 and from Opus 5 to Opus 5.5 for the kind of change that hides underneath an id swap.