Opus 5.5 and Sonnet 5.5 retirement dates for saved Formats

Anthropic's model status table lists Claude Opus 5.5 as not retiring sooner than September 22, 2027, and Claude Sonnet 5.5 as not sooner than September 28, 2027. Neither is deprecated today. The date that is near is Claude Haiku 4.5, not sooner than October 15, 2026.

The dates are from Anthropic's Model deprecations page, read on 2026-10-02. It calls them tentative, and they apply to Anthropic-operated platforms.

Which Claude models have a date now?

Deprecated means still working but no longer recommended. Anthropic says it gives at least 60 days' notice before retiring a publicly released model, and that requests to a retired model fail.

What happens to a Sume Format that names a retired model?

The Formats API documents model as the Agents catalog id of the orchestrating LLM, and an id outside the catalog is 400 invalid_request. The repo's registry also keeps retired rows with a successor. Opus 5 and Sonnet 5 are retired rows that move onto Opus 5.5 and Sonnet 5.5, so a stored pick of the old id runs on the new one. The Formats API documents the same pattern for the retired gpt-5.6-sol, which runs on gpt-6-sol.

That is Sume's catalog behavior, and it is separate from Anthropic's date. Anthropic's date says when its own API stops serving an id. Sume's successor map says what Sume runs when your request names a retired row. Do not rely on a successor you have not seen in the receipt.

How do you keep a pinned model honest?

A silent move from one model to another is the failure to guard against, and a logged model per run is the cheapest guard.

• Read model on every receipt. The receipt carries the catalog id the orchestrator ran on, so a successor shows up there.
• Store that id next to the output when you save a result you may need to reproduce.
• Keep the model field out of your Format body if you do not need a pin, and the default runs.
• Watch cost, not just id: a successor with a different price changes usage.debited_usd_micros.

What should you do about Haiku 4.5?

Its tentative date is the nearest one, October 15, 2026, although Anthropic's table still shows it Active with no deprecation notice. The repo has a Haiku 4.5 row in the Agents catalog (routed through OpenRouter, so Anthropic's own API date may not be the one that applies) with no successor defined, so the docs and the code give no promise of where a pinned Haiku request would go if Anthropic retires it. If you pin Haiku 4.5 for cheap steps, pick a replacement now and test it, rather than waiting for a 400.

For Opus 5.5 and Sonnet 5.5 the practical answer is that nothing is due this year. Check Anthropic's page when you plan a quarter, and re-run an eval before any move.

How do you plan a migration without a rush?

Treat Anthropic's table as the clock and your receipts as the evidence. When a model you use moves to Deprecated, Anthropic assigns a retirement date and names a recommended replacement. The September 30, 2026 notice for Claude Sonnet 4.5 is a recent example: retirement on November 30, 2026, with claude-sonnet-5-5 as the replacement. That is roughly two months, which matches the 60 days' notice Anthropic promises.

On Sume the steps are short. List the model ids in your saved calls. Run your usual input on the replacement with the model field and compare the two receipts, as in the A/B recipe. Then change the id in your code, and keep the old receipts so you can explain a change in cost or style later.

Sume does not publish its own retirement calendar for catalog rows in the docs, so treat Anthropic's page as the vendor signal and the receipt's model as the Sume signal.