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Claude Platform · Forced move · Tracked since October 13, 2026 · Sources checked Oct 13

Time to bail on Claude Sonnet 4.5 on the Claude API?

Time to Bail · Boarding pass

FromClaude Sonnet 4.5 on the Claude API
ToYour pick

Act. You can stay.

Claude-sonnet-4-5-20250929 retires November 30, 2026. Move to claude-sonnet-5-5 first.[1]

Act means: change a setting or plan before the date. You can stay.

Gate closes
Tentative retirement date
Time left
46days
Status
Act

Claude Sonnet 4.5 retires on the Claude API on November 30, 2026

Anthropic plans to retire Claude Sonnet 4.5 on November 30, 2026. Requests to it will fail after that. Anthropic names claude-sonnet-5-5 as the replacement.

How it is winding down

  1. Sep 30Developers toldDone
  2. Nov 30Tentative retirement dateNext

What to do before November 30

Tick steps as you go. Your progress stays in this browser.

  1. Find calls to the old model

    Search your code and settings for claude-sonnet-4-5-20250929.

  2. Switch to claude-sonnet-5-5

    Change the model name. Read Anthropic's migration guide for changed behavior.

  3. Test before November 30

    Run your usual prompts and check output, tool use and cost.

Facts we checked

Facts and their sources
Tentative retirement dateNovember 30, 2026[1]
Modelclaude-sonnet-4-5-20250929 (Claude Sonnet 4.5)[1]
Developers toldSeptember 30, 2026[1]
Replacementclaude-sonnet-5-5[1]
After retirementRequests to the model will fail[1]
Where this date appliesThe Claude API, Claude Platform on AWS and Microsoft Foundry[1]
Amazon Bedrock and Google CloudSet their own retirement dates[1]
Apps that call Claude Sonnet 4.5Requests fail after November 30, 2026[1]

Sources

Check it yourself. Every fact above links here.

  1. Model deprecations Anthropic · primary · checked Oct 13
Read the published editorial report

What changed

Time to bail on Claude Sonnet 4.5 on the Claude API? Act. You can stay. Claude-sonnet-4-5-20250929 retires November 30, 2026. Move to claude-sonnet-5-5 first.

On our scale this is Act: change a setting or plan before the date. You can stay.

Anthropic plans to retire Claude Sonnet 4.5 on November 30, 2026. Requests to it will fail after that. Anthropic names claude-sonnet-5-5 as the replacement.

Here are the facts we checked:

  • Tentative retirement date: November 30, 2026 (Anthropic)
  • Model: claude-sonnet-4-5-20250929 (Claude Sonnet 4.5) (Anthropic)
  • Developers told: September 30, 2026 (Anthropic)
  • Replacement: claude-sonnet-5-5 (Anthropic)
  • After retirement: Requests to the model will fail (Anthropic)
  • Where this date applies: The Claude API, Claude Platform on AWS and Microsoft Foundry (Anthropic)
  • Amazon Bedrock and Google Cloud: Set their own retirement dates (Anthropic)
  • Apps that call Claude Sonnet 4.5: Requests fail after November 30, 2026 (Anthropic)

You can stay on Claude Platform. You have to change a setting or plan before the date.

Leaving is a choice here, not a must.

Anthropic is the main source for this page. Claude Platform has not said more than what is listed here. If a fact is not on this page, we do not know it yet.

Who is affected

Apps that call Claude Sonnet 4.5: Requests fail after November 30, 2026.

The date to remember is November 30, 2026. Make the change before then.

What to do before November 30

  1. Find calls to the old model. Search your code and settings for claude-sonnet-4-5-20250929.
  2. Switch to claude-sonnet-5-5. Change the model name. Read Anthropic's migration guide for changed behavior.
  3. Test before November 30. Run your usual prompts and check output, tool use and cost.

A few tips:

  • Make the change yourself before the date. Do not wait for the last reminder email.
  • Write down your current plan or settings first, so you can compare after the change.
  • After the change, open your settings again and check that it worked.

How to tell your users

If the change affects your members or team, send one short email. Say what changes for them and when. Put the most important line first.

If there is a date, send a short reminder a few days before it. Keep a copy of the list you sent it to.

Options people mention

Listed for convenience. Not ranked. Not paid. These names come up in threads and reviews; that does not show where people moved.

Before you pay, check the price page of each tool yourself. Prices change, and we only list what our sources say.

Questions people ask

No questions collected yet.

Sources

Thanks.

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