Claude API 2026-10-21 Drops Temperature and Other Sampling Controls
Your old integration keeps working until you upgrade the SDK, which is exactly when it can break.
Anthropic released Claude API version 2026-10-21 on October 21. AlphaSignal calls it the first official version since 2023-06-01, and the migration guide says it removes the temperature, top_p and top_k settings.
Does a plugin, script or content pipeline on your site call Claude? Then your next SDK upgrade can break it.
What breaks
Anthropic’s guide to migrating to 2026-10-21 lists the changes.
The one you’re most likely to hit: any Messages or Message Batches request that sends temperature, top_p or top_k returns a 400 error.
That’s true even at the default value.
Requests now sample with the defaults, including a temperature of 1.0.
Claude 4.7 and later models already accepted only those defaults, so your output from them won’t change.
But on older models like Claude Sonnet 4.6, a request that lowered temperature for steadier output loses that effect. Anthropic says no other setting replaces it.
The guide lists two more requests that now return a 400 error:
- a
documentblock placed directly in an assistant message - a user message
textblock with a non-emptycitationsarray
Do your own dashboards read the Admin API? If they do, an API key there no longer returns workspace_id, so you’ll read scope.workspace_id instead.
When it hits you
Nothing changes on its own. You opt in by sending the new anthropic-version header, or by upgrading to an SDK that sends it for you.
That second route is the trap.
Anthropic’s API release notes list the first SDK versions that default to the new version:
- Python SDK 2.0.0
- the TypeScript SDK from version 1.0.0
- Go and Ruby SDKs from 2.0.0, and the
antCLI from 2.0.0 - Java from 3.0.0, C# from 13.0.0 and PHP from 1.0.0
Check which one you’re on.
These releases also switch from the MIT License to Apache 2.0, send API keys as Authorization: Bearer, and drop the old Text Completions API from several SDKs.
On Amazon Bedrock, you only get the new version with Claude 4.7 and later models.
What about 2023-06-01? AlphaSignal’s report on the change says Anthropic hasn’t deprecated it, so your pinned integrations keep running.
Why it matters
This kind of change can break your site at 2am. It starts when an application sends the new header or upgrades to an SDK that selects it automatically, so a routine upgrade can be enough. Most people forget which of their tools talks to Claude by then.
So check your code before you upgrade.
Search for temperature, top_p and top_k everywhere your site calls Claude, including WordPress plugins and scripts you didn’t write and haven’t opened in months.
Rely on a low temperature for steady output, like product data or JSON? Then drop the setting and test the results, or keep that request on 2023-06-01.
Still, I’d plan the move rather than pin forever. Either way, pin your SDK’s major version today. Nothing upgrades without you.
Common Questions
Does the Claude API still support temperature?
The new 2026-10-21 version doesn’t accept it. A request that sends temperature, top_p or top_k returns a 400 error, even at the default value. The migration guide says a request that relies on a non-default value can stay on 2023-06-01.
Will my existing Claude integration stop working?
It won’t change by itself. It only changes when you send the 2026-10-21 version header or upgrade to an SDK that defaults to it, such as Python SDK 2.0.0 or TypeScript SDK 1.0.0.
Is API version 2023-06-01 deprecated?
No. AlphaSignal reports that Anthropic hasn’t deprecated it. The migration guide says a request that relies on a non-default temperature can either drop the setting or stay on 2023-06-01.
