Claude API Version 2026-10-21: New SDKs and Apache 2.0
Anthropic released API version 2026-10-21 with new default SDK and ant CLI versions, Apache 2.0 licensing, and enforcement status fields for user profiles.
By Claudekit Bot Published 2 min read
- Source
- platform.claude.com
On October 21, 2026, Anthropic released API version 2026-10-21, along with major new versions of every client SDK and the ant CLI. If you call the Claude API directly or through an official SDK, this update affects your upgrade path, your dependency licensing, and how you monitor end customers.
What happened
According to the Claude Platform release notes for October 21, 2026, Anthropic shipped four changes:
- A new API version,
2026-10-21, with a migration guide titled “Migrating to API version 2026-10-21.” - New SDK and CLI releases that send API version
2026-10-21by default. - A license change for those SDKs and the CLI, from the MIT License to Apache 2.0.
- New enforcement fields on user profiles.
Key details
The new versions that default to 2026-10-21 are:
- Python SDK 2.0.0
- TypeScript SDK 1.0.0
- C# SDK 13.0.0
- Go SDK 2.0.0
- Java SDK 3.0.0
- PHP SDK 1.0.0
- Ruby SDK 2.0.0
antCLI 2.0.0
Anthropic notes that these SDK and CLI versions also contain breaking changes that don’t depend on the API version. Upgrading a package may require code changes even if you weren’t planning to adopt the new API version. The release notes direct readers to the “Switch to 2026-10-21” and “SDK and CLI changes” sections of the docs.
User profiles now include enforcement_status and enforcement_actions fields. These fields show whether Anthropic has restricted or banned one of your end customers. To find every profile with an open restriction or ban, list your profiles using the new enforcement_status[] filter. The relevant doc section is “Check whether Anthropic has restricted or banned a profile.”
Why it matters for Claude builders
Because the new SDKs change the default API version, a routine dependency bump can change the API behavior your app receives. Combined with the SDK-level breaking changes, these upgrades need planning. Pin your current SDK version until you have read the migration guide and the SDK and CLI changes page.
The switch from MIT to Apache 2.0 matters if your organization reviews open source licenses. Flag the change to whoever handles dependency compliance before you upgrade.
If your product serves end customers through user profiles, the new enforcement fields give you a direct way to detect restrictions and bans. Consider building a periodic check with the enforcement_status[] filter so your support or trust team can act on restricted accounts.
Next step: read the October 21 release notes and the linked migration guide before you upgrade any SDK or the ant CLI.
Source
Frequently asked questions
Which SDK versions send API version 2026-10-21 by default?
According to Anthropic's release notes, the new defaults are Python SDK 2.0.0, TypeScript SDK 1.0.0, C# SDK 13.0.0, Go SDK 2.0.0, Java SDK 3.0.0, PHP SDK 1.0.0, Ruby SDK 2.0.0, and ant CLI 2.0.0.
Did the license for the Claude SDKs change?
Yes. The release notes say the new SDK and CLI versions are licensed under Apache 2.0 instead of the MIT License.
Are there breaking changes beyond the API version?
Yes. Anthropic states that the new SDK and CLI versions have breaking changes that don't depend on the API version, and points to its SDK and CLI changes documentation for details.
How can I find end customers that Anthropic has restricted or banned?
User profiles now include the `enforcement_status` and `enforcement_actions` fields. To find profiles with an open restriction or ban, list your profiles with the new `enforcement_status[]` filter.