--- title: "Claude API 2026-10-21 for Your Company | By The People Tech" description: "Anthropic has released Claude API version 2026-10-21. New SDKs send it by default, carry breaking changes and move from MIT to Apache 2.0." url: https://bythepeople.tech/claude/whats-new/claude-api-version-2026-10-21 --- [Claude for Business](/claude) [What’s New](/claude/whats-new) Claude API version 2026-10-21 and new SDKs New feature Released 21 October 2026 · 4 min read # Your next Claude SDK update is a _breaking_ change. Anthropic has released Claude API version 2026-10-21, with new client SDKs and a new ant CLI that send it by default. The new SDK and CLI versions also carry breaking changes of their own and move from the MIT License to Apache 2.0. At a glance API version 2026-10-21 New SDKs and ant CLI Send 2026-10-21 by default Breaking changes Yes, in SDKs and CLI License MIT to Apache 2.0 Migration guide Published by Anthropic On this page * [What changed](#changed) * [What it means](#means) * [What to do this week](#steps) * [Questions](#questions) Published by [Fatjon (Tony) Kalemaj](/about-us/tony-kalemaj) COO & Head of Applied AI 01 · What changed ## What Anthropic shipped. What changed: the Claude API has a new version, and the official SDKs now request it unless told otherwise. A team that moves an SDK to the new major version moves to API version 2026-10-21 by default. It also takes on SDK changes that apply whatever API version is sent. Anthropic publishes a migration guide for the API version and a separate page for the SDK and CLI changes, so this is planned work for whoever owns your Claude integrations. ### 1. API version 2026-10-21 1\. A new version of the Claude API. Anthropic's guide, Migrating to API version 2026-10-21, shows how to upgrade. ### 2. Python SDK 2.0.0 2\. Sends API version 2026-10-21 by default. ### 3. TypeScript SDK 1.0.0 3\. Sends API version 2026-10-21 by default. ### 4. C#, Go and Java SDKs 4\. C# SDK 13.0.0, Go SDK 2.0.0 and Java SDK 3.0.0 send API version 2026-10-21 by default. ### 5. PHP and Ruby SDKs 5\. PHP SDK 1.0.0 and Ruby SDK 2.0.0 send API version 2026-10-21 by default. ### 6. ant CLI 2.0.0 6\. The command-line tool also sends API version 2026-10-21 by default. ### 7. Breaking SDK changes 7\. Anthropic says the new SDK and CLI versions have breaking changes that don't depend on the API version. They are listed on its SDK and CLI changes page. ### 8. Apache 2.0 license 8\. The new SDK and CLI versions are licensed under Apache 2.0 instead of the MIT License. 02 · What it means ## What it means for _your_ seat. This release concerns code that calls the Claude API: the internal tools that summarise a data room, triage inbound email or draft a weekly status report. The work sits with the people who maintain those tools, with a license question for whoever reviews open-source software at your firm. ### Leadership This is maintenance work for the people who build on Claude. Ask who owns your Claude integrations and when they plan the upgrade. Expect a testing step before anything changes in production. ### IT and engineering Pin your current SDK versions so a routine dependency update does not pull in the new major versions untested. Read Anthropic's migration guide and the SDK and CLI changes page, then upgrade one integration at a time, starting with a low-risk tool such as a weekly status report before an IC memo or credit agreement workflow. ### Operations If a tool you rely on is built on the Claude API, such as inbound email triage or a board pack drafting helper, ask its owner when it will move to the new SDK. Plan a check of its output after the change, since the new SDKs carry breaking changes. ### Risk and compliance At these versions the Claude SDKs and ant CLI move from the MIT License to Apache 2.0. If your firm keeps a register of open-source licenses in production software, update it and route the change through the review your policy requires. Treat the SDK upgrade as a production change with the usual change record. 03 · This week ## What to do this week. 0 of 3 done 1. 01 · List every system that calls the Claude API : Include scripts that use the ant CLI. Note the SDK language and version each one runs today. 2. 02 · Pin SDK versions until you have reviewed : Hold current major versions so an automatic update does not move a tool to Python SDK 2.0.0 or TypeScript SDK 1.0.0 before anyone has tested it. 3. 03 · Read both migration pages, then test one tool : Work through Migrating to API version 2026-10-21 and the SDK and CLI changes page. Upgrade one low-risk integration first and log the Apache 2.0 license change for review. Sources Facts and dates are Anthropic’s own. What it means and what to do are our view, from the firms we work with. Drafted with Claude from these sources, checked against them figure by figure, and published 22 October 2026. * [Claude Platform release notes](https://platform.claude.com/docs/en/release-notes/overview) ## The short answers. ### What is Claude API version 2026-10-21? It is a new version of the Claude API released by Anthropic. Anthropic's guide, Migrating to API version 2026-10-21, shows how to upgrade. ### Which Claude SDK versions use API version 2026-10-21 by default? 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 all send API version 2026-10-21 by default. ### Do the new Claude SDKs have breaking changes? Yes. Anthropic says the new SDK and CLI versions have breaking changes that don't depend on the API version, and lists them on its SDK and CLI changes page. ### What license do the Claude SDKs use now? The new SDK and ant CLI versions released alongside API version 2026-10-21 are licensed under Apache 2.0 instead of the MIT License. Read next [21 October 2026 : Claude Duet research preview](/claude/whats-new/claude-duet) [21 October 2026 : Claude Security scans continuously and tracks fixes](/claude/whats-new/claude-security-continuous-scanning) [15 October 2026 : Claude Code Review is generally available](/claude/whats-new/claude-code-review-generally-available) Newsletter ## Keep up with _every_ release. One email when something ships or retires that matters to a company: what changed, what it means, the date and what to do. Unsubscribe any time. Work email How did you hear about us? How did you hear about us? ChatGPT Claude Perplexity Another AI assistant Google or Bing search LinkedIn YouTube Someone referred me An event or webinar Our newsletter Somewhere else ## Want this working inside your firm? We run Claude workshops on your own documents and stay on as your teams adopt each release. 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