On Oct 21 Anthropic released Claude API version 2026-10-21, its first official version since 2023. It removes the temperature, top_p and top_k sampling parameters and drops old Admin API field names, while new SDK majors (Python 2.0, TypeScript 1.0, Go 2.0, Java 3.0 and more) default to it. Version 2023-06-01 is not deprecated.

Key Takeaways

  • ✓Version: 2026-10-21 is the Claude API's first official version since 2023; 2023-06-01 is not deprecated and more frequent versions are planned
  • ✓Breaking: sending temperature, top_p or top_k returns a 400 on every model; Claude 4.7+ models behave as before
  • ✓SDKs: Python 2.0.0, TypeScript 1.0.0, Go 2.0.0 (/v2 path), Java 3.0.0, C# 13.0.0, Ruby 2.0.0, PHP 1.0.0, ant CLI 2.0.0
  • ✓Auth: SDKs send the API key as Authorization: Bearer and hold 1 credential per client; SDK license moves to Apache 2.0
  • ✓Platforms: Claude API, Claude Platform on AWS, Microsoft Foundry, Google Cloud; Bedrock only for Claude 4.7+, see the migration guide
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Project Links & Resources

Direct Access
Direct access to official project resources and documentation
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Claude API versioning
platform.claude.com/docs/en/api/versioning
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Migrating to API version 2026-10-21
platform.claude.com/docs/en/api/migration-2026-10-21
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In-Depth Technical Analysis

Background

Since 2023 the Claude API has run on anthropic-version: 2023-06-01, with Messages, tool use and Managed Agents layered on additively. On Oct 21 Anthropic shipped API version 2026-10-21, its first official version release since 2023, and says it will release versions more often so developers can handle breaking changes before a new model requires them. 2023-06-01 is not deprecated.

What changes

The Messages API drops temperature, top_p and top_k: sending any of them returns a 400 on every model. A document block placed directly in an assistant message, or a user text block with non-empty citations, also returns a 400. The Admin and Enterprise Analytics APIs stop returning old field names (e.g. roles becomes role_ids; API keys' workspace_id becomes scope.workspace_id). New SDK majors ship alongside: Python 2.0.0, TypeScript @anthropic-ai/sdk 1.0.0, Go 2.0.0 (module path ends in /v2), Java 3.0.0, C# 13.0.0, Ruby 2.0.0, PHP 1.0.0 and the ant CLI 2.0.0. SDKs now send the API key as Authorization: Bearer, hold one credential per client, split MessageParam into per-role types, remove legacy Text Completions from several SDKs and the CLI, and move to the Apache 2.0 license.

Benchmarks

This is an API and SDK release, not a model release; no benchmarks were published. Per Anthropic, Claude 4.7 and later models already accept only default sampling values, so they behave the same; on models like Claude Sonnet 4.6, requests that lowered temperature lose that effect with no replacement setting.

How to adopt

Available on the Claude API, Claude Platform on AWS, Microsoft Foundry and Google Cloud; on Amazon Bedrock only for Claude 4.7 and later. Work through the migration guide, remove sampling parameters, update any proxy that reads X-Api-Key to read Authorization, upgrade to the matching SDK major, and test against 2026-10-21 before release. Requests that depend on a non-default temperature can stay on 2023-06-01 for now.

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