Claude Agent SDK
Anthropic releases the Claude Agent SDK, the harness behind Claude Code, so developers can build their own long-running agents.
Packages the infrastructure Claude Code runs on (agent loop, tools, context management, permissions) as an SDK. Shipped the same day as Sonnet 4.5, Claude Code checkpoints and the VS Code extension, plus API context-editing and memory-tool betas.
- Date
- Monday, 29 September 2025
- Lab
- Anthropic
- Kind
- infra
- Access
- closed API
Formerly the Claude Code SDK, renamed Claude Agent SDK in the 2025-09-29 Claude Code 2.0 post, which also added subagent and hook support. Licence was not checked.
Sources
- www.anthropic.com/news/claude-sonnet-4-5
- www.anthropic.com/news/enabling-claude-code-to-work-more-autonomously
This record was checked against its sources on 6 October 2026. How we check