# Claude Agent SDK

> **TL;DR.** [Claude Agent SDK](https://code.

- **Category:** AI / Developer Tools / Agent Frameworks
- **Stage:** established
- **Age:** 247 days
- **Origin date:** 2025-09-29
- **First detected:** 2026-04-15
- **Canonical URL:** https://earlyterms.com/term/claude-agent-sdk
- **Sources:** 8 primary URLs

## Definition

[Claude Agent SDK](https://code.claude.com/docs/en/agent-sdk/overview) is Anthropic's programmatic toolkit for building AI agents on Claude. It exposes the same tool-loop, context management, subagent orchestration, hooks, permissions, and MCP integration that power Claude Code — as a Python and TypeScript library where a single `query()` iterator streams messages while Claude reads files, runs commands, and edits code.

Anthropic announced the SDK on September 29, 2025 alongside Claude Sonnet 4.5, as a rename of the earlier Claude Code SDK ([migration guide](https://platform.claude.com/docs/en/agent-sdk/migration-guide)). The rename signalled the harness had grown beyond coding — internally it was already powering deep research, video, and note-taking — and needed a name that did not pin it to one vertical.

## Analogy

Rails for agents: not the model, not the hosted runtime, but the opinionated middle layer that turns a chat endpoint into something that can do work on a computer.

## Why it's emerging now

The Sep 29, 2025 rename from Claude Code SDK was itself the story: Anthropic standardized on 'agent,' not 'coding,' as the SDK's frame. Six months later, Managed Agents (Apr 8, 2026) gave it a hosted sibling, Apple shipped it in Xcode 26.3, and a 214MB-per-session critique framed the second wave of open-source alternatives.

## Related terms

- *alias:* Claude Code SDK
- *child:* Managed Agents
- *child:* Claude Code
- *related:* Agent Harness
- *related:* Model Context Protocol
- *related:* MCP Server
- *related:* Coding Agents
- *related:* AGENTS.md
- *parent:* Anthropic Messages API
- *competitor:* LangGraph
- *competitor:* Pydantic AI
- *competitor:* Vercel AI SDK

## Sources

1. [Agent SDK overview (official Anthropic docs)](https://code.claude.com/docs/en/agent-sdk/overview)
2. [Anthropic engineering: Building agents with the Claude Agent SDK](https://claude.com/blog/building-agents-with-the-claude-agent-sdk)
3. [Introducing Claude Sonnet 4.5 (SDK rename announcement, Sep 29 2025)](https://www.anthropic.com/news/claude-sonnet-4-5)
4. [anthropics/claude-agent-sdk-python (6.4k stars)](https://github.com/anthropics/claude-agent-sdk-python)
5. [Hacker News — Claude Agent SDK vs Messages API for production](https://news.ycombinator.com/item?id=47669957)
6. [Hacker News — Claude Agents SDK: 214MB per session on macOS](https://news.ycombinator.com/item?id=47729284)
7. [Hacker News — Apple's Xcode now supports the Claude Agent SDK](https://news.ycombinator.com/item?id=46874771)
8. [Migration guide: Claude Code SDK to Claude Agent SDK](https://platform.claude.com/docs/en/agent-sdk/migration-guide)

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_Generated by EarlyTerms · https://earlyterms.com/term/claude-agent-sdk_