Two libraries land on most shortlists when you start an agent project in 2026: Anthropic's Claude Agent SDK and Vercel AI SDK 6. Both build agents that use tools, stream, and speak MCP. They were built by teams with different beliefs.
This is the short version. The full guide is on my blog: Claude Agent SDK vs Vercel AI SDK 6: Which to Pick (2026).
The short version
Pick the Claude Agent SDK when your model is Claude and you want the same runtime that powers Claude Code, with caching, compaction, and built in tools on day one. Python and TypeScript.
Pick the Vercel AI SDK 6 when you need multi provider support, your stack is TypeScript and React or Next.js, or you want chat, tools, images, reranking, and speech in one library.
Side by side at a glance
| Area | Claude Agent SDK | Vercel AI SDK 6 |
|---|---|---|
| Languages | Python, TypeScript | TypeScript only |
| Models | Claude only | Any provider through AI Gateway |
| Agent API |
query() with ClaudeAgentOptions
|
ToolLoopAgent class |
| Built in tools | Read, Write, Edit, Bash, Glob, Grep, WebSearch | None by default, you define them |
| Subagents | First class, own context window | Not built in |
| MCP support | First class | First class as of v6, OAuth supported |
| Prompt caching | On by default | Provider dependent, opt in |
| Context compaction | Automatic | Manual |
| DevTools UI | None | Local UI at localhost:4983
|
| Frameworks | Any | Next.js, React, Svelte, Vue, Node.js |
The Anthropic SDK is opinionated and Claude shaped. The Vercel SDK is flexible and provider neutral.
Same agent in both
Claude Agent SDK
import { query } from "@anthropic-ai/claude-agent-sdk";
for await (const message of query({
prompt: "What changed in HTTP/3 in 2025?",
options: {
allowedTools: ["WebSearch", "WebFetch"],
systemPrompt: "You are a research assistant. Always cite sources.",
},
})) {
if ("result" in message) console.log(message.result);
}
WebSearch and WebFetch are built in.
Vercel AI SDK 6
import { ToolLoopAgent, tool } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";
const webSearch = tool({
description: "Search the web. Returns the top three results.",
inputSchema: z.object({ query: z.string() }),
execute: async ({ query }) => results,
});
const agent = new ToolLoopAgent({
model: anthropic("claude-opus-4-7"),
instructions: "You are a research assistant. Always cite sources.",
tools: { webSearch },
});
const result = await agent.generate({
prompt: "What changed in HTTP/3 in 2025?"
});
You bring your own search function. Swap anthropic(...) for openai(...) and the rest of the file is unchanged.
Where each wins
The Claude Agent SDK wins on built in tools, subagents with their own context window, hooks that mirror Claude Code, and defaults that match production. Prompt caching is on, compaction is automatic, retries are sensible.
The Vercel AI SDK 6 wins on provider flexibility, the DevTools UI at localhost:4983, one line human in the loop with needsApproval, and having image, audio, and reranking in the same library.
A simple way to choose
Are you locked to Claude models?
Yes → Claude Agent SDK
No → TypeScript and React stack?
Yes → Vercel AI SDK 6
No → Claude Agent SDK Python build
For LangChain comparisons, the Claude Agent SDK vs LangChain post has the answer.
The full guide covers MCP wiring on both sides, defaults and cost, the June 15 2026 Agent SDK billing change, and a longer FAQ: Claude Agent SDK vs Vercel AI SDK 6: Which to Pick (2026).
