Best AI SDK for Building LLM Apps
The libraries developers use to build LLM features. Ranked by which tools AI agents actually pick when developers build — measured live across Claude, GPT, Gemini.
As of Jun 24, 2026, the AI SDK AI agents pick most is OpenAI SDK at 51%, measured across Claude, GPT, Gemini.
| # | Tool | Pick Rate | Default Rate | Shortlist |
|---|---|---|---|---|
| 1 | OpenAI SDK | 51% [44%–57%] | 31% | 90% |
| 2 | Vercel AI SDK | 14% [10%–19%] | 41% | 19% |
| 3 | LangChain | 5% [3%–9%] | 11% | 26% |
| 4 | LlamaIndex | 1% [0%–3%] | 0% | 14% |
| 5 | Anthropic SDK | 0% [0%–2%] | 0% | 28% |
What is an AI SDK?
An AI SDK is the library a developer uses to build LLM features — calling a model, streaming a reply, doing tool/function calling, generating structured output, or orchestrating retrieval and agents. Some are single-provider client libraries; others are provider-agnostic abstractions or higher-level frameworks for chains, agents, and RAG.
LLM features are moving from novelty to default, and the SDK choice decides how locked-in you are to one provider, how much streaming and tool-calling plumbing you write yourself, and how cleanly it drops into your framework. Because agents are now writing this code, the library a coding agent reaches for is increasingly the one that ships.
How to choose
What separates the AI SDK options.
A provider SDK is simplest if you've committed to one model; an abstraction lets you swap providers and compare.
First-class streaming to the UI, function/tool calling, and structured output save a lot of glue code.
Tight Next.js/React integration (streaming hooks, server actions) matters for web apps.
For chains, agents, and RAG over your own data, a higher-level framework does more than a raw client.
Best AI SDK for your use case
| If you need… | Reach for | Why |
|---|---|---|
| Just call OpenAI's models | OpenAI SDK | The direct, official client when you've committed to GPT models. |
| Provider-agnostic, streaming UI in Next.js | Vercel AI SDK | Clean streaming hooks and a unified API across model providers. |
| Complex chains, agents, and RAG | LangChain | The broad orchestration framework for multi-step pipelines and tools. |
| Data-centric RAG and indexing | LlamaIndex | Built around ingesting, indexing, and querying your own data. |
AI SDK: incumbents vs new entrants
The space ranges from official single-provider client SDKs to provider-agnostic abstractions and full orchestration frameworks for agents and RAG.
The official client most developers reach for by default to call an LLM.
The broad orchestration framework for chains, agents, and tools.
Provider-agnostic with first-class streaming and React/Next integration; rising fast.
Data-framework focus — ingesting, indexing, and querying your own documents for RAG.
The official SDK for calling Claude directly.
Why AI agents decide this category
This is the most reflexive category there is: a coding agent building an AI feature picks the AI SDK, and it overwhelmingly reaches for the client it has seen most. Whoever owns that default owns how the next wave of AI apps gets built — and the gap between 'named in conversation' and 'actually imported in code' is unusually wide here.
Frequently asked questions
What is an AI SDK?
An AI SDK is a library for building LLM features into an app — calling models, streaming responses, tool/function calling, structured output, and sometimes orchestrating RAG and agents. Some target one provider; others are provider-agnostic or full frameworks.
What is the best AI SDK for Next.js?
The Vercel AI SDK is the most common pick for Next.js thanks to its streaming hooks and provider-agnostic API; the OpenAI SDK is the direct route if you've committed to GPT. The ranking above shows what agents actually import.
LangChain vs Vercel AI SDK — what's the difference?
LangChain is a broad orchestration framework for chains, agents, and tools; the Vercel AI SDK is a lighter, provider-agnostic library focused on calling models and streaming results into a UI.
How do I add a chatbot to my app?
Pick an AI SDK, create a server route that calls a model, and stream the reply to a chat UI. The Vercel AI SDK and OpenAI SDK are the most common starting points; see the ranking for what agents choose.
Which AI SDK do coding agents pick most?
Measured live across Claude, GPT, and Gemini on this page. The coding-surface result — what gets imported — is the most telling cut for this category.