--- title: "Letta vs Vercel AI SDK: Which is Better in 2026? | App Stack Builder" description: "Letta vs Vercel AI SDK compared for 2026 — pricing, free tiers, features, pros & cons. See which agent framework tool is the better fit for your startup." source: https://appstackbuilder.com/compare/letta-vs-vercel-ai-sdk retrieved: 2026-10-29 --- ![](https://appstackbuilder.com/logos/letta.png) vs ![](https://www.google.com/s2/favicons?domain=sdk.vercel.ai&sz=128) # Letta vs Vercel AI SDK: Which is Better in 2026? Agent Framework Choosing between [Letta](https://appstackbuilder.com/tools/letta) and [Vercel AI SDK](https://appstackbuilder.com/tools/vercel-ai-sdk)? Both are popular agent framework tools. Below we compare them on pricing, free tiers, features, and pros & cons so you can pick the right fit for your stack. Letta is for: Teams building agents that must remember users and context across sessions and restarts, with memory as the core design. Vercel AI SDK is for: TypeScript and React teams adding streaming chat, tool calling and structured output to a web app, with any model provider. Quick verdict There’s no single winner; pick on your constraint. Choose Letta if your agent must remember users and past sessions over weeks or months. Choose Vercel AI SDK if you’re building AI features into a React or Next.js app. ## Letta vs Vercel AI SDK — Side by Side | | Letta | Vercel AI SDK | | --------------------- | ------------------------------------------------------------------------ | ------------------------------------------------------------------------------- | | Category | Agent Framework | Agent Framework | | What it is | Agent server and SDKs: agents with persistent memory | Code library: TypeScript toolkit for AI apps and agents | | Languages | Python and TypeScript SDKs | TypeScript/JavaScript | | Licence | Apache 2.0 | Apache 2.0 | | Managed / paid option | Letta API: free tier, Pro $20/month plus usage | None; deploy anywhere | | Project status | Active | Active; v6 | | Pricing | Free · paid from $20/mo | Free | | Starting price | Free tier available | Free tier available | | Free tier | ✓ | ✓ | | Rating | 4.0 | 4.6 | | Best for | Agent Framework — long-term memory, stateful agents, self-host or hosted | Agent Framework — React and Next.js apps, streaming chat UI, provider switching | ## Pros & Cons ![](https://appstackbuilder.com/logos/letta.png) [Letta](https://appstackbuilder.com/tools/letta) * ✓Memory is the design centre, not an add-on * ✓Agents survive restarts with state intact * ✓Comes from the MemGPT paper * ✗Younger project with a moving API * ✗Memory model is opinionated ![](https://www.google.com/s2/favicons?domain=sdk.vercel.ai&sz=128) [Vercel AI SDK](https://appstackbuilder.com/tools/vercel-ai-sdk) * ✓Best DX for TS/React AI apps * ✓Provider-agnostic * ✓Free and open-source * ✓Great streaming & UI hooks * ✗TypeScript/JS only * ✗Less suited to complex Python agent graphs ## Key Features Compared ### Letta * ✓Persistent, self-editing agent memory (from the MemGPT research) * ✓Agents keep their state across restarts * ✓Self-hosted server, or the hosted Letta API * ✓Hosted plans: free tier and Pro at $20 a month with pay-as-you-go usage * ✓Letta Code, an open-source coding agent with memory across sessions * ✓Apache 2.0 licence ### Vercel AI SDK * ✓One API across OpenAI, Anthropic, Google and other providers * ✓Streaming, tool calling and structured output * ✓UI hooks for chat interfaces in React and other frameworks * ✓AI SDK 6 adds an agent abstraction, tool approval steps, DevTools and MCP support * ✓Runs on any host, not only Vercel * ✓Apache 2.0 licence ### Choose Letta if… * ✓Your agent must remember users and past sessions over weeks or months. * ✓You want agents that keep state when the process restarts. * ✓You want the choice of self-hosting or a hosted API. [Letta review & pricing ](https://appstackbuilder.com/tools/letta) ### Choose Vercel AI SDK if… * ✓You’re building AI features into a React or Next.js app. * ✓You want to switch model providers without rewriting calls. * ✓You need streaming UI and tool calls more than complex multi-agent graphs. [Vercel AI SDK review & pricing ](https://appstackbuilder.com/tools/vercel-ai-sdk) ## Frequently Asked Questions Is Letta better than Vercel AI SDK?⌄ There’s no single winner; pick on your constraint. Choose Letta if your agent must remember users and past sessions over weeks or months. Choose Vercel AI SDK if you’re building AI features into a React or Next.js app. What is the difference between Letta and Vercel AI SDK?⌄ What it is — Letta: Agent server and SDKs: agents with persistent memory. Vercel AI SDK: Code library: TypeScript toolkit for AI apps and agents. Languages — Letta: Python and TypeScript SDKs. Vercel AI SDK: TypeScript/JavaScript. Managed / paid option — Letta: Letta API: free tier, Pro $20/month plus usage. Vercel AI SDK: None; deploy anywhere. Project status — Letta: Active. Vercel AI SDK: Active; v6. Letta vs Vercel AI SDK: which is cheaper?⌄ Letta pricing: Free · paid from $20/mo. Vercel AI SDK pricing: Free. Confirm current pricing on each tool's official site, as plans change. Which is rated higher, Letta or Vercel AI SDK?⌄ In our catalog, Letta rates 4.0 out of 5 and Vercel AI SDK rates 4.6 out of 5, so Vercel AI SDK has a slight edge on reviews. When should I skip both Letta and Vercel AI SDK?⌄ Skip Letta if you only need short-lived task agents. A lighter SDK is simpler. Skip Vercel AI SDK if your team writes Python. LangChain, CrewAI or the OpenAI Agents SDK fit better. Sources · tool facts checked October 2026 1. 1.[Letta Code (Letta docs)docs.letta.com ](https://docs.letta.com/letta-code) 2. 2.[AI SDK 6 announcement (Vercel)vercel.com ](https://vercel.com/blog/ai-sdk-6) See more options in our guide to the [best agent framework tools for startups](https://appstackbuilder.com/categories/agent-framework). ## Still not sure which to pick? Get a free, AI-powered tech stack — including the best agent framework pick for your budget and team — in 60 seconds. [Build my stack free ](https://appstackbuilder.com/build-stack)