Xsai
Minimalist AI SDK for JavaScript: tiny bundle, cross-runtime, OpenAI-compatible.
If bundle size is critical and you use OpenAI-compatible APIs, xsai is a smart choice. It's not for teams needing native multi-provider SDKs or extensive documentation. Consider Vercel AI SDK for broader provider support, or OpenAI's own SDK if you only need one provider.
- Web developers needing lightweight AI features in browser or edge
- CLI tool creators wanting minimal dependency footprint
- Edge/Serverless developers with strict bundle size limits
- JavaScript/TypeScript devs migrating from Vercel AI SDK for size savings
- Non-OpenAI-compatible API users (e.g., Cohere, AI21)
- Teams needing built-in SDKs for every major provider
- Enterprise teams requiring dedicated support or SLAs
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Skip Xsai if you need native SDKs for non-OpenAI-compatible providers like Cohere or AI21, or if you require extensive official documentation and enterprise SLAs.
Xsai is free and open-source (MIT), so it's ideal for any stage of development. No per-seat or usage fees. Compared to Vercel AI SDK (also free but larger bundle), xsai saves on bandwidth and install time.
In short
Xsai — Minimalist AI SDK for JavaScript: tiny bundle, cross-runtime, OpenAI-compatible. Best for Web developers needing lightweight AI features in browser or edge, CLI tool creators wanting minimal dependency footprint, Edge/Serverless developers with strict bundle size limits. Free to use.
What's new in Xsai
Checked 11 days agoAcross the latest 2 updates: 1 feature update and 1 changelog entry.
Viability Score
How likely is Xsai to still be operational in 12 months? Based on 4 signals — momentum (how recently it shipped), wrapper dependency, revenue model, and web presence.
Last calculated: July 2026
How we score →Key Features
- Text generation via OpenAI-compatible APIs
- Structured data generation and extraction
- Speech transcription (Whisper-compatible)
- Image generation
- Streaming: text, structured data, speech, images
- Tool calling (function calling)
- Embeddings generation
- Cross-runtime: Browser, Node.js, Deno, Bun, Edge
- Minimal bundle: 40x smaller install, 13x smaller bundle
- Extension packages: transformers, codex, MCP, unspeech
- Top-level packages: xsai, xsfetch, xsschema
- xsmcp integration for MCP (Model Context Protocol)
- Open-source (MIT license)
- Active community on GitHub Discussions
- ESM and CommonJS module support
About Xsai
Xsai is a lightweight, open-source AI SDK for JavaScript/TypeScript developers who need OpenAI-compatible API access without the bloat of larger SDKs. It mirrors the Vercel AI SDK interface but delivers a dramatically smaller footprint: 40x smaller install size and 13x smaller bundle size (per Packagephobia and Bundlephobia). Supporting Browser, Node.js, Deno, Bun, and Edge Runtime, xsai focuses on OpenAI-compatible APIs but also works with Anthropic and Google via their compatible endpoints. Extensions include transformers, codex, MCP (Model Context Protocol), and unspeech. It provides text generation, structured data extraction, speech transcription, image generation, streaming, tool calling, and embeddings. Current version 0.5.0-beta.6 (July 2026) follows v0.4 "AIAIAI" (June 2026). Ideal for performance-critical web apps, CLI tools, and edge deployments.
Behind the Verdict
Xsai excels where every kilobyte counts—browser extensions, edge functions, and CLI tools shipped via npx. The cross-runtime support (Node.js, Deno, Bun, Edge, Browser) is genuinely impressive. The ecosystem of extensions (xsai-transformers, xsai-codex, xsmcp) adds flexibility. However, being in early beta means breaking changes are possible. Documentation is spartan, and advanced features rely on community packages. If you need dedicated support, SLAs, or native SDKs for Cohere/AI21, look elsewhere.
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Real-world workflow fit
Concrete scenarios for the personas Xsai actually fits — and what changes day-one when you adopt it.
You need to generate a text summary inside a Cloudflare Worker with a strict 1 MB bundle limit. Install xsai (2 KB gzipped) and use @xsai/generate-text to call OpenAI's API.
Outcome: Worker deploys quickly, stays under bundle limit, and generates summaries in <200ms.
You build an npx-based CLI tool for diff summarization that runs on any machine. Use xsai for text generation without bloat.
Outcome: The CLI runs instantly on first use, with minimal install time.
You create a Chrome extension that extracts structured data from web pages. Use xsai streaming + xsschema to parse JSON directly.
Outcome: Extension loads fast, no noticeable delay, and structured data appears in real-time.
Use Cases
- Generate text responses from user prompts with streaming support.
- Transcribe audio to text using OpenAI-compatible speech APIs.
- Create structured data extraction pipelines for web scraping or data processing.
- Implement AI-powered tool calling in serverless functions.
- Build lightweight AI chatbots for browser extensions or Edge workers.
- Generate embeddings for semantic search or recommendation systems.
Models Under the Hood
as of 2026-07-06
Limitations
- Only supports OpenAI-compatible APIs; no native support for other providers.
- Being in early beta (v0.5.0-beta.6), stability and breaking changes may occur.
- Documentation is still maturing, and some advanced features (e.g., extensive provider integrations) rely on community extensions.
as of 2026-07-06
Where the pricing makes sense
The company stage and team size where Xsai's pricing actually pencils out — and where peers do it cheaper.
Xsai is free and open-source (MIT), so it's ideal for any stage of development. No per-seat or usage fees. Compared to Vercel AI SDK (also free but larger bundle), xsai saves on bandwidth and install time.
Setup time & first value
How long it actually takes to get something useful out of Xsai — broken out by persona, not the marketing-page minute.
For a developer familiar with OpenAI APIs, setup takes about 10 minutes: npm install @xsai/generate-text, import the client, and call generateText(). The minimal API means you can have a working prototype in under 30 minutes.
Switching to or from Xsai
How to bring data in from common predecessors and how to get it back out — written for the switcher, not the buyer.
- →From Vercel AI SDK: Replace imports with xsai equivalents; adjust provider configuration for OpenAI-compatible endpoints.
- ↗To Vercel AI SDK: Increase bundle size but gain broader provider support and richer documentation.
Integrations
Resources & Guides
Official links
Tools that pair well with Xsai
Common stack mates teams adopt alongside Xsai, with the specific reason each pairing earns its keep.
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