asyntheticai/asynthetic

Asynthetic is a tool that gives AI coding agents accurate, up to date information about how software libraries have changed between versions. AI models are trained on data with a cutoff date, so when they try to help you upgrade a library, they sometimes write code using old syntax that no longer works, or miss a change that quietly breaks your build without any error. Asynthetic tries to fix that specific problem. It works as an MCP server, a kind of plugin that AI coding assistants like Claude Code, Cursor, or Windsurf can connect to. Once connected, the agent can ask a tool called get_migration for a specific package and version range, and Asynthetic replies with a list of breaking changes for that upgrade, each one showing the old code, the new code, and a link to the official source that documented the change. It currently covers two library upgrades in depth: Next.js from version 14 to 15, and the AI SDK from version 4 to 5, with about 40 breaking changes cataloged across both. Each answer also reports a confidence level such as high, medium, or low, depending on whether the change has actually been tested on a real build rather than just read from documentation. If Asynthetic has no information about a particular upgrade, it says so directly rather than guessing, which the README treats as a core design rule: a wrong answer is worse than no answer. You can use the hosted version with one command, or run it locally and offline using npx, or clone the project and self host it with your own Postgres database through Supabase. The project is written in TypeScript and is source available under the BSL 1.1 license, meaning you can self host it freely but cannot resell it as a competing hosted service. That license is set to convert automatically to the Apache 2.0 license in 2030. It is currently a free public beta.