RΞASON – Open-source TypeScript framework for LLM apps

In plain words

REASON is an open-source TypeScript framework designed for building applications with large language models. It takes a minimalist, first-principles approach to handle modern LLM capabilities like agents with tools, retrieval-augmented generation pipelines, and function calling. Built for developers working with LLMs, REASON aims to provide a thoughtful alternative to quick-launch frameworks by focusing on foundational design principles and extensibility.

written from the facts on this page · September 2026

From the sources

The five principles of a good LLM framework.

I see LLMs as a new programming primitive, akin to databases in the 70s and the explosion of web technologies in the 2000s. They offer programmers a unique capability: the power to infuse code with reasoning and natural language understanding. Yet, new primitives need new abstractions. With RΞASON I hope to have created that. RΞASON is a backend open-source Typescript framework for building great LLM apps. This blog post will explore some of RΞASON's features and its design philoshopy. It won't be a tutorial — if you wish to learn how to use RΞASON, go to our docs , which is the best place to learn how to use RΞASON. I don't, however, see LLMs as a completely new way to program — LLMs…from tryreason.dev

In the maker’s words, at launch

Hi HN! I'm Inacio, the author of REASON. I've been tinkering with LLMs since the GPT-3 API's release May 2020. Seeing the emergence of many frameworks in the last 15 months has been exciting. While many understandably focused on launching quick, I found myself intrigued by a different question: what would a…

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  RΞASON – Open-source TypeScript framework for LLM apps2023 · github.com · ▲7

  Hi HN! RΞASON is an OSS Typescript framework for developing LLM apps that uses Typescript's interfaces to get structured output from an LLM. While there are other TS LLM frameworks, I think RΞASON fills a unique space in the market: it's laser-focused on only three areas and, most importantly, actively stays away from pre-made prompting & retrieval. I've been in the LLM space since GPT-3 originally came out, and I've always had problems with other frameworks, such as LangChain. I dislike that they focus a ton on out-of-the-box prompting & pre-made agents — I, as the dev, should be the one in…

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  Axilla – Open-source TypeScript framework for LLM apps2023 · github.com · ▲161

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  Hey HN, I made Browser-Use, an open-source tool that lets (all Langchain supported) LLMs execute tasks directly in the browser just with function calling. It allows you to build agents that interact with web elements using natural language prompts. We created a layer that simplifies website interaction for LLMs by extracting xPaths and interactive elements like buttons and input fields (and other fancy things). This enables you to design custom web automation and scraping functions without manual inspection through DevTools. Hasn't this been done a lot of times? Good question, as a general…

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  Hello HN! The day has finally come to stop adding features and start sharing what I've been building the last 5-6 months. It's a bit of CrewAI, OpenDevon, LangFuse/Cloud all in one, providing devs who prefer TypeScript an integrated framework thats provides a lot out of the box to start experimenting and building agents with. It started after peeking at the LangChain docs a few times and never liking the example code. I began experimenting with automating a simple Jira request from the engineering team to add an index to one of our Google Spanner databases (for context I'm the…

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