A new open source legal AI tool vibe coded by former Latham & Watkins associate William Chen is causing market excitement, with end users claiming it will change their negotiation strength.
Announcing its launch on LinkedIn last week, Chen said that Mike has a parity with Harvey and Legora, but it is free. “Harvey is valued at $11B. Legora just raised at $5.5B. I built their entire web application in two weeks and I’m making it open-source and free for everyone to use. Say hi to Mike: mikeoss.com,” he said.
Mike is an assistant that can create, edit, or review documents, powered by Claude or Gemini. It has a projects vault where you can upload your files and share them with colleagues, and tabular review for bulk-reviewing documents. It also has workflows containing instructions for the assistant or presets for tabular review.
Chen says that by making Mike open source and available on GitHub, he is embracing a different philosophy to Harvey and Legora, which he describes as ‘black boxes’. Mike instead gives law firms, developers and legal engineers the ability to run and customise legal AI systems locally rather than relying entirely on proprietary platforms.
Open-source software has long been associated with transparency and flexibility, allowing users to inspect, modify and adapt code to their own needs rather than relying on vendor roadmaps. Law firms can also host models internally, addressing data sharing and confidentiality concerns.
In terms of security, Chen says on LinkedIn: “Now a common question is whether Mike is as secure as compared to Harvey and Legora. My answer is yes, it can be as secure as you want it to be. To clarify, the site online at mikeoss.com, is meant to be a demo site, for people to test and try out. I have put the code out in open source (Github link in the website) so can download it and run it locally in your computer. Your files and data never have to leave your computer.”
James Harrison, former IT Director of Leigh Day, told Legal IT Insider: “Mike doesn’t kill Harvey or Legora, but it absolutely changes the negotiation. Once a working open-source alternative is sitting on GitHub, the conversation in renewal meetings moves from ‘Is this magic?’ to ‘What exactly am I paying enterprise prices for?’”
Mike will also likely form the basis of further startup offerings.
According to Shawn Curran, founder of Jylo, who while director of legal technology at Travers Smith built and open sourced GenAI chatbot YCNBot, this is just the beginning of an exciting new vibe coding trend. “The experts who have practice experience in legal have the power now to write software now,” he told Legal IT Insider. “Almost certainly their output will be more targeted and arguably more valuable than the software built over the last 20 years. Whether through vibe coding or using platforms like ours to make it easy to build custom workflows, this is an exciting new trend.”
