Mike OSS Offers Free Alternative to $11B Legal AI Giant

A former Latham & Watkins associate has launched Mike, a free, open-source legal AI tool that matches proprietary platforms valued in the billions.

William Chen built and released Mike in May 2026, offering law firms and legal teams a free alternative to enterprise legal AI platforms Harvey and Legora. Chen developed the full web application in two weeks and published the code publicly on GitHub, allowing anyone to download, run, and customise the tool.

This launch matters because it directly pressures the legal AI market, where leading platforms carry valuations of billions of dollars, by offering comparable functionality at no cost.

What Mike Does

Mike is an AI assistant that can create, edit, and review legal documents. It supports file storage through a project’s vault, enables bulk document review through tabular review, and includes customisable workflows for setting instructions or review presets.

The tool runs on either Claude or Gemini as its underlying AI model. Law firms can choose to run Mike locally on their own systems, meaning files and data never leave their internal environment.

Chen positions this as a direct response to the closed nature of existing platforms. Harvey is currently valued at $11 billion, and Legora raised its latest funding round at a $5.5 billion valuation.

The Open Source Difference

Open-source software allows users to inspect, modify, and adapt the underlying code. This contrasts with proprietary platforms, which Chen describes as black boxes, where users cannot see how the system works or change how it behaves.

By publishing Mike on GitHub, Chen gives law firms, developers, and legal engineers the ability to build on top of the tool rather than depending on vendor-controlled updates and roadmaps.

This approach also addresses a significant concern in legal work: data confidentiality. Firms that run Mike locally keep all client files and documents within their own infrastructure, removing the need to share data with a third-party platform.

Chen addressed security questions directly on LinkedIn: "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 so you can download it and run it locally on your computer. Your files and data never have to leave your computer."

Market Reaction

Legal technology professionals have responded quickly to the launch. James Harrison, former IT Director of Leigh Day, told Legal IT Insider that Mike shifts the balance in enterprise software renewal conversations.

Harrison said: "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?'"

This reaction points to a broader shift in how legal teams may approach vendor negotiations. When a free, functional alternative exists, firms gain leverage when discussing pricing and features with established platforms.

A Growing Trend

Chen is not alone in applying this approach to legal technology. Shawn Curran, founder of legal workflow platform Jylo, previously built and open-sourced YCNBot, a generative AI chatbot, while serving as director of legal technology at Travers Smith.

Curran told Legal IT Insider: "The experts who have practice experience in legal have the power now to write software now. Almost certainly their output will be more targeted and arguably more valuable than the software built over the last 20 years."

Curran described this as the beginning of a wider vibe coding trend, where legal professionals with domain expertise use AI-assisted development tools to build software themselves, without traditional engineering teams. He noted that platforms like Jylo are designed to make it easier for legal professionals to build custom workflows independently.

Mike is also expected to serve as a foundation for future startup products built on top of its open-source codebase.

Chen's background as a former associate at Latham & Watkins, a global law firm, gives him direct experience with the workflows Mike is designed to support. This domain knowledge shapes the tool's focus on document creation, review, and collaboration, tasks that are central to legal practice.

The launch reflects a moment where legal professionals with technical skills are building their own solutions rather than waiting for commercial vendors to meet their needs. Whether Mike becomes a standalone product, a negotiating reference point, or a base layer for new startups, its arrival signals a shift in what law firms can demand and expect from legal AI providers.

About Mike OSS

Mike is an open-source legal AI tool created by William Chen, a former associate at Latham & Watkins. It is freely available at mikeoss.com and on GitHub. The tool supports document creation, editing, review, tabular bulk review, and workflow customisation, and runs on Claude or Gemini. It can be deployed locally for full data control.