Blackletter, a law firm that integrates top-tier lawyers with a proprietary frontier technology platform, today announces a US$6 million seed round led by Lerer Hippeau, with participation from Seven Stars, Maple VC, Garage Capital, Ripple Ventures and leading AI founders like Aidan Gomez, Ivan Zhang, and Nick Frosst of Cohere; Jae Lee, CEO of Twelve Labs, and Sara Hooker, CEO of Adaption Labs.

Blackletter arrives as legacy firms race to adopt AI and evolve. Blackletter is challenging the status quo, pairing technology and seasoned lawyers to reinvent the practice of law and the client experience.

Blackletter will use the funding to further build out its platform and to grow its bench of best-in-class lawyers and engineers. Blackletter co-founders Jonathan Rosenbluth and David Stewart previously held product and engineering leadership roles at Cohere. Co-founder Avi Brudner was COO of Blue J, a leading AI software company serving tax professionals.

Blackletter combines frontier AI with an unwavering commitment to old-fashioned client service. It uses an outcome-based, fixed fee model to properly align incentives with its clients. To deliver quality work at exceptional speeds and more reasonable fees, Blackletter’s top-tier lawyers work inside BlackletterOS, its custom legal operating system and harness.

BlackletterOS draws on its co-founders’ experience developing and deploying frontier agentic AI systems at Cohere. BlackletterOS quarterbacks all legal matters, proactively working through multi-step assignments, and continuously digesting each client’s business context and preferences so that it gets better with every engagement. Blackletter’s benchmarking shows its lawyers completing tasks in less than half the time they would take at a legacy firm, and the output of BlackletterOS is consistently more accurate than work produced by leading legal software. On every matter, Blackletter’s lawyers make legal judgments, shape advice, communicate it to their client—and are accountable for the result.

BlackletterOS’s accumulated client knowledge is the foundation for Blackletter Proactive Intelligence (BPI), which the firm is developing to articulate legal needs and identify strategic business opportunities. BPI enables Blackletter’s lawyers to function not only as legal counsel but also strategic growth partners to its clients.

“The old law firm model is structured to benefit the firm and its senior partners, not the clients it serves or even many of the lawyers who work there. We built Blackletter the other way around. Our technology and structure unlock an opportunity for Blackletter to be a critical partner to our clients, delivering strategic advice that drives real impact,” said Jonathan Rosenbluth, co-founder and CEO of Blackletter. “Our proactive technology offering reflects our core conviction—that law should be an enabler for a business, not a tax on it.”

Since coming out of stealth in June 2026, Blackletter has built a client list of more than 75 early-stage and growth-stage companies and investors, including Ada, Antidote, Crux, Fanatics Betting & Gaming and Twelve Labs. Blackletter is handling a broad range of files for its clients, from complex transactions to day-to-day matters. The firm’s current practice areas include corporate, commercial, financing, M&A and employment.

Blackletter recently advised the atmospheric data startup WindBorne Systems on its $37 million Series B, the largest confirmed financing led by a challenger firm. “Blackletter’s advice has been 100x more sane than other firms. Clear answers, fast, from people who actually understand what a startup needs,” said John Dean, WindBorne’s CEO and co-founder.

“The legal industry is ready for structural change and truly functional solutions, which AI is making possible for the first time,” said Graham Brown, Managing Partner at Lerer Hippeau. “The Blackletter team combines native frontier AI experience with expertise in rapidly scaling legal operations, uniquely positioning them to execute on their mission to transform this massive legacy industry.”

About Blackletter

Blackletter is a radically new kind of law firm, which integrates elite lawyers with frontier technology. Working only on fixed fees, Blackletter is built to deliver strategic, proactive advice and exceptional outcomes. BlackletterOS, the firm’s proprietary legal platform, puts frontier AI to work on every matter, while Blackletter’s lawyers own every file and every client relationship. Blackletter was co-founded by Jonathan Rosenbluth, David Stewart and Avi Brudner. Learn more at blackletterfirm.com.

About Lerer Hippeau

Lerer Hippeau is an early stage venture capital firm based in New York City. Since 2010, we’ve been our founders’ first and most aligned institutional partner, backing them from “Day -1,” often before there’s an obvious market emerging, or a consensus-seeking crowd forming. Our portfolio comprises more than 400 leading enterprise and consumer businesses, including Zipline, Palmetto, Hungryroot, ZenBusiness, Guideline, Mirror, and Warby Parker. Learn more at lererhippeau.com.

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