Big law's open-source moment
2026-10-22 · Models
The first wave of legal AI was bought. The second is being built — and open source moves the know-how back to the firm.
The shift is not about licences. It is that the method is moving from the vendor back to the firm.
The first wave of legal AI was bought: six-figure licences, a vendor in the room, a security questionnaire the size of a novel. The second wave is being built.
Firms are assembling their own precedents, prompts and evaluation sets because the generic product never quite fits how they work. Open source accelerates that — not because partners love GitHub, but because a firm can read the code, host it privately and keep privileged material inside its own walls.
The interesting shift is not the licence. It is that the know-how is moving from the vendor back to the firm.
Written for legal professionals. Not legal advice. Always verify every authority and let a named lawyer sign off.