A precedent-search agent that gave a 40-lawyer firm its evenings back
Archway LLP
Open the live demo →of eval questions answered with correct citations
92%
median associate research time saved per week
11 hrs
total inference cost at firm-wide usage
£380/mo
The problem
§ 01Archway, a 40-lawyer commercial firm, had three decades of precedent documents spread across a document management system that search had effectively given up on. Associates spent hours reconstructing work the firm had already done — and partners knew it, because they were billing the rework.
The firm had been pitched 'AI transformation' twice by larger consultancies. Both proposals started with a six-figure platform and ended without a measurable definition of success.
The build
§ 02We started with the measurement, not the model: fifty real questions from partners, with the documents a good answer should cite. That evaluation set was the contract for the whole engagement.
The pipeline ingests the DMS nightly, chunks documents with their legal structure intact, and serves a retrieval agent that always cites its sources — answers without grounding are refused, not improvised. Claude does the reasoning; the firm's documents do the knowing.
We shipped to five partners first, watched the traces, fixed the retrieval misses, and only then rolled out firm-wide with usage analytics and a running-cost dashboard the managing partner can read.
“Every other vendor led with the demo. Lathe led with how we'd know it was working. That's why this one actually stuck.”
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