Fareed Khan

Vellum is a glass-box agentic ICD-10 coder. Five Claude Opus roles read a hospital discharge summary, resolve each finding to a current code through live terminology tools, challenge one another, and sign off a chart. What makes it a product rather than a black box is that every code carries a receipt: the sentence the model quoted, and a deterministic verdict, with no model and no network, on whether that sentence exists in the note. The motivating finding is that a fluent model sometimes invents its citation, quoting a sentence that was never written, and a more capable model makes the fabrication more convincing. A code whose citation cannot be found is never accepted on the system's own authority. I evaluated it in two stages. On ninety real inpatient notes, self-hosted open models hallucinate most of their codes, and even with retrieval plateau near 0.16 exact F1. On four identical synthetic notes, the deployed pipeline reaches 0.93 to the best open configuration's 0.57, and it is the only one that grounds every code and fabricates none. The limits are stated as plainly as the numbers.