Large language model platform supports hospital tasks inside secure network
The LLENS Platform for On-Premises Large Language Model Agents in a Japanese University Hospital: Development and Evaluation Study
Computation and LanguageArtificial Intelligence
Summary
Hospitals often have secure networks that prevent outside software from accessing sensitive patient records. The authors created LLENS, a platform that runs a large AI language model inside such a secure hospital network in Japan. This system helps doctors by reading hospital documents and answering questions accurately when it can interact with the documents. The AI performs better when it can access documents dynamically rather than relying on limited preselected data. LLENS has been running at the hospital since 2026, helping with tasks like injury response and data analysis.
What this means in practice
- •For hospital it teams: Deploy AI assistants within secure hospital networks that handle sensitive patient data and support physician desk work safely.
- •For enterprise ai developers: Build internal AI platforms for document processing and question answering when external cloud access is prohibited.
Authors
Ken Enda, Jien Saito, Masami Mukai, Feng Han, Emir Turkes, Tatsumi Kusakabe, Reona Umeki, Kazuhiro Sumiyoshi, Mitsuya Numata, Takumi Tanikawa, Akira Endoh, Kenji Hirata, Atsushi Yoshida, Kohsuke Kudo, Shinya Tanaka
Abstract
Large language model agents that use tools could take on part of the electronic health record and desk work that occupies physicians' time, but in many hospitals the medical information systems run inside closed networks, so the model and the agent harness must also sit inside. We designed, implemented, and deployed LLENS, a clinical support AI agent platform that runs inside the closed network of Hokkaido University Hospital on one host with 8 NVIDIA H200 GPUs, the open-weight model Kimi K2.6 (~1 trillion parameters), and a web application rebuilt from Open WebUI. The harness has 10 components, including page image reading, full-text attachment input, a path-addressed document tree without a vector index, a network-isolated sandbox, artifact return, self-checking of generated output, subagents, and saved procedures. Kimi K2.6 was chosen from 3 open-weight candidates and scored 480/500 on the 2026 Japanese Medical Licensing Examination; it generated 119 tokens/s for one user and served 16 concurrent requests at 908 tokens/s in total. On 180 questions over hospital documents (3 seeds each), mean accuracy was 10.7% with no documents, 81.3% with fixed retrieval (top 10 chunks of one lexical search), and 97.2% with interactive access, in which the model reads with document tools and the sandbox (15.9 percentage points above fixed retrieval, 95% CI 10.9-21.3); the difference lay in filtering/counting questions (16.7% vs 87.8%). Five scenarios with synthetic data ran on combinations of the components: needlestick injury response, batch adverse event grading, scanned referral letter transcription, falls data aggregation and plotting, and investigation of 3 topics by subagents. The platform has run on the hospital network since September 14, 2026.