Can we use a System One model in the browser?

I ran Laya, an open 421M-parameter decision model, in a browser tab and measured what it costs: download, speed and accuracy.

In mid-September, TypeSafe AI released Jev, a "System One" model. It doesn’t write text. You give it some input and a few typed questions, and it gives back answers with probabilities. A few days later Convai Innovations released an open alternative, Laya: 421M parameters, Apache 2.0, free to download. A model that small raises an obvious question for anyone who builds web apps: Can it run right in the browser, with no server, no API key, and nothing leaving the page? I tested it.

Setup

• Model: convaiinnovations/laya, the general English checkpoint. ModernBERT-large plus a decision head, 421,293,830 parameters.
• Browser build: layaForWeb, a community port to ONNX Runtime Web 1.30. It has two weight-only quantized builds:
  • The 8-bit one (q8e8) uses int8 block-128 MatMulNBits weights.
  • The 4-bit one (q4e8) uses int4 block-32 weights.
  • Both keep the embeddings in int8.
• Machine: Apple Silicon Mac (14 cores, Apple GPU with Metal 3), macOS 26.5, ~105 Mbit/s connection.
• Browsers: An embedded Chromium 152 browser inside a desktop app for loads, speed, and accuracy. Google Chrome 153 for memory and the background-tab test.
• Input: The port’s support-ticket preset (“App crashes on launch… I have a demo in one hour!”) with three questions: which team (a choice of 3), how urgent (a 4-level score), and is the customer angry (yes/no). Each question becomes its own sequence, and all of them go through one batched session.run(): 220 tokens for three questions, 75 for one.
• Timing: session.run()