HashAgent – Share an AI agent as a URL, runs locally via WebGPU

masonhsu

Hi HN, author here. HashAgent started with a simple question: can you run a useful AI agent with zero hosting costs? The answer I landed on: the user's own device is the server. How it works: - The entire agent definition (name, system prompt, greeting, generation config) is encoded as compressed base64url JSON in the URL hash fragment. The hash never hits a server — sharing a link is sharing the agent. - Inference runs in-browser via WebGPU. Two runtimes: WebLLM (MLC) for Llama 3.2 / Phi / Mistral / Qwen, and Transformers.js for newer ONNX models like Gemma 4 E2B and LFM2 1.2B. First load downloads the weights, then they're cached and work offline. - Tools are split into two tiers. Local tier (calculator, time, Wikipedia, weather via direct CORS calls) never touches my infrastructure. Gateway tier (web search, page reading) goes through open-source Cloudflare Pages Functions because search engines don't allow browser CORS — this can be switched off in settings, at which point nothing touches any server I run. - Each turn runs a temperature-zero planning pass that can only emit a JSON tool call matching an allowlisted schema, separate from the answer pass — so 1B-class models don't accidentally "hallucinate" tool invocations mid-prose. Honest limitations: - Model ceiling is ~8B quantized on 16GB+ desktops. Phones are realistically 1B-class (LFM2 1.2B / Llama 3.2 1B). These are single-task agents, not GPT-4 replacements. - iOS is the hard wall: WebKit caps a single tab at roughly 1.5GB regardless of how much RAM the iPhone has, so iPhones are locked to the smallest models. Mid-range Android often outruns the newest iPhone here. - First load is a 700MB–2GB download depending on the model. After that it's cached. - Optional short links (/s/<id>) store the agent payload in KV for social previews — the full hash URL remains self-contained and works even if this deployment disappears. MIT licensed: https://github.com/mason131928/hashagent Happy to answer anything about squeezing LLMs into browser memory limits — the iOS jetsam debugging alone was a journey.

voodooEntity

Funny, i did this myself some months ago - its actually not that tricky to run a llm in your browser. Tho, the problem is that the models fitting in there are well relativly "tiny" in my opinion. Cool idea tho to make it as accessible (:

iamcoder18

What models have you been able to run with this?

bicepjai

One click agent run on browser, What can go wrong :)

vivzkestrel

so thats the library it uses under hood https://npmx.dev/search?q=%40mlc

postpress

This is excellent! The Web Platform is great for agents, especially given the browser already is the user's agent itself. Give Prompt API (or other providers, Transformers.js, LiteRT-LM) a try. You can have agents communicate over WebRTC as well: https://xt-ml.github.io/shadow-claw/