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---
title: Elffuss Code
emoji: 🧑‍💻
colorFrom: purple
colorTo: pink
sdk: static
app_file: index.html
pinned: false
license: apache-2.0
short_description: A VS Code-style IDE with a local AI agent, in-browser
tags:
  - webgpu
  - transformers.js
  - local-llm
  - agent
  - code
  - gemma
---

# 🧑‍💻 Elffuss Code — a VS Code-style IDE with an AI agent, 100% in your browser

Open a local folder and a full web IDE unfolds around it — real Monaco (the VS Code editor),
a file tree, tabs — with an AI agent that **reads, searches and edits your project for real**.
The model runs on **your** GPU via WebGPU. Your code never leaves your machine.

> ⚠️ **Open it full-screen** ([direct link](https://kikocis-elffuss-code.static.hf.space)) — the
> File System Access API (opening a local folder) is blocked inside the embedded iframe.

![demo](https://utopiaia.com/demos/elffuss/elffuss-code-demo.gif)

In the demo a **small model running entirely in the browser** reads `calc.py`, finds a real
bug and fixes it with a minimal edit — genuine tool-calling, not autocomplete.

## Why it's different

- **Your code stays local.** The folder is opened via the File System Access API — no upload, no account.
- **The model runs on your GPU** (WebGPU, Gemma-4 E4B via LiteRT-LM; ONNX/transformers.js as fallback).
- **Real tool-calling**: `code.tree`, `code.read`, `code.search`, `code.edit`, `code.write` — you watch every call.
- **Edits, not rewrites**: the agent patches the lines that change, even in files of several megabytes.
- **Long tool results don't break the conversation**: they are compacted to fit the model's context instead.
- **Context retrieval that works beyond English** — accents and Cyrillic included (measurements below).
- **Real editor**: Monaco, file tree, tabs, `Ctrl+S`, and git branch/last commit parsed straight from `.git`.
- **Zero install, zero build.** Vanilla ES modules.
- **Your language**: the whole IDE follows your browser's language (English, Spanish and more).
- External providers (OpenAI, Anthropic, Ollama) are **opt-in**; keys stay in your browser.
- Optional local **bridge** for real `node` / `npm` / `python` execution — downloaded from the main site.

## How it's built

Write-ups on the full stack — model, runtime, agent harness, editor and filesystem access,
all in one tab: **<https://bitacora.utopiaia.com/#elffuss>**

## Context management — how it's measured

The context packer isn't chosen by intuition. Numbers measured at the **same token budget**:

**Real agent sessions** (25 sessions, 174 probes, fact recall, no LLM judge):

| | recall |
|---|---|
| tail truncation | 7.0 % |
| previous version | 15.1 % |
| **current** | **65.3 % ± 8.5** |

**Long-term memory** (200 questions, F1 from the benchmark's own repo, a real model answering, ~8 % of the context):

| | F1 |
|---|---|
| **the FULL context, uncompressed** | **22.56** |
| tail truncation | 6.62 |
| hand-written heuristics | 6.07 |
| BM25 without IDF | 20.34 |
| BM25 | 23.59 |
| embeddings | 23.95 |
| **rank fusion (BM25 + embeddings)** | **28.09** |

**Retrieving well beats having everything**: 28.09 vs 22.56 using 8 % of the tokens. Irrelevant context
isn't neutral ballast — it distracts.

Two more things that were measured, not assumed: turning the heuristics on cost **−3.02 F1**, and
removing IDF costs **−3.25**. Semantic search doesn't replace lexical search, it covers its blind spot:
with no vocabulary overlap between question and answer, embeddings win (24.28 vs 18.60); with overlap,
BM25 wins (29.33 vs 23.58) — and fusion keeps both.

References: BM25 (Robertson et al., TREC-3 1994) · IDF (Spärck Jones, 1972) · RRF (Cormack et al., SIGIR 2009) ·
MMR (Carbonell & Goldstein, SIGIR 1998) · attention sinks (Xiao et al., ICLR 2024) · valid time (Snodgrass & Ahn, SIGMOD 1985).

The full story, including what went wrong: <https://bitacora.utopiaia.com/posts/16-beaten-by-doing-nothing.html>

## The Elffuss family

- 🌐 Full app: <https://code.elffuss.com>
- 💻 Source (Apache-2.0): <https://github.com/KikoCis/elffuss-code>
- ✳️ Elffuss Claw — an agentic OS in your browser: <https://claw.elffuss.com> · [Space](https://huggingface.co/spaces/KikoCis/elffuss-claw)
- 🧬 Shared core: <https://github.com/KikoCis/elffuss>
- 🗣️ Elffuss Translator — speech-to-speech translation on your device: <https://translator.elffuss.com>
- 📝 Elffuss Copilot — live call notes that never leave your browser: <https://copilot.elffuss.com>
- 📰 All apps and the blog: <https://elffuss.com>