Gem Coder

Gem Coder is Team 4276's private robot-code assistant. It connects to a DGX Spark running vLLM and can work safely with one project folder on the student's own computer. Its built-in subsystem skill teaches the team's WPILib architecture and provides subsystem and constants templates.

For the DGX Spark administrator guide, see DGX Spark setup.

Student quick start (Windows)

1. Connect to the classroom Wi-Fi.
2. Open the Gem Coder folder your instructor shared with you.
3. Double-click Start Gem Coder.cmd.
4. Keep the small black window open while using Gem Coder. The app opens in the browser automatically.
5. Ask a coding question.

No terminal commands, server address, workspace URL, or workspace token are needed for the normal student workflow.

Work with a project

1. Select Connect a project in the sidebar.
2. Select Choose folder.
3. Pick the folder where the project is saved, then select Connect project.

Gem Coder can inspect, search, edit, and build only inside the selected folder. It keeps file and search activity out of the conversation. Before it edits a file or runs a build, it asks the student to approve or reject that action. It answers only coding-related questions and briefly redirects unrelated questions back to coding. Its built-in instructions emphasize teaching the student how to reason through a problem instead of simply completing the work.

Requirements

Node.js 18 or newer is the only local prerequisite for the normal Gem Coder browser workflow. No package installation is required. If Node.js is missing, ask an instructor or school IT for help.

node --version

Skills

Gem Coder includes the 4276-subsystem-code skill. It is available automatically and contains Team 4276's subsystem conventions, base-class reference, and Java templates. Students do not need to install it.

Gem Coder chooses a relevant skill automatically. To select one explicitly, start the message with its name prefixed by $:

$4276-subsystem-code Create an elevator subsystem.

An explicit $skill-name reference is validated and its full SKILL.md is loaded before the request is sent to the model. Type $ in the chat box to open the skill picker; use the arrow keys and Enter or Tab to select a skill.

Additional skills add reusable instructions and supporting text files. To install one:

1. Select Skills in the sidebar.
2. Select Choose SKILL.md under Install a skill.
3. Choose the skill's SKILL.md file. Supporting files in the same folder are installed with it.
4. Select Install skill.

A minimal skill looks like this:

explain-code/
└── SKILL.md

---
name: explain-code
description: Explain unfamiliar code in student-friendly language.
---

When asked to explain code, start with its purpose, then walk through the
important parts and define unfamiliar terms.

Gem Coder shows each available skill's name and description to the model, but does not load every skill's full instructions. It loads a skill only when the request clearly matches its description or the student names it. For example, start a new chat with Use explain-code to help me understand this function. Skills may include references and templates in subfolders; Gem Coder can read those text files when SKILL.md refers to them. Installing a skill does not run scripts from the skill folder. To uninstall one, open Skills and select Remove beside its name; this deletes only Gem Coder's installed copy.

Bundled skills live in bundled-skills alongside the app and cannot be removed from the Skills screen. Additional skills are stored per Windows user in %LOCALAPPDATA%\GemCoder\skills. On Linux and macOS they are stored under $XDG_DATA_HOME/GemCoder/skills, or ~/.local/share/GemCoder/skills when XDG_DATA_HOME is not set. Advanced users can override the location with:

node companion.mjs --serve-app --skills-dir /path/to/skills

Linux and macOS

On Linux or macOS, open a terminal in the Gem Coder folder and run:

sh "Start Gem Coder.sh"

Keep the terminal open while using Gem Coder; press Ctrl+C to stop it. The launcher checks for Node.js 18 or newer and opens the app in your browser. If the browser does not open automatically, open http://127.0.0.1:8787. Linux supports browsing for project folders and skill files through Zenity or KDialog in a desktop session. Install either with your package manager if needed (for example, sudo apt install zenity on Ubuntu). You can also paste the path into the connection dialog. On macOS, enter the path manually.

Verify a development checkout

Run the built-in integration test (no package installation is required):

node --test companion.test.mjs

Instructor setup

Distribute the complete Gem Coder folder, including Start Gem Coder.cmd, Start Gem Coder.sh, companion.mjs, linux-picker.mjs, pick-folder.ps1, and index.html. The default browser app configuration is:

DGX Spark IP: 192.168.1.180
Model:        gem-coder

Gem Coder automatically turns that address into http://192.168.1.180:8000/v1. Replace the example with the current Spark IP, which you can find by running hostname -I on the DGX Spark.

The local companion binds only to 127.0.0.1; it is not exposed to the local network. It scopes file access to the folder the student selects.

Start vLLM on the DGX Spark:

cd ~/git/code_gem
source .venv/bin/activate
export VLLM_USE_DEEP_GEMM=0

vllm serve ./models/Qwen/Qwen3.6-35B-A3B-FP8 \
  --host 0.0.0.0 \
  --port 8000 \
  --served-model-name gem-coder \
  --max-model-len 32768 \
  --max-num-seqs 2 \
  --enable-auto-tool-choice \
  --tool-call-parser qwen3_xml