How a CS class at UIUC knows you are cheating

How a CS class at UIUC uses your VSCode editing history and ai agent’s server cache to file FAIR allegation against you.

I do not support the use of AI to do all the coursework, neither do I support scanning all student files to gather proof that you have used AI. This post is not intended to attacking anyone (I really liked and enjoyed most of the classes, A LOT).

I am not a course staff for this class and none of them shared any information with me. Anything written here should be treated as pure speculations.

VSCode Timeline

Back in 2020, VSCode introduced a new feature called “Timeline”, see release note here.

This feature creates a json file under User/History/xxxxxx with an entries.json that contains the name of the source file being edited and the names of temporary snapshots of the file alongside with their timestamps:

{
    "version": 1,
    "resource": "file:///xxx",
    "entries": [
        {
            "id": "TaJo.c",
            "timestamp": 1776134288492
        },
        {
            "id": "FiDo.c",
            "timestamp": 1776134299434
        }
    ]
}

for VSCode server, the directory is located at ~/.vscode-server/User/History

Various Agentic Coding tools

Similar to vscode timeline, claude/gemini/codex stores their logs on the server in the following, monitored using auditd:

~/.aider.chat.history.md
~/.claude
~/.codeium/windsurf
~/.codeium
~/.codex
~/.gemini
~/.antigravity-server
~/.vscode-server/data/User/History
root/.aider.chat.history.md
root/.claude
root/.codeium/windsurf
root/.codeium
root/.codex
root/.gemini
root/.antigravity-server
root/.vscode-server/data/User/History

Fortune Teller

According to a screenshot, the internal tool used is called Fortune Teller, and from those screenshots, other courses might also be using them.

It does a few things:

1. check you CPS

   This can potentially be done by running diff on different versions of your code found in entries.json and then calculate the file change against time spent.

2. check non UTF-8 characters