Docs

Start with the page for what you are doing.

Development: run TandemCode locally, run the checks, and make common changes.
Architecture: the parts of the system, how a request and a run move through them, and where each piece lives in the code.
Judge and sandbox: how submissions are judged and what isolates them.
Self-hosting: run your own instance on one Linux host.
Decisions: why the system is shaped the way it is.

Adding a problem is in CONTRIBUTING.md.

Keeping these pages current

These pages go stale when they copy what the code already says. So they follow a few rules:

Explain what and why. Leave exact values in the code. A page names the constant or file that holds a limit, port or timeout (MAX_SOCKETS_PER_USER in app/websocket/room_chat.py), and does not repeat its value.
Link to files and directories, not line numbers.
Change a page in the same pull request as the behaviour it describes. The pull request template asks.
Decision records are written once and not edited. When a decision changes, add a new record that replaces the old one, and mark the old one as replaced.
CI checks every relative link in the repository's Markdown, so a moved or deleted file fails the build.