CSES Forge от Karan Yadav

CSES Forge turns any CSES (cses.fi) problem page into a full in-page IDE, so you can read the problem, write code, test it, and submit — all without ever leaving the tab.

Key features:
• Problem statement, constraints, and examples shown right next to your code, scraped straight from the page (with math rendered).
• A real Monaco code editor (the same engine behind VS Code) for C++, Python, and Java, with adjustable font size and word wrap.
• Code is saved automatically per problem and per CSES account, so nothing gets lost or mixed up if you switch accounts.
• A Test Cases panel pre-filled from the problem's own examples — add your own inputs, hit Run, and see output for every case instantly.
• One-click Submit that fills in and submits CSES's own official submission form, so your real verdict always comes from CSES's judge, not a third party.
• Light/dark theme that automatically follows CSES's own theme toggle.
• Resizable panels so you can arrange the workspace however you like.

No account, sign-up, or backend server required. CSES Forge runs entirely client-side in your browser, and only talks to cses.fi (to read problems and submit) and a public code-execution API (to run your test cases).

Open source: https://github.com/karanBRAVO