Decagon lets you edit problem statements, tests, solutions, files and scoring, build packages, and commit revisions — all backed by local folders you control. Each problem is one folder bound to one Polygon problem.
Independent project, not affiliated with Codeforces. Pushing the final package into a round still happens on the Codeforces website.
 Info — limits, checker/validator, points mode |
 Statements — per-language fields & resources |
 Files — solutions, source, resources & attachments |
 Tests — groups, points & generation scripts |
- Install — download the installer from the Releases page, or run
from source:
npm installthennpm run dev. - Add your API key — in Polygon, go to Settings → API keys and create one. Enter the key and secret in Decagon (stored encrypted on your device; it never leaves your machine).
- Create or import a problem:
- New project — scaffolds a local folder. Open it and either bind an existing Polygon problem id, or create a brand-new problem on Polygon (with any name).
- Import from Polygon — pulls an existing problem by its id into a new folder.
This is the core idea, so it's worth 20 seconds:
- Save writes to your local folder only. Every file and section has its own Save button, enabled only when you have unsaved changes.
- Push to Polygon uploads your saved folder to Polygon. (Unsaved edits aren't pushed — Decagon warns you.)
- Pull downloads the current state from Polygon into the folder.
- If a file changed outside the app since you opened it, Decagon asks whether to keep your in-app version or load the version from disk.
One exception: saving a generation script also pushes it to Polygon, since scripts must be on Polygon to generate tests.
| Tab | What you do there |
|---|---|
| Info | Time/memory limits, input/output files, interactive flag, checker/validator/interactor, and points mode (off / on / treat checker points as %). |
| Statements | Edit each field (legend, input, output, scoring, notes, …) per language, plus shared resources (images, .sty). |
| Files | One place for every file, in four sections: Solution files (each with a tag — main, correct, wrong answer, TLE, …), Source files (generators, validators, checkers — use testlib.h), Resource files (headers, .sty), and Attachments. A unit's Type dropdown moves it between sections. Resource files support experimental grader advanced properties (stages / assets / cpp.* python.*). |
| Tests | Manual and script-generated tests per testset, the generation script, scoring groups (points/feedback policy, dependencies), and points per test. Bulk-edit groups/points across many tests. |
| Validator tests | Feed an input to the validator and assert it's accepted or rejected. |
| Checker tests | Feed input/output/answer and assert the checker's verdict. |
| Packages | Build a package (full / verify), see its status, and download the ZIP. |
| Commit | Save a revision of your working copy on Polygon. |
| Manage access | View your access level (read-only — change collaborators on the Polygon site). |
A sidebar on the right stays visible across tabs: a Project status card summarizes the problem at a glance (statements, checker/validator, test & solution counts, owner, access, revision, latest package, uncommitted changes) and a Notifications panel keeps a log of recent actions so toasts that auto-dismissed aren't lost.
- Pull (or Import) to get the latest problem state.
- Edit a statement / solution / test, and Save that item.
- Push to Polygon when you're happy with the saved changes.
- Build a package in the Packages tab and download it.
- Commit to save a revision.
- Upload the package into your round on the Codeforces website (manual step).
- Removing a test locally and pushing deletes it on Polygon. Other items (files, solutions, statements, resources, validator/checker tests) have no delete API — remove those on the Polygon website.
- Testsets can't be created here (no API) — make them on the Polygon site, then Pull.
- Binary files (e.g. statement images) are pulled but not pushed back.
- Stress testing and access management have no API, so they aren't editable here.