Inline for Codeforces

Unofficial. Not affiliated with, endorsed by, or sponsored by Codeforces.

Browse contests, gyms, and group contests, read statements, run samples, submit, and keep a searchable local history of every attempt — without leaving VS Code.

Before you install — read this

Browsing works with nothing else installed. Opening a problem, viewing a group, and submitting all need a second, free browser extension — that's not a rare case, it's most of what this extension does. Why: Codeforces blocks this extension's own network requests outright, and its submit form has a CAPTCHA only a human in a browser can solve. There's no way around either from inside VS Code. Full detail in Architecture, below.

If that's a dealbreaker, this extension isn't for you yet. If it's fine, the companion takes about two minutes to set up — run Codeforces: Setup walkthrough after installing, or follow Install below.

Requirements

• VS Code 1.85+
• Google Chrome (or a Chromium browser that can load an unpacked MV3 extension) — for the companion, needed for anything beyond browsing
• A Codeforces account, if you plan to submit

Install

You've already got this extension — that's how you're reading this. The one extra step is the companion browser extension.

1. Get the companion

Chrome Web Store — submitted, pending review; not live yet. Once it's live, this becomes a one-click install and the manual steps below won't be needed.

Manual install (works today):

1. Open the latest release on GitHub and download codeforces-inline-companion-*.zip from Assets.
2. Unzip it anywhere.
3. In Chrome, go to chrome://extensions, turn on Developer mode (top right), click Load unpacked, and select the folder you just unzipped.

2. Connect it to VS Code

1. In VS Code, run Codeforces: Relay info — copy the port and token it shows.
2. In Chrome, open the companion's card on chrome://extensions → Details → Extension options → paste the port and token → Save.
3. Stay signed in to codeforces.com in that Chrome profile, with a tab open.

Codeforces: Setup walkthrough covers this in the app, with the reasoning. Codeforces: Check companion tells you if it's working.

Quick start

1. Open the Codeforces icon in the Activity Bar. The tree populates immediately — Contests, Gym, Problemset, Groups — no setup, no login.
2. (Optional, no login needed) Set codeforces.handle in Settings to see your solved/attempted marks.
3. Click a problem. First time, you're asked for a workspace folder — where your solutions and history live; it's global, not per-project.
4. Write your solution, then Ctrl+Alt+R to run the samples in the Results panel, or Ctrl+Alt+Enter to submit.
5. For groups: Codeforces: Add group, paste the group code or its URL.

Features

• Sidebar: Contests, Gym, Problemset (browse by rating), and your groups, with solve/attempt state and API-backed solved marks.
• Statement webview beside your solution file, with samples, limits, and images.
• Results panel (below the tree): one card per test — PASS/FAIL badge, runtime, input/expected/actual with the first differing line highlighted. Passing cards collapse; failing ones stay open. Add your own test cases. Compile errors show verbatim, in the panel, not a toast. Submit and watch the verdict from the same panel.
• Submission compiler shown in the status bar next to the open problem — click to change it. Picking a different language scaffolds that language's file in the same problem folder (never touching one that already exists); run and submit always act on whichever file is focused, not a global setting, so C++ and Python solutions for the same problem coexist and compile independently.
• Local archive of everything you've done — every run and every submission, including the ones Codeforces refused outright — searchable offline in a dedicated Archive view (its own Activity Bar icon): browse by judge → contest/group/gym → problem, a timeline per problem (consecutive identical outcomes collapse into one row), click any entry to reopen that exact source read-only and diff it against your current file.
• Codeforces: Stats — attempted / solved / solve rate / attempts-per-solve, a verdict breakdown, and a language breakdown, from that local history. Click a group, gym, or contest in the Archive view for the same scorecard scoped to just that one.

Commands

Ctrl+Alt+R / Ctrl+Alt+Enter only fire with an editor focused, and deliberately avoid Ctrl+Alt+B / Ctrl+Alt+S, which the cph extension claims. Rebind them under codeforces.runTests / codeforces.submit in Keyboard Shortcuts if you like.

Settings

Architecture — why the companion extension is required

With the companion unloaded, browsing and solve marks still work (read-only API). What needs it — opening a statement, listing a group's contests and problems, submitting, and polling a verdict — is forced, not a preference:

1. Node can't reach Codeforces' HTML at all. Codeforces runs Cloudflare in a mode that rejects Node's TLS handshake fingerprint before the request reaches Codeforces — every HTML route returns a 403 "Just a moment…". A valid session cookie does not help; neither does importing cf_clearance + the browser User-Agent (tried, still 403 — the block is on the TLS fingerprint, not the cookies). Only codeforces.com/api/* is exempt.
2. A browser service-worker fetch isn't a page fetch either. The companion's background fetch also gets a Cloudflare 403 — it sends Sec-Fetch-Site: none and no Referer, and Cloudflare scores it as non-browser. So the companion re-runs each read as a real page-context fetch (chrome.scripting.executeScript, MAIN world) inside a logged-in codeforces.com tab, which sends the right headers and the right TLS. You must keep one codeforces.com tab open that has passed the "Just a moment" check.
3. The submit form has a Cloudflare Turnstile CAPTCHA. There is no way to produce a valid Turnstile token headlessly. The companion opens the submit page and fills in the compiler, problem and source; you solve the Turnstile and click Submit yourself. VS Code then finds the new submission and polls the verdict (also via the companion).
4. Group contests are invisible to the API. contest.list has no group parameter with or without a signed key, so group contest/problem lists are scraped from /group/<code>/… — through the companion, per point 1.
5. Codeforces has no write API. /apiHelp has promised submit methods "soon" for years. Don't wait for it.

The extension runs a token-guarded localhost relay on 127.0.0.1 (codeforces.relayPort, default 27121); the companion polls it, and the two sides check a protocol version on every health check so an out-of-sync pair fails with a clear message instead of a silent hang. Codeforces: Relay info shows the port and token to paste into the companion's options once; Codeforces: Check companion reports whether it's connected. Reads are cached hard on disk (statements 30 days, group lists 15 minutes) since each one is a poll round-trip. If Cloudflare's under-attack mode is ever off, codeforces.directSubmit posts straight from the extension instead.

See browser/README.md for the companion in detail and browser/PRIVACY.md for what it does and doesn't send anywhere.

Local archive layout

Everything lives under your workspace folder, keyed by { judge, scope, contestRef, index } so another judge (LeetCode, AtCoder, …) could slot in beside codeforces/ without a migration:

<root>/
  codeforces/
    group-<code>-<contestId>/  gym-<contestId>/  contest-<contestId>/
      A/
        A.cpp                       one file per language you've tried
        A.py                        — .meta.json below is shared by all of them
        .meta.json                  ref, problem, samples, user tests
        runs/<timestamp>.json       one per local run, tagged with language
        attempts/<timestamp>.json   one per submission, tagged with language
  .archive-index.json               rolled-up index for fast reads

.meta.json + attempts/ are the source of truth for the tree's solve state and Codeforces: Stats — they hold tries Codeforces refused outright, which user.status never shows. Pre-existing group-*/gym-*/<digits>/ folders and .cf/*.json files (an earlier, pre-1.0 layout) are migrated into this layout the first time you point the extension at a folder that has them: copy, verify, then remove the originals (build artifacts like A.exe are left where they are).

Privacy

The extension talks to codeforces.com and (for the companion pairing) 127.0.0.1 — nothing else, no analytics, no telemetry. Your session lives in VS Code's SecretStorage. Full detail, permission-by-permission, in browser/PRIVACY.md.

License

GPL-3.0-or-later — see LICENSE. In short, for anyone forking this: if you distribute a modified version, it must also be open source under the GPL.

Contributing

Building from source, the repo layout, the self-test suite, and where the HTML scrapers are most likely to break next are all in CONTRIBUTING.md.