NowCoder MCP Server | 牛客 MCP Server

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A local MCP server for searching NowCoder problems, reading statements, importing browser tasks, running saved code, and submitting after confirmation.

Quick Start

git clone https://github.com/ketherworks/nowcoder-mcp-server.git
cd nowcoder-mcp-server
npm ci
npm run build

Open MCP: Open User Configuration in VS Code and add:

{
  "inputs": [
    {
      "type": "promptString",
      "id": "nowcoder-cookie",
      "description": "NowCoder Cookie request-header value",
      "password": true
    }
  ],
  "servers": {
    "nowcoder": {
      "type": "stdio",
      "command": "node",
      "args": ["C:/path/to/nowcoder-mcp-server/packages/nowcoder/dist/index.js"],
      "env": {
        "NOWCODER_SESSION_COOKIE": "${input:nowcoder-cookie}",
        "COMPETITIVE_COMPANION_PORT": "10043"
      }
    }
  }
}

Start the server from MCP: List Servers. VS Code prompts for the Cookie once and stores the input securely. For public reads, remove the Cookie input and NOWCODER_SESSION_COOKIE; the browser-import port can stay.

Try these prompts:

Search NowCoder for "binary graph" and return the first 10 problems.
Import NowCoder problem NC218144.
Open a NowCoder browser-import window.
Read my NowCoder competition profile and latest 20 submissions.
Run the first sample for my saved main.cpp on NowCoder.
Prepare my saved main.cpp for submission.

What It Can Do

Workflow	Available actions
Problems	Search the ACM catalog and read normalized statements, samples, limits, and tags.
Browser import	Receive one problem from Competitive Companion on a loopback-only port.
Account	Check the local login state, read a compact profile, and list submissions without source code.
Run	Upload a confirmed immutable code snapshot for one platform sample run, then poll the result.
Submit	Build a two-minute preview, ask for confirmation, submit once, and poll without resubmitting.

Tool Reference

• oj_capabilities: discovers the active transport, authentication mode, operation risk, and language support.
• oj_health: reports transport and parser health from real adapter activity.
• oj_fetch_problem: converts an official problem page into a typed OjProblemDocument with statement, limits, samples, tags, provenance, and hashes.
• oj_search_problems: searches the official ACM catalog by keyword with bounded cursor pagination.
• oj_open_import_window: opens a one-shot Competitive Companion receiver on loopback for up to 60 seconds.
• oj_complete_import: receives the browser task, samples, and limits as a typed import preview.
• oj_fetch_profile: reads a compact competition profile by numeric ID, or resolves the signed-in account.
• oj_list_submissions: pages through verdict, problem, language, time, memory, code length, and submission time without reading source code.
• oj_platform_run: uploads an immutable code artifact after confirmation and runs one sample on NowCoder.
• oj_poll_run: continues a dispatched platform run by requestId without uploading code again.
• oj_prepare_submission: validates account, problem, language, file hash, and code size, then creates a two-minute preview without submitting.
• oj_commit_submission: shows an MCP-native confirmation form, obtains a fresh short-lived token, and submits exactly once after acceptance.
• oj_poll_submission: polls a submission created by this process and never resubmits it.
• nowcoder_auth_status: validates the local session and returns a redacted login state.

Submission Flow

1. Save the source file, then call oj_prepare_submission. The server resolves its file: URI and verifies the on-disk bytes, canonical problem, account or team, contest, language, and SHA-256.
2. Call oj_commit_submission; VS Code displays the confirmation form.
3. Accept to create one real submission, then call oj_poll_submission for the verdict.

Declining or cancelling creates no submission. An ambiguous network timeout returns outcome_unknown and is never retried automatically.

Browser Import

Install Competitive Companion and set its custom port to 10043. Call oj_open_import_window, click the green plus on the problem page, then call oj_complete_import. The loopback listener closes after receiving one problem or after 60 seconds.

Problem IDs

Use a URL or one of the compact IDs below:

NC218144       -> https://ac.nowcoder.com/acm/problem/218144
11244/A        -> https://ac.nowcoder.com/acm/contest/11244/A

Login

Sign in to NowCoder in a browser, inspect a request to ac.nowcoder.com, and use its complete Cookie request-header value when VS Code prompts. Restart the MCP server after rotating the session.

The Cookie is read once at process startup and never returned through MCP output. The complete Cookie is sent only to validated ac.nowcoder.com pages; the access-token host receives only csrf_token and NOWCODER* cookies, while question metadata and judge hosts receive no Cookie. Redirect targets are checked before a follow-up request receives authentication.

Security

• Local stdio transport only.
• Exact HTTPS host and path allowlists, public-IP DNS validation, and TLS address pinning.
• Shared 10-second request deadline, 2 MiB response limit, 16 KiB Cookie limit, and bounded redirects.
• Strict tool schemas with no Cookie field; redacted errors and authentication status.
• Cookie, CSRF token, and short-lived judge token never enter MCP output, MCP errors, process logs, or submission previews.
• Judge actions re-read a saved local file: URI before confirmation and again before upload; dirty, changed, or mislabeled artifacts are rejected.
• Every real submission requires a fresh confirmation; platform self-test also confirms before uploading code.
• Anti-bot challenges are surfaced as challenge.required for the user to complete in a browser.

Development

npm run typecheck:test --workspace @ketherworks/nowcoder-oj-mcp
npm test --workspace @ketherworks/nowcoder-oj-mcp
npm run pack:check --workspace @ketherworks/nowcoder-oj-mcp

Tests use synthetic sessions, static fixtures, and loopback-only TLS servers.