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chess-context: Instructions file for Claude Code

CLAUDE.md

chess-context CLAUDE.md is an instructions file for Claude Code from rutvij26/chess-context. It costs 991 tokens per session, scanned A, original, MIT.

A set of project instructions for a chess analysis server. The server connects to chess data and analysis engines through a standard tool interface and includes opening and training features.

In plain words
What is it for?
Use it when developing or maintaining the chess server, including its TypeScript build, chess-engine integration, caches, data sources, analysis tools, and opening or puzzle features.
Why use it?
It gives an agent the project’s current status, commands, structure, and design decisions so work follows the repository’s conventions.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions CLAUDE.md.

This is rutvij26/chess-context's own configuration. It tells Claude Code how to work on chess-context itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything chess-context configures →

not rated 5repo 2d ago A scan 991 tokens original MIT
View source ↗ rutvij26/chess-context rutvij26.github.io
Reuse

Borrowing it

Nothing to install: this file belongs to rutvij26/chess-context. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/rutvij26/chess-context/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/rutvij26/chess-context

Made for: Claude Code.

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Per session 991 This file is loaded in full into every session.
When invoked 991 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00991 $0.00991
Opus 5.5 $0.00396 $0.00396
Sonnet 5.5 $0.00198 $0.00198
Haiku 4.5 $0.00099 $0.00099

Measured 2mo ago against content hash 9da974e1d8c7, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

chess-context CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 85 lines

How it starts

The opening of the file, as written. The whole thing — 85 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

Status

v0.7.0 — 12 tools live. Opening & training tools added: get_opening_theory, find_opening_gaps, generate_puzzles. Next: v0.8 (endgame analysis, tilt detection).

Commands

cd mcp-server
npm run build   # TS → dist/
npm run dev     # tsx (no build)
npm start       # dist/index.js

stdio transport — not HTTP. Connect via Claude Desktop.

Structure

mcp-server/src/
  index.ts              # entry, tool registration
  config.ts             # env vars
  types/index.ts        # interfaces + Zod schemas
  cache/index.ts        # SQLite position cache + LRU player stats cache
  cache/sqlite-cache.ts # SQLite-backed eval persistence (survives restarts)
  engines/stockfish.ts  # WASM UCI wrapper
  engines/lichess-eval.ts # cloud eval (tried first)
  intelligence/         # pure fns, no I/O
  data/                 # chesscom-api.ts, lichess-api.ts
  tools/                # one handler per tool

Architecture

3 layers: Foundation (engines, data, cache) → Intelligence (pure fns, semantic annotations) → Tools (MCP handlers).

Key Decisions

  • Stockfish: WASM via npm, single-threaded, loaded with createRequire from ESM
  • Init: fire-and-forget after server.connect() — don't block MCP handshake (~30–60s warmup)
  • Eval routing: cache → Lichess cloud → Stockfish
  • HTTP: axios everywhere (immune to Stockfish's fetch=null side effect)
  • Logs: console.error() only — stdout is MCP JSON-RPC
  • TS: strict + exactOptionalPropertyTypes. Imports use .js extensions. "type": "module"

Env Vars

Var Default Desc
STOCKFISH_DEPTH 18 default depth
STOCKFISH_QUIET_DEPTH 10 quiet positions (pass 1)
STOCKFISH_CRITICAL_DEPTH 16 critical positions (pass 2)
STOCKFISH_TIMEOUT 30000 ms per position
STOCKFISH_READINESS_TIMEOUT 90000 ms to wait for engine init before rejecting tool calls
LICHESS_TOKEN — optional, higher rate limits (allows LICHESS_CLOUD_CONCURRENCY=25)
LICHESS_CLOUD_CONCURRENCY 10 max concurrent cloud eval requests (safe default; raise to 25 with a token)
EVAL_CACHE_DB ~/.chess-context/eval-cache.db SQLite eval cache path

Read the full file on GitHub · 85 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2mo ago First seen · 85 lines · 991 tokens per session scan A 9da974e1d8c7

Subscribe to this mod's changes

chess-context CLAUDE.md is an instructions file published in the GitHub repository rutvij26/chess-context (5 stars, last pushed 2d ago), licensed MIT. It adds 991 tokens to every session, about $0.0040 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

chessclaudelichessmcpmodel-context-protocolstockfish
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