Source Authorship Forensics · CCRL 40/40

Arasan — the veteran that picked up an AI assistant

A source read of jdart1/arasan-chess — the single most interesting find of the CCRL top-50 sweep.

Author Jon DartLanguage C++Scope In development since 1994Eval NNUE + classical heritageCCRL 40/40 #32Stockfish similarity Moderate →

Verdict · Human (AI-assisted)

Human beyond any doubt — and, at 30 years old, now assisted by AI.

Arasan has been developed by Jon Dart since 1994 — one of the longest-running engines in computer chess, predating the entire notion of AI code generation by decades. Its authorship is not in question.

Yet Arasan was the only engine in the entire CCRL top-50 scan to trip the AI-marker test: it ships a src/CLAUDE.md — a project-instructions file (code conventions, architecture) for the Claude Code assistant. Like Triumviratus, this is a veteran expert using AI as a tool in a long-established workflow — the opposite of AI-generated code.

Confidence: High — a human engine of record, with a documented AI-assisted workflow.

One of three standouts from a sweep of the CCRL 40/40 top 50 — see the full survey, or the wider engine-forensics index.

1The only AI-marker in the elite set

Across ~30 cloned top-50 engines, exactly one carried an AI-assistant artifact.

# src/CLAUDE.md
# Project: Arasan
## Code Conventions
- clang-format for formatting; indent 4, spaces not tabs
- static constants UPPER_CASE; class/struct names Uppercase; functions lowercase
## Project Structure
- /src ... /nnue (NNUE code) ... /syzygy ... /utils

Tool, not author. A CLAUDE.md that documents an existing codebase’s conventions and architecture presupposes a large, mature project for the assistant to help navigate — here, three decades of it. It marks Arasan as AI-assisted, in exactly the sense a veteran developer adopting a modern tool would be.

2Compare & contrast with Stockfish

Where it resembles Stockfish
Bitboard core; NNUE evaluation; Syzygy tablebases
Modern alpha-beta search stack
Actively developed and competitively rated

Where it differs / is its own
A 30-year independent lineage predating the NNUE era
CECP/xboard roots (not just UCI); its own GUI
Own long-evolved evaluation and structure
Moderate, not close, similarity to Stockfish

Bottom line

Arasan is a human-written engine of record — three decades of one developer’s work — that has quietly adopted an AI assistant, as its CLAUDE.md shows. It was the sole AI-marker hit in the CCRL top-50 sweep, and it lands in the same AI-assisted band as Triumviratus: unambiguously human, tool-augmented. The most human-pedigree engine in the set is also, neatly, the one that proves AI assistance is now everywhere — even at the 30-year mark.