diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 00000000..c66be4df
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,33 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code when working with this repository.
+
+## Shared Instructions
+
+Project-level AI coding instructions are maintained in a single shared location:
+
+- **[`.github/copilot-instructions.md`](.github/copilot-instructions.md)** — the primary reference for project overview, architecture, development workflow, testing, coding standards, and contribution guidelines.
+
+Please read that file for full context before making changes.
+
+## Quick Reference
+
+```bash
+# Build (required before testing)
+npm run build
+
+# Lint and auto-fix
+npm run lint
+npm run fix
+
+# Run all tests
+npm test
+
+# Run tests for a specific Node.js version
+npm run test:20
+npm run test:22
+npm run test:24
+
+# Watch mode (rebuild on change)
+npm run start
+```