Claude Code Has 6 Ways to Authenticate. I Built a Cross-Platform Installer Because of It

TL;DR Claude Code supports 6 different authentication methods with a strict priority order. Get the order wrong and your Pro subscription silently gets overridden by an API key, costing you real money. I built claude-auth-setup — a cross-platform installer (Bash + Batch + PowerShell) that handles the whole thing correctly. MIT licensed, ~17KB of bash, zero runtime dependencies. This post walks through the design decisions, the cross-platform tax, and the testing approach. The Problem The Claude