Migrating Claude Code to a custom backend in 2 lines (and what to actually watch for)

TL;DR: Claude Code's ANTHROPIC_BASE_URL env var lets you redirect every request to any compatible backend in one shell line. Almost no one does it, but it unlocks caching, rate-limit pooling, multi-vendor routing, audit logging, and billing routing without rewriting any code. Here's the 2-line setup, the things that quietly break, and the production checklist for actually running it.

The 2-line setup

export ANTHROPIC_BASE_URL=https://your-proxy.example.com

export ANTHROPIC_API_KEY=your-key

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