ProxAI is a transparent reverse proxy that enforces hard hourly/daily spending caps per LLM API client. Change one base_url — no SDK required. Works with OpenAI, Anthropic, Mistral, Groq, DeepSeek, and 5 more. Over cap → 429 before the upstream is ever called. Worst case is your cap, not your credit card. Self-hostable: single Go binary, ~10 MB Docker image (amd64/arm64), no telemetry. Or use the hosted beta at proxai.eu — free, no credit card. AGPL-3.0. Built end-to-end with Claude Code.