AI Cost Gate is a local-first cost black box for AI agents. • OpenAI-compatible request path • Attribute spend by project / agent / model • Budgets that can return HTTP 429 so agents stop when spend trips • Metadata-oriented — designed so prompt bodies stay on your side • Pro = one-time source license, self-host on SQLite or Postgres Free companion tools (pricing, burn estimator, prompt cost, MCP templates, checklist): https://tools.aicostgate.com