ThinkWatch is a Rust workspace implementing an AI gateway platform that fronts multiple model providers and MCP (Model Context Protocol) servers. It exposes OpenAI-compatible chat/completion endpoints, streaming, MCP tool-call routing, content filtering, and provider failover. The backend is split into crates: `common` (shared lifecycle/limits/access), `auth` (PoW login, API keys), `gateway` (model routing), `mcp-gateway` (MCP server proxying), `server` (REST admin/audit/trace endpoints), and `test-support` (integration test client). A React/TypeScript frontend in `web/` provides an admin console, setup wizard, limits panels, and MCP server management. Data flows: requests enter the gateway, pass through `check_limits`, `check_budget`, `check_access`, then `run_post_invoke`; `trace_id` is propagated across gateway, MCP, audit, and app logs stored in ClickHouse; Postgres holds users, API keys, budgets, and MCP server configs; Redis/Lua scripts enforce rate limits.