Vibe Check MCP is a production-ready MCP (Model Context Protocol) server that provides metacognitive oversight for AI agents. It implements the research-backed Chain-Pattern Interrupt (CPI) methodology to prevent reasoning lock-in by injecting reflective pauses during agent workflows. The server exposes six tools: `vibe_check` for generating clarifying questions via a secondary LLM, `vibe_learn` for logging patterns of mistakes and successes, and three constitution management tools (`update_constitution`, `reset_constitution`, `check_constitution`) for per-session behavioral rules. It supports multiple LLM providers (Gemini, OpenAI, Anthropic, OpenRouter) with automatic fallback to static questions when the LLM is unavailable, and maintains session history for context-aware feedback. The architecture is a monolithic MCP server with dual transport modes: stdio for local agent clients (Claude Desktop, Cursor, Windsurf, VS Code) and streamable HTTP for remote access. A CLI tool (`vibe-check-mcp`) automates installation into all major MCP client configurations with atomic writes and backup creation, handles secret management via interactive prompts or env files, and provides diagnostic commands. The server includes robust HTTP security hardening: DNS-rebinding protection via Host header validation, loopback-only CORS by default with a configurable allowlist, explicit JSON body size limits, and proper JSON-RPC error responses instead of HTML pages. The codebase is well-organized with separation of concerns, extensive unit and integration tests (over 30 test files), CI/CD with security scanning, and clean abstraction layers such as a central model registry and request-scoped transport wrappers.