Complete Bun.js ecosystem guidance for runtime APIs, file I/O, package management, testing, SQLite, and security; use proactively when setting up Bun projects, replacing Node.js APIs with Bun-native APIs, writing bun test suites, implementing Bun.serve services, using bun:sqlite with prepared statements, configuring workspaces and lockfiles, hardening shell and SQL boundaries, or optimizing Bun performance and migration workflows.