What problem does it solve? Navigating a large Express backend codebase with dozens of endpoints, middleware layers, and services is slow and error-prone. This Skill provides a structured knowledge base of the Threaded Stack Core API so you can quickly locate routes, understand middleware order, and modify services correctly. ## Core Features & Use Cases - Endpoint Reference: Covers admin CRUD routes, agent run/SSE streaming, OpenAI-compatible chat completions, sandbox lifecycle, shell sessions, and Stripe payment webhooks. - Architecture Guidance: Documents middleware setup order, service layer (SecretResolver, ProxyService, EgressProxy, Scheduler, SandboxService), and WebSocket server dispatch. - Use Case: When adding a new quota-limited POST route, consult the Skill to see how enforceQuota maps routes to quota keys and where auth middleware is applied in accounts.ts. ## Quick Start Ask the AI to explain how the sandbox shell session flow works in the backend, including authentication and reconnection handling.