Agent Express

Agent Express is an open-source framework designed for building sophisticated agentic applications using TypeScript. It leverages a familiar middleware pattern, similar to popular web frameworks like Express.js, allowing developers to construct agents by chaining composable (ctx, next) functions. Key features include: * Express.js-like middleware pattern for agent development * Three core concepts: Agent, Session, and Middleware * Five essential hooks for customization * Built-in middlewares for budget tracking, guardrails, and observability * Memory compaction and tool management capabilities The framework simplifies the complex 'model-tool-model' loop inherent in agentic applications, mapping it directly to the request-response cycle of a web server. This approach provides a clear, structured way to manage context flow through an agent's operations, making it intuitive for developers already familiar with middleware architectures. Agent Express is built for production environments, offering robust features like input/output validation, per-session budget caps, and human-in-the-loop tool approval gates. It integrates seamlessly with major provider SDKs (Anthropic, OpenAI, Google, Mistral, Groq, DeepSeek) and supports advanced functionalities such as real-time streaming, model routing based on complexity, and OpenTelemetry metrics and traces. This makes it an ideal choice for engineering teams focusing on reliable and scalable agent system deployment.