# Flue Flue is an open-source ([[Apache 2.0 License]]) agent development framework from the Astro team (withastro). It is a programmable [[TypeScript]] harness for building durable [[AI Agents|AI agents]] and workflows, "write once, deploy anywhere, use any LLM", and is built on top of Pi, an open agent harness. The pitch: raw LLM API calls work for simple chatbots, but real autonomy (think [[Claude Code]]-style agents) needs sessions, sandboxes, tools, and recovery, which Flue provides. ## Core Building Blocks - **Agents**: autonomous entities that hold context across conversations and work toward goals - **Workflows**: bounded, code-guided processes that coordinate agent behavior from input to completion - **Sandboxes**: secure execution environments (virtual to container-based) for tool use and file modification - **Tools**: typed API actions for controlled changes - **Skills**: reusable packages of specialized expertise/guidance - **Subagents**: task delegation to specialized agents - **[[Durable Execution]]**: progress persists through server failures via durable streams that resume interrupted work ## Architecture Layered: an application layer (sessions, tools, skills) atop a foundation (runtime, sandbox, database), all powered by the Pi harness. Concerns are split into development (agents/workflows), execution (sandboxes/targets), and integration (providers/ecosystem). ## Packages - `@flue/runtime`, harness and sandbox - `@flue/cli`, CLI tooling - `@flue/sdk`, client SDK - `@flue/opentelemetry`, `@flue/postgres`, integrations ## Ecosystem - **Models/providers**: any LLM, with credential management across providers - **Targets**: Node.js, [[Cloudflare]] Workers, CI systems - **Integrations**: [[Model Context Protocol (MCP)|MCP]] server support; observability via OpenTelemetry, Braintrust, Sentry; channels for Slack, Teams, Discord, GitHub - Written in TypeScript (~90%); ~5.9k GitHub stars at the time of noting ## References - https://github.com/withastro/flue - https://www.flueframework.com/ - https://flueframework.com/docs ## Related - [[AI Agents]] - [[Agentic Engineering]] - [[Durable Execution]] - [[TypeScript]] - [[Claude Code]] - [[Model Context Protocol (MCP)]] - [[Cloudflare]] - [[Apache 2.0 License]] - [[Large Language Models (LLMs)]] - [[Artificial Intelligence (AI)]]