Flue

Flue is a TypeScript framework for building the next generation of AI agents, designed around a built-in agent harness. It is runtime-agnostic — think Astro or Next.js, but for agents — letting you write once and deploy to Node.js, Cloudflare Workers, GitHub Actions, GitLab CI/CD, and more. Agents are fully headless and programmable with no TUI, no GUI, and no assumption of a human operator. Most agent logic lives in Markdown (skills, context, and AGENTS.md), keeping TypeScript code minimal.

• Agent Harness Framework: Build agents that act autonomously to solve problems and complete tasks, modeled after the familiar Claude Code / OpenCode / Codex developer experience but 100% headless.
• Virtual Sandbox by Default: Powered by just-bash, the built-in virtual sandbox is faster, cheaper, and more scalable than full containers — ideal for high-traffic agents.
• Container Sandbox Support: Opt into real Linux environments via connectors (e.g., Daytona) for full coding agents with git, Node.js, a browser, and a cloned repo.
• Skills & Roles: Define reusable agent skills in Markdown and assign roles at the agent, session, or per-call level for fine-grained orchestration.
• Session & Task Management: Persist message history and sandbox state across requests; use session.task() for focused one-shot child agents with their own message history.
• MCP Tool Integration: Connect to remote MCP servers at runtime via connectMcpServer(), keeping secrets in env rather than prompts or filesystem context.
• Typed Results: Pass a Valibot schema to session.prompt() or session.skill() to get schema-validated, typed data back from any agent call.
• CLI Tooling: Use flue dev for a watch-mode dev server, flue run for one-shot CI invocations, and flue build to produce deployable artifacts for Node.js or Cloudflare.
• Multi-Model Support: Works with Anthropic Claude, OpenAI, Google Gemini, Moonshot Kimi, and any model available via OpenRouter.
• Open Source: Licensed under Apache 2.0 — free to use, modify, and distribute.