Applications using Vercel's AI SDK agent harnessThe scaffolding around a model that turns it into a working agent — the loop, the tools it can call, and the rules for when to stop.Full definition → layer can add fx, its lightweight open-source coding AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition →, through the same interface used to run other supported agents. The adapter announcement describes configuring HarnessAgent with the official fx adapter, which communicates with fx through Agent Client Protocol.
The change concerns integration work: the harness layer provides one API for running coding agents in an application, so a developer can add fx without building a separate integration. The announcement lists fx alongside Claude Code, Cline, Codex, Cursor, Deep Agents, Grok Build, OpenCode and Pi as supported harnesses.
Terms in this piece · Glossary
agent harness — The scaffolding around a model that turns it into a working agent — the loop, the tools it can call, and the rules for when to stop.
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
