Cline became ‘agentic’ before it was cool, but building on the bleeding edge usually leads to some structural debt. Over time, the agent loop and the VS Code extension became a package deal—making it a headache to maintain or move to new environments. Its tough to just keep layering features on a rigid core. Cline, the open-source AI coding agent used by millions of developers, shipped a significant architectural change this week: it extracted its internal agent harness into a standalone, open-source TypeScript SDK called @cline/sdk, and is rebuilding all of its own products on top of it.
Rather than adding another layer on top of that architecture, the Cline team chose to rebuild the foundation.
What the SDK is, and How It is Structured
The core agent harness has been abstracted into a pluggable agent SDK (@cline/sdk). It now powers Cline across VS Code, JetBrains, and the CLI, and is open-sourced so any team can build on it. A key behavioral benefit of this redesign: long-running work no longer dies with a UI restart, and sessions can move across surfaces — the agent loop stays stateless and reusable while the runtime around it becomes durable, portable, and product-agnostic.
The SDK is a layered TypeScript stack where each layer has a single responsibility and dependencies flow strictly downward.
