Cline

What Cline is

Cline is an open-source autonomous coding agent. Its GitHub repository, cline/cline, was created on 6 July 2024, and its description presents the project as an agent that can be used as an SDK, as an IDE extension, or as a CLI assistant ^[1]. The website and the services around it are operated by Cline Bot Inc. ^[2]

Agentic coding tools differ from ordinary code completion. Instead of suggesting the next line, the model is given tools: it reads files, edits them, runs commands, and looks at the result before deciding what to do next. Making that loop dependable is mostly engineering work — handling context, asking for permission before risky actions, and recovering when a step fails.

Where it came from

Cline says the extension was first built in 2024, right after Claude 3.5 Sonnet was released, and describes it as one of the very first agentic coding experiences ^[3]. The VS Code extension has since been installed by more than 11 million developers ^[3].

That install count is the clearest measure of how far the project spread: a single extension, distributed through a marketplace developers already used, became the main way people met the agent.

Six product surfaces

Cline's site lists six product surfaces: Desktop, Cloud, IDE, CLI, SDK and ClinePass ^[2]. Alongside the extension, the project runs an MCP Marketplace and a public changelog ^[2].

The 2026 harness rebuild

Earlier in 2026, Cline rebuilt its foundation around the Cline SDK, pulling the agent harness out of the extension into a shared, modular runtime ^[3]. The harness is the layer that ties the model to its tools — the code that assembles context, issues tool calls, applies file edits and handles permissions. Keeping it inside the extension meant it lived in one place only; moving it into a shared runtime makes it a component that other surfaces can use.

That kind of restructuring is risky precisely because so much depends on it. Cline's first attempt at migrating users to the new harness broke badly enough that it had to be rolled back immediately ^[3].

Where it stands

The repository had 71,438 stars when checked in November 2026 ^[1]. Between the original extension, the six product surfaces and the shared SDK underneath them, Cline is a case study in how a coding agent that started as a single IDE plugin grows into a set of products built on one runtime.