Cline Releases Cline SDK: An Open-Source Agent Runtime Now Powering Its CLI and Kanban, With IDE Extensions Being Migrated

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.

From the bottom up:

@cline/shared is the foundation package carrying types, schemas, tool helpers, hook contracts, and extension registration utilities — no higher-layer dependencies. @cline/llms sits above it, owning the provider gateway and model catalogs. It covers Anthropic, OpenAI, Google, AWS Bedrock, Mistral, LiteLLM, and any OpenAI-compatible endpoint such as vLLM, Together, and Fireworks, with all provider logic kept out of the agent loop so switching providers is a config change, not a code change. @cline/agents runs above that as a browser-compatible, stateless agent execution loop handling iteration, tool orchestration, and event emission — importantly, it does not own session storage, built-in file/shell tools, or Node-specific orchestration, which is what makes it embeddable in browser environments. At the top sits @cline/core, the Node runtime/orchestration layer responsible for sessions, storage, built-in tools, hub and remote transports, automation and scheduling, telemetry, and plugin/extension loading.

@cline/sdk itself is a public surface that re-exports everything from @cline/core. For engineers who want a smaller footprint, the packages are individually installable: you can pull in just @cline/llms for an LLM proxy, or just @cline/agents for a stateless loop in a serverless or browser environment, without pulling in the full Node runtime stack.

The Cline team also reports that the new CLI completes the same tasks faster and at lower token cost than the old one in internal runs.

A Rebuilt Agent Harness With Measurable Benchmark Results

With Cline 2.0, the team rewrote the prompts, simplified the loop, tightened context management, improved feedback loops and error handling, and rethought how tools are defined and surfaced to the model.

The Cline team published Terminal Benchmark 2.0 (tbench.ai) results to back this up. On frontier models, Cline CLI running claude-opus-4.7 scored 74.2%, compared to Anthropic’s published score of 69.4% for Claude Code on the same model. On claude-opus-4.6, Cline CLI scored 71.9% versus Claude Code’s published 65.4%. On open-weight models, Cline scored 55.1% on kimi-k2.6, compared to 37.1% for OpenCode and 45.5% for Pi-Code on the same model, with those runs performed by the Cline team using pass@1 scoring as of May 8, 2026.

The Plugin System and Extensibility Layer

One of the practical additions for dev teams building on the SDK is the plugin architecture. A plugin can register tools, observe lifecycle events, add rules and commands, and shape what the agent sees. Plugins can be loaded from configured paths or workspace locations, and can start as a local .ts or .js module, later becoming a package directory with a cline.plugins manifest so teams can prototype locally and package reusable capabilities when they are ready.

Beyond plugins, the SDK provides additional extensibility points including custom tools, MCP connectors, and skills. To add a new custom provider, you implement an ApiHandler and register it using the @cline/llms registry — the architecture docs list registerProvider and registerModel as the correct exported functions for runtime registry extension.

Native Multi-Agent Support

A notable design decision is that multi-agent coordination does not require a separate orchestration layer. The SDK includes agent teams and subagents natively, so a session can delegate to specialists, track progress, and exchange handoff notes, all inside the same core runtime. Subagents run with their own model, tools, and prompts.

Scheduled CRON jobs, checkpointing, web search, and MCP connectors are all handled natively out of the box.

Getting Started

The SDK requires Node.js 22 or later.

# Install the SDK
npm install @cline/sdk

# Install the CLI globally
npm i -g @cline

# Or give your agent the Cline SDK skill
npx skills add cline/sdk-skill

Documentation is available at docs.cline.bot/sdk. Working examples — including plugin examples and multi-app builds — are in the sdk/apps/examples and sdk/examples directories of the Cline GitHub repository. The release is licensed under Apache 2.0.

Marktechpost’s Visual Explainer

# Full SDK — recommended starting point
npm install @cline/sdk

# CLI globally (terminal-first usage)
npm i -g @cline

# Add the SDK skill to your coding agent
npx skills add cline/sdk-skill

# Browser-compatible stateless loop only
npm install @cline/agents @cline/shared @cline/llms

# Just the provider layer (LLM proxy use case)
npm install @cline/llms @cline/shared

import { Agent } from "@cline/sdk"

const agent = new Agent({
  providerId:    "anthropic",
  modelId:       "claude-sonnet-4-6",
  apiKey:        process.env.ANTHROPIC_API_KEY,
  maxIterations: 10,
})

agent.subscribe((event) => {
  if (event.type === "assistant-text-delta")
    process.stdout.write(event.text ?? "")
})

const result = await agent.run(
  "Write a Python fn to check if a number is prime."
)

// Anthropic
{ providerId: "anthropic", modelId: "claude-sonnet-4-6" }

// OpenAI
{ providerId: "openai",    modelId: "gpt-4o"            }

// Any OpenAI-compatible endpoint
{ providerId: "openai",    baseUrl: "https://your-vllm/v1" }

import { AgentPlugin, createTool } from "@cline/sdk"

const myPlugin: AgentPlugin = {
  name: "my-plugin",
  tools() {
    return [createTool({
      name:        "fetch_docs",
      description: "Fetch internal API docs by slug",
      async run({ slug }) {
        return fetchFromInternalDocs(slug)
      },
    })]
  },
}

# Connect agent to Telegram, WhatsApp, Slack
cline connect

# Headless CI: auto-approve + structured JSON output
cline -y --json "Run tests and fix any failures"

# Pipe git diff into the agent
git diff origin/main | cline "Review these changes"

Key Takeaways

• Cline extracted its internal agent harness into an open-source TypeScript SDK (@cline/sdk), which re-exports @cline/core; the CLI and Kanban are already migrated, with VS Code and JetBrains extensions migration ongoing
• The SDK is a four-layer stack: @cline/shared (types/utilities) → @cline/llms (provider gateway) → @cline/agents (browser-compatible stateless loop) → @cline/core (Node runtime: sessions, storage, built-in tools, automation, telemetry)
• Sessions are now durable across surfaces — long-running work no longer dies with a UI restart
• Native support for plugins, subagents, CRON jobs, checkpointing, MCP connectors, and multi-provider switching without touching the agent loop
• Install via npm install @cline/sdk (requires Node.js 22+); docs at docs.cline.bot/sdk

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