Cline released @cline/sdk today — its internal agent harness extracted into an open-source TypeScript SDK under Apache 2.0, now powering its CLI and Kanban surfaces, with the VS Code and JetBrains extensions migrating onto it. The structure is a four-layer stack with strict downward dependencies: @cline/shared carries types, schemas, tool helpers, and hook contracts; @cline/llms is the provider gateway handling Anthropic, OpenAI, Google, AWS Bedrock, Mistral, LiteLLM, and OpenAI-compatible endpoints; @cline/agents is the browser-compatible stateless execution loop handling iteration, tool orchestration, and event emission; and @cline/core is the Node-side runtime managing sessions, storage, built-in tools, hub/remote transports, automation, scheduling, telemetry, and plugin loading. @cline/sdk itself re-exports @cline/core as the public surface. Node 22+ required.
The native feature set is the part that matters for anyone evaluating open-source agent stacks: plugin architecture, multi-agent and subagent support, CRON scheduling, checkpointing, session persistence across surfaces, web search, and native MCP connectors. That maps almost directly to what Claude Code provides as a closed runtime, with the difference being that @cline/sdk lets you import the loop into your own application rather than running through a vendor CLI. For teams building agentic IDE tooling that does not want to live downstream of Anthropic's release cadence, the SDK is the first credible open-source pick at this level of feature completeness.
The headline benchmark numbers Cline published are sharp — and the honest reading requires a caveat. On Terminal Benchmark 2.0, Cline CLI scored 74.2% on claude-opus-4.7 versus Anthropic's published 69.4%; on claude-opus-4.6, 71.9% versus Anthropic's 65.4%. The article announcing the SDK does not disclose the comparison harness methodology or task composition, which means the apples-to-apples claim runs entirely on Cline's own framing. On open-weight models, Cline CLI reports 55.1% on Kimi-K2.6 versus 37.1% for OpenCode and 45.5% for Pi-Code, pass@1 as of May 8. Those open-model numbers are the more interesting signal for builders looking outside the closed-model lock-in: a real spread across alternative coding agents on the same model, even without full harness disclosure.
For builders: if you have been evaluating agent runtimes for a custom IDE, internal tool, or product surface, @cline/sdk is the new reference point. The four-layer split makes it usable from CI, from a browser sandbox (via @cline/agents), or as a Node service (via @cline/core), and Apache 2.0 leaves the licensing clean for commercial integration. The pragmatic next step is to run the SDK against your own benchmark with your own harness rather than trusting either Cline's or Anthropic's headline numbers — the test that decides what to ship is the one with your tasks, not someone else's. The npm package is @cline/sdk, and the migration of the VS Code and JetBrains extensions onto the same runtime is the signal of intent: this is the long-term core, not an experimental side project.