Events

Subscribe to runtime and session events for UIs, logs, monitoring, and cancellation.

The SDK exposes two related event surfaces:

AgentRuntimeEvent from @cline/agents, delivered through agent.subscribe(listener).
AgentEvent / CoreSessionEvent from @cline/core, delivered through core session adapters and cline.subscribe(listener).

Use this page for event handling patterns. For event shapes, see Events reference.

AgentRuntime Events

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

await agent.run("Explain this codebase")
unsubscribe()

AgentRuntimeEvent is the low-level event stream from the browser-compatible runtime.

Core / Host-Facing Agent Events

AgentEvent is the host-facing event shape used by @cline/core session orchestration. For direct Agent usage, prefer agent.subscribe(...) and AgentRuntimeEvent.

Common host-facing event categories:

Category	Events	Use for
Content	`content_start`, `content_update`, `content_end`	Text/reasoning/tool UI
Iterations	`iteration_start`, `iteration_end`	Progress tracking
Usage	`usage`	Token/cost tracking
Notices	`notice`	Recovery and status updates
Completion	`done`, `error`	Final state and failure handling

ClineCore Session Events

Use cline.subscribe() for session-level events:

const unsubscribe = cline.subscribe((event) => {
  console.log(event.type, event.sessionId)
})

await cline.start({ /* ... */ })
unsubscribe()

Pass a sessionId filter when you only want one session:

const unsubscribe = cline.subscribe(listener, { sessionId })

Streaming UI Pattern

Subscribe to events to build real-time UIs:

agent.subscribe((event) => {
  switch (event.type) {
    case "assistant-text-delta":
      onUpdate({ type: "text", content: event.text ?? "" })
      break
    case "tool-started":
      onUpdate({ type: "tool_start", content: event.toolCall.toolName })
      break
    case "tool-finished":
      onUpdate({ type: "tool_end", content: event.toolCall.toolName })
      break
    case "run-finished":
      onUpdate({ type: "done", content: event.result.status })
      break
  }
})

For a complete working example of streaming agent events to a browser via SSE, see the multi-agent example. It spawns multiple agents in parallel and streams each agent's events to separate UI cards.

Usage Tracking Pattern

let totalTokens = 0

agent.subscribe((event) => {
  if (event.type === "usage-updated") {
    totalTokens = event.usage.inputTokens + event.usage.outputTokens
  }
})

Runtime State Snapshots

Call snapshot() when you need the current state:

const snapshot = agent.snapshot()
console.log(snapshot.status, snapshot.iteration, snapshot.usage)