Cline SDK

The Cline SDK lets you embed Cline as a programmable coding agent in your Node.js applications. It exposes the same capabilities as the Cline CLI and VS Code extension — file editing, command execution, browser use, MCP servers — through a TypeScript API that conforms to the Agent Client Protocol (ACP).

Installation

npm install cline

If you want direct ACP type imports as well:

npm install @agentclientprotocol/sdk

Requires Node.js 20+.

Quick Start

import { ClineAgent } from "cline";

const CLINE_DIR = "/Users/username/.cline";
const agent = new ClineAgent({ clineDir: CLINE_DIR });

// 1. Initialize — negotiates capabilities
const initializeResponse = await agent.initialize({
    protocolVersion: 1,
    // these are the capabilities that the client (you) supports
    // The cline agent may or may not use them, but it needs to know about them to make informed decisions about what tools to use.
    clientCapabilities: {
        fs: { readTextFile: true, writeTextFile: true },
        terminal: true,
    },
});

const { agentInfo, authMethods } = initializeResponse;
console.log("Agent info:", agentInfo); // contains things like agent name and version
console.log("Auth methods:", authMethods); // contains a list of supported authentication methods. More auth methods coming soon

// 2. Authenticate if needed
// If you skip this step, ClineAgent will look in CLINE_DIR for any existing credentials and authenticate with those
await agent.authenticate({ methodId: "cline-oauth" });

// 3. Create a session.
// A session represents a conversation or task with the agent. You can have multiple sessions for different tasks or conversations.
const { sessionId } = await agent.newSession({
    cwd: process.cwd(),
    mcpServers: [], // mcpServers field not supported yet, but exposed here to maintain conformance with acp protocol
});

// 4. Agent updates are sent via events. You can subscribe to these events to get real-time updates on the agent's progress, tool calls, and more.
const emitter = agent.emitterForSession(sessionId);

emitter.on("agent_message_chunk", (payload) => {
    process.stdout.write(
        payload.content.type === "text"
            ? payload.content.text
            : `[${payload.content.type}]`,
    );
});
emitter.on("agent_thought_chunk", (payload) => {
    process.stdout.write(
        payload.content.type === "text"
            ? payload.content.text
            : `[${payload.content.type}]`,
    );
});
emitter.on("tool_call", (payload) => {
    console.log(`[tool] ${payload.title}`);
});
emitter.on("error", (err) => {
    console.error("[session error]", err);
});

// 5. Send a prompt and wait for completion
const { stopReason } = await agent.prompt({
    sessionId,
    prompt: [{ type: "text", text: "Create a hello world Express server" }],
});

console.log("Done:", stopReason);

// 6. Clean up
await agent.shutdown();

Core Concepts

Agent Lifecycle

The SDK follows the ACP lifecycle:

initialize() → authenticate() → newSession() → prompt() ⇄ events → shutdown()

Step	Method	Purpose
Init	`initialize()`	Exchange protocol version and capabilities
Auth	`authenticate()`	OAuth flow for Cline or OpenAI Codex accounts. Optional step if cline config directory already has credentials
Session	`newSession()`	Create an isolated conversation context
Prompt	`prompt()`	Send user messages; blocks until the turn ends
Cancel	`cancel()`	Abort an in-progress prompt turn
Mode	`setSessionMode()`	Switch between `"plan"` and `"act"` modes
Model	`unstable_setSessionModel()`	Change the backing LLM (experimental)
Shutdown	`shutdown()`	Abort all tasks, flush state, release resources

Sessions

A session is an independent conversation with its own task history and working directory. You can run multiple sessions concurrently.

const { sessionId, modes, models } = await agent.newSession({
  cwd: "/path/to/project",
  mcpServers: [], // mcpServers field not supported yet, but exposed here to maintain conformance with acp protocol
})

The response includes:

sessionId — use this in all subsequent calls
modes — available modes (plan, act) and the current mode
models — available models and the current model ID

Access session metadata via the read-only sessions map:

const session = agent.sessions.get(sessionId)
// { sessionId, cwd, mode, mcpServers, createdAt, lastActivityAt, ... }

Prompting

prompt() sends a user message and blocks until the agent finishes its turn. While the prompt is processing, the agent streams output via session events.

const response = await agent.prompt({
  sessionId,
  prompt: [
    { type: "text", text: "Refactor the auth module to use JWT" },
  ],
})

The prompt array accepts multiple content blocks:

// Text + image + file context
await agent.prompt({
  sessionId,
  prompt: [
    { type: "text", text: "What's in this screenshot?" },
    { type: "image", data: base64ImageData, mimeType: "image/png" },
    {
      type: "resource",
      resource: {
        uri: "file:///path/to/relevant-file.ts",
        mimeType: "text/plain",
        text: fileContents,
      },
    },
  ],
})

Content Block Types

Type	Fields	Description
`TextContent`	`{ type: "text", text: string }`	Plain text message
`ImageContent`	`{ type: "image", mimeType: string, data: string }`	Base64-encoded image
`EmbeddedResource`	`{ type: "resource", resource: { uri: string, mimeType?: string, text?: string, blob?: string } }`	File or resource context

Stop Reasons

prompt() resolves with a stopReason. The ACP StopReason type defines the full set of possible values:

Value	Meaning
`"end_turn"`	Agent finished normally (completed task or waiting for user input)
`"error"`	An error occurred

Note: Cline currently returns "end_turn" or "error". Other StopReason values like "max_tokens" or "cancelled" are part of the ACP type but may not be produced by the current implementation.

Streaming Events

Subscribe to real-time output via ClineSessionEmitter. Each session has its own emitter.

const emitter = agent.emitterForSession(sessionId)

Event Types

All events correspond to ACP SessionUpdate types:

Event	Payload	Description
`agent_message_chunk`	`{ content: ContentBlock }`	Streamed text from the agent
`agent_thought_chunk`	`{ content: ContentBlock }`	Internal reasoning / chain-of-thought
`tool_call`	`ToolCall`	New tool invocation (file edit, command, etc.)
`tool_call_update`	`ToolCallUpdate`	Progress/result update for an existing tool call
`plan`	`{ entries: PlanEntry[] }`	Agent’s execution plan
`available_commands_update`	`{ availableCommands: AvailableCommand[] }`	Slash commands the agent supports
`current_mode_update`	`{ currentModeId: string }`	Mode changed (plan/act)
`user_message_chunk`	`{ content: ContentBlock }`	User message chunks (for multi-turn)
`config_option_update`	`{ configOptions: SessionConfigOption[] }`	Configuration changed
`session_info_update`	Session metadata	Session metadata changed
`error`	`Error`	Session-level error (not an ACP update)

emitter.on("agent_message_chunk", (payload) => {
  // payload.content is a ContentBlock — usually { type: "text", text: "..." }
  process.stdout.write(payload.content.text)
})

emitter.on("agent_thought_chunk", (payload) => {
  console.log("[thinking]", payload.content.text)
})

emitter.on("tool_call", (payload) => {
  console.log(`[${payload.kind}] ${payload.title} (${payload.status})`)
})

emitter.on("tool_call_update", (payload) => {
  console.log(`  → ${payload.toolCallId}: ${payload.status}`)
})

emitter.on("error", (err) => {
  console.error("Session error:", err)
})

The emitter supports on, once, off, and removeAllListeners.

Permission Handling

When the agent wants to execute a tool (edit a file, run a command, etc.), it requests permission. You must set a permission handler or all tool calls will be auto-rejected.

agent.setPermissionHandler(async (request) => {
  // request.toolCall — details about what the agent wants to do
  // request.options — available choices (allow_once, reject_once, etc.)

  console.log(`Permission requested: ${request.toolCall.title}`)
  console.log("Options:", request.options.map(o => `${o.optionId} (${o.kind})`))

  // Auto-approve everything:
  const allowOption = request.options.find(o => o.kind.includes("allow"))
  if (allowOption) {
    return { outcome: { outcome: "selected", optionId: allowOption.optionId } }
  } else {
    return { outcome: { outcome: "rejected" } }
  }
})

Permission Options

Each permission request includes an array of PermissionOption objects:

`kind`	Meaning
`allow_once`	Approve this single operation
`allow_always`	Approve and remember for future operations (sent for commands, tools, MCP servers)
`reject_once`	Deny this single operation

Important: If no permission handler is set, all tool calls are rejected for safety.

Modes

Cline supports two modes:

plan — The agent gathers information and creates a plan without executing actions
act — The agent executes actions (file edits, commands, etc.)

// Switch to plan mode
await agent.setSessionMode({ sessionId, modeId: "plan" })

// Switch back to act mode
await agent.setSessionMode({ sessionId, modeId: "act" })

The current mode is returned in newSession()

Model Selection

Change the backing model with unstable_setSessionModel(). The model ID format is "provider/modelId".

await agent.unstable_setSessionModel({
  sessionId,
  modelId: "anthropic/claude-sonnet-4-20250514",
})

This sets the model for both plan and act modes. Available providers include anthropic, openai-native, gemini, bedrock, deepseek, mistral, groq, xai, and others. Model Ids can be found in the NewSessionResponse object after calling agent.newSession(..)

Note: This API is experimental and may change.

Authentication

The SDK supports two OAuth flows:

// Cline account (uses browser OAuth)
await agent.authenticate({ methodId: "cline-oauth" })

// OpenAI Codex / ChatGPT subscription
await agent.authenticate({ methodId: "openai-codex-oauth" })

Both methods open a browser window for the OAuth flow and block until authentication completes (5-minute timeout for Cline OAuth). For BYO (bring-your-own) API key providers, you can pre-configure credentials using the Cline CLI before using the SDK:

# Configure an Anthropic API key (default directory: ~/.cline/data/)
cline auth -p anthropic -k "sk-ant-..." -m anthropic/claude-sonnet-4-20250514

# Configure an OpenRouter API key
cline auth -p openrouter -k "sk-or-..." -m openrouter/anthropic/claude-sonnet-4

This writes credentials to ~/.cline/data/. Once configured, the SDK will use these credentials automatically — no authenticate() call needed. Using a custom directory: If you specify a custom clineDir when creating ClineAgent, you must use the same path with --config when running cline auth:

// SDK code using custom directory
const agent = new ClineAgent({ clineDir: "/custom/path" })

# CLI auth command must use the same path
cline auth -p anthropic -k "sk-ant-..." -m anthropic/claude-sonnet-4-20250514 --config /custom/path

Cancellation

Cancel an in-progress prompt turn:

await agent.cancel({ sessionId })

API Reference

Constructor

new ClineAgent(options: ClineAgentOptions)

interface ClineAgentOptions {
  /** Enable debug logging (default: false) */
  debug?: boolean
  /** Custom Cline config directory (default: ~/.cline) */
  clineDir?: string
  /** Additional runtime hooks directory */
  hooksDir?: string
}

The clineDir option lets you isolate configuration and task history per-application:

const agent = new ClineAgent({
  clineDir: "/tmp/my-app-cline",
})

Methods

`initialize(params): Promise<InitializeResponse>`

Initialize the agent and negotiate protocol capabilities.

const response = await agent.initialize({
  clientCapabilities: {},
  protocolVersion: 1,
})

// Response includes:
{
  protocolVersion: 1,
  agentCapabilities: {
    loadSession: true,
    promptCapabilities: { image: true, audio: false, embeddedContext: true },
    mcpCapabilities: { http: true, sse: false }
  },
  agentInfo: { name: "cline", version: "<installed_version>" },
  authMethods: [
    { id: "cline-oauth", name: "Sign in with Cline", description: "..." },
    { id: "openai-codex-oauth", name: "Sign in with ChatGPT", description: "..." }
  ]
}

Client Capabilities

The clientCapabilities object in initialize() declares what your environment supports. It is part of the ACP protocol handshake.

Capability	Type	Description
`fs.readTextFile`	`boolean`	Client supports file read requests
`fs.writeTextFile`	`boolean`	Client supports file write requests
`terminal`	`boolean`	Client supports terminal command execution

When using ClineAgent directly (SDK use), the agent always uses standalone providers for file operations and terminal commands — it reads/writes files and runs shell commands on the local machine regardless of what you pass here. Simply pass {}:

await agent.initialize({ protocolVersion: 1, clientCapabilities: {} })

These capabilities only affect behavior when ClineAgent is used through the AcpAgent stdio wrapper (e.g., IDE integrations), where an ACP connection delegates operations back to the client.

`newSession(params): Promise<NewSessionResponse>`

Create a new conversation session.

const session = await agent.newSession({
  cwd: "/path/to/project",
  mcpServers: [
    {
      type: "stdio",
      name: "filesystem",
      command: "npx",
      args: ["-y", "@modelcontextprotocol/server-filesystem", "/path/to/dir"],
      env: {},
    },
  ],
})

// Response includes:
{
  sessionId: "uuid-string",
  modes: {
    availableModes: [
      { id: "plan", name: "Plan", description: "Gather information and create a detailed plan" },
      { id: "act", name: "Act", description: "Execute actions to accomplish the task" }
    ],
    currentModeId: "act"
  },
  models: {
    currentModelId: "anthropic/claude-sonnet-4-20250514",
    availableModels: [{ modelId: "anthropic/claude-sonnet-4-20250514", name: "claude-sonnet-4-20250514" } /* ... */]
  }
}

Note: newSession() may throw an auth-required error if credentials are not configured yet.

`prompt(params): Promise<PromptResponse>`

Send a user prompt to the agent. This is the main method for interacting with Cline. Blocks until the agent finishes its turn.

const response = await agent.prompt({
  sessionId: session.sessionId,
  prompt: [
    { type: "text", text: "Create a function that adds two numbers" },
  ],
})

// Response: { stopReason: "end_turn" | "max_tokens" | "cancelled" | "error" }

`cancel(params): Promise<void>`

Cancel an ongoing prompt operation.

await agent.cancel({ sessionId: session.sessionId })

`setSessionMode(params): Promise<SetSessionModeResponse>`

Switch between plan and act modes.

await agent.setSessionMode({ sessionId, modeId: "plan" })

`unstable_setSessionModel(params): Promise<SetSessionModelResponse>`

Change the model for the session. Model ID format depends on the inference provider. See NewSessionResponse object to get modelIds.

await agent.unstable_setSessionModel({
  sessionId,
  modelId: "anthropic/claude-sonnet-4-20250514",
})

`authenticate(params): Promise<AuthenticateResponse>`

Authenticate with a provider. Opens a browser window for OAuth flow.

await agent.authenticate({ methodId: "cline-oauth" })

Current methodIds we support:

methodId	Description
`cline-oauth`	use cline inference provider
`openai-codex-oauth`	use your chatgpt subscription
more coming soon!…

`shutdown(): Promise<void>`

Clean up all resources. Call this when done.

await agent.shutdown()

`setPermissionHandler(handler)`

Set a callback to handle tool permission requests. The handler receives a RequestPermissionRequest and must return a Promise<RequestPermissionResponse>.

agent.setPermissionHandler(async (request) => {
  // request.toolCall — details about what the agent wants to do
  // request.options — available choices (allow_once, reject_once, etc.)
  const allow = request.options.find(o => o.kind === "allow_once")
  return {
    outcome: allow
      ? { outcome: "selected", optionId: allow.optionId }
      : { outcome: "cancelled" }
  }
})

`emitterForSession(sessionId): ClineSessionEmitter`

Get the typed event emitter for a session.

const emitter = agent.emitterForSession(session.sessionId)

`sessions` (read-only Map)

Access active sessions:

for (const [sessionId, session] of agent.sessions) {
  console.log(sessionId, session.cwd, session.mode)
}

Error Handling

SDK methods throw standard JavaScript errors. Key error scenarios:

Method	Error	Cause
`newSession()`	`RequestError` (auth required)	No credentials configured — call `authenticate()` or pre-configure via CLI
`prompt()`	`Error("Session not found")`	Invalid `sessionId`
`prompt()`	`Error("already processing")`	Called `prompt()` while a previous prompt is still running on the same session
`unstable_setSessionModel()`	`Error("Invalid modelId format")`	Model ID must be `"provider/modelId"` format (e.g., `"anthropic/claude-sonnet-4-20250514"`)
`authenticate()`	`Error("Unknown authentication method")`	Invalid `methodId` — use `"cline-oauth"` or `"openai-codex-oauth"`
`authenticate()`	`Error("Authentication timed out")`	OAuth flow not completed within 5 minutes

try {
  const { sessionId } = await agent.newSession({ cwd: process.cwd(), mcpServers: [] })
} catch (error) {
  if (error.message?.includes("auth")) {
    // Need to authenticate first
    await agent.authenticate({ methodId: "cline-oauth" })
  }
}

Session-level errors during prompt() execution are emitted on the session emitter rather than thrown:

emitter.on("error", (err) => {
  console.error("Session error:", err.message)
})

Full Example: Auto-Approve Agent

import { ClineAgent } from "cline";

async function runTask(taskPrompt: string, cwd: string) {
    const agent = new ClineAgent({ clineDir: "/path/to/.cline" });

    await agent.initialize({
        protocolVersion: 1,
        clientCapabilities: {},
    });

    const { sessionId } = await agent.newSession({ cwd, mcpServers: [] });

    // Auto-approve all tool calls
    agent.setPermissionHandler(async (request) => {
        const allow = request.options.find((o) => o.kind === "allow_once");
        return {
            outcome: allow
                ? { outcome: "selected", optionId: allow.optionId }
                : { outcome: "cancelled" },
        };
    });

    // Collect output
    const output: string[] = [];
    const emitter = agent.emitterForSession(sessionId);

    emitter.on("agent_message_chunk", (p) => {
        if (p.content.type === "text") output.push(p.content.text);
    });

    emitter.on("tool_call", (p) => {
        console.log(`[tool] ${p.title}`);
    });

    const { stopReason } = await agent.prompt({
        sessionId,
        prompt: [{ type: "text", text: taskPrompt }],
    });

    console.log("\n--- Agent Output ---");
    console.log(output.join(""));
    console.log(`\nStop reason: ${stopReason}`);

    await agent.shutdown();
}

runTask("Create a README.md for this project", process.cwd());

Full Example: Interactive Permission Flow

import { ClineAgent, type PermissionHandler } from "cline";
import * as readline from "readline";

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});
const ask = (q: string) => new Promise<string>((res) => rl.question(q, res));

const interactivePermissions: PermissionHandler = async (request) => {
    console.log(`\n⚠️  Permission: ${request.toolCall.title}`);

    for (const [i, opt] of request.options.entries()) {
        console.log(`  ${i + 1}. [${opt.kind}] ${opt.name}`);
    }

    const choice = await ask("Choose (number): ");
    const idx = parseInt(choice, 10) - 1;
    const selected = request.options[idx];

    if (selected) {
        return {
            outcome: { outcome: "selected", optionId: selected.optionId },
        };
    } else {
        return { outcome: { outcome: "cancelled" } };
    }
};

async function main() {
    const agent = new ClineAgent({});
    await agent.initialize({ protocolVersion: 1, clientCapabilities: {} });

    const { sessionId } = await agent.newSession({
        cwd: process.cwd(),
        mcpServers: [],
    });

    agent.setPermissionHandler(interactivePermissions);

    const emitter = agent.emitterForSession(sessionId);
    emitter.on("agent_message_chunk", (p) => {
        if (p.content.type === "text") process.stdout.write(p.content.text);
    });

    // Multi-turn conversation
    while (true) {
        const userInput = await ask("\n> ");
        if (userInput === "exit") break;

        const { stopReason } = await agent.prompt({
            sessionId,
            prompt: [{ type: "text", text: userInput }],
        });

        console.log(`\n[${stopReason}]`);
    }

    await agent.shutdown();
    rl.close();
}

main();

Exported Types

All types are re-exported from the cline package. Key types:

Type	Description
`ClineAgent`	Main agent class
`ClineSessionEmitter`	Typed event emitter for session events
`ClineAgentOptions`	Constructor options (`debug`, `clineDir`, `hooksDir`)
`ClineAcpSession`	Session metadata (read-only)
`ClineSessionEvents`	Event name → handler signature map
`AcpSessionStatus`	Session lifecycle enum: `Idle`, `Processing`, `Cancelled`
`AcpSessionState`	Session state tracking (status, pending tool calls)
`PermissionHandler`	`(request: RequestPermissionRequest) => Promise<RequestPermissionResponse>`
`RequestPermissionRequest`	Permission request details (sessionId, toolCall, options)
`RequestPermissionResponse`	Permission response with outcome
`PermissionOption`	Permission choice (`kind`, `optionId`, `name`)
`SessionUpdate`	Union of all session update types
`SessionUpdateType`	Discriminator values (`"agent_message_chunk"`, `"tool_call"`, etc.)
`SessionUpdatePayload`	Typed payload for a given `SessionUpdateType`
`SessionModelState`	Current model and available models
`ToolCall`	Tool call details (id, title, kind, status, content)
`ToolCallUpdate`	Partial update to an existing tool call
`ToolCallStatus`	`"pending" \| "in_progress" \| "completed" \| "failed"`
`ToolKind`	`"read" \| "edit" \| "delete" \| "execute" \| "search" \| ...`
`StopReason`	`"end_turn" \| "cancelled" \| "error" \| "max_tokens" \| ...`
`ContentBlock`	`TextContent \| ImageContent \| AudioContent \| ...`
`TextContent` / `ImageContent` / `AudioContent`	Individual content block types
`McpServer`	MCP server configuration (stdio, http)
`ModelInfo`	Model metadata (`modelId`, `name`)
`PromptRequest` / `PromptResponse`	Prompt call types
`NewSessionRequest` / `NewSessionResponse`	Session creation types
`InitializeRequest` / `InitializeResponse`	Initialization types
`SetSessionModeRequest` / `SetSessionModeResponse`	Mode switching types
`SetSessionModelRequest` / `SetSessionModelResponse`	Model switching types
`TranslatedMessage`	Result of translating a Cline message to ACP updates

See the ACP Schema for the full type definitions.

Relationship to ACP

The Cline SDK implements the Agent Client Protocol Agent interface. The key difference from a standard ACP stdio agent is that the SDK uses an event emitter pattern instead of a transport connection:

ACP Stdio (via `AcpAgent`)	SDK (via `ClineAgent`)
Session updates sent over JSON-RPC stdio	Session updates emitted via `ClineSessionEmitter`
Permissions requested via `connection.requestPermission()`	Permissions requested via `setPermissionHandler()` callback
Single process, single connection	Embeddable, multiple concurrent sessions

If you need stdio-based ACP communication (e.g., for IDE integration), use the cline CLI binary directly. The SDK is for embedding Cline in your own Node.js processes.

Home

Getting Started

Core Workflows

Customization

Cline CLI

Features

Models & Providers

MCP (Extending Cline)

Tools Reference

Troubleshooting

Contributing

​Cline SDK

​Installation

​Quick Start

​Core Concepts

​Agent Lifecycle

​Sessions

​Prompting

​Content Block Types

​Stop Reasons

​Streaming Events

​Event Types

​Permission Handling

​Permission Options

​Modes

​Model Selection

​Authentication

​Cancellation

​API Reference

​Constructor

​Methods

​initialize(params): Promise<InitializeResponse>

​Client Capabilities

​newSession(params): Promise<NewSessionResponse>

​prompt(params): Promise<PromptResponse>

​cancel(params): Promise<void>

​setSessionMode(params): Promise<SetSessionModeResponse>

​unstable_setSessionModel(params): Promise<SetSessionModelResponse>

​authenticate(params): Promise<AuthenticateResponse>

​shutdown(): Promise<void>

​setPermissionHandler(handler)

​emitterForSession(sessionId): ClineSessionEmitter

​sessions (read-only Map)

​Error Handling

​Full Example: Auto-Approve Agent

​Full Example: Interactive Permission Flow

​Exported Types

​Relationship to ACP