claude-runner

claude-runner

The easiest way to build AI agents with Claude. MCP-native, sandbox-ready, 5 lines to start.

Built on the official Claude Agent SDK. One dependency. Zero bloat.

import { Runner } from 'claude-runner';

const runner = new Runner();
const result = await runner.run('Analyze this codebase and suggest improvements');
console.log(result.text);

Why claude-runner?

The official @anthropic-ai/claude-agent-sdk is powerful but low-level — 40+ options, 20+ message types, raw async generators. Every developer builds their own wrapper.

claude-runner is that wrapper:

	raw Agent SDK	claude-runner
Lines to start	20+	5
Message types	20+ nested	7 flat events
MCP config	Object only	Shorthand strings
Sandbox	Manual spawnClaudeCodeProcess	sandbox: 'e2b'
Session resume	resume: id option	runner.resume(id)
Permissions	canUseTool callback	permissions: 'auto'
Custom tools	tool() + createSdkMcpServer()	defineTool()

Install

npm install claude-runner

Requires Claude Code CLI to be installed and authenticated.

Quick Start

Simple await

import { Runner } from 'claude-runner';

const runner = new Runner();
const result = await runner.run('Fix the failing tests in this project');

console.log(result.text);           // Claude's response
console.log(`Cost: $${result.cost}`); // API cost
console.log(`Turns: ${result.turns}`); // Agentic turns

Streaming

for await (const event of runner.stream('Refactor the auth module')) {
  switch (event.type) {
    case 'text':
      process.stdout.write(event.text);
      break;
    case 'tool_start':
      console.log(`\n[${event.tool}]`);
      break;
    case 'tool_end':
      console.log(`[${event.tool}] done (${event.duration}ms)`);
      break;
    case 'done':
      console.log(`\nCost: $${event.result.cost.toFixed(4)}`);
      break;
  }
}

Session Resume

// First run — Claude analyzes and asks for approval
const r1 = await runner.run('Create a test plan for the auth module');
console.log(r1.text); // "Here's the plan... approve?"

// Resume — continue the conversation with full context
const r2 = await runner.resume(r1.sessionId, 'Approved. Generate the tests.').result;
console.log(r2.text); // "Tests generated at..."

Multi-turn (mid-stream messages)

const stream = runner.stream('Build a REST API for user management');

// Inject guidance while Claude is working
setTimeout(() => stream.send('Use Express, not Fastify'), 5000);

for await (const event of stream) {
  if (event.type === 'text') process.stdout.write(event.text);
}

MCP Servers

Connect to any MCP server with shorthand strings or full config objects.

const runner = new Runner({
  mcp: {
    // Command string (auto-parsed)
    github: 'npx @modelcontextprotocol/server-github',

    // URL (HTTP/SSE server)
    docs: 'https://api.example.com/mcp',

    // Full config
    postgres: {
      command: 'npx',
      args: ['@modelcontextprotocol/server-postgres', process.env.DATABASE_URL!],
      env: { PGPASSWORD: process.env.PGPASSWORD! },
    },
  },
});

const result = await runner.run('How many users signed up last week?');

All MCP tools are auto-discovered and auto-allowed. Claude sees them and can use them immediately.

Custom Tools

Define tools that run in your process:

import { Runner, defineTool } from 'claude-runner';
import { z } from 'zod';

const weather = defineTool(
  'get_weather',
  'Get current weather for a city',
  { city: z.string() },
  async ({ city }) => ({
    content: [{ type: 'text', text: `72°F and sunny in ${city}` }],
  })
);

const runner = new Runner({ tools: [weather] });
const result = await runner.run('What is the weather in San Francisco?');

Permissions

Control what Claude can do:

// Auto-approve everything (for CI, sandboxed environments)
const runner = new Runner({ permissions: 'auto' });

// Deny unknown tools (safe default)
const runner = new Runner({ permissions: 'deny-unknown' });

// Interactive approval
const runner = new Runner({
  permissions: 'prompt',
  onPermission: async ({ tool, description }) => {
    return confirm(`Allow ${tool}? ${description}`);
  },
});

// Fine-grained policy
const runner = new Runner({
  permissions: {
    allow: ['Read', 'Glob', 'Grep', 'mcp__github__*'],
    deny: ['Bash(rm *)'],
    prompt: ['Bash', 'Write'],
  },
  onPermission: async (req) => confirm(`Allow ${req.tool}?`),
});

Sandbox (Coming Soon)

Run agents in isolated environments:

// E2B cloud sandbox
const runner = new Runner({ sandbox: 'e2b' });

// Docker container
const runner = new Runner({ sandbox: 'docker' });

// Custom spawner
const runner = new Runner({
  sandbox: (options) => myCustomSpawner(options),
});

Subagents

Define programmatic subagents:

const runner = new Runner({
  agents: {
    researcher: {
      description: 'Research agent for gathering information',
      prompt: 'You are a research assistant. Search thoroughly.',
      tools: ['Read', 'Glob', 'Grep', 'WebSearch'],
      model: 'haiku',
    },
    coder: {
      description: 'Coding agent for implementation',
      prompt: 'You are an expert programmer. Write clean code.',
      tools: ['Read', 'Write', 'Edit', 'Bash'],
      model: 'sonnet',
    },
  },
});

API Reference

Runner

class Runner {
  constructor(options?: RunnerOptions);

  run(prompt: string, overrides?: RunOverrides): Promise<RunResult>;
  stream(prompt: string, overrides?: RunOverrides): RunStream;
  resume(sessionId: string, prompt?: string): RunStream;

  get lastSessionId(): string | null;
  abort(): void;
}

RunResult

interface RunResult {
  text: string;            // Final response text
  sessionId: string;       // For resume
  cost: number;            // USD
  duration: number;        // ms
  usage: { input; output }; // Token counts
  turns: number;           // Agentic turns
  toolCalls: ToolCallSummary[];
  error?: string;
}

RunEvent (7 types)

Type	Fields	When
text	text	Each streamed text chunk
tool_start	tool, id	Tool execution begins
tool_end	tool, id, duration	Tool execution ends
session_init	sessionId, model, tools	Session initialized
mcp_status	server, status	MCP server connected/failed
error	message, code?	Error occurred
done	result	Run complete

RunStream

interface RunStream extends AsyncIterable<RunEvent> {
  result: Promise<RunResult>;   // Await final result
  text: Promise<string>;        // Await full text
  send(message: string): void;  // Inject mid-stream message
  interrupt(): Promise<void>;   // Pause execution
  abort(): void;                // Stop completely
  sessionId: string | null;     // Current session ID
}

RunnerOptions

Option	Type	Default	Description
model	string	'claude-sonnet-4-6'	Claude model (shorthands supported — see below)
cwd	string	process.cwd()	Working directory
systemPrompt	string | { preset: 'claude_code' }	minimal	System prompt
mcp	Record<string, McpConfig | string>	{}	MCP servers
tools	ToolDefinition[]	[]	Custom tools
agents	Record<string, AgentDefinition>	—	Subagents
sandbox	'local' | 'e2b' | 'docker' | SpawnFn	'local'	Execution environment
permissions	'auto' | 'prompt' | 'deny-unknown' | PermissionPolicy	'deny-unknown'	Permission handling
onPermission	(req) => Promise<boolean>	—	Permission callback
maxTurns	number	—	Max agentic turns
maxBudget	number	—	Max cost in USD
effort	'low' | 'medium' | 'high' | 'max'	—	Effort level
sdkOptions	object	—	Pass-through to Agent SDK

Models

Use shorthand names or full model IDs:

// Shorthands
const runner = new Runner({ model: 'opus' });      // claude-opus-4-6
const runner = new Runner({ model: 'sonnet' });     // claude-sonnet-4-6
const runner = new Runner({ model: 'haiku' });      // claude-haiku-4-5

// Version-specific shorthands
const runner = new Runner({ model: 'opus-4.5' });   // claude-opus-4-5-20250918
const runner = new Runner({ model: 'sonnet-4.5' }); // claude-sonnet-4-5-20250514
const runner = new Runner({ model: 'opus-4.6' });   // claude-opus-4-6
const runner = new Runner({ model: 'sonnet-4.6' }); // claude-sonnet-4-6

// Full model IDs also work
const runner = new Runner({ model: 'claude-opus-4-6' });

// Per-run override
const result = await runner.run('Quick task', { model: 'haiku' });

Shorthand	Full Model ID
opus	claude-opus-4-6
opus-4.6	claude-opus-4-6
opus-4.5	claude-opus-4-5-20250918
sonnet	claude-sonnet-4-6
sonnet-4.6	claude-sonnet-4-6
sonnet-4.5	claude-sonnet-4-5-20250514
haiku	claude-haiku-4-5-20251001
haiku-4.5	claude-haiku-4-5-20251001

Runtime Support

claude-runner is runtime-agnostic. No framework lock-in.

• Node.js 18+
• Bun
• Deno
• Electron (for desktop apps)
• Any cloud — AWS, GCP, Azure, self-hosted

How It Works

claude-runner is a thin wrapper (~500 lines) around the official @anthropic-ai/claude-agent-sdk. It:

• Normalizes your options into the SDK's 40+ field Options object
• Starts a query() session with MCP servers, permissions, and tools configured
• Transforms the SDK's 20+ SDKMessage types into 7 flat RunEvent types
• Manages session lifecycle (resume, multi-turn, abort)

You get the full power of Claude Code (skills, agents, tools, MCP) through a simple API.

License

MIT