cursor-cli-demo

Cursor background agent using the Cursor CLI and Trigger.dev

Learn how to run Cursor's headless CLI agent inside a Trigger.dev task, parsing NDJSON stdout into a Realtime Stream that renders live in a browser terminal.

Tech stack

• Next.js – App Router frontend with server actions to trigger runs
• Cursor CLI – Headless AI coding agent spawned as a child process
• Trigger.dev – Background task orchestration with real-time streaming to the frontend, observability, and deployment

Video

background-cursor.mp4

Running the project locally

1. Install dependencies

   pnpm install

2. Configure environment variables

   cp env.local.example .env.local

   • TRIGGER_SECRET_KEY – From Trigger.dev dashboard (starts with tr_dev_ or tr_)
   • TRIGGER_PROJECT_REF – Your project ref (starts with proj_)
   • CURSOR_API_KEY – Your Cursor API key for headless CLI access

3. Start development servers

   # Terminal 1: Next.js
   pnpm dev
   
   # Terminal 2: Trigger.dev
   npx trigger.dev@latest dev

4. Open http://localhost:3000 in your browser to see the demo

Features

• Build extensions – Installs cursor-agent into the task container image via addLayer, so any system binary can ship with your task
• Realtime Streams v2 – NDJSON from a child process stdout is parsed and piped directly to the browser using streams.define() and .pipe()
• Live terminal rendering – Each cursor event (system, assistant, tool_call, result) renders as a distinct row with auto-scroll
• Long-running tasks – cursor-agent runs for minutes; Trigger.dev handles lifecycle, timeouts, and retries
• Machine selection – medium-2x preset for resource-intensive CLI tools
• Model picker – Switch between Claude models from the UI before triggering a run
• Bundled binary support – Spawns cursor-agent's own node binary for native module ABI compatibility

Relevant files

• extensions/cursor-cli.ts – Build extension + spawn helper that returns a typed NDJSON stream and waitUntilExit()
• trigger/cursor-agent.ts – The task: spawns the CLI, pipes the stream, waits for exit
• trigger/cursor-stream.ts – Realtime Streams v2 stream definition
• components/terminal.tsx – Realtime terminal UI with useRealtimeRunWithStreams
• lib/cursor-events.ts – TypeScript types and parsers for cursor NDJSON events
• trigger.config.ts – Trigger.dev config with the cursor CLI build extension