Building Autonomous Agent Loops That Run Overnight on macOS
Building Autonomous Agent Loops That Run Overnight
The most productive hours for an AI desktop agent are the ones when you are asleep. Set up a cron loop, point it at your task queue, and wake up to completed work.
Here is how to build reliable overnight agent loops on macOS.
The Architecture
A typical autonomous loop has three components:
- Scheduler - a launchd plist or cron job that fires at regular intervals
- Task source - a queue of work items the agent pulls from (could be a file, a database, or an API)
- Execution layer - the agent runtime with access to both native macOS apps (via MCP servers) and web browsers (via Playwright)
The scheduler fires hourly or at whatever cadence makes sense. The agent picks up the next task, executes it, logs the result, and exits cleanly.
Native Apps vs Web
Overnight agents typically need two different interaction modes:
- macOS MCP server for native applications - controlling Finder, Mail, Calendar, or any app that exposes Accessibility API elements
- Playwright for web automation - logging into dashboards, scraping data, posting content, filling forms
The key is that both modes work without a visible display. Native macOS apps can be controlled through Accessibility APIs even when the screen is locked. Playwright runs a headless browser by default.
Practical Considerations
Running agents overnight introduces challenges you do not face during interactive use:
- Error recovery - the agent must handle failures gracefully since no human is available to intervene
- Timeout management - set hard time limits per task to prevent a single failure from blocking the entire queue
- Resource cleanup - close browser instances and release memory between tasks
- Idempotency - tasks should be safe to retry if the agent crashes mid-execution
- Wake/sleep handling - configure macOS power settings to prevent the machine from sleeping during scheduled runs
A Minimal Setup
Create a launchd plist that runs your agent script every hour. The script should pull one task from the queue, execute it with a 10-minute timeout, log the result to a dated file in /tmp, and exit. Keep the first version simple - complexity should come from observed failures, not anticipated ones.
Start with low-stakes tasks like data collection and monitoring. Graduate to actions that modify state only after you trust the error handling.
Fazm is an open source macOS AI agent. Open source on GitHub.