How to build an Agentic OS using Fable 5 part 1

Most people don't realize that Claude Fable 5 can run for hours unintended, dispatch its own subagents, and do a whole week of work in a single night. Here's how to build an actual Agentic OS using Fable 5. Start by configuring the Agentic OS engine. The model string should be set to Fable 5 and make sure to set max tokens to 64K, so it caps the thinking plus the responses. Effort is always set to low to max, but never extra high unless you're working with an agentic loop. And here's the part most people miss. Refusals need to come back as HTTP 200. In this way, your scripts have to check for stop reason, refusal, and not just exit code. Create a bash script called loop.sh and it runs on a cron job every morning and runs your entire system. First, use a cheap AI model like when to look at your project and ask if anything changed or needs attention. If yes, Fable steps up as the manager. It does not do the actual work, but writes down exactly what needs to be changed. Then use Sonnet to do the actual work and a fresh copy of Fable that checks it like an inspector. Next, build out the report card. Every task the system finishes gets logged as a pass or fail. Each type of task will earn its own grade over time. Once something passes 20 times with a 95% success rate, the system is then allowed to do it completely on its own. But if the grade ever drops below 90%, the system will lose that privilege and you get an email. So this way you never have to guess whether to trust your AI, the numbers will speak for you. Build out a goals directory. The system writes down a simple test to prove it still works and then it reruns one of those tests every single day. The moment something you built three weeks ago quietly breaks, it flags it. It tells you exactly what changed since the last work. This is how nothing you build will ever fall apart without you noticing. I created a step-by-step guide to build out this agentic system with many more builds using Fable 5. Just like the video and comment agent and I'll send it to you. Follow for part 2 with the rest of builds for the Agentic OS system with Fable 5.