Closing the Loop

What is "Closing the Loop"?

"Closing the loop" is the fundamental principle that separates effective AI-assisted coding from frustrating "vibe coding." It means designing your development workflow so that AI agents can verify their own work through automated feedback—compiling code, running tests, checking outputs, and iterating until the results are correct.

The concept was popularized by Peter Steinberger, creator of Claudebot, who calls it "the big secret" to productive agentic engineering.

Why Closing the Loop Matters

AI excels at coding but often struggles with creative writing. The difference? Code can be validated:

1. Compilation: Does the code build without errors?
2. Linting: Does it follow style and best practices?
3. Testing: Do unit and integration tests pass?
4. Execution: Does it produce expected outputs?

When agents can run these checks themselves, they can iterate toward correct solutions without human intervention. Without feedback loops, agents produce "slop"—code that looks plausible but doesn't actually work.

How to Close the Loop

Design for CLI Verification

Build your systems so agents can verify work through command-line tools:

# Agent can run these to validate its own work
npm run lint      # Check style
npm run test      # Run tests
npm run build     # Verify compilation

Create Dedicated Test Harnesses

For complex features, build CLI tools specifically for agent verification:

"I debugged a Mac app feature by telling Codex: 'Build a CLI just for debugging that invokes all the same code paths.' It cooked for an hour and fixed the race condition itself." — Peter Steinberger

Avoid Browser-Based Verification

Web-based testing loops are slow and fragile. Prefer headless, CLI-based verification:

"The browser loop is insanely slow. You want something that loops fast." — Peter Steinberger

Comparison: With vs Without Loop Closure

Key Quotes

"That's why AI is so good at coding but mediocre at writing—there's no easy way to validate creative work. But code I can compile, lint, execute, verify the output."

"If you design it the right way, you have a perfect loop."

Related Reading

• AI Agents - The systems that benefit from closed loops
• RALPH Loop - A technique that depends on loop closure
• Peter Steinberger - Pioneer of the concept