https://cavinmyers.com/blog Articles by Cavin Myers on software engineering, web development and the projects he builds. en Fri, 18 Sep 2026 12:00:00 GMT https://cavinmyers.com/blog/agent-harness https://cavinmyers.com/blog/agent-harness Fri, 18 Sep 2026 12:00:00 GMT Cavin Myers Tutorial A hands-on lab for building an AI agent harness from scratch in Python: a tool-calling loop, guardrails, provider switching, a run viewer and a build doctor, one phase at a time. https://cavinmyers.com/blog/agent-harness/phase-0 https://cavinmyers.com/blog/agent-harness/phase-0 Fri, 18 Sep 2026 12:00:00 GMT Cavin Myers Tutorial Set up the repo, a virtual environment and a free Groq API key, then send one prompt to a model and get text back. No tools and no loop yet. https://cavinmyers.com/blog/agent-harness/phase-1 https://cavinmyers.com/blog/agent-harness/phase-1 Fri, 18 Sep 2026 12:00:00 GMT Cavin Myers Tutorial Give the model three tools and write the loop that runs its tool calls, feeds the results back and keeps going until it has an answer. https://cavinmyers.com/blog/agent-harness/phase-2 https://cavinmyers.com/blog/agent-harness/phase-2 Fri, 18 Sep 2026 12:00:00 GMT Cavin Myers Tutorial Put a checkpoint between the model and your machine: a command allowlist, off-limits paths, an approval prompt, a timeout, and a log of every attempt. https://cavinmyers.com/blog/agent-harness/phase-3 https://cavinmyers.com/blog/agent-harness/phase-3 Fri, 18 Sep 2026 12:00:00 GMT Cavin Myers Tutorial Wrap the backend in a provider class so switching models, or adding a second provider, is a one-line config change instead of a rewrite. https://cavinmyers.com/blog/agent-harness/phase-4 https://cavinmyers.com/blog/agent-harness/phase-4 Fri, 18 Sep 2026 12:00:00 GMT Cavin Myers Tutorial Build a small React viewer that reads the run log and turns each agent run into a timeline you can watch live and explain. https://cavinmyers.com/blog/agent-harness/phase-5 https://cavinmyers.com/blog/agent-harness/phase-5 Fri, 18 Sep 2026 12:00:00 GMT Cavin Myers Tutorial Hand the harness a failing test run and get back a guarded fix you approved, plus a short explanation of what broke. https://cavinmyers.com/blog/building-the-miacademy-browser-extension https://cavinmyers.com/blog/building-the-miacademy-browser-extension Fri, 03 Jul 2026 12:00:00 GMT Cavin Myers Build Notes How I built a Manifest V3 Chrome/Edge/Firefox extension that hides distracting navigation on Miacademy.co so my kids can focus on the actual lesson.