Watercolor: on a workbench, a small machine's translucent casing is lifted to reveal a glowing circular gear mechanism, two sealed black boxes standing beside it

Day 1 | 120 Lines to Understand the Agent Loop: miniharness Teardown and 3 Counterintuitive Findings

Previous post: Day 0 | L3 Kickoff: A Short History of Harnesses, From Your Batch Script to Pi and DeepSeek Harness. Make sure you understand the Harness concept from Day 0 and the API calls from L2 Days 0-3, and let’s start dismantling the loop. This is an L3 exercise post. Upcoming navigation: Day Type Topic Day 2 Core Constraints and interception: hooks and permissions Day 3 Exercise Adding an approval gate with hooks Day 4 Core Extensions vs plugins: Pi vs DSH Day 5 Exercise Writing a Pi extension Day 6 Exercise Composing DSH Cordis plugin modes Day 7 Core Agent Teams and task DAGs Day 8 Core Memory and learning: Hermes, Nowledge Mem, EvoMap Day 9 Exercise Designing your own skill system Day 10 Wrap-up L3 graduation check Why This Is an Exercise Post The previous post traced the evolution of Harnesses. From Anthropic’s controlled experiment to the Pi and DeepSeek Harness routes, we learned one thing. Beyond the model, that guiding structure is what actually decides success. ...

2026-09-07 · 8 min · Alex Wang
Watercolor: a half-built tower wrapped in wooden construction scaffolding, warm light glowing from the unfinished floors, a slender crane silhouette beside it

Day 0 | L3 Kickoff: A Short History of Harnesses, From Your Batch Script to Pi and DeepSeek Harness

Previous post: Day 16: L2 Complete! Next Stop: Harness Engineering Evolution and the L3 Blueprint. Make sure you have understood or mastered the skills Day 16 covered, and let’s start L3 from here. This is the L3 entry point. Upcoming posts: Day Type Topic Day 1 Exercise Reading the Agent Loop in 120 lines Day 2 Core Constraints and interception: hooks and permissions Day 3 Exercise Adding an approval gate with hooks Day 4 Core Extensions vs plugins: Pi vs DSH Day 5 Exercise Writing a Pi extension Day 6 Exercise Composing DSH Cordis plugin modes Day 7 Core Agent Teams and task DAGs Day 8 Core Memory and learning: Hermes, Nowledge Mem, EvoMap Day 9 Exercise Designing your own skill system Day 10 Wrap-up L3 graduation check Start by Remembering Your Day 4 Script Think back to Day 4 of L2. In that lesson we wrote a batch script: read files from a folder, call the API on each one, write the results back, and when a step failed, log the error first, then keep going. ...

2026-08-27 · 12 min · Alex Wang