Pi

Previous post: Day 1 | 120 Lines to Understand the Agent Loop: miniharness Teardown and 3 Counterintuitive Findings. Now that we understand the loop’s core structure, let’s ask a more fundamental question: of the remaining thousands of lines, what belongs and what doesn’t? This is an L3 core lesson. Upcoming navigation: Day Type Topic Day 3 Core Hard constraints in the Harness: static contracts and lifecycle hooks Day 4 Exercise Rewrite your AGENTS.md + add an interception hook Day 5 Core Tools as interface: three extension paths Day 6 Exercise Give your Agent a new tool Day 7 Core Meta-architecture: Everything is a Plugin Day 8 Core Memory, traces, and observability Day 9 Exercise Capstone: build a team-level CI/CD automated Harness Day 10 Wrap-up L3 graduation assessment + Harness future trends Why “More Features” Is a Reverse Optimization In Day 1 we dismantled the loop, showing that the core logic takes only about a hundred lines; the remaining thousands consist of structure, constraints, tools, permissions, and planning modes—all the extra capabilities designed to let Agents “do more things.” ...

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. ...