Drawing set · Series 01

At the Boundary

Everything interesting in software happens at a boundary: a request enters a server, a document enters a parser, a prompt leaves for a model. Every serious bug in seven years of production work sat on one of those lines. This set is one numbered sheet per lesson, drawn the way architects draw buildings, from systems that carry real users and real money.

Read in any order. Each sheet names the ones it belongs with. The letter after GL is the discipline: S security, A artificial intelligence, E engineering, P product, R record of what shipped.

Week 1Where the bugs live

  • Sheet 001: The bug is never where you're looking. It's at the boundary.
    GL-E-001September 5, 2026FOR INFORMATION

    The bug is never where you're looking. It's at the boundary.

    A boundary is any line where data changes hands: a request enters a server, a document enters a parser, a prompt leaves for a model.

  • Sheet 002: How to read a sheet.
    GL-E-002September 6, 2026FOR INFORMATION

    How to read a sheet.

    The letter after GL is the discipline: S security, A AI, E engineering, P product, R record of what shipped.