A while back I shared Plumbline -- a spec-driven workflow of AI-agent skills that build code in a trackable, accountable way, coordinating entirely through files instead of calling each other. The pitch was "trust, but verify": make the filesystem the contract, so you can actually inspect the contract. It just hit v1.0, and getting there taught me something I didn't see coming. Quick re-intro for anyone new, then what changed -- including the part where my own framework embarrassed me (on purpose). THE 30-SECOND REINTRO To build a house well you follow the plans, double-check the work, and keep everything plumb. Your spec is the plumbline. Plumbline splits a build into single-responsibility skills that never call each other -- they hand off through files: scaffold --> architect --> foreman --> builder --> inspector (once) (spec) (blueprint) (code) (proof) Each stage reads the last one's file and writes its own. The spec is one file and stays the source of truth end to end. The inspector runs with fresh eyes and proves the software against the spec -- "done" means shown, not asserted. THE NEW PROBLEM I WALKED INTO A skill is read COLD. A fresh agent -- or a different model entirely -- loads one skill with zero memory of the conversation it was written in. So every shared convention that lives only "in the author's head" is a silent failure waiting to happen. One skill writes a status line one way, another reads it slightly differently, nothing errors -- the run just quietly goes wrong. I had skills silently agreeing on dozens of little things -- how a spec tags a finished criterion, the exact words the inspector stamps, file-naming patterns -- and that agreement existed nowhere except in my head and a handful of separate files that were free to drift apart. THE FIX: A CONTRACT THE SKILLS GET CHECKED AGAINST So v1.0 adds a TERMS file -- a single, canonical definition of every token, status line, and convention the skills share. Every skill reads it first and stops if it can't. The shared ground is explicit instead of assumed.