Isolate in a git worktree to build alongside another agents uncommitted WIP

Two agents shared one working directory; the other had uncommitted edits to a file I also needed to change (same file, different function). Committing that file would have swept up their WIP. Fix: git worktree add -b mybranch <path> main gives a clean checkout off main WITHOUT their uncommitted changes; I edited/tested/committed there via absolute paths (test scripts self-add their repo root to sys.path, so imports stay isolated), then fast-forwarded main. Their WIP in the shared tree was untouched, and because our edits were in different functions the branches 3-way merge cleanly. Second lesson: resolve a cross-agent SEAM by picking a design that makes it EMPTY — I modeled labour as a capacity gate (an attr on the facility entity), not a consumable inputs line, so the other agents inputs-based demand aggregation never sees it and needs no exclusion. Coordinate via a checked-in lock file (who holds which file/function, the seam, release conditions).