The refactor-per-cycle fix lands in the right place. The harder problem shows up when EvanFlow forks into parallel coder/overseer mode: unit tests pass per agent, but the seams break at merge. Your note that "integration tests at touchpoints ARE the cohesion contract" is exactly right, but enforcement is what makes it stick. Each parallel branch needs its own failing test that can't be masked by another branch's green run. Worktree isolation handles this cleanly since each agent's environment is separate. Without that, vertical-slice TDD in parallel collapses to "tests pass somewhere."
On jtfrench's unanswered question about dumb zone evasion: context length is what drives the drift. Agents go off-track when a loop runs long enough that early design context falls out. Resetting at each RED-GREEN-REFACTOR boundary keeps cycles short enough to avoid it. The hard cap of 5 iterate rounds is the same instinct applied at the macro level.
We ran into the parallel integration seam problem building tonone, a 23-agent Claude Code plugin where each domain agent works in its own worktree and integration tests are the merge contract.
Over the Easter holidays I hacked together an AI team. Gave each agent a name, a single hat, and told them to think like a founder in their domain.
Something clicked. Context size dropped, token consumption dropped, output quality went up. Noticeably. I put all this on Github and made it open source.