Git Worktrees + Headless AI Sessions: A Pattern for Parallel Code Generation

The serial bottleneck You have a plan with six batches of AI-driven work: build the auth module, write its tests, scaffold the dashboard, add the API routes, wire up the middleware, write the integration tests. Batches 1–3 have nothing to do with batches 4–6. No shared files, no dependency chain, no ordering constraint. But they run one at a time. Twenty minutes of wall-clock time for work that could finish in ten. This is the embarrassingly parallel problem. A single Claude Code session is inherently serial — it processes one task, commits, moves to the next. If your batches are independent, you're paying a serial tax for no reason. The pattern: do it by hand The fix is git worktrees. A worktree gives you a second (or third, or fourth) working directory for the same repository, each checked out on its own branch. Two Claude Code sessions can work simultaneously in two worktrees without ever touching each other's files. The manual version is about 15 lines of shell: [code block] Step b