Swarming Claude Code and Codex in Parallel: Running Multiple Agents at Once with tmux and Git Worktrees

In my previous post about a cost budget advisor , I built a mechanism that checks how much quota is left before it runs anything. This time I want to take that idea one step further: instead of cycling a single Codex through jobs one after another, run several of them at the same time as a swarm. I'll walk through the actual code for a three-layer protocol where workers declared in plan.json are expanded by orchestrate-worktrees.js into a tmux session plus git worktrees, so each Codex runs in parallel without interfering with the others. The problem: running Codex serially on the same branch When you run Codex jobs one after another on a single repository, you hit issues like: A commit from the previous job changes the preconditions for the next one Task B keeps waiting until Task A finishes When a conflict happens, the "which change is correct" decision bounces back to a human Separating branches with git worktree reduces the conflict risk to zero. Combining that with tmux to launch everything in parallel is the design for this post. The big picture: a three-layer protocol plan.json ← declaration layer (what goes to which worker) ↓ orchestrate-worktrees.js ← orchestrator layer (creates worktrees, launches tmux) ↓ orchestrate-codex-worker.sh ← worker layer (runs Codex, writes artifacts) The orchestrator doesn't know about the workers, and the workers don't know about each other. Artifacts are consolidated into three files under .orchestration/{session}/{worker_slug}/ . File Role task.md Work instructions for the worker (generated by the orchestrator) status.md State: not started → running → completed / failed handoff.md Codex output + git status (written by the worker) Declaring the plan in plan.json { "sessionName" : "refactor-sprint" , "repoRoot" : "~/my-project" , "worktreeRoot" : "~/worktrees" , "coordinationRoot" : "~/my-project/.orchestration" , "baseRef" : "HEAD" , "replaceExisting" : true , "launcherCommand" : "bash ~/.claude/scripts/orchestrate-codex-worker