How to run multiple Claude Code sessions in parallel on macOS

If you use Claude Code seriously, you eventually hit the same wall: one session isn't enough. You want one agent refactoring, another writing tests, a third chasing a bug — all at once. Then you look up and every terminal tab is named zsh, and you have no idea which one is doing what.

Running multiple Claude Code sessions in parallel is less about raw speed and more about staying oriented. Here's how to do it well on macOS.

Start with the terminal, and feel the pain

The zero-tool version: open several terminal tabs or panes (iTerm2, tmux, or the built-in Terminal) and start claude in each, one per project directory. This works for two or three agents.

It falls apart around five. The tabs look identical, you alt-tab into the wrong one, and you type a prompt meant for repo A into repo B. There's no shared view of "what is every agent doing right now."

The three problems you're actually solving

1. Identity — knowing at a glance which window belongs to which project.
2. Broadcast — sending the same instruction to several agents at once (run the tests, pull main, apply this fix).
3. Durability — not losing your fleet when one process crashes or the machine restarts.

Any setup that runs many agents needs an answer to all three. tmux gives you identity (named panes) but not broadcast-to-a-subset or crash recovery of the underlying sessions.

A tiling approach

The approach we prefer is to give every session its own tile on one screen, each tagged with the project's name, a color, and a live status indicator. One glance replaces five alt-tabs.

Add two things on top:

• ⌘-click to group panels, then type once and broadcast to the whole group. Kicking off the same migration across ten repos becomes one action instead of ten.
• Crash-proof restore: if the app or machine goes down, relaunching brings every panel back in its own folder and resumes its own session — the fleet equivalent of claude --resume.

This is exactly what we built Agent Tile to do. But the principles apply to whatever you use: optimize for identity, broadcast, and durability, in that order.

Practical tips regardless of tool

• One directory per agent. Keep each session scoped to a single repo or worktree so its context stays clean.
• Name before you launch. A window you can't identify is a prompt you'll misfire.
• Review is the new bottleneck. With five agents producing diffs, your job shifts from writing to reading fast and saying "no, back up." Budget time for it.
• Don't over-parallelize. Three agents you actually supervise beat eight you don't.

Running a fleet of AI coding agents is a management problem more than a tooling one. The tool just decides how much friction stands between you and a clear picture of what your agents are doing.