Yes, you can run several Claude Code agents on the same project at once, and it is a genuinely fast way to work. The catch is that they cannot see each other. Two agents will happily edit the same file, rename the same function, or reshape the same API in parallel, and the second write quietly wins. The fix is not to slow down. It is to give the agents a shared view of what each other is building, so they route around each other instead of colliding.
Can you run multiple Claude Code agents at once?
You can. Open the project in two terminals, start claude in each, and you have two agents working the same repository. People run three, five, sometimes more, one per feature. On a single machine the limit is your own attention. The problems start the moment two of those agents touch the same thing.
Why they overwrite each other
Each Claude Code agent works from its own context window. It reads a slice of the codebase, forms a plan, and edits. It has no idea another agent exists, let alone what that agent is halfway through changing. So both agents can read the same file, generate independent edits, and write back. The later write lands on top of the earlier one. Neither agent knows it happened, and nothing fails loudly until something downstream breaks.
The sharper version of this is interface drift. One agent renames POST /api/checkout to take a new field. Another agent, in parallel, writes ten call sites against the old shape. Both diffs are internally consistent. The merge is clean. The break happens where the two halves meet, which is exactly where no single agent was looking. We go deeper on this in interface contract drift and AI agents and merge conflicts.
The git worktree workaround, and its ceiling
The most common workaround is git worktrees: give each agent its own checkout of the repo on its own branch, so their file edits cannot physically clash. It works, and for fully independent tasks it is a good idea. But it has a ceiling:
- Worktrees isolate files, not intent. If two agents redesign the same interface in separate worktrees, you still get the conflict, just later, at merge time.
- Setup overhead: a separate install per worktree, separate ports or databases, env files to copy, stale trees to prune.
- It only helps on one machine. The moment a teammate's agent on another laptop is involved, worktrees do nothing.
Worktrees stop two agents from typing into the same file. They do not make the agents aware of each other. That awareness is the actual missing piece.
Share the contract, not the code
The insight is that agents do not need to share their source. They need to share the small set of things they are about to disagree on: the shape of an interface, the intent of what each is building, and an alert the instant a shared contract changes. That is a tiny amount of information compared to a codebase, and it is the part that actually prevents collisions.
Aethereum is a layer over MCP that does exactly this. When one agent declares a contract or changes one, every other agent on the project hears about it right away, before it writes against the old shape. Your source never leaves your machine. Only the contracts and a one-line note of intent are shared.
How to set it up
One command wires every agent in the project, and then you keep using Claude Code exactly as you do now:
npx aethereum initThat spins up a free room, no signup, and configures Claude Code (and Cursor, Codex, and other MCP agents) to share contracts and intent automatically. When agent A reshapes POST /api/checkout, agent B is told the moment it happens. If you also work across machines, the same room keeps a laptop and a desktop in sync, which we cover in syncing Claude Code across machines.
Running agents as a team rather than solo? The teams setup and the hackathon guide walk through the same idea for more people and more machines.