How to run Claude Code, Cursor, and Codex on one team without conflicts

You do not need to make everyone use the same agent. You need to make every agent see the same thing. Here is the agent-agnostic playbook for running Claude Code, Cursor, and Codex on one team without the conflicts that come from three blind agents editing one codebase.

Tool standardization is a fantasy. One developer is fastest in Claude Code, another lives in Cursor, a third runs Codex from the terminal, and forcing them all onto one tool trades real productivity for a tidy diagram. The better move is to let people keep their agent and give the agents a common nervous system. The common denominator that makes it possible is MCP, which all three speak natively.

The failure modes you are avoiding

Before the setup, name the enemy. These are the exact ways three agents on one repo go wrong:

• Silent contract drift.Cursor's agent renames a field, Claude Code's agent is still coding against the old name. Neither knows. CI finds out.
• The uncommitted gap. The change exists on one laptop and has not been pushed. Git cannot warn anyone because Git has not seen it yet.
• Duplicate work.Two developers' agents refactor the same module in the same hour because neither shared intent.
• Channel rot. Someone posts the change in Slack. No agent reads Slack. The announcement reaches humans, not the tools doing the work.

Every one of these comes from the same root: each agent has its own context window and no idea the others exist. It is why 27.67% of AI agent PRs hit merge conflicts and a majority of teams have shipped AI code that broke production. The fix is shared context, not a shared tool.

The setup, step by step

The whole point is that the steps are the same regardless of agent, because the coordination lives in plain MCP. Here is the playbook:

• 1. Pick the shared room once. The team agrees on one coordination layer. With Aethereum that is a single account, free to start, and one room per repo.
• 2. Run init in each repo, on each machine. npx aethereum init detects the agent and writes the right config and hooks. One command, whether the developer is on Claude Code, Cursor, or Codex.
• 3. Confirm the tools loaded. Each agent should now expose share_intent, declare_contract, and get_team_context. If a tool is missing, the config probably has a JSON typo, validate it with the MCP JSON validator.
• 4. Let it run. On supported agents, hooks inject team context at session start and surface alerts before each prompt. No one has to remember to check.
• 5. Verify the loop. Have one agent declare a contract, then start a session in a different agent on another machine and watch it pick up the change. That is the gasp moment, and it is the whole product.

Need the config built for you first? The MCP config generator produces a valid client config for any of the three agents, and the full per-agent walkthrough lives in the docs.

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$ npx aethereum init   # in each repo, on each machine
# detected: claude code | cursor | codex
# wrote MCP config + hooks for the detected agent
# tools available: share_intent, declare_contract, get_team_context

What actually flows between the agents

The room holds three things and nothing else: each agent's current intent, the active interface contracts, and alerts when a contract an agent depends on changes. No source code, no files, no diffs leave any machine, only the small slice of interface metadata an agent explicitly publishes.

So when the Cursor developer's agent changes the auth endpoint, it declares the new contract. When the Claude Code developer starts a session on a different laptop, their agent calls get_team_context()and immediately learns the contract changed and that it depends on it. The Codex developer's shared intent that they are mid-refactor is visible to both. Three agents, one shared set of tools, one coherent picture.

Anti-patterns to skip

• Do not standardize the tool. You will lose the productivity that made each person fast. Standardize the context layer instead.
• Do not rely on Git to coordinate. The collision happens before the commit. By the time Git sees it, the conflict already exists.
• Do not route coordination through humans. Slack and standups are too slow and too lossy for changes that happen every few minutes inside an agent.
• Do not over-install MCP servers. Pick a tight set, see the best MCP servers in 2026, and keep the coordination layer as the one that spans the team.

Takeaway

Running Claude Code, Cursor, and Codex on one team is not a tooling compromise, it is a coordination choice. Let everyone keep the agent they love, then give all of those agents one shared room over MCP so a contract change in any tool reaches every other tool as live context across machines. That is the gap built-in single-agent coordination cannot reach, see agent teams vs cross-machine sync for why. Set it up with npx aethereum init, free to start.