agentcourier

[agentcourier]

agentcourier

Let your AI agents talk to each other, securely, across machines.
An MCP server for agent-to-agent messages and files between Claude Code, Codex, GitHub Copilot and any other MCP client,
on your laptop, an HPC cluster or a colleague's machine. End-to-end encrypted, no server, no cloud.

[CI] [PyPI] [Post-quantum hybrid encryption] [License]

What it does

• Messages and files between agents. An agent on your laptop asks the agent on the cluster to check a simulation; the answer comes back into the same conversation. Files can be sent too.
• Pair once, then it just works. Machines are paired once. Agents can close and restart; they keep their names, and messages for an agent that is offline wait until it is back.
• Works with running sessions. In Claude Code, messages appear directly in the session. Other clients read them with one tool call, and you get a desktop notification.
• Only machines you paired. No accounts, no server, no cloud. Every connection is encrypted end to end, including protection against future quantum computers.
• Guardrails built in. Personal data and secrets are masked, files are screened for malware, and agents are told to treat incoming messages as untrusted.

To an agent, agentcourier is a normal MCP server with the tools courier_send, courier_send_file, courier_inbox, courier_peers and courier_set_name.

Get started

1. Install on each machine (one small program, no admin rights needed):

pip install agentcourier

Or, with Rust: cargo install --git https://github.com/alhermann/agentcourier.

2. Pair two machines once. On the machine the other one connects to (for example your cluster):

agentcourier invite laptop

It prints a one-time code. On the other machine, paste it and say how to reach the first one (here through an SSH tunnel):

ssh -N -L 17312:127.0.0.1:7312 you@cluster-login-nodeagentcourier join agentcourier-… hpc 127.0.0.1:17312

Tip: name machines after their owners (agentcourier invite jana), so you can say "ask Jana's agent".

3. Add agentcourier to your agents:

claude mcp add --scope user agentcourier -- agentcourier mcp --channelclaude --dangerously-load-development-channels server:agentcourier

{  "servers": {    "agentcourier": { "type": "stdio", "command": "agentcourier", "args": ["mcp"] }  }}

[mcp_servers.agentcourier]command = "agentcourier"args = ["mcp"]

If your system cannot find the agentcourier command, use the full path that pip or cargo printed during installation.

4. Talk. Tell your agent, for example: "Ask my Claude on hpc whether the mesh study has finished, and send it results/summary.csv."

Each session gets a clear name from its tool and project, such as copilot-paper or claude-femsim; its full address is claude-femsim@hpc. You can also tell an agent "call yourself fe-runs". Agents look up who is online, and who was seen before, with courier_peers.

Check what is going on

agentcourier peers      # who is reachable, and agents seen beforeagentcourier status     # connections, paired machines, refused attemptsagentcourier log        # recent activity (no message text)agentcourier untrust X  # cut off a machine immediately

Common questions

How do I let two Claude Code sessions talk to each other?

Add agentcourier to Claude Code (step 3). Every session gets a name, such as claude-femsim, and can message any other session by that name, on the same machine or on a paired one.

Can Claude Code, Codex and GitHub Copilot talk to each other?

Yes. agentcourier is a standard MCP server, so agents from different vendors reach each other the same way, for example a Copilot window on your laptop and a Claude Code session on a server.

How do I connect an agent on my laptop with one on a remote server or HPC cluster?

Run agentcourier on both, pair them once, and connect through an SSH tunnel; no firewall changes or admin rights are needed. See the guide, including a setup for two office PCs that only share an SSH server.

What if the two machines cannot reach each other at all?

Run a relay on a third machine that both can reach, such as a group server or a small virtual machine: agentcourier relay. Both machines connect out to it, so they need no open ports or admin rights. You run it yourself, it lets in only the machines you invite, and it forwards encrypted traffic it cannot read. See the guide.

Can my agent talk to a colleague's agent?

Yes, once your two machines are paired. Each of you names the other's machine, so you can say "ask Jana's agent". Incoming messages are treated as untrusted text, and agents ask their user before acting on them.

Is it secure, and does it need a server or an account?

No server, accounts or cloud are involved: only machines you paired can connect, and every connection is encrypted end to end with post-quantum protection. If you add your own relay, it cannot read messages either. Personal data and secrets are masked, and received files are screened for malware. Details and limits are in Security.

How is this different from A2A or multi-agent frameworks?

Frameworks such as AutoGen, CrewAI or LangGraph run several agents inside one program, and A2A connects agent services over the web. agentcourier connects the coding agents you already use, in their running sessions, across machines and people.

Learn more

• User guide: names and addresses, connecting across networks and through a relay, files, notifications, commands, configuration, clusters
• Security: how pairing, encryption, masking and file screening work, and their limits

License

Apache-2.0