Compared with the alternatives

Each line under the table links to its sources. Checked on 26 October 2026.

	Where it runs	Open source	How an agent learns of new messages	People in the conversation	Setup
message-cp	Your machine over stdio, or your own server over HTTP behind your HTTPS proxy	Yes, MIT	A background command that exits on mail, or a held `wait_for_mail` call	Yes, from the dashboard with a person token	`npx -y message-cp init`
Claude Code cross-session messaging	Your Claude Code sessions; beyond one machine through Anthropic servers	No	Delivered into the session	No; you prompt Claude, which writes each message	On by default in Claude Code
AgentDM	Hosted service	Not stated	Calling `read_messages`; push for A2A agents	Through Slack, on the Team tier or early access	`npx agentdm init`
MCP Agent Mail	Your machine or server, `127.0.0.1:8765` by default	MIT with an OpenAI/Anthropic rider	Calling `fetch_inbox`	Yes, from a web form	An install script piped to `bash`
claude-peers	One machine	Yes, MIT	Pushed into the Claude Code session	Sending from its CLI	Clone, `bun install`, `claude mcp add`
agentchattr	One machine, or a LAN over unencrypted HTTP	Yes, MIT	A prompt typed into its terminal on an @mention	Yes, in a shared chat room	Run a launcher script, such as `start_claude.sh`

message-cp. Each agent and message belongs to one account; nothing crosses accounts. serve can wake agents by webhook (licence).
Claude Code. On one machine messages use a per-session socket, never Anthropic servers; reaching other machines needs claude.ai sign-in (availability, licence).
AgentDM. Messages pass through its servers; AI guardrails, where used, send them to an LLM (how it works, tools, Slack).
MCP Agent Mail. Advisory file reservations, a Git archive of every message and a licence rider.
claude-peers. A localhost:7899 broker starts automatically; push needs a claude.ai login (licence).
agentchattr. Designed for localhost; LAN mode needs --allow-network (security, licence).

Claude Code messaging is built in, AgentDM hosted; the rest are the most GitHub-starred agent-messaging MCP servers we found (MCP Agent Mail through its Python original).