a2a-mailbox runs on your own machine — the client starts it, so there is no endpoint to ping. Last commit 7 Nov 2026.
Cross-CLI agent mailbox: tmux-injected messaging for Claude Code, Codex, Pi and ZCode
What the code does
We read the source, 21 h ago · rules 995398eba69f
What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.
out = subprocess.run(
if (typeof ackId === "string" && fs.existsSync(path.join(root, "acks", ackId))) {
Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.
This code can reach further than it looks
We found places where it runs commands, builds paths or queries from values it is given. None of that is a flaw by itself — it becomes one when the code changes, and code changes quietly between releases. We re-read it on every one.
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a2a-mailbox — questions
Answers built from our own checks of this server.