File-based agent messaging

File-based agent messaging is inter-agent communication built on plain files in a maildir-style directory structure (new/, cur/, held/, seen/) instead of on a network service. For AI agent sessions on one machine, files have security properties a socket cannot offer for free: there is no daemon to run, no port to expose, no privileged installation step — and most importantly, every message inherits the operating system's ownership and permission model. agentixmesh uses exactly this transport: mailbox directories are created owner-only (mode 0700), message filenames carry 128 bits of entropy (token_hex(16)) so they cannot be guessed, and the sender's identity is established from kernel-enforced file ownership rather than from anything in the message. Delivery is a hook that injects new messages as inert DATA frames into the receiving session, deduplicated by a replay guard and fail-closed: on any internal error the hook delivers nothing rather than something half-sanitized. The same properties define the honest boundary: a maildir is local by nature, so this transport covers one machine. Coordinating across machines needs a different design with signed identities — a deliberate scale-up step, not a bigger maildir.

Getting it running takes a minute — see the quickstart; the cross-machine step is AgentsWeaver.