dsh-cross-session-messaging

dsh ships two built-in cross-session features, yet neither is genuine peer-to-peer messaging: subagents are strictly parent-child, and @session mentions are one-way, read-only recall. When a frontend assistant on a dev machine needs a database assistant on an intranet host to produce a CREATE TABLE statement and send it back, that bidirectional, cross-specialty, cross-process exchange has no built-in channel at all. This plugin closes exactly that gap.

It provides a centerless, peer-to-peer, cross-process (optionally cross-machine) message channel driven entirely by the model. Agents discover peers via cross_session_list_agents and send text via cross_session_send_message, so no human acts as a relay. Incoming messages are injected as relay text carrying no user authorization; the receiver still enforces its own tool-approval flow. Delivery is at-least-once with content dedup, backed by sender-side spooling, exponential backoff, a dead-letter queue, and receiver-side persistence before acknowledgement. Local transport uses Unix sockets; cross-machine transport uses TCP with mandatory TLS and a static peer list. There is no central server, and the on-disk registry serves as the single source of truth.

It is designed for workflow orchestrators who split distinct responsibilities across independent dsh sessions or machines and want the agents to collaborate autonomously, as well as for developers who need to pass context between sessions without weakening each session's permission model or approval chain.