dsh-agent-mailbox

Across the existing DeepSeek Harness messaging plugins, nearly all assume the participants are DSH sessions themselves. An MCP client, an A2A agent, or any external driver simply has no first-class way to address another agent, so a human ends up copy-pasting every message by hand. dsh-agent-mailbox closes that gap: any MCP client, any DSH session, and any A2A agent can directly send threaded, prioritised messages with attachments to each other, broadcast to everyone, search the full history, and track delivery receipts. The log is append-only with HMAC signing on every record and secret redaction on ingest, and every reading tool repeats a trust-boundary note so message content is treated as data, never as instructions.

The plugin also ships SSE streaming, long-poll wake-up, an A2A agent card for zero-config discovery, a presence registry, and content-addressed attachments. It runs entirely local with zero runtime dependencies and no build step — no broker, no external service, no npm account required. Inside a DSH session, four slash commands cover reading, sending, peer listing, and search; outside, the full surface is exposed over HTTP and JSON-RPC 2.0.

It is aimed at teams that need a lightweight, auditable message channel between heterogeneous agents: pushing intermediate results from one MCP coding assistant to a reviewer agent, persisting a decision for later retrieval, or connecting an A2A pipeline without standing up MQTT, Kafka, or any other external messaging infrastructure.