Show HN: MCP Agent Mail, Like Gmail for Coding Agents (github.com)

MCP Agent Mail is an open-source, “Gmail for coding agents” that adds a mail-like coordination layer for multiple autonomous coding tools (Claude Code, Codex, Gemini CLI, etc.). Announced as a FastMCP HTTP server you can run locally (scripts provided to auto-detect and install agents), it gives agents memorable identities, inbox/outbox mailboxes, threaded/searchable message history, attachments, and advisory file reservations (“leases”) to signal edit intent. The goal is lightweight, asynchronous coordination so agents don’t overwrite each other, lose parallel-context, or force humans to shuttle messages between toolchains. Technically it uses a dual-persistence model: human-readable message artifacts are written into a per-project Git archive for auditability, while SQLite (FTS5) provides fast full-text search and directory/index queries (bm25 scoring with LIKE fallback). The server exposes resource:// URIs for fast reads, supports macros for common flows (macro_start_session, macro_claim_cycle), and offers granular APIs (register_agent, reserve_file_paths, send_message, fetch_inbox). Leases can be exclusive with TTL and enforced via an optional pre-commit guard; auth supports static bearer or JWT+JWKS. A lightweight server-rendered web UI and project discovery (LLM-assisted sibling suggestions) are included. For multi-repo projects this enables explicit cross-repo handshakes and threaded summaries, reducing merge conflicts, token costs, and human coordination overhead in complex multi-agent development.