mcp-agent-mail-rust

MCP Agent Mail (Rust)

"It's like Gmail for your coding agents!"

A mail-like coordination layer for AI coding agents, exposed as an MCP server with 45 tools and 25 resources, Git-backed archive, SQLite indexing, an interactive 16-screen TUI, a server-rendered web UI, and an agent-first robot CLI. The Rust rewrite of the original Python project (1,700+ stars).

Supported agents: Claude Code, Codex CLI, Gemini CLI, Oh My Pi (OMP), GitHub Copilot CLI, and any MCP-compatible client.

Watch the 23-minute walkthrough to see seven AI coding agents send over 1,000 messages to each other while implementing a development plan over two days.

curl -fsSL "https://raw.githubusercontent.com/Dicklesworthstone/mcp_agent_mail_rust/main/install.sh?$(date +%s)" | bash

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Table of Contents

• TL;DR
• Why This Exists
• What People Are Saying
• Design Philosophy
• Rust vs. Python: Stress Test Results
• Installation
• Quick Start
• Agent Configuration
• Server Modes
• Operator CLI Surface
• The 45 MCP Tools
• TUI Operations Console
• Robot Mode (am robot)
• File Reservations
• Multi-Agent Coordination Workflows
• Web UI
• Deployment Validation
• Configuration
• Architecture
• ATC Learning Implementation Map
• Core Data Model
• How the System Works
• Search Architecture
• Coordination Algorithms and Safety Invariants
• Consistency and Recovery Model
• Comparison vs. Alternatives
• Development
• Performance and Benchmarking
• Mailbox Diagnostics (am doctor)
• Troubleshooting
• Limitations
• FAQ
• Appendix: Protocol Transcript
• Appendix: TUI vs. Web vs. Robot
• Documentation
• About Contributions
• License

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TL;DR

The Problem: Modern projects often run multiple coding agents at once (backend, frontend, scripts, infra). Without a shared coordination fabric, agents overwrite each other's edits, miss critical context from parallel workstreams, and require humans to relay messages across tools and teams.

The Solution: Agent Mail gives every coding agent a persistent identity (e.g., GreenCastle), an inbox/outbox, searchable threaded conversations, and advisory file reservations (leases) to signal editing intent. Everything is backed by Git for human-auditable artifacts and SQLite for fast indexing and search.

Why Use Agent Mail?

Feature	What It Does
Advisory File Reservations	Agents declare exclusive or shared leases on file globs before editing, preventing conflicts with a pre-commit guard
Asynchronous Messaging	Threaded inbox/outbox with subjects, CC/BCC, acknowledgments, and importance levels
Token-Efficient	Messages stored in a per-project archive, not in agent context windows
25 MCP Resources	Read-only inbox, thread, reservation, tooling, identity, and attention views for cheap lookups
45 MCP Tools	Infrastructure, identity, messaging, contacts, reservations, search, macros, product bus, and build slots
16-Screen TUI	Live operator cockpit for messages, threads, agents, search, reservations, metrics, health, analytics, attachments, archive browsing, and ATC
Web UI	Server-rendered /mail/ routes for human oversight, unified inbox review, search, attachments, and overseer messaging
Robot Mode	19 agent-optimized CLI subcommands with toon/json output (md for thread and message views) for non-interactive workflows
Git-Backed Archive	Every message, reservation, and agent profile stored as files in per-project Git repos
Hybrid Search	Search V3 via frankensearch. The lexical tier ships by default; semantic and hybrid routing need a build with the hybrid feature (feature = "hybrid") and the runtime opt-in AM_SEARCH_SEMANTIC_ENABLED=true. Without both, every query runs lexical.
Pre-Commit Guard	Git hook that blocks commits touching files reserved by other agents
Dual-Mode Interface	MCP server (mcp-agent-mail) and operator CLI (am) share tools but enforce strict surface separation

Quick Example

# Start the server (the installer already configured your detected coding agents;
# `am setup run` re-runs that setup at any time)
am

# That's it. Server starts on 127.0.0.1:8765 with the interactive TUI.

# Agents coordinate through MCP tools:
#   ensure_project(human_key="/abs/path")
#   register_agent(project_key="/abs/path", program="claude-code", model="opus-4.6")
#   file_reservation_paths(project_key="/abs/path", agent_name="BlueLake", paths=["src/**"], ttl_seconds=3600, exclusive=true)
#   send_message(project_key="/abs/path", sender_name="BlueLake", to=["GreenCastle"], subject="Starting refactor", body_md="Taking src/**", thread_id="FEAT-123")
#   fetch_inbox(project_key="/abs/path", agent_name="BlueLake")

# Or use the robot CLI for non-interactive agent workflows:
am robot status --project /abs/path --agent BlueLake
am robot inbox --project /abs/path --agent BlueLake --urgent --format json
am robot reservations --project /abs/path --agent BlueLake --conflicts

What Agent Conversations Look Like

Example exchange between two agents coordinating a refactor:

┌──────────────────────────────────────────────────────────────────────────────┐
│ Thread: FEAT-123 - Auth module refactor                                      │
├──────────────────────────────────────────────────────────────────────────────┤
│                                                                              │
│ ┌──────────────────────────────────────────────────────────────────────────┐ │
│ │ GreenCastle -> BlueLake                                 2026-02-16 10:03 │ │
│ │ Subject: Starting auth refactor                                          │ │
│ ├──────────────────────────────────────────────────────────────────────────┤ │
│ │ I'm reserving src/auth/** for the next hour. Can you focus on the API    │ │
│ │ tests in tests/api/** instead?                                           │ │
│ │ [ack_required: true]                                                     │ │
│ └──────────────────────────────────────────────────────────────────────────┘ │
│                                                                              │
│ ┌──────────────────────────────────────────────────────────────────────────┐ │
│ │ BlueLake -> GreenCastle                                 2026-02-16 10:04 │ │
│ │ Subject: Re: Starting auth refactor                                      │ │
│ ├──────────────────────────────────────────────────────────────────────────┤ │
│ │ Confirmed. Releasing my reservation on src/auth/** and taking            │ │
│ │ tests/api/** exclusively. Will sync when I hit the auth middleware       │ │
│ │ boundary.                                                                │ │
│ │ [ack: OK]                                                                │ │
│ └──────────────────────────────────────────────────────────────────────────┘ │
│                                                                              │
│ ┌──────────────────────────────────────────────────────────────────────────┐ │
│ │ BlueLake -> GreenCastle                                 2026-02-16 10:31 │ │
│ │ Subject: Re: Starting auth refactor                                      │ │
│ ├──────────────────────────────────────────────────────────────────────────┤ │
│ │ Found a broken assertion in tests/api/auth_test.rs:142 -- the expected   │ │
│ │ token format changed. Heads up if you're touching the JWT issuer.        │ │
│ └──────────────────────────────────────────────────────────────────────────┘ │
│                                                                              │
│ ┌──────────────────────────────────────────────────────────────────────────┐ │
│ │ GreenCastle -> BlueLake                                 2026-02-16 10:33 │ │
│ │ Subject: Re: Starting auth refactor                                      │ │
│ ├──────────────────────────────────────────────────────────────────────────┤ │
│ │ Good catch. I just changed the claims struct. Updated the test fixture   │ │
│ │ in my commit. Releasing src/auth/** now -- all yours if you need it.     │ │
│ └──────────────────────────────────────────────────────────────────────────┘ │
│                                                                              │
└──────────────────────────────────────────────────────────────────────────────┘

No human relay needed. Agents negotiate file ownership, flag breaking changes in real time, and hand off work through structured, threaded messages stored in Git.

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Why This Exists

Modern projects often run multiple coding agents at once (backend, frontend, scripts, infra). Without a shared coordination fabric, agents overwrite each other's edits, miss critical context from parallel workstreams, and require humans to relay messages across tools and teams.

Agent Mail has been available since October 2025 and was designed around real multi-agent coding workloads across providers such as Claude Code, Codex CLI, and Gemini CLI. The adjacent Beads and bv tools make it more useful as a full coordination stack: Beads tracks work, bv helps pick the right next work, and Agent Mail carries the coordination traffic.

The Footguns Agent Mail Avoids

No "broadcast to all" mode. Given the option, many agents will overuse broadcast-style messaging. That is the equivalent of default reply-all in email: lots of irrelevant noise and wasted context.

Carefully refined API ergonomics. Bad MCP documentation and poor agent ergonomics quietly wreck reliability. Agent Mail's 45 tool definitions have gone through repeated real-world iteration so they work predictably without wasting tokens.

No git worktrees. Worktrees can slow development velocity and create reconciliation debt when agents diverge. Agent Mail takes the opposite approach: keep agents in one shared space, surface conflicts quickly, and give them tools to coordinate through them.