agmsg

agmsg is an open-source, MIT-licensed tool built by fujibee that lets CLI AI agents — Claude Code, Codex, Gemini CLI, GitHub Copilot CLI, and others — message each other directly through a shared local SQLite database. It eliminates the need for a human to manually relay information between agent sessions. The project launched on Product Hunt on June 9, 2026, where it was reported as #5 Product of the Day with 219 upvotes and 39 comments.

What It Is

agmsg is a lightweight cross-agent messaging transport for CLI-based AI coding agents. Its core job is to let peer agent sessions — running in different tools or different terminal windows — exchange messages without any human copy-paste in the middle. It is explicitly not MCP, not a subagent spawner, and not a message queue: the SQLite file is the shared floor, and agents are the players. The only runtime dependencies are bash and sqlite3.

How the Transport Works

The architecture is intentionally minimal:

• Storage: A single SQLite file in WAL mode, stored at ~/.agents/skills/<cmd>/db/messages.db by default (overridable via AGMSG_STORAGE_PATH).
• Concurrency: WAL mode allows multiple readers and a single writer to coexist without conflicts; writes are short and serialized at the file level.
• No daemon, no network: All communication is local filesystem access. There is no broker, no socket, and no background process.
• Message content: Plain text only — agents pass summaries and references (file paths, commit SHAs, issue numbers), not raw context dumps.

Delivery modes control how incoming messages reach an agent: monitor (real-time push via Claude Code's Monitor tool, ~5s latency), turn (checked between assistant turns via a stop hook), both (monitor with turn as a fallback), or off (manual only). Mode is set per-project and is configurable at any time.

Supported Agents and Platforms

agmsg installs a skill definition (SKILL.md) that is auto-discovered by each supported agent type:

• Claude Code: /agmsg slash command; supports all delivery modes including real-time monitor.
• Codex: $agmsg skill invocation; supports turn and off modes only (no Monitor tool equivalent).
• Gemini CLI: $agmsg; Gemini support and whoami auto-detect contributed by community contributor @MiuraKatsu.
• GitHub Copilot CLI: /agmsg; Copilot CLI support contributed by @roundrop; supports turn and off only.
• Antigravity: $agmsg.
• Native Windows / Git Bash: Support contributed by @TOMONOSUKEJP.

Teams are N-agent: the README notes the authors run their own 8-agent team on it. Messages persist in SQLite across sessions, and history.sh can replay a room into a fresh agent.

Identity and Role Model

Each agent session registers a team name and an agent name on first use. The actas command allows multiple roles per project (e.g., tech-lead and biz-analyst in the same workspace), with exclusive locking so two sessions cannot hold the same role simultaneously. The drop command releases a role lock. This exclusivity model is enforced at the transport level to prevent two agents from both acting on the same inbound message.

Why It Got Attention

The README's demo — two Claude Code instances autonomously playing tic-tac-toe against each other with no human in the loop — illustrated the peer-agent coordination use case concretely. The project accumulated 440 GitHub stars and 22 forks shortly after its June 2026 launch. Community-built derivative projects (agmsg-shogi, agmsg-go, agmsg-mcp) emerged alongside the core tool, and five external contributors added support for Gemini, Copilot CLI, Windows, watcher scoping, and OpenCode.

Update: Active Development as of June 2026

The repository was last pushed on June 11, 2026, nine days after the Product Hunt launch. The roadmap items mentioned in the README include a claim/lock table for task coordination and a config-file layer for storage-driver configuration. The actas exclusivity model was added as a partial solution to the concurrent-task-grab problem. The project is under active development with 28 open issues.