ClaudeMailbox/node

@kuns/claude-mailbox

Standalone MCP mail server that lets parallel Claude sessions coordinate with each other.

Install

One-time per machine:

npm config set @kuns:registry=https://git.kuns.dev/api/packages/releases/npm/
npm install -g @kuns/claude-mailbox

Then:

claude-mailbox install-autostart   # registers per-OS autostart, no admin needed by default

See the repository README for the full architecture, MCP tool reference, and .mcp.json snippet.

Claude Code hook (auto-check inbox)

Register a UserPromptSubmit hook so Claude pulls pending mailbox messages before every prompt:

claude-mailbox install-hook --name alice            # patches ~/.claude/settings.json
claude-mailbox install-hook --name alice --project  # patches <cwd>/.claude/settings.json
claude-mailbox uninstall-hook                       # remove again

The hook is idempotent (running install-hook twice does nothing the second time) and only touches the UserPromptSubmit block — other hooks and settings are preserved.

Under the hood the hook runs claude-mailbox check --name <mailbox> --hook, which:

• prints unread messages in a Claude-friendly format,
• silently exits 0 if the inbox is empty or the daemon is unreachable (no context noise),
• marks the messages delivered so they aren't injected again next prompt.

Cost: one local HTTP round-trip plus Node coldstart per prompt (~100ms on Windows).

Push delivery (watch)

For long-running autonomous sessions, run the watcher as a background bash task so peer messages surface immediately via BashOutput:

claude-mailbox watch --block --name <mailbox>

Exit codes: 0 delivered or renamed, 1 error, 2 daemon unreachable, 3 timeout. See the repository README for the full contract.

Troubleshooting

npm install returns 401 Unauthorized

The Gitea registry usually serves the releases scope publicly, but if your instance requires auth you'll need a read token:

npm config set //git.kuns.dev/api/packages/releases/npm/:_authToken=<token>

Cannot find module 'node:sqlite' or similar

claude-mailbox uses Node's built-in node:sqlite, stable since Node 24. On Node 22.5–23.x it works only with --experimental-sqlite. Upgrade to Node 24 LTS or newer: nvm install 24 && nvm use 24 (or winget install OpenJS.NodeJS.LTS on Windows).