pi-slack-bridge

A pi extension that connects your Pi agent harness terminal session to Slack via Socket Mode.

This is a fork of tintinweb/pi-messenger-bridge which purely focusses on the integration of Slack. It provides opinionated Quality-of-Life features like Markdown formatting via the Slack Block Kit API, tmux-backed Session Management (create new or switch to former Pi Session) and more.

Summarized featureset:

• Send messages, receive responses with pi from Slack
• Run deterministic remote commands (/slk-bridge ... in pi's terminal, .bridge ... in Slack DMs)
• Upload/download files between Slack and pi
• Manage multiple pi sessions per Slack thread (each session gets its own thread)
• Switch between sessions, spawn new ones, and hand off seamlessly
• Session message replay - when resuming a session, prior conversation history is replayed into the Slack thread
• Opt sessions in/out of automatic bridge takeover

Currently only one terminal session at a time can be bridged to Slack.

Setup

1. Install

pi install npm:pi-slack-bridge

Or install from local path:

pi install /path/to/pi-slack-bridge

2. Configure Slack

Create a Slack app with Socket Mode in Settings > Socket Mode enabled. You need both tokens:

• Bot Token (xoxb-...) — in Settings > Install App
• App-Level Token (xapp-...) — create one in Settings > Basic Information > App-Level Tokens with the connections:write scope

In Features > App Home enable Messages Tab so you can interface with the App via DMs.

Following Bot Token scopes (in Features > OAuth & Permissions) need to be enabled for the Slack Bridge to function fully:

• chat:write - for exchanging Messages to/from Pi
• files:read - for File sending to Pi
• files:write - for File receiving from Pi
• im:history - for viewing message history with Slack user
• im:read - for saving metadata for session management
• reactions:write - to show the User via ⏳ reaction that prompt is processing
• user:read - to correctly identify user for authentication

Configure the Slack Bridge via the interactive menu:

/slk-bridge
# Select "Configure"
# Enter bot token
# Enter app token

Or via CLI:

/slk-bridge configure <bot-token> <app-token>

Or set environment variables:

export PI_SLACK_BOT_TOKEN="xoxb-your-slack-bot-token"
export PI_SLACK_APP_TOKEN="xapp-your-slack-app-token"

3. Connect

/slk-bridge connect

The bridge automatically connects after token configuration or on next pi launch if autoConnect is set in the ~/.pi/slk-bridge.json.

4. Authenticate Users

When a Slack user messages the bot for the first time, they receive a 6-digit challenge code. The code appears in their pi terminal.

The user then enters the code in the bot chat to become a trusted user.

After the first successful claim, unknown users are silently ignored. To re-open claiming: call /slk-bridge releaseclaim in a Pi terminal session

Main deviations from pi-messenger-bridge

Slack as first-class transport

• Change of semantics - msg-bridge -> slk-bridge
• File Upload and Receive - send and receive Files over Slack to/from your Pi Agent session
• Markdown Formatting - Slack messages are now properly formatted with Markdown Blocks
• stop - send stop in Slack to abort an agent turn. Inspired by badlogic/pi-telegram
• Reflect pi status in Slack message footer - each latest message has a Slack footer annotation which reflects the state of your Pi agent (current path, model, context window,...)

tmux-backed Session Management

The goal is to pick up your Pi session from Slack or from the terminal whenever you want. For this, tmux is used as the backbone to create new Pi sessions, switch to older ones or list previous ones. Only one tmux session can exist at time to function as a container for a newly created or switched-to Pi session.

There are 3 main commands introduced:

• /slk-bridge new [path] - kill current Pi session and start a new one inside a tmux session. Include path as an optional argument to start the session in a path on your OS
• /slk-bridge list-sessions [number] - list the recent 10 sessions of your Pi agent. Include an optional number argument to list the last number sessions.
• /slk-bridge switch <number> - switch to a session denoted by the number in the list-sessions command. The old tmux session (if it exists) gets used for switching the Pi terminal session.

Each command is implemented in a deterministic fashion inside the Pi Agent harness so that no LLM call is triggered. To optout/optin a local terminal session being bridged to Slack, use /slk-bridge optout or /slk-bridge optin respectively.

Whenever a session is switched, it gets assigned its own new thread in the DM with the Slack App bridged to your Pi agent. A user can also switch to a session by continuing the respective thread in Slack.

Deterministic Dot Commands

The user can use .bridge as a sort-of replacement to trigger some / commands to Pi. Currently only supports skills and prompt templates next to pi-slack-bridge native commands. To list all available commands, send . in Slack.

Security

• Config file: ~/.pi/slk-bridge.json (chmod 600 — owner read/write only)
• Config directory: ~/.pi/ (chmod 700 — owner only)
• Downloads: ~/.pi/slk-bridge-downloads/slack/
• Handoffs: ~/.pi/slk-bridge-handoffs/
• Environment variables take precedence over file config
• Challenge-based authentication (6-digit code, 3 attempts, 2-minute expiry)
• Transport-namespaced user IDs prevent impersonation
• After first successful claim to the Slack app, unknown users are silently ignored until the user manually releases claim via /slk-bridge releaseclaim

Troubleshooting

Enable debug mode to see detailed logs:

export SLK_BRIDGE_DEBUG=true

Or set in config:

{ "debug": true }

Common Issues

• "Another instance is connected" — the single-instance guard prevents duplicate Slack connections. Use /slk-bridge connect in the active session or force-acquire by typing in the target session.
• No Slack messages received — verify Socket Mode is enabled in your Slack app configuration and both tokens are correct.
• Handoff not working — ensure tmux is installed and pi is in your PATH. Handoff spawns pi --session <target> in tmux.

Development

git clone https://github.com/comsysto/pi-slack-bridge.git
cd pi-slack-bridge
npm install
npm run build        # compile TypeScript
npm run typecheck    # type-check without emitting
npm run test         # run vitest suite
npm run lint         # biome lint
npm run lint:fix     # biome lint with auto-fix

Load directly from source (faster for development)

pi -e src/bridge/index.ts
/slk-bridge connect

Test suite

npm run test

Covers config loading, lock acquisition, Slack block splitting, conversation history extraction, and formatting.

Acknowledgements

First of all, thanks to the tremendously useful Pi project by Earendil.

Thanks to @tintinweb for providing the pi-messenger-bridge extension this builds upon. Furthermore thanks to @badlogic and @llblab for their pi-telegram-bridge implementations that inspired some features in this extension like Markdown formatting.

Finally, thanks to @antirez for providing the ds4 inference engine that enabled substantial development with a local deepseek-v4-flash.

Transparency about coding agent use

This project used the Pi Agent Harness with the gpt-5.4 model in the beginning to establish the Slack-only focus. Later, new features, refinements and refactors heavily took advantage of a locally hosted deepseek-v4-flash via antirez/ds4 on a Macbook Pro M3 Max.

License

MIT