slack

SlackBridge.Claude

Remote control Claude Code from Slack. Post prompts in a Slack channel from your phone, get responses back in threads.

You (Slack)  →  Socket Mode WebSocket  →  C# MCP Server (stdio)  →  Claude Code session
                                       ←  reply/react/edit tools  ←

How It Works

• Messages you send in Slack are forwarded to your Claude Code session as MCP channel notifications
• Claude Code processes the prompt and replies back via threaded Slack messages
• One Slack channel per Claude Code instance — channel name auto-derives from the working directory (e.g., project MyApp → #my-app)
• Uses Socket Mode (no public URL needed, works on free Slack plans)
• The channel is auto-created if it doesn't exist

Prerequisites

• .NET 10 SDK
• Claude Code CLI installed
• A Slack workspace where you can create apps

Setup

1. Create a Slack App

1. Go to api.slack.com/apps and click Create New App → From scratch
2. Name it whatever you like (e.g., "Claude Bridge") and select your workspace

2. Configure Bot Token Scopes

Under OAuth & Permissions → Scopes → Bot Token Scopes, add:

Scope	Purpose
channels:history	Read messages in public channels
channels:read	List channels to find/resolve the target channel
channels:manage	Auto-create the channel if it doesn't exist
chat:write	Post replies and messages
reactions:read	Read reactions
reactions:write	Add/remove emoji reactions on messages
files:write	Upload files to Slack
users:read	Resolve user display names

3. Enable Socket Mode

Under Socket Mode, toggle it on. This generates an App-Level Token — create one with the connections:write scope. Save this token (xapp-...).

4. Enable Event Subscriptions

Under Event Subscriptions, toggle it on, then under Subscribe to bot events, add:

• message.channels — triggers when a message is posted in a public channel

5. Install the App

Under Install App, click Install to Workspace and authorize. Save the Bot User OAuth Token (xoxb-...).

6. Set Environment Variables

Set these as persistent environment variables (not just shell exports — they need to be available to Claude Code):

# Linux/macOS
export SLACK_BOT_TOKEN="xoxb-your-bot-token"
export SLACK_APP_TOKEN="xapp-your-app-token"

# Windows (PowerShell — sets permanently for your user)
[System.Environment]::SetEnvironmentVariable('SLACK_BOT_TOKEN', 'xoxb-your-bot-token', 'User')
[System.Environment]::SetEnvironmentVariable('SLACK_APP_TOKEN', 'xapp-your-app-token', 'User')

Optionally set SLACK_CHANNEL to override the auto-derived channel name.

7. Build & Publish

git clone https://github.com/blakeja/slack-bridge-claude.git
cd slack-bridge-claude

# Development (requires .NET 10 SDK):
dotnet build -c Release

# Self-contained publish (no .NET runtime needed on target machine):
# Windows
dotnet publish src/SlackBridge.Claude -c Release -r win-x64
dotnet publish src/SlackBridge.Claude.Hook -c Release -r win-x64

# macOS (Apple Silicon)
dotnet publish src/SlackBridge.Claude -c Release -r osx-arm64
dotnet publish src/SlackBridge.Claude.Hook -c Release -r osx-arm64

# macOS (Intel)
dotnet publish src/SlackBridge.Claude -c Release -r osx-x64
dotnet publish src/SlackBridge.Claude.Hook -c Release -r osx-x64

# Linux
dotnet publish src/SlackBridge.Claude -c Release -r linux-x64
dotnet publish src/SlackBridge.Claude.Hook -c Release -r linux-x64

8. Run with Claude Code

claude --dangerously-load-development-channels server:slack-bridge

This starts Claude Code with the SlackBridge MCP server. The server will:

1. Connect to Slack via Socket Mode
2. Find or create a channel named after the current directory
3. Listen for messages and forward them to Claude Code
4. Provide tools for Claude Code to reply, react, and edit messages

9. Invite the Bot

The bot auto-creates the channel, but if the channel already exists, make sure the bot is a member. In Slack, go to the channel and run /invite @YourBotName.

Usage

Once running, just send a message in the Slack channel. Claude Code will:

1. React with :eyes: to acknowledge receipt
2. Process the prompt
3. Reply in a thread with the response
4. React with :white_check_mark: when done

Long responses are automatically chunked to fit Slack's message limits.

MCP Tools

The server exposes four tools to Claude Code:

Tool	Description
reply	Post a threaded reply (auto-chunks long messages)
react	Add/remove emoji reactions on messages
edit_message	Update a previously posted bot message
upload_file	Upload a file to the channel (from content or file path)