Ark

A Slack gateway for AWS Bedrock Agents via Socket Mode. Ark connects Slack conversations to a Bedrock Agent using WebSocket (no public endpoint needed), forwards messages, and posts streamed responses back.

• Direct messages - the bot responds in a flat conversation
• Channel mentions - the bot responds in a thread

Slack thread timestamps are used as Bedrock session IDs, so follow-up messages in the same thread maintain conversation context.

Prerequisites

• Crystal 1.10+
• A Slack app with Socket Mode enabled and scopes: app_mentions:read, chat:write, im:history, reactions:write
• An AWS Bedrock Agent with an alias
• AWS credentials with Bedrock access (and optionally Firehose)

Configuration

All configuration is via environment variables:

* Either AWS_PROFILE or both AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY must be set. Explicit keys take priority over profile. When using AWS_PROFILE, credentials are read from ~/.aws/credentials and region from ~/.aws/config.

Development

cp .env.example .env  # fill in your values
make build            # debug binary
make test             # run specs
make lint             # run ameba
make format           # format source

Environment variables in your shell take precedence over .env values.

Docker

docker build -t ark .
docker run -e SLACK_BOT_TOKEN=... -e SLACK_APP_TOKEN=... \
  -e BEDROCK_AGENT_ID=... -e BEDROCK_AGENT_ALIAS_ID=... \
  -e AWS_ACCESS_KEY_ID=... -e AWS_SECRET_ACCESS_KEY=... \
  ark

The image uses a multi-stage build (Crystal Alpine -> Alpine) with a static binary.

Project structure

src/
  main.cr                     # Entry point, config, signal handling
  ark/
    gateway.cr                # Slack Socket Mode event loop
    config.cr                 # Environment variable configuration
    slack/
      client.cr               # Slack Web API client
      socket_mode.cr          # Socket Mode WebSocket connection
      mrkdwn.cr               # Markdown -> Slack mrkdwn conversion
      block_kit.cr            # Block Kit table support
      types.cr                # Constants and MIME type mapping
    bedrock/
      agent.cr                # Bedrock Agent client
      event_stream.cr         # AWS binary event stream decoder
      session.cr              # Session ID utilities
      types.cr                # Request/response types
    aws/
      signer.cr               # AWS SigV4 signing (via awscr-signer)
      credentials.cr          # AWS credential struct
      firehose.cr             # Kinesis Firehose analytics publisher