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README.md

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 # hubot-slack
 
+### Important Notice
+
+**This project is no longer under active development.** If you’re just getting started, we recommend taking a look at [Bolt for JS with Socket Mode](https://slack.dev/bolt-js/concepts#socket-mode) first. If you’ve been using this project, only critical issues (such as severe security issues) will be addressed, but we advise planning to migrate to the newer SDK.
+
 This is a [Hubot](http://hubot.github.com/) adapter to use with [Slack](https://slack.com).
 
 [![Hubot Slack Adapter CI Builds](https://github.com/slackapi/hubot-slack/actions/workflows/ci-build.yml/badge.svg)](https://github.com/slackapi/hubot-slack/actions/workflows/ci-build.yml)