The 'hermes gateway setup' instructions for Slack were missing:
- The 'Subscribe to Events' step entirely (message.im, message.channels,
app_mention, message.groups)
- Several required scopes (app_mentions:read, groups:history, users:read,
files:write)
- Warning about bot only working in DMs without message.channels
- Step to invite the bot to channels
The 'hermes setup' flow (setup.py) and the website docs (slack.md)
already had the correct information — only gateway.py was outdated.
Reported by JordanB on Slack.